lab power supply - Page 1
Forum section: electronics / beginners

author: glinjik
author_rank: Regular Contributor
timestamp: December 12, 2019, 10:46:09 am
content: hi i need to build variable power supply can anyone point me to the eev blog power supply diagram please

author: tooki
author_rank: Super Contributor
timestamp: December 13, 2019, 06:22:20 am
content: It never came to fruition, but instead morphed into the still unfinished μSupply portable PSU project. (I originally joined the forums while looking for the same thing as you, wondering what had happened to the PSU design!)

author: German_EE
author_rank: Super Contributor
timestamp: December 13, 2019, 07:49:15 pm
content: Two alternatives:Build one of thesehttps://www.electronics-lab.com/project/0-30v-laboratory-power-supply/He even supplies the Eagle files and the Gerbers-Buy one of thesehttps://www.ebay.com/itm/0-30V-DC-Power-Short-Circuit-Module-Board-2MA-3A-Adjustable-Protection-Tools-Kit/323969090433Seven bucks and free shipping.

author: MarkF
author_rank: Super Contributor
timestamp: December 14, 2019, 12:14:34 am
content: Here are a few DIY circuits you can play with:

author: glinjik
author_rank: Regular Contributor
timestamp: December 14, 2019, 09:56:46 am
content: wow thank you for replys i rather like the look of the last one do you think possible to replace the c1061 with a 2n3055 and the bc337 doing the volt adjust for an igbt and last the bc337 doing the curent adjust to 2 e13005-1 in paralel? im sorry for the questions but its items i already have my transformer puts out about 17v after rectifier at about 3 amps max (i only need about 1 amp or less

author: glinjik
author_rank: Regular Contributor
timestamp: December 14, 2019, 10:05:09 am
content: this is what i have built so far but find the voltage meter unstable under load

author: MarkF
author_rank: Super Contributor
timestamp: December 14, 2019, 06:59:02 pm
content: For my first byte of the apple, I would use:- a TIP3055 for the C1061- 2N2222 for the BC337

author: glinjik
author_rank: Regular Contributor
timestamp: December 14, 2019, 07:35:48 pm
content: after experimenying with it im not gonna continue it seems flawed by voltage variations for input changes and output changes so lookang at this next one looks more stable although im not sure about the qulity of the 317 i have here 5 of them and they all give different output on same power supply

author: glinjik
author_rank: Regular Contributor
timestamp: December 14, 2019, 07:39:31 pm
content: only going to use 1 2n3055 i dont need high amps il only fry myself (again) forgetting to unplug the transformer them moving it makes an interesting tingly feeling just before dropping it again and usind bad words

author: glinjik
author_rank: Regular Contributor
timestamp: December 14, 2019, 07:40:59 pm
content: and why is my country uk? im in Russia although im english

author: glinjik
author_rank: Regular Contributor
timestamp: December 14, 2019, 08:11:44 pm
content: can anyone tell why there is caps on the rectifier part or is this just simbolising the internals of the bridge rectifier?

author: george.b
author_rank: Frequent Contributor
timestamp: December 14, 2019, 08:34:02 pm
content: Quote from: glinjik on December 14, 2019, 07:35:48 pmI would only use an LM317 that came from a reputable source. Had my share of woes from counterfeit LM317s.Quote from: glinjik on December 14, 2019, 08:11:44 pmTo reduce noise when the diodes switch. It's not absolutely necessary.

author: glinjik
author_rank: Regular Contributor
timestamp: December 14, 2019, 08:44:11 pm
content: thank you for your replies unfortunately here its difficult and expensive to get parts from a reputable dealer even they sell fake parts for a 317 from like rs it can take several weeks to get it, just for me to fry the thing

author: MarkF
author_rank: Super Contributor
timestamp: December 14, 2019, 09:00:01 pm
content: Quote from: glinjik on December 14, 2019, 07:35:48 pmIf you are not doing any current limiting, why are you NOT using the suggested high current configuration from the datasheet?

