Hello ! Help needed regarding model railway lighting  ?. - Page 1
Forum section: electronics / beginners

author: Chris Uddin
author_rank: Contributor
timestamp: April 02, 2022, 03:37:58 am
content: Hi, I would really appreciate your knowledge and expertise?.I bought an LED light strip from Amazon which is about 10 mm in width to put into my Oxford Rail 00 scale coaches.The strip is 12-volt DC and the output 30 Watts, there are 300 lights on the Strip that will be cut down to sections of 18 LEDs per strip.I know nothing about electronics so I was wondering if maybe you could give me a little bit of help in obtaining the correct parts needed for these led lights and help wiring everything correctly.If I wire up one end of the coach to pick-ups which are above the wheels and then wire the pickups at the other end the opposite way round would that mean that I would be able to run the coach in opposite directions so that the lights stay on without the need to turn the coach around ?.If this is not the case I believe I may need a bridge rectifier which will do the job but I don't know what bridge rectifier I would need given the voltage and the wattage. ??Plus would I be able to adjust the brightness in anyway, I was looking at variable resistors and wouldn't know if these can be used with this particular lighting strip?.I know there are led lighting strips from Germany that have built in adjustable dimmers but I found these to be expensive and so thought this way could be cheaper.I was able to dim the strip using a power controller when testing if the lights worked which did the job but if this was a locomotive the lights would be dim when this was going slow and then get brighter when going faster so obviously I can't use that but what I will be using is the Bachmann Dynamis Ultima DCC unit to power the track from UK mains voltage.Any help you could give me surrounding all of this including suitability of my light strip with parts needed and "how to do this" would really be gratefully appreciated.Many thanks,Chris Uddin.Please remove if this is not suitable in this section.

author: RJSV
author_rank: Super Contributor
timestamp: April 02, 2022, 10:59:29 am
content: I can try to pick this apart, but better to ask someone directly doing RR models. The resistor uses a '3 digit code', so that's '82' ohms times 1, or literally means add on no zeros. (822 would mean '8200 ohms', for example).Now, at nominal 20 mA, that 82 ohms only drops , atV = IR, drops V= 1.36 volts, way too little, unless that LED strip has series runs, of, say three LEDs. Each series run, of three would have 4-1.36 or 2.6 volts per LED, about right.So you have to check, is it 3 in series, with those sets repeated, in parallel ? But that wouldn't be the case, if there are those 'cut' pads indicated, every LED. ?Not sure how that fits in, with plans to do every 18 LEDs?But a bridge rect, that's going to drop, about .7 to .9 volts, in each leg (total 1.4 to 1.8 is dropped, from original 12 V). Just use approx 10.4 volts in calculations. Of course, that's going to be a bridge rect, in each RR Car.Not clear what you mean by carriage contacts...is that an accessory contact ? Because you want to be separate from any engine controller.At this point, I have to say, maybe better to focus on others doing this specific project...There has got to be other sources, for exactly that.I don't know what that power take-off is, is thatDC 12 V ? Should be some standard way the polarity is defined ?At any rate, each LED generally drops about 2.4 V, very roughly, and you can't use that as a set point: Must use the current (voltage is like the reaction), at roughly 10 to 20 or so mA.Power, is approx 20 mA X 2.5 V = .050 W per LEDwhile the strip is looking like .100 W per LED. The estimate differs because the 100 mW figure includes the resistor power (I think...).You need to check, are each of those LED s in parallel ?I'm guessing it's sets of 3, with each 'set' in parallel.Then, if it's 18 per rail car, just do it as 6 sets, of 3.Again, better to spend, like 15 minutes on net search, for other RR setups.Ask more, or let folks know if you get results- - Rick B.

author: MarkF
author_rank: Super Contributor
timestamp: April 02, 2022, 02:14:48 pm
content: Quote from: Chris Uddin on April 02, 2022, 03:37:58 am18 LEDs per coach seems excessive. What is the spacing of the LEDs on the strip? You would only want a single strip the length of the coach. You must cut the strip at the indicated places. Normally in groups of three. I would guess 6 or 9 LEDs per coach.QuoteDCC power is a constant +/- voltage pulse width encoded signal.https://dccwiki.com/DCC_PowerYou will need to block the negative voltage to keep from destroying the LEDs. To do this and dim the LEDs, I would put a diode and a resistor in series with the positive leg of the LED strip to one coach pickup and connect the negative leg of the LED strip directly to the other pickup. The diode will block the unwanted half to protect the LED strip and allow you to place the coach on the track in either direction.CAUTION: Connecting the LED strip directly to DCC power will destroy the LEDs. DCC track voltage is +/-14V or more.The diode will point toward the positive LED strip pin. The resistor will probably be in the 100Ω to 2KΩ range. A half watt resistor should be able to handle the power drop. Choose a value to suit your desired brightness. You will not be able to change the brightness on the fly.Connections:Note, I added a capacitor if you have problems with flickering. Leave it out to start.

author: rstofer
author_rank: Super Contributor
timestamp: April 02, 2022, 03:12:36 pm
content: There's a ton of help on Google if you search for 'model railroad coach lighting with ddc'

author: RJSV
author_rank: Super Contributor
timestamp: April 02, 2022, 06:59:38 pm
content: Thanks MarkF for clarifying.Running the numbers, it looks like better to assume a large DCC +/- Voltage swing. I calculated for both cases, using 9 total LEDs or if it's 6 total, within each RR CAR.Using DCC at only +/- 14 volts makes for R2 value that's too small, in case of DCC being, say, +/- 18 V.That was to use R2= 125 ohm. (R2 is that one resistor put in series, with ALL groups of LEDs, to drop DCC down to 12V into your LED strips.)That is, R2= 125 ohms for your '9' LED total, or similar,R2 = 187 ohms if doing '6' LED option.But that gets into trouble, at higher DCC:I calculated your nominal goal, of 8 mA, goes way up, to approx 14 mA, assuming high DCC voltage of +/- 18 V.A safer margin, might be 200 ohms, for your '9' total, or 333 ohms, for option with '6' total LEDs.My choice would be, to use slightly higher R2, say, 320 ohms or 440 ohms, according to LED count.So, repeating that, it would be 3 strings, of 3 each, put that on a 320 ohms R2. OR, if it is 2 strings, of 3 each, put that on a 440 ohm R2.For me, I would add a tiny switch, that would double the R2 value,...experiment with that, for a 'Dimmed' mode that you can switch to, with a couple of seconds.The calculations just use:Formula for power = V X IOhm's law: V = IRPLUS:. White LED nominal drop approx 2.5 V

author: rstofer
author_rank: Super Contributor
timestamp: April 02, 2022, 07:07:24 pm
content: Just install the LEDs and proposed resistor on a breadboard.Those LEDs are going to be too bright for any coach. Getting a realistic lighting level is going to take some experimenting.

author: Benta
author_rank: Super Contributor
timestamp: April 02, 2022, 07:25:57 pm
content: 30 W LED strip for 00 scale coaches?They are going to light up like the Castle Bravo thermonuclear test.

author: RJSV
author_rank: Super Contributor
timestamp: April 02, 2022, 07:36:18 pm
content: Yeah, but OP wanted to cut that down. Still, my preference would be to not 'point' any LED outward, through any holes or RR car windows, as that's a bright distraction, as the train moves. Even at 1/10 watt it's too bright, directly pointed, or at least consider some light diffusing material, in betweenWhere's our Industrial Designer, when we need one?Those folks ROCK...like a little Artist-Engineer!More creative extremes might, later, take your project into R/C control, to change colors / brightness, etc.Just have to find some small R/C 'Color Disks'.I believe, some of those are OPTICAL using infra-Red comm link, with little hand control (credit card size).

author: rstofer
author_rank: Super Contributor
timestamp: April 02, 2022, 07:40:15 pm
content: I would start here:https://www.ebay.com/itm/184894257352

author: RJSV
author_rank: Super Contributor
timestamp: April 02, 2022, 07:42:30 pm
content: And, oh yeah, you could ALWAYS SKIP all this......Just see how 2 batteries, AAA rechargable, can those fit ? Then, you are done...NO DCC connection !(Common sense overtaking me)

author: Chris Uddin
author_rank: Contributor
timestamp: April 02, 2022, 08:19:47 pm
content: I brought the wrong type of lights then?, regards, chris.

author: MarkF
author_rank: Super Contributor
timestamp: April 02, 2022, 08:23:22 pm
content: I would mount the LED strip either on the ceiling of the coach or on the floor. Having them shine down from the ceiling would be realistic.And yes, they are going to be far too bright. You will want to cut the intensity down to 25% at least.Don't modify the resistors on the strip. Just add an additional resistor in series with the rail pickup as I showed.I didn't do any calculations. Just a guess at the resistor value.However, I did re-light my old locomotives with LEDs. I put in 5mA LEDs and set the current to 1mA and they are still too bright. One locomotive I was not able to fit the current limit chip (LM334) and just set a low current. The LEDs tolerate a large voltage range. The LEDs in this locomotive come on at 4V and blow you away at 12V.

author: MarkF
author_rank: Super Contributor
timestamp: April 02, 2022, 08:29:25 pm
content: Your coaches are what? About 9" long? Guessing at the LED spacing on the strip; you would use 6 LEDs per coach? Maybe only 3. That would spread out the lighting for the full length? Then just dim them way down to a glow.The LED strip will probably be the easiest to mount.

author: Chris Uddin
author_rank: Contributor
timestamp: April 02, 2022, 08:36:22 pm
content: Thank you very much Mark F for your reply it was very much appreciated, I thought I would need to do a complete the length of the coach which came to 18 LEDs in total, the coaches at about 11.5 inches long and I can appreciate now that could be far too many and could be far too bright, so would I be ok in maybe doing them in three strips of three and join them together but would that be no different to keeping it one long strip ?, one in the middle and one at each end of the coach ?, maybe use a resistor to dim them down a bit ??, UK voltage is 16 V so obviously this is higher then what the lights will take, if there's anything else that you'd like to add I'd be very happy to hear from you, once again thanks very much and all the best, Chris.

author: Chris Uddin
author_rank: Contributor
timestamp: April 02, 2022, 08:40:18 pm
content: Thank you Rick B for your reply it was very much appreciated although a little over my head but I appreciate your help nevertheless, once again thanks very much and all the best, Chris

author: Chris Uddin
author_rank: Contributor
timestamp: April 02, 2022, 08:42:53 pm
content: The lights do run in series of three, I generally think people tend to copy other people and buy things that others have brought and go from there especially if there's a video available of somebody using a particular set of LEDs that may be a particular colour or may have things on them like variable resistors and things to reduce the brightness of the lights, but basically what I've done is buy a set of strip lights which I think would have been used around the home, for lighting up cupboards or kitchens as they have a clear plastic waterproof coating on them which for me isn't a problem because inside a railway coach roof you wouldn't see it and I don't think it would look too thick or bulky and obviously this coating wouldn't be needed but I did find these lights to be of about the same size and were a lot cheaper then what already exists for the Railway modeller and have decided to use these instead of the more expensive things. Chris

author: Chris Uddin
author_rank: Contributor
timestamp: April 02, 2022, 08:55:17 pm
content: Mark F - What would a bridge rectifier do then? ( small square black box with 4 pins on it ), is that something I would need or use in this case,? Is this the same as a variable resistor ??.

author: Chris Uddin
author_rank: Contributor
timestamp: April 02, 2022, 08:59:13 pm
content: Yes Rick, I could buy ready made lights that you put a small round battery into but the problem with these is that they never make them long enough so that they go to the ends of the coach and you only find the bit that's lit is where the people sit and not at the end where the doors are.

author: rstofer
author_rank: Super Contributor
timestamp: April 02, 2022, 10:05:17 pm
content: Quote from: Chris Uddin on April 02, 2022, 08:55:17 pmIt straightens out the track polarity such that the LED circuit always has the correct polarity regardless of the track polarity. Connect the AC side to the track pickups and the DC side to the LED driver. I'm not sure this is necessary on a DDC system. Still, it protects the driver circuitry.Breadboard...

author: MarkF
author_rank: Super Contributor
timestamp: April 02, 2022, 10:19:23 pm
content: Quote from: Chris Uddin on April 02, 2022, 08:55:17 pmA bridge rectifier is four diodes configured to convert AC into DC. The diodes fold the negative part of the waveform into the positive part. It is essentially converting an +/- signal into a positive only signal. You can make a bridge rectifier from four discrete diodes. The bridge is just a convenience package.You could use a bridge rectifier on a DC layout where the AC pins would go to the rail pickups and the (+) and (-) pins would go to your LED. This would allow the LEDs to come ON independent of polarity of the rail power.Here is a picture of AC power before and after the bridge rectifier. In comparison, I added the DCC waveform at the bottom.And NO. The bridge rectifier is NOT a resistor. The bridge rectifier contains diodes which only allow current in one direction. A resistor will slow down (i.e. reduce) the current in both directions.Think of a resistor as a water faucet where you can adjust how fast the water comes out. And think of bridge rectifiers and diodes as a water bucket with a hole in the bottom. The water can drip out onto the ground but can't get back up into the bucket. (Lame I know... )

author: MarkF
author_rank: Super Contributor
timestamp: April 02, 2022, 10:22:17 pm
content: Quote from: rstofer on April 02, 2022, 10:05:17 pmYou could use a bridge rectifier. But on a DCC system a single diode will do just as well. And be much cheaper.Edit:On a DCC system the frequency of the track power is much higher than 60Hz. So, losing the negative portion doesn't have that much of an impact. And since DCC is positive and negative, it doesn't matter how you connect to the rails.

author: RJSV
author_rank: Super Contributor
timestamp: April 02, 2022, 11:34:02 pm
content: I mean, you would likely find the placing of those 2 AAA batteries to be too much weight ? Plus, of course having to 'start over', as the LED strip requires more than the 2 cells (at 1.8 to 3.0 volt range).I like the suggestion, to build your options on a bread board, first. Maybe that's a hassle looking and buying a solderless 'plug' board, that's all 0.1 inch spaced, for ICs.But, keeping to original intent, I bet just placing R2 as a 2 Kohm resistor, would actually give a better starting point. Sounds good, to split up the strip, according to the RR cabin (each with 3 LED and that R1 = 82 ohms that comes with each strip section.It's maybe later, that you can branch out, try this and that. Color and 'remote control', can be added, at your leisure, without impeding the decided upon config.In that vein, probably some 'sound' emitting options.Anyway; Is a couple of standard AAA batteries too much weight? Might be if in a lot of the cars.It's looking like, a 9 V battery could get plenty of light, even though it's 12 V nominal, for the strip.But, again, how about just keep that in your notes, for maybe later?That way, you could build, using one diode to block the negative voltage coming from the DCC and save the bridge rectifier in a drawer.TRY, R2 = 2 K ohms, first, as everyone anticipates that's a good start, not too bright.Thanks.

author: Chris Uddin
author_rank: Contributor
timestamp: April 02, 2022, 11:44:13 pm
content: ok thanks for that, what does a R2 = 2 K ohms resistor look like ? and what diode is needed for each coach ?? then I connect both of these first inline of the first strip of 3 then connect the 1st to the 2nd and then to the 3rd via wires from each + and - contact "yes" ?, thanks.