author: David Hess
author_rank: Super Contributor
timestamp: December 15, 2019, 02:29:28 am
content: Quote from: george.b on December 14, 2019, 08:34:02 pmWhether they are needed depends on the diodes and application. Some rectifiers have a very fast and hard reverse recovery like a step recovery diode which produces broadband RF spikes at the power line frequency. This varies by type, manufacturer, and even lot but usually occurs with standard recovery rectifiers which are often constructed with a PIN structure like a step recovery diode.It is a major problem with audio and instrumentation circuits. Solutions to prevent it include adding bypass capacitors directly across the diodes, adding EMI suppression beads in series with the diodes, selecting standard recovery diodes which do not have the problem, and using faster diodes which have a controlled recovery characteristic. Trying to filter the noise at the input and output of the rectifier is a lost cause because it will already be radiating, parasitic capacitance will allow it blow by the filters, and because it will already have become common mode noise through the transformer's primary to secondary capacitance.I first ran across the problem with some home built 7815, 7915, 7805 power supplies which only had to be powered on to cause problems with audio circuits anywhere in the room and to show up on oscilloscopes. Tests determined that swamping the junction capacitance of the diodes with roughly 10 times the value prevented the interference so that is what I did. Later I noticed capacitors across rectifiers in many service schematics and sometimes EMI suppression beads as well.Below is the lab power supply schematic that I would emulate from National Semiconductor linear brief 28. Instead of using expensive LM395 integrated power transistors, the power pass element could be replaced with suitable integrated regulators or bare transistors or some combination of the two.

author: not1xor1
author_rank: Frequent Contributor
timestamp: December 15, 2019, 06:03:27 am
content: Quote from: David Hess on December 15, 2019, 02:29:28 amthat's a nice circuit (unlike the other ones) but it looks like LM308 is no longer available and LM101 is hard to find and very expensive, although there are cheap LM301 in sot8 package from onsemi.replacing those opamps with modern parts would require a different compensation network and careful selection of parts complying with the same input range (and other features) of the original ones or mirroring the design (regarding polarity) to rather use the so-called single power supply opamps that usually include the negative rail as input range.

author: glinjik
author_rank: Regular Contributor
timestamp: December 15, 2019, 07:45:34 am
content: sorry misunderstood i am limiting the current but what i meant was i dont need high amps, i want a range between ma and 1 amp. as i understand it if i dont limit the current then if i put a big load on then it will just suck the amps untill the transformer gets hot and i get my own global meltdown unless im wrong (high probability)

author: glinjik
author_rank: Regular Contributor
timestamp: December 15, 2019, 10:07:14 am
content: can someone advise please which of these caps is best for this part the electrolitic i have its the non polarised ones im strugling with

author: glinjik
author_rank: Regular Contributor
timestamp: December 15, 2019, 10:09:09 am
content: some reason this capture didnt upload in last post

author: glinjik
author_rank: Regular Contributor
timestamp: December 15, 2019, 10:23:10 am
content: ref post 20 the blue ones are not caps they are resistors at 0.67oops

author: Calvin
author_rank: Regular Contributor
timestamp: December 15, 2019, 11:56:44 am
content: Hi,You might want to have a look at "High Performance Portable DC Bench Power Supply: Save Money and Free Up Bench Real Estate by Building Your Own"https://www.analog.com/en/technical-articles/high-performance-portable-dc-bench-power-supply.htmlon AnalogDevices´s website (actually a LinearTechnology design). They include gerber files and BoM (search for DC2132A).Add a decent SMPS or Trafo-supply, a nice casing and a couple of those cheap ebay voltage modules (up to 5 digits) and You´re there.Seems that that design is really top notch.regardsCalvin

author: EEVblog
author_rank: Unknown
timestamp: December 15, 2019, 11:58:15 am
content: Quote from: tooki on December 13, 2019, 06:22:20 amIt hasalwaysbeen the uSupply portable USB PSU project.

author: EEVblog
author_rank: Unknown
timestamp: December 15, 2019, 11:59:59 am
content: Quote from: Calvin on December 15, 2019, 11:56:44 amBeware though, the LT3081 has design issues, which is why I eventually dropped it.