author: MarkF
author_rank: Super Contributor
timestamp: April 03, 2022, 12:34:35 am
content: There's no need for anything fancy here.Just hook-up a diode, resistor and LED strip to your DCC power and see if you like it.Try different resistor sizes until you get something you like.Put it in your coach.Almost any diode will do. Try a common 4000 series diode. 1N4002, 1N4003, 1N4004, ... 1N4007. I would stay away from the 1N4001 because its reverse voltage is only 50V which is close to DCC voltages.Make sure the diode is in the correct direction (i.e. the white band points toward the (+) on the LED strip)!!!

author: MarkF
author_rank: Super Contributor
timestamp: April 03, 2022, 12:39:40 am
content: You should just be able to cut the strip into 3 diode groups and then add jumper wires between each group of three where you cut to space them out.You only need one diode and resistor per coach between the wheel pickups and the first group of three LEDs.

author: Chris Uddin
author_rank: Contributor
timestamp: April 03, 2022, 12:57:11 am
content: Mark F you are an absolute star my friend thank you very much indeed, I think I already have these resistors and the only thing I don't have is the diode but funnily enough the picture I was about to show on here before you messaged me was of the one you said not to get so thanks for that !, is there still no point in putting a long strip of 18 the full length of the coach and doing what you have said ?, I know it means using more led's but it also means that I don't have to cut 3 strips of 3 and joins each of them together by means of soldered wire ??. Chris.

author: MarkF
author_rank: Super Contributor
timestamp: April 03, 2022, 01:05:03 am
content: You could use a 1N4001 for testing if that's all you have. Or any other rectifying diode. I just wouldn't use it as a permanent solution.You still might want to use a strip of LEDs the full length of the coach in order to have uniform lighting. However, some darker spots might make it look realistic (burnt out lights in the coach or selections of the coach without lights).If you really want to get fancy, you could put a DCC decoder (similar to waht's in the locomotive) in the coach. Then you could turn ON different areas during operation. Or control dimming if you connected the LEDs instead of a motor.

author: Chris Uddin
author_rank: Contributor
timestamp: April 03, 2022, 01:12:23 am
content: So just before I go and turn in for the night because here in the UK it's 02:10 p.m. Sunday morning and our clocks went Forward by one hour last weekend so we've lost an hour's sleep here, so can I ask Mark am I right in thinking the higher the number on the diode the dimmer the light will be ??.

author: MarkF
author_rank: Super Contributor
timestamp: April 03, 2022, 01:21:47 am
content: Quote from: Chris Uddin on April 03, 2022, 01:12:23 amYes if I understand your question. The more groups of three you have the higher the current demand will be. With the same feed resistor (i.e. the 1KΩ for example) the higher the voltage drop across said resistor. Leaving less current for each LED group.This is all trial-and-error since LED brightness varies greatly among different LED types.

author: Brumby
author_rank: Unknown
timestamp: April 03, 2022, 01:23:41 am
content: Quote from: Chris Uddin on April 03, 2022, 01:12:23 amNo. The difference between 1N4001, 1N4004, 1N4007, etc. is the reverse voltage they can tolerate. That is, the voltage they can block (without exceeding their design capability) when the polarity is opposite of what you need.For example, I have a bunch of 1N4004 on hand because they can handle up to 400V - and they're cheap as chips. A 1N4007 can handle up to 1000V.The brightness will be affected by theforwardvoltage drop - which, for these diodes, will be pretty much the same. So, there will be no brightness differences.Usually, you select a diode that has a lot of headroom. For your application, the 1N4001 at 50V is a bit close to the voltages you are working with and while it could probably work quite satisfactorily, it is safer to go with something higher in voltage. That's why I have 1N4004's as part of my "jellybean" stash.

author: MarkF
author_rank: Super Contributor
timestamp: April 03, 2022, 01:30:02 am
content: Quote from: MarkF on April 03, 2022, 01:21:47 amSorry. Are you asking about multiple diodes or multiple LEDs?1N4000 Series diode specification: (Get the cheapest you can find that's not a 1N4001)

author: Chris Uddin
author_rank: Contributor
timestamp: April 03, 2022, 01:43:35 am
content: Mark F - you have been a great help and I really appreciate the time that you've taken to try and guide me through what are to me big hurdles ?, so I will endeavour to try what you and others have suggested, I will also try take pictures as I go so that you can see how I'm doing and I look forward to being in contact with you again soon once I've started that process, so once again my friend thank you very much, I've really enjoyed chatting with you and the other helpers and I look forward to chatting with you again soon and if there is anything else that you can think of or if I have problems in the meantime I'm sure I won't hesitate to ask and I'm sure you won't hesitate to contact me, have a good day till we speak again, kind regards, Chris.P.S. Thank you for clarifying that and in relation to the last question I was talking about using one diode and one resistor per coach with one long length of LED lights which I said before was 18, the full length of the coach but it is probably better as these are close together to do 3 blocks of 3 with one diode and one resistor per coach and the diode I will probably choose would be the 4004 on your recommendation, I was thinking of buying a selection of these diodes just so that I can see what each one does and then pick the one that suits best but the brightness is not down to the the diode as you've already said but down to the resistor and I have loads of the resistors that you pictured so happy days.I just have to learn a little bit about resistors now ?, Chris.

author: Chris Uddin
author_rank: Contributor
timestamp: April 03, 2022, 01:54:42 am
content: Here is an ebay link - would these be any good to me ?, are they a better way of using a diode ??https://www.ebay.co.uk/itm/232772146305?hash=item36324d1481:g:w6QAAOSwCRRa~Xi~

author: MarkF
author_rank: Super Contributor
timestamp: April 03, 2022, 01:55:30 am
content: Buying a selection of the 1N4000 Series is not very useful. The 1N4004 are good up to 400V which would cover 90% of any place you might want to use a diode. All the diodes in the series will react almost the same.If you really want to have different samples, a better selection of general purpose diodes would be:- 1N4000 Series @ 1A- 1N5390 Series @ 1.5A- 1N5400 Series @ 3AThree different current ratings. Pick one in the middle of the voltage range (200V to 600V). Cheapest you can find.The only real difference in each series is its reverse voltage capability.

author: MarkF
author_rank: Super Contributor
timestamp: April 03, 2022, 01:59:06 am
content: Quote from: Chris Uddin on April 03, 2022, 01:54:42 amThose are surface mount. I would stay away unless you plan on building circuit boards.Surface mount parts are hard to structurally mount unless you're putting them on a board.Diodes with wires (i.e. through-hole) are a better for general purpose usage.Don't buy from eBay. Get them from Digikey or Mouser or Farnell.Too many counterfeit parts on eBay, Amazon and others.

author: MarkF
author_rank: Super Contributor
timestamp: April 03, 2022, 02:17:19 am
content: Model Railroading is in my blood too.You might be interested in a recent topic of mine:https://www.eevblog.com/forum/projects/any-old-time-ho-model-railroaders-out-there/msg3996535/#msg3996535Also, I've been following the Chadwick Model Railway. He has lots of good tips.https://www.youtube.com/channel/UCMjSsrcmA4BNeAnh2NxYp0Q/videos

author: Chris Uddin
author_rank: Contributor
timestamp: April 03, 2022, 02:24:44 am
content: Yes I watch Chadwick model railway too, I'm glad to hear that you're also into model railways so that's brilliant news. Ok so I'll stay away from eBay, here is a link to information regarding the the DCC unit I am using and I think I may have to use a resistor with a higher amp output ?, Would I be correct ?, I'll let you decide Mark, cheers myfriend. Chris.https://www.bachmanntrains.com/home-usa/dwg/dwgs/Introduction_to_Dynamis_DCC_System.pdf

author: MarkF
author_rank: Super Contributor
timestamp: April 03, 2022, 03:51:27 am
content: You have to start somewhere. Just pick a value and see what you get with the 18 LEDs if that's wbat you settled on.If you have a DC power supply, you can set it to 14V and try resistor values with you LED strip. Noting that the diode will drop an additional 0.5V when you get one. Causing the LEDs to be slightly dimmer. It will get you in the ballpark.

author: sw2022
author_rank: Contributor
timestamp: April 03, 2022, 07:50:48 am
content: Quote from: MarkF on April 02, 2022, 10:22:17 pmI suspect the bridge rectifier idea, as opposed to using a cheaper diode, came about because of the need to accept different polarities from the two pickups either end of the coach here? If you always know which pickup input is +V then a single diode is fine. If the inputs can change around then you would need to feed the LEDs via a bridge rectifier connected to both pickup pairs to get correct polarity for the LEDsSteve

author: Chris Uddin
author_rank: Contributor
timestamp: April 03, 2022, 11:03:44 am
content: Please refer to the pictures - I've just put the light strip inside the roof for the coach just to see how bright it is against the dark tinted windows, what I'm using to power it is a combi controller and it's just wired crudely but firmly, now when I put the Direction controller one way it won't light up but when I change direction the other way and turn the power up it starts to get brighter and the more I turn the dial the brighter it gets until it's turned up full and this is without using a resistor, after about 10-15 secs on full power something happens and the strip goes dim, can you tell me what's happening, is something about to burn out because I'm a little unsure.? Personally I would like it at that full brightness or if not a little less bright, I think that having this many led's within the length of the coach looks fine, it gives an even light spray with no dark spots but at this stage I'd be happy for it to just be constant, so I wondered if there's any thought as to what might be happening, thanks, Chris.P.S. The resistors I've used have been pictured in an earlier post above and I found these to be too dim, in fact they're way too dim so if I need to use a resistor I need something that is going to make the light strip just as bright as shown in the picture. ?

author: Chris Uddin
author_rank: Contributor
timestamp: April 03, 2022, 11:05:53 am
content: pictures

author: MarkF
author_rank: Super Contributor
timestamp: April 03, 2022, 11:45:38 am
content: I was assuming the windows were clear. A very dark tint will require a much brighter light.I looked up the Combi controller. It's controlled output is 0V to 12V up to 0.75A. It should be enough to drive the 18 LED strip.Placing the direction switch in reverse may destroy the LEDs and the reason for the diode when using DCC.The DCC power after the diode will be at least 14V. Two volts higher than the 12V LED strip. Hence, the need for the resistor.I'm not sure why the LEDs dim after a few seconds. Do you have a meter? Can you measure the output of the Combi while lighting the LEDs? Is the voltage dropping? It could be the Combi is overheating which would mean the LEDs are pulling much more power than I suspect.You could try just driving one 3 LED group to see if it's an overheating issue.

author: MarkF
author_rank: Super Contributor
timestamp: April 03, 2022, 11:56:01 am
content: Quote from: sw2022 on April 03, 2022, 07:50:48 amNo. It's to accept different polarities of the track. Not the pickups.The bridge rectifier idea comes from the old days when the track was powered with DC. The track polarity is swapped in order for the train to go in reverse. The bridge provides the same polarity no matter which direction the train is running.

author: RJSV
author_rank: Super Contributor
timestamp: April 03, 2022, 02:26:51 pm
content: That controller has no 'deliberate' explicit current limit setting, right? Because one of the mistakes (I've ) made, on the test bench, is to apply voltage, straight to my opto-isolater device (LED input).I had hard time understanding, that LED voltage is a kind of 'reaction' measurable if you've got a multimeter across one LED while you do the supply increase.You need to apply an adjustable CURRENT, that's what your main resistor is limiting. By adjustable, I mean by swapping that main resistor (approx 1 K to 3 K or more).It's a hard 'rule' to respect, as I'm thinking, why not just 'turn up' the voltage, until light starts glowing.I was...actually, waiting for your narration to describe a"a horrific snap sound, with a TON of black smoke..."!Also, have heard about same applied ' current Vs voltage' issue with charging little batteries; must use 'current', not voltage.To do that, just include your 'main' voltage dropping resistor (2k to 4 k), and THEN play with turning up the controller.Sorry, if you getting maybe too much advice, from all directions, but that's the process. I'd stick with markf giving the best advice, probably because has model RR experience.

author: rstofer
author_rank: Super Contributor
timestamp: April 03, 2022, 02:41:10 pm
content: The common LED datasheet has two numbers you care about: Vf(forward voltage drop) at some nominal (recommended) operating current and the associated If(forward current that will produce that voltage drop).To get maximum recommended output, both numbers must be met. More often than not, Ifshould be scaled back to limit brightness. The common red LED is rated for 20 mA but is entirely adequate at 10 mA and perhaps even 5 mA.So, E=I*R (Ohm's Law) and R=E/I but E, in this case, is the voltage that the resistor must drop at the rated current for a given VccR = (Vcc- Vf) / IfIt's just that simple. Note how Vcc- Vfis exactly the voltage across the resistor and when added to Vfgives Vcc.

author: RJSV
author_rank: Super Contributor
timestamp: April 03, 2022, 03:09:56 pm
content: I might add to that:Let's say, you've got 2.67 volts and 12 mA.Now, if you swap in a very slightly higher resistor, you might see 2.65 volts. That curve is going to be very non-linear. Might mean, that the operation of the LED itself, causes slight heating, moves the place on that curve.Maybe the voltage goes to 2.66 v. Now what ? You adjust again? Looking at your 'current' meter reading, you adjust the voltage fine adjust knob, to get back to 10 mA, your desired place. A couple minutes ago by...now things have drifted, again. Maybe you accidently set a small amount too high, 2.9 volts. Led is starting to go over spec, overheats. Doesn't sound that extreme, you 'only' moved voltage up a little. But the current increased, as that curve is, well, non-linear.By setting the current (maximum in your case), you have a maximum, with that extra resistor in there.Otherwise, you can reach a point where a little off on voltage can cause current to be way off. Plus, this is with the DCC being pulsed, it's an average rather than straight dc.Confusing, yeah.

author: MarkF
author_rank: Super Contributor
timestamp: April 03, 2022, 03:54:37 pm
content: The 12V LED strip that I have uses 0.120A with 18 LEDs.The strip has 180Ω resistors in each group of three LEDs.From your pictures, your strip has 82Ω resistors.Twice the current. They are driving them very hard.This is how a LED strip is wired:Still within the power range of your Combi power pack.Maybe applying a reverse polarity voltage to the strip has damaged some of the LEDs and causing an excessive current draw?

author: Chris Uddin
author_rank: Contributor
timestamp: April 03, 2022, 04:57:39 pm
content: I think rstofer and rick have added these comments to elaborate just how confusing things can be and dare I say it too see if I cry, I now have to tell you that as I was reading the comments and it was all going over my head tears did start to fall and I started to wonder what the point was adding LED lights to model railway coaches and who needs it anyway??.Mark F, I was thinking about why the lights may have gone dim, I was doing it from a direct power feed without no resistors or diodes in line so would that have had anything to do with it?, probably not?, but I have to ask the question, there is another variable as well the red and black wires I'm using aren't as thick as the wires that come connected to the LEDs, maybe this wire is too thin and not adequate enough for the voltage hence it'll only take so much? And this originally would have been the wire that I would have used to power the track so who knows, poor wires, too many LEDs, no diodes or resistors and at this stage the list is endless.