author: glinjik
author_rank: Regular Contributor
timestamp: December 15, 2019, 12:16:30 pm
content: hi thank you for your replies but from ebay is no goer here as for real estate lol not much needed here 3 dmms one soldering station oh and a mastech esr meter all in my portacabin 6 x 3 meters so space not a problem i suppose i could just go buy a power supply but i really am learning soooo much from building this i mean like using transistors in parralel caps in parralel balast resistors the list is endless and i damn well enjoing doing it apart from burning 7 out of 8 fingers both thumbs and frying myself on the transformer and my wife moaning when i stole the wire cleany thing for my soldering station and ive just learnt just cos it looks like a zener it dont mean it is actually a fast switch and whet i thout were caps turn out to be resisters ive not enjoyed learing like this for years im a happy chappie

author: Calvin
author_rank: Regular Contributor
timestamp: December 15, 2019, 12:35:28 pm
content: Hi,@eevblogWould You mind to elaborate on the issues of the LT3081.I saw that You tried the LT3080 and had issues.Searching for ´LT3081´ didn´t find me a thread with valuable infos about LT3081 probs.regardsCalvin

author: tooki
author_rank: Super Contributor
timestamp: December 15, 2019, 12:47:22 pm
content: Quote from: EEVblog on December 15, 2019, 11:58:15 amWell then what’s this, then? It makes no mention of portable or USB:https://youtu.be/CIGjActDeoMIt wasn’t until part11that you expressly mention wanting to make it portable:https://youtu.be/xa9Lyb45oJMAnd not until part 14 did you name it uSupply.So while it might have always been envisionedin your mindas the uSupply, anyone watching the PSU series from the beginning (as I did) would see it as morphing from a more traditional PSU design into the uSupply. And for sure, for someone looking for how the “lab PSU” series continues, it’s not self-evident from the video titles that the uSupply is the continuation. Looking for “PSU part 14” comes up dry.

author: David Hess
author_rank: Super Contributor
timestamp: December 15, 2019, 01:18:18 pm
content: Quote from: not1xor1 on December 15, 2019, 06:03:27 amThe LM101 is the military temperature range version of the LM301 and the LM301 can be replaced with the LM301A which is readily available. (1) The LM308 as used here may be replaced with practically any device although the LT1008 from Linear Technology is an improved direct replacement. The LT1012 and LT1097 are also improved replacements which include internal compensation.The LM301A would be very difficult to replace in this circuit because:1. Its input common mode range includes the positive supply making it especially suitable for a high side current sense amplifier or in this case, a high side current error amplifier. There are many modern rail-to-rail input parts and several older JFET input parts which meet this requirement however ...2. Its external compensation pin can is used here to clamp its output to improve overload recovery time. The list of modern operational amplifiers which can support this mode of operation is very short. The aforementioned LT1008, LT1012, and LT1097 are the only common modern possibilities I am aware of. Analog Devices makes some parts which might be able to do this but since they do not publish schematics, there is no way to know without reverse engineering them.I mostly listed this example circuit as something to study because it includes many lessons in practical design like low output capacitance, active pull-down, and direct high side current sensing. There are ways to externally clamp an internally compensated operational amplifier however they get complicated very quickly so it is very rare.(1) The LM301A is an LM301 with improved input bias current over temperature. The LM301 was only produced for a very short time before being replaced with the A version.

author: glinjik
author_rank: Regular Contributor
timestamp: December 15, 2019, 02:20:06 pm
content: progress so far well used the 2 tanilum caps i think they are called and works great so far very stabe of course no load no heating up but anyway its cool so far

author: Jwillis
author_rank: Super Contributor
timestamp: December 17, 2019, 05:53:08 am
content: The yellow caps you showed don't look like tantalums . They look more like monolithic ceramics . I could be wrong . If they are indeed tantalums there should be a marking on them that shows a polarity.Monolithic Ceramics will just have a number code. If they are monolithic ceramics it won't be a problem using them in your circuit.