author: MarkF
author_rank: Super Contributor
timestamp: April 03, 2022, 05:08:49 pm
content: Your LED strip is designed to run directly from 12V. The resistors to limit the current are built into the strip. You can see them in your picture (the black squares with 820 written on them). The extra resistor and diode are to handle the higher 14V and +/- voltage of the DCC power. They are not need for a plain 12V DC voltage.My guess is that your 18 LED strip should be pulling 0.24A. Your wires are short and shouldn't need to carry much current. The larger wires you're talking about are probably to drive the entire strip in the package which will require much more power. I don't think your wires are an issue. I still think you damaged the LEDs in the little piece you cut off.I would like to see you take some measurements to determine what your Combi output is doing and how much current your strip is drawing. Do you have a meter and do you know how to take these measurements?

author: sw2022
author_rank: Contributor
timestamp: April 03, 2022, 05:20:12 pm
content: Quote from: MarkF on April 03, 2022, 11:56:01 amKnowing nothing about model/real railways here as you can tell, but - can the carriages be run 180 degrees reversed, or are they always run unidirectionally? If so another reason to use a bridge in a DC system I guess,Steve

author: RJSV
author_rank: Super Contributor
timestamp: April 03, 2022, 05:45:51 pm
content: ...Just lighten up, and realize, Electronics is hard, but look at all the industry players, who would be pleased to see you...succeed and get some fun/ relaxing entertainment.I think, we are 'fighting' over your topic, maybe almost to the point where you might (mistakenly) feel left out.Nope, you are the CUSTOMER here, ultimately. Without your interesting questions, nothing would progress.I think, I at least, need to work on my own skills, regarding how to best help.All these posts, are preserved, so there's plenty chances to go back and re-read something, if question comes back up, maybe 6 months from now.We learning here now, too.Personal Message feature can help, also, as you shouldn't be shy about anything, really.Think, how powerful the minds are, here. Not me, I'm kind of learning, as I go.Hey, maybe Steve Wozniak, is secretly helping you here...(via fake name)!

author: MarkF
author_rank: Super Contributor
timestamp: April 03, 2022, 05:53:04 pm
content: Quote from: sw2022 on April 03, 2022, 05:20:12 pmOn a DC layout (old school):The coaches can be placed on the track in either direction. After they are on the track, the track voltage can be of either polarity. This allows the locomotive to run in either direction independent of its orientation on the track. It's a simple DC motor and the voltage polarity allows it to run in either direction.The polarity of track voltage and coach orientation is unpredictable and free to be in any combination.On a DCC layout:The track power is typically +/-14V pulses containing encoded commands. Each locomotive has a decoder with a unique address and acts upon commands addressed to that locomotive. The decoder in the locomotive generates DC power with the appropriate polarity to move in the desired/commanded direction from that voltage. Think of DCC as a switch mode power supply where the frequency is command encoded pulses instead of a fixed frequency. The decoder also handles lights, sound, momentum, braking, plus lots more.

author: RJSV
author_rank: Super Contributor
timestamp: April 03, 2022, 06:48:01 pm
content: Oh yeah, with all the back and forth messages, forgot an important point:When you did the try out, controller driving the LED strip, the fact that it sat there couple seconds, then something obviously went bad tells something had definitely gone bad, not just a hookup that was dim to start with. That sounds a lot like a thermal excess, or the reverse breakdown (mentioned by markF).I think, better to try anything, after protecting by putting in diode, no question. Better to include that extra resistor, otherwise you could STILL be overdriving the LEDs, even with that controller dialed way back. Excess voltage is excess voltage. You might have still been putting in big voltage, as that DCC output is dialed way, way back, perhaps at 5% control setting.The instantaneous voltage. Isn't that a pulse-width controller ?Putting a bunch of pulses, at full voltage of +/- 14v, is not the same as a DC average, even though the power is same, in average, the instantaneous varies. And that puts you up and down that non-linear curve, whereas a pure DC supply only puts you on one point, in the voltage/current curve.I'm thinking the LED can handle a brief surge (100 uSec), but, obviously, using that DCC controller without protection (2 k resistor) did cause a slow-emerging problem.Just include that 'R2', and diode, and we are in good shape, and DCC controller is kept to reasonable limits, for playing with the DCC. Remember, that controller acts as a voltage source, the right way for motors but not for LEDs. The extra resistor keeps things honest (in range).

author: Chris Uddin
author_rank: Contributor
timestamp: April 03, 2022, 06:58:56 pm
content: Thank you Rick I found that to be a very good explanation and I understood that quite well so many thanks for that.

author: MarkF
author_rank: Super Contributor
timestamp: April 03, 2022, 07:00:04 pm
content: That littleGaugemaster Combi Controlleris NOT DCC and can only output 12V.So the only way he could have damaged the LED strip is to have powered with reverse polarity.As far as I know, he doesn't have a diode to test the LED strip on DCC power.It seems to me the either or both the LED strip or the Combi power pack are damaged in some way.He did mention powering the LEDs in reverse polarity.Without knowing the output voltage and current, we have no way of knowing what's going on.

author: Chris Uddin
author_rank: Contributor
timestamp: April 03, 2022, 07:06:07 pm
content: Mark F - I do have a voltage meter but I don't know how to use it. I thought I would buy one but I've never needed it until now so maybe you can point me in the right direction as to what probe I should put where and which position the dial should be at.

author: Chris Uddin
author_rank: Contributor
timestamp: April 03, 2022, 07:32:18 pm
content: I think somebody said they thought I'd cut my strip lights down to a strip of 18 ?, this is not the case, I haven't cut anything as yet, I am powering a 5m reel of leds.

author: MarkF
author_rank: Super Contributor
timestamp: April 03, 2022, 07:55:44 pm
content: Quote from: Chris Uddin on April 03, 2022, 07:32:18 pmNo wonder. I doubt your Combi has enough power to drive the whole spool of LEDs.

author: Chris Uddin
author_rank: Contributor
timestamp: April 03, 2022, 07:58:36 pm
content: should I still use the test meter? sorry mate

author: MarkF
author_rank: Super Contributor
timestamp: April 03, 2022, 08:02:03 pm
content: Cut off 18 LEDs from the end without a connector and use them to test with.You can ONLY cut the strip where the gold contacts are! Cut down the middle of the pads.How to measure:To measure the voltage, select 20V DC position on the meter. With the leads connected to the meter and the LED strip as shown, read the voltage and insure it doesn't change when the LEDs dim.To measure the current, select the 10A position on the meter. With the leads connected to the meter (note the change) and the (+) connection broken with the meter leads connected, read the current on the meter.TAKE SPECIAL CARE THAT THE LEADS ARE CONNECTED TO THE METER CORRECTLY!

author: MarkF
author_rank: Super Contributor
timestamp: April 03, 2022, 08:06:27 pm
content: You're still going to want to test the voltage at the LED strip when you connect them to the DCC power.You don't want the voltage after the extra resistor and diode (i.e. directly at the LED strip) to be higher than 12V. If it is, you will need to increase the resistor value.

author: Chris Uddin
author_rank: Contributor
timestamp: April 03, 2022, 08:11:00 pm
content: 1st reading 20V - 925 full power709 when dim2nd reading 10A - 000

author: Chris Uddin
author_rank: Contributor
timestamp: April 03, 2022, 08:14:19 pm
content: correction 2nd reading 170 and it completed the circuit and the leds lit up

author: MarkF
author_rank: Super Contributor
timestamp: April 03, 2022, 08:14:55 pm
content: Quote from: Chris Uddin on April 03, 2022, 08:11:00 pmNone of that makes sense. Check you connections.The voltage should be 12V max and the current should be 0.24AIs that 9.25V and 7.09V when dimAnd 0.17A or 1.7A?

author: Chris Uddin
author_rank: Contributor
timestamp: April 03, 2022, 08:22:07 pm
content: 1st 20v - 9.50dim - 7.152nd 10a - 1.65dim 1.24 down to 0any good ?