author: glinjik
author_rank: Regular Contributor
timestamp: December 17, 2019, 06:19:25 am
content: thank you for clearing that up you are correct not tantalums that bit of the circuit worked fine yesterday untill i put a 5w resister load to see what amps im getting and my 4 1000mf caps went up in a kind of smoke cloud lol i just dont have a big enough cap for this at the moment oh i think the two 2n3055 transistors blew as well cant complain at least i only fryed a few components and not myself this time at least the fuse didnt blow

author: Jwillis
author_rank: Super Contributor
timestamp: December 17, 2019, 08:03:36 am
content: What is the voltage rating of your electrolytic capacitors and The voltage of your transformer secondary.If you measure the AC voltage of the secondary you take that measurement and multiply by 1.4 to get the rectified voltage With filter caps . So for example if your transformer is putting out 12VAC . 12 X 1.4 = 16.8 VDC after rectification and filter caps . 16V capacitors will be right on the edge of destruction at that voltage. Try to double the capacitor voltage rating over the rectified voltage. Don't just take the voltage of the rectifier and try to match the capacitors to that voltage because as soon as you put a filter capacitor in circuit that voltage will rise potentially exceeding the rating of the filter caps your installing . If you can salvage old televisions there are usually some big high voltage ones in those . For your simple power supply a couple 220uF or 470uF 200 - 400 V capacitors would be more than adequate.If your going to parallel transistors you need to bias them to prevent load hogging and thermal runaway. Usually this can be done simply by putting a resistor at the base and a very low resistor ( 0.1 ohms is plenty) with a high wattage (5W) at the emitter of each transistor. Even in a single transistor circuit, biasing will keep that transistor from exceeding its rated current capability if the power supply is over loaded by shorting .

author: glinjik
author_rank: Regular Contributor
timestamp: December 17, 2019, 09:50:08 am
content: hi thank you for your reply the caps were 4 x 1000mf 50v transformer is 20.02 so with you calculation 28.02v should have been ok i was trying to get as close to the capacitance as possible had in series i thought the capacitance was really important ie got loads of big voltage caps but with low capacitance 22omf 400v, 150mf 450v, 100mf 450v etc i the emmiters have 0.5 \$\Omega\$5w ceramic resistors, should i put a big chunky diode at the output to prevent shorting? thanks for your reply hope you dont mind my noob questions it was kinda fun to watch those caps pop though lol

author: glinjik
author_rank: Regular Contributor
timestamp: December 17, 2019, 10:05:54 am
content: this is what ive done minus the dead caps

author: Doctorandus_P
author_rank: Super Contributor
timestamp: December 17, 2019, 11:01:27 am
content: You can also have a look at:https://hackaday.io/search?term=powersupplyfor inspiration.Some of the projects there looks suspiciously like Dave's old project, such as:https://hackaday.io/project/23249-digital-battery-operated-powersupplyAlso, think about adding a switched pre-regulator.You can build one by modifying a cheap SMPS module from Ali / Ebay / China.The basic way to do it is to add a PNP transistor to your circuit with the emitter to the power input, and the base connected to the output voltage.(With added resistor for current limiting and 1 or 2 diodes in series to increase the voltage drop.The collector of the PNP transistor then gets connected to the voltage sens pin of your SMPS board.Such SMPS modules are cheaper then the big aluminimum heat sink it replaces.Stuff like this is also so easy to find on the 'net.How about a picture search for schematics?https://duckduckgo.com/?q=eevblog+power+supply+schematic&t=h_&iar=images&iax=images&ia=images

author: glinjik
author_rank: Regular Contributor
timestamp: December 17, 2019, 11:09:29 am
content: Quote from: Doctorandus_P on December 17, 2019, 11:01:27 amhi thank you for your reply but i dont want to put modules in, im learning an awful lot from doing this so to buy modules would be pointless if you know what i mean but i did see somewhere about adding pnp transistors ill have a look at hackaday in a bit but thank you

author: EEVblog
author_rank: Unknown
timestamp: December 17, 2019, 11:10:17 am
content: Quote from: tooki on December 15, 2019, 12:47:22 pmThese prototypes must be a figment of my imagination.From left to right, dated 7/8/09, 3/5/10, 31/8/10I showed that first prototype to Leo Simpson at Silicon Chip when he visited Altium in 2009 and dropped by my cubicle to say hi. Almost got it published in SC, but I just kept fiddling with it.

author: EEVblog
author_rank: Unknown
timestamp: December 17, 2019, 11:12:47 am
content: Quote from: Calvin on December 15, 2019, 12:35:28 pmSorry my memory of the exact issue is rusty. Something to do with back diode protection killing the chip. I wasn't the one that found it.I think there was talk on the forum at the time whether LT would recall the chip.