author: MarkF
author_rank: Super Contributor
timestamp: April 03, 2022, 08:28:34 pm
content: That looks like the entire LED strip is trying to draw twice the current from the Combi than it's capable of providing.That's why the voltage is dropping down to 9V and fading on down to 7V. You are going to burn up the Combi if you continue to drive the entire strip.Don't do any more testing with the whole LED strip. Cut off your 18 LEDs at the indicated location.

author: MarkF
author_rank: Super Contributor
timestamp: April 03, 2022, 08:31:43 pm
content: Be very very careful when you have the red meter lead plugged into the 10ADC terminal. The meter connection between the 10ADC and the COM is essentially a short circuit. The resistance between those two terminals is very low.When you put the switch on the 20 in the Voltage DC area, you can only measure voltages between 0V and 20V. You need to select the proper range for other cases (i.e. you need to have some idea what to expect).

author: Chris Uddin
author_rank: Contributor
timestamp: April 03, 2022, 08:37:31 pm
content: I've cut it down to 18 now, same test20v full power 14.55 no dimming10A full power -0.46 no dimming

author: MarkF
author_rank: Super Contributor
timestamp: April 03, 2022, 08:39:37 pm
content: Quote from: Chris Uddin on April 03, 2022, 08:37:31 pm14.55V is too high. Remember it's a 12V strip.Don't turn up your voltage above 12V.

author: Chris Uddin
author_rank: Contributor
timestamp: April 03, 2022, 08:41:05 pm
content: OK !That's about 75 on the dial

author: MarkF
author_rank: Super Contributor
timestamp: April 03, 2022, 08:43:53 pm
content: That's near 1/2 an amp for each coach.How many coach do you plan to have?Your DCC power pack is going to start complaining...Consider modern locomotive motors are now only drawing 1/4A. Each coach will remove two locomotives from your layout.How hard might it be to strip off the dark window glass and replace it with clear or a lighter shade so you can dim down the LED strips?

author: Chris Uddin
author_rank: Contributor
timestamp: April 03, 2022, 08:54:56 pm
content: Can't do it with any of the windows I'm afraid on any of the coaches and there's probably about 27 coaches in total which will be 3 lots of 9, Possibly not all running at the same time and the light can come down a bit to maybe between 5.5 - 6V per coach which is between 30 and 35 on the dial. Would that help ?

author: MarkF
author_rank: Super Contributor
timestamp: April 03, 2022, 08:56:40 pm
content: The current draw for each coach is what you want to control.What's the current at that level?

author: Chris Uddin
author_rank: Contributor
timestamp: April 03, 2022, 09:01:07 pm
content: 30 on the dial - 20V - 5.23may even take one led out making 17

author: MarkF
author_rank: Super Contributor
timestamp: April 03, 2022, 09:08:04 pm
content: You can't just take out one LED. It must be in groups of three LEDs.The voltage here isn't important other than it must be less than 12V.(You will still need to determine a suitable resistor value.)When it's all said and done, you will need to balance the total current required by all the locomotives and coach LEDs that you want to run simultaneously with the current capabilities of your DCC power pack(s). And how you divide up the track if you are using more than one DCC power pack.

author: MarkF
author_rank: Super Contributor
timestamp: April 03, 2022, 09:13:43 pm
content: From your latest picture, it looks like you can take out one group. Leaving 15 LEDs.You can measure the voltage from your DCC power pack and set that Combi to the same value - 0.7V (i.e. the voltage drop due to the diode you will be adding) to start guessing at the resistor value you will need.

author: Chris Uddin
author_rank: Contributor
timestamp: April 03, 2022, 09:19:15 pm
content: Ok, well maybe I could fit the LEDs in as is that's to say 18 per strip, and with regard to the resistor yes that would need to be sorted out ? I was thinking maybe the 5000 series for the diode because of the power pack having a max of 5Amps and there will only be one power pack as I highlighted to you yesterday and I'm not sure about the resistor, obviously I would like to keep the brightness of the strip around by 5.5-6v which I think will be as bright as I'd like it to be. Did I make sense about the DCC power pack. ?

author: Chris Uddin
author_rank: Contributor
timestamp: April 03, 2022, 09:22:34 pm
content: 15 is too sort I could have bought some battery operated ones about the same sort of length and they are just far too short

author: MarkF
author_rank: Super Contributor
timestamp: April 03, 2022, 09:37:15 pm
content: No. It's not based on the power pack's capabilities or how many power packs you have.It's based on how much current each strip in the coach is going to use.The strips already limit the current and you are going to add a resistor to limit the current more.(Those 1N5400 series diodes have a diameter close to the size of a pencil. Very big.)Any reduction in current needed is going to be worth doing.If you can drop down to 15 LEDs instead of 18, I would recommend that you do so.By too short, do you mean the strip doesn't reach both ends?What do 15 LEDs look like if you turn the coach right side up on the desk enclosed like it will be when it's assembled? You will have a lot of reflected light inside. Even add a strip of aluminium foil on the bottom of the coach to reflect more. I can't impress upon you enough that you want to reduce that 0.5A of current.Ideally, I would like to see it down around 0.2A per coach.The strip of 18 LEDs I used in my 3D printer only uses 0.120A.https://www.amazon.com/gp/product/B00HSF65MC/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&th=1

author: Chris Uddin
author_rank: Contributor
timestamp: April 03, 2022, 09:55:10 pm
content: Could I do this. 5 sets 3 each joined together and have them spaced out evenly along the roof, I'm sure that could work and it might not look to bad as long as that brightness is still - that is key.

author: MarkF
author_rank: Super Contributor
timestamp: April 03, 2022, 10:01:02 pm
content: I'm beginning to believe the key is to buy a different strip of LEDs.Sorry...With your strip, I would say 6 LEDs total. Space out two groups of three.

author: MarkF
author_rank: Super Contributor
timestamp: April 03, 2022, 10:08:01 pm
content: What was the current through the 18 LEDs at the desired brightness?Maybe you could space out three groups (i.e. half what you have now)?

author: Chris Uddin
author_rank: Contributor
timestamp: April 03, 2022, 10:11:28 pm
content: Mark, you've spent more than enough time on me my friend and I really appreciate all the help that you've given me up to now, it must be really frustrating for you to try and help me with both of us being so far apart but I will understand if you want to call it a day and quit while you've still got some sanity, maybe I should look at different led's , I don't know now, I'll leave it up to you and I'll say goodnight at this end and you can let me know tomorrow, I'm sure it's been a long day for you, thanks mate, chris.

author: MarkF
author_rank: Super Contributor
timestamp: April 03, 2022, 10:17:00 pm
content: I just made dinner.However, I'm retired now and don't mind helping. Being so far apart and not being able to put probes where I would like to make assessments makes it challenging some times.You're really putting my Photoshop skills to the test though...

author: Chris Uddin
author_rank: Contributor
timestamp: April 03, 2022, 10:45:50 pm
content: Hope you enjoy your dinner, I've just looked on ebay and I know you said stay away for there but is this the type of thing your talking about, LEDs that are further apart and have everything built in including an adjustable dimmer ?https://www.ebay.co.uk/itm/382464701774

author: MarkF
author_rank: Super Contributor
timestamp: April 03, 2022, 10:46:50 pm
content: Based on the numbers you gave me, I believe the resistor is going to be much lower than I predicted.My guess is that it will be around 22Ω.I would start however with a 100Ω resistor and slowly increase the voltage of the Combi to max insuring all the while that the voltage at the LED strip does not exceed 12V.22Ω red-red-black100Ω brown-black-brownYou can measure them with the Ω setting (lower left) on your meter. Just select the correct range.

author: MarkF
author_rank: Super Contributor
timestamp: April 03, 2022, 10:51:52 pm
content: Quote from: Chris Uddin on April 03, 2022, 10:45:50 pmYes. But, I would try to find ones without the dimmer. The dimmer is geared to use the entire strip.You could just use the Amazon ones I linked to and use 18 LEDs. Their current draw is low enough to do just what you are doing now. I you decide on them, I will go measure them again to be sure. The 0.12A would be low enough to possibly run 6 coaches depending on what else you're running.

author: MarkF
author_rank: Super Contributor
timestamp: April 03, 2022, 10:58:46 pm
content: Here's a picture I posted of my printer with 18 LEDs driven directly with 12V.LEDs mounted inside the upper horizontal support with a plastic frosted cover over them.Same LED spacing as your current strip.

author: Brumby
author_rank: Unknown
timestamp: April 04, 2022, 10:07:11 am
content: Quote from: Chris Uddin on April 03, 2022, 10:11:28 pmFrustrating ... not very likely. More of a challenge - but one that many of us relish. We like to see people learn ... and achieve their goals!QuoteIf MarkF ever gets there, he'll let you know. Until then, please feel free to ask your questions. If you are genuinely interested and are a reasonable person (which it seems you are), you will get a lot of help here.Hang in there!

author: MarkF
author_rank: Super Contributor
timestamp: April 04, 2022, 10:15:59 am
content: I can always talk 'trains'.

author: Brumby
author_rank: Unknown
timestamp: April 04, 2022, 11:16:22 am
content: (Like that wasn't obvious)

author: Brumby
author_rank: Unknown
timestamp: April 04, 2022, 11:19:21 am
content: How to make the LEDs you already have, fit. Three examples - but you can get the idea of what's involved:NOTE: The groups of 3 - and where the cut points are.

author: MarkF
author_rank: Super Contributor
timestamp: April 04, 2022, 11:41:04 am
content: I believe the real issue here is that the LED strip he has is a real power hog.As I mentioned earlier, the built-in series resistor for each group in his strip is 82Ω.While the resistor in the strip I have is 180Ω. Less than half the power of his strip.I think he said his DCC system can supply 5A. From their PDF, it seemed to indicate only 2.5A???Trying to share the 0.5A required for each coach with his locomotives is going to be very limiting.If he can get that down closer to 100mA per coach just by using a different LED strip, it be worth while making the change IMHO.

author: Brumby
author_rank: Unknown
timestamp: April 04, 2022, 12:27:52 pm
content: Just checked a few of the LED strips I have ..... the lowest value resistor I found is 150Ω.82Ω really does point to some high power LEDs. Still, I wouldn't dismiss them as unsuitable for the application. I suspect it's just a matter of finding the right series resistor to give the level of brightness he's after - which I would expect is waaaaayyyy dimmer than what they are capable of.

author: MarkF
author_rank: Super Contributor
timestamp: April 04, 2022, 03:01:08 pm
content: That's also a problem. The coach windows are almost opaque and he needs the LEDs to be as bright as possible.

author: sw2022
author_rank: Contributor
timestamp: April 04, 2022, 04:50:36 pm
content: Quote from: MarkF on April 03, 2022, 05:53:04 pmMarvellously clear explanation of how much things have moved on since I was a boy!Steve

author: Chris Uddin
author_rank: Contributor
timestamp: April 04, 2022, 09:25:25 pm
content: Brumby - that was what I was thinking but I got the feeling that I'd completely messed it up by getting the wrong lights to start with and weren't able to do what you have pictured, I'm grateful for everyone's help and obviously everybody has their own way of doing things to maybe achieve the same ends. I just didn't want Mark F to get frustrated with me as one of his last comments the other day was,"I'm beginning to believe the key is to buy a different strip of LEDs.Sorry...With your strip, I would say 6 LEDs total. Space out two groups of three".So I decided to call it a night and see see what was said the next day but in the next posting Mark F said everything was ok ok and he wasn't getting frustrated and it was about to have his dinner, so that left me feeling a little bit better but I still couldn't help feeling that being a newbie is not always a good thing. Thank you for the pictures Brumby if I can do that in your picures and maybe use a bridge rectifier which I've been advised to do by someone else and maybe use a capacitor should I need one to stop the flickering (text below) then that would be the way forward but I will stick with Mark F, he has helped me so much so far and I hope one day I will be able to reward him by showing him the finished job.I was told by someone else - "You need a bridge rectifier at one end of the led strip. do not connect both ends up to picks ups". Check outhttps://www.layouts4u.net/coach-lighting-tail-lights/dcc-kits-and-tail-lights/bridge-rectifier"You can also add one of these between the pick up wire and the rectifier to stop flicker. Its a handy device and saves you a lot of trouble. I didn't need it as my strips came with capacitor solder tab and a variable resistor built in hence why I spend the extra money to get a better product.https://www.layouts4u.net/coach-lighting-tail-lights/dcc-kits-and-tail-lights/anti-flicker-dimmerHope that helps. I am also no expert. I just follow others ;-)

author: MarkF
author_rank: Super Contributor
timestamp: April 04, 2022, 11:20:19 pm
content: Chris,You can use any of those kits if you want. They will work with your LED strip.I only steered you away from them because you can buy the individual parts for less then half the cost of a kit.I did a quick part search on Digikey (see attached results).The Anti Flicker/Dimmer kit is £3.50 while the same parts (USA dollars):- 1000uF Capacitor for $0.53- 500Ω Pot for $0.90- Bridge Rectifier for $0.43Total for parts = $1.86As you can see, a single diode and resistor will only cost $0.12.The one caveat is that it only works on DCC.If you would want to run on DC only, than the bridge would be a better choice.All considered, a bridge, resistor and capacitor would probable be the best overall design.You could also mount them on small proto-boards to make the circuit more robust.https://www.amazon.com/ELEGOO-Prototype-Soldering-Compatible-Arduino/dp/B072Z7Y19F/ref=pd_day0_sccl_1/130-3262584-0852258?pd_rd_w=owmbq&pf_rd_p=8ca997d7-1ea0-4c8f-9e14-a6d756b83e30&pf_rd_r=TNPSR68BA57ZKHEMDVVJ&pd_rd_r=1e8f753c-a5f3-45e5-a240-398235769464&pd_rd_wg=zvJcu&pd_rd_i=B072Z7Y19F&psc=1Ooooh, all the choices.

author: Chris Uddin
author_rank: Contributor
timestamp: April 05, 2022, 12:09:35 am
content: Yes Mark, it certainly makes a big difference cost wise but I suppose in the States you can get things off-the-shelf two a penny, years ago go I wanted to do a Star Trek uniform and found it difficult to get the material here in the UK where as in the United States you could probably get the material off-the-shelf the correct size the correct colour the correct pattern without any problem so for me it's times like that when I wish I've lived in the States and I'm sure it's the same with model railways there are probably things over there that would either be too expensive to have or use here or are too advanced for the British model railway fraternity. Thankyou mark for sticking with me and I hope we can get back on track with my project?.Now that I've gone and brought those lights I may as well try and use them, I today ordered some diodes, resistors and things to have a bit of a play with which haven't cost a lot but at least I can try them what sort of effects I can get, and while I'm on the topic of my project I did like the idea that Brumby posted about having five strips of 3 in a row, so if that's acceptable and it makes things a little bit easier than doing it in one long strip of 18 ? then I would like to try that way with a bridge rectifier, resistor and strip lights.30 x 1A 1000V Rectifier Diode 1N4007 Series (228-100) = £1.801 x Carbon Film Resistor CR25 1/4W 1R (228-500) = £0.061 x Carbon Film Resistor CR25 1/4W 100R (228-501) = £0.061 x Carbon Film Resistor CR25 1/4W 150R (228-502) = £0.061 x Carbon Film Resistor CR25 1/4W 180R (228-503) = £0.061 x Carbon Film Resistor CR25 1/4W 220R (228-504) = £0.061 x Carbon Film Resistor CR25 1/4W 270R (228-505) = £0.061 x Carbon Film Resistor CR25 1/4W 330R (228-506) = £0.061 x Carbon Film Resistor CR25 1/4W 390R (228-507) = £0.061 x Carbon Film Resistor CR25 1/4W 470R (228-508) = £0.061 x Carbon Film Resistor CR25 1/4W 560R (228-509) = £0.061 x Carbon Film Resistor CR25 1/4W 680R (228-510) = £0.061 x Carbon Film Resistor CR25 1/4W 820R (228-511) = £0.061 x Carbon Film Resistor CR25 1/4W 1K2 (228-513) = £0.061 x Carbon Film Resistor CR25 1/4W 1K5 (228-514) = £0.061 x Carbon Film Resistor CR25 1/4W 1K8 (228-515) = £0.061 x Carbon Film Resistor CR25 1/4W 2k2 (228-516) = £0.061 x Wirewound Axial Resistor 0.1R (228-570) = £0.131 x Wirewound Axial Resistor 150R 2.5W (228-575) = £0.251 x 1/4W Metal Film Resistors 1% Assortment Kit 400 Pieces

author: MarkF
author_rank: Super Contributor
timestamp: April 05, 2022, 12:42:03 am
content: Yes. Break your strip into groups of three and space them out.Try to see how few groups you can use with longer and longer spacing and still have the effect you want.You showed me a picture of a bridge. Stick it onto the front because it will drop the voltage by about 1 volt.Keep checking the current while you're trying different group spacing.For example, a dimmer four groups might use less current than a brighter three groups.The goal is to get the lowest current.

author: Chris Uddin
author_rank: Contributor
timestamp: April 07, 2022, 01:57:59 am
content: Hello guys, hi everyone that's been helping me, here in the UK It's 02:58am thursday, I've been trying a few resistors which I received today now I went through a lot of Brown carbon film ranging from CR25 1/4W 1R - through to CR25 1/4W 2K2 resistors, 1 amp 1000 v rectifier diode 1N4007 a couple of green wirewound axial resistors 0.R & 150R 2.5W and I'm still yet to go through the mountains of blue 1/4W metal film resistors 1% assortment kit of 400 and a series.I've come to the conclusion that the lower you go down in resistor the dimmer the led lights would go, I thought that the 1 amp 1000 v rectifier diode 1N4007 came closest to the brightness that I wanted and this was done with the lights being in one single strip, now I have cut the lights into 5 blocks of 3 and I will try the resistors again to see whether it makes any difference and bear in mind at this stage I've not yet used the bridge rectifier which I'm still waiting for, so I don't know whether that will reduce some of the brightness as well as the resistor, as soon as I have do some things later today I will hopefully post some pictures and let you know how things have going, it will probably be my daytime but your night-time so please forgive me if I'm disturbing you wherever you are in the world and I look forward to hearing from you all when I'm able to post something, all the best guys, cheers, Chris.

author: RJSV
author_rank: Super Contributor
timestamp: April 07, 2022, 04:39:11 am
content: Looking scrambled to me.Any clear result, trying the (repeated) pleas to include the protection, of a bridge. Maybe stay on that. That protects the strip you bought.Maybe, resist the temptation, to rush off and 'test' like 190 different resistors...meanwhile, all of a sudden, discussion shifts to...the diode. I thought, it was decided to use the bridge. Did you order just that?That bridge is protecting your stuff.And, waters getting so muddy: Are you still trying to use that original, strip? That was damaged, or operating incorrect, got too hot, right ?Things just seem to go round and round.Then, mid-sentence, it's 'DCC', all of a sudden.The advice line, was, to protect your stuff, from reverse voltage being applied. Damage can happen, no matter how many other things you try.Protect first. Change, like ONE thing, at a time.It's also very likely, your eye can't distinguish, between 500 ohms and 580 ohms brightness, anyway.Why even test, if that, original, strip is still in the mix.Did that ever 'recover', in subsequent tests, without changing 3 other things, plus some other mid-sentence 'mention', of how a diode, maybe causing 5.6 amps (whatever that meant).Thanks

author: MarkF
author_rank: Super Contributor
timestamp: April 07, 2022, 12:35:05 pm
content: Quote from: Chris Uddin on April 07, 2022, 01:57:59 amI'm confused.You say the lower the resistor value the dimmmer the LEDs are. That just can't be.You must be doing something else to see that effect.Remember, lower the resistance is like approaching a short circuit (i.e. not having a resistor).Are you reading the resistor values correctly? Measure them. Set your meter to the 200 or 2000 range.As far as a diode or a bridge, they only come into play when you get to the point of attaching the LEDs to your DCC system. With your Combi, the diodes are only going to drop the voltage a little (up to 1V with a bridge, less with the diode). It's like turning the Combi down a little.The bridge will be like having two diodes in series if you want to see the result before getting a bridge.Your goal is to find a resistor value that gives you the desired brightness with the Combi at max (i.e. what the LEDs will see using DCC). You don't need to try all your resistor values. Just a few (1K, 470, 100, 47, 10) to get in the ball park. I'm going to guess it will be 22 ohms with the 18 LED strip.The second goal (and most important) is to find a resistor value that gives a max voltage of 12V right at the LED strip input.Set your Combi to max and try resistors to have less than or equal to 12V at the LEDs (between the resistor and LEDs). Then try different combinations of LED groups to get the effect and voltage at strip. With fewer groups of LEDs, the resistor value will need to be increased. You want to see if you can find an acceptable brightness in the coach with fewer groups with a higher resistor.

author: RJSV
author_rank: Super Contributor
timestamp: April 07, 2022, 03:11:34 pm
content: Looking better, sorry if I 'ranted' a bit. But here is some helpful comments:Our 'language' in U.S. is imperfect, as we say "Is it getting POWER ?...", but meaning is most often answered, using Voltage, like:"Yeah, it's getting 5.3 Volts."So; it 'reads' a bit smoother, to mention units, which get switched, naturally, to Volts (not Watts). Plus, common mention leaves out the meter range.That means, a person more likely, instead of a string of unanchored digits, with Voltmeter set to '30 volts' range:. '30. 5.3. 0.3',better to say " yeah, I'm getting 5.3 volts, on LED, so it's powered...".Very confusing, at first, but that's the real world, imperfect.I'm thinking, regarding setting your levels, at some point you will be trying things, using TRACKS and a RR car, (with the combi first), so the carriage orientation could be reversed...Diode protects against that...But a (single ) diode won't power your car lights, both directions, of car, or both halves of +/- DCC.Perhaps, later, you might be forced to replace the windows, in each car. But one thought, doing THAT allows you to place, a RED or BLUE window...Maybe an 'armoured' PAYROLL CAR !You've got a great project, perhaps publish your own article, later, if there is some good Model Lovers mag.-- Rick B.

author: MarkF
author_rank: Super Contributor
timestamp: April 07, 2022, 04:54:31 pm
content: Quote from: RJHayward on April 07, 2022, 03:11:34 pmMy understanding is that the OP has very little, to no, technical knowledge. So, you HAVE to read between the lines.You can see that when the OP began using his meter, we got some really strange comments. But he got there in the end.Right now I'm not sure he knows how to read the resistor color codes.With a little more guidance, he will get the results he wants.The key here is asking the right questions so we understand what sometimes seems strange.Several times I've missed the big picture here by assuming what seems obvious to me.As to the bridge which seems to be a big issue for you, it all comes down to where he is going to run the coaches. If it's DCC only, then a diode will be sufficient. If in DCC analog mode or strictly DC (his Combi), then a bridge will be required. Something I haven't ask. Using a bridge will give him the most flexibility.I've been a little too focused on finding the lowest cost solution.