author: MarkF
author_rank: Super Contributor
timestamp: December 17, 2019, 01:16:41 pm
content: Quote from: EEVblog on December 17, 2019, 11:12:47 amLT3080 wierdness - dave's power supply (eev224) gone mad

author: glinjik
author_rank: Regular Contributor
timestamp: December 17, 2019, 04:57:03 pm
content: update and question so after advice fromQuote from: Jwillis on December 17, 2019, 08:03:36 ami installed a 450v 150mf cap and that seems ok my little melt down did destroy both 2n3055's what im thinking now is no load i get a steady22.02v under load it drops to 19.59v its only a 12v led light as a load what im wondering is this can it be made more stabe? the variable resistor pot at P3 does nothing for caibration of volt meter im using a digi one im guesing that pot was designed to calibrate a analogue version also if i connect volt meter as per diagram it only shows 9 volts? maybe volt meter should be connected direct to output? can i get rid of c8,c9.d10.r8p3 amnd c10 and put a big output filter cap there instead i know a lot of questions and you all prob think im a thick noob but im loving this project

author: glinjik
author_rank: Regular Contributor
timestamp: December 17, 2019, 05:01:04 pm
content: also want to incorporate this fan control

author: MarkF
author_rank: Super Contributor
timestamp: December 17, 2019, 07:11:27 pm
content: Since you only want an adjustable supply with less than 1A, I suggest you go back to basics and get that working first.If the digital volt meter you want to use covers the maximum output voltage the LM317 will be set to, you can just wire it directly to the outputs.Quote from: glinjik on December 17, 2019, 04:57:03 pmIf the 150uF 450V cap is all you have on the input, it's way too small.You will have a large ripple on the input to the LM317 with it.You need something in the range of 6800uF @ 50V to not have that voltage drop on the output.What is the rating of the transformer secondary you are using?Put the fan control you shown across the 'input' of the LM317.

author: glinjik
author_rank: Regular Contributor
timestamp: December 17, 2019, 07:41:04 pm
content: Quote from: MarkF on December 17, 2019, 07:11:27 pm

author: rdl
author_rank: Super Contributor
timestamp: December 17, 2019, 09:01:57 pm
content: What is the output voltage of the transformer secondary?

author: glinjik
author_rank: Regular Contributor
timestamp: December 18, 2019, 05:44:49 am
content: output voltage is 19.81vac and 26vdc after rectification and output from circuit 22.38vdc interesting i can get as low 3.4mv unloaded mv under load is mainly impossible to control need to put in a secondery volt control

author: glinjik
author_rank: Regular Contributor
timestamp: December 18, 2019, 04:25:24 pm
content: update to my beginner’s power supply all working as it should no problems yet although lm317 does not seem to be getting warm i added a small heatsink anyway as with the bridge rec just in case also added connectors for volt control. the 2n3055's and volt meter next want to change the current control to a potentiometer and also put that on a connector the output will also change to a clip connector I figured if I blow it up it will be east to remove the board from the case just using clips, next is fan control once that’s working I will add it to the schematic for any other beginners I’ve part done the schematic for any one’s interest

author: glinjik
author_rank: Regular Contributor
timestamp: December 19, 2019, 09:30:49 am
content: after looking at various ways to control a fan rather than just having it running found a little 555 timer fan control uses a npn transistor and thermistor so I’ve incorporated it into the scheme but before I build it in was wondering if any of you enlightened chaps might cast your eyes over the scheme so far oh i re drew the 555 to reflect it in reality rather than schematically its easyer to follow for me

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: December 19, 2019, 11:17:15 am
content: Quote from: MarkF on December 14, 2019, 12:14:34 amWas going to start a new thread, but where's the fun in that when I can hijack this one.The above PSU specifies garden variety parts. What if I wanted to feed in 12vdc for a output range of up to 9 volts. What is a good solution for that -5v reference using off the shelf parts?Are those buck/boost IC's considered off the shelf?

author: MarkF
author_rank: Super Contributor
timestamp: December 19, 2019, 12:46:06 pm
content: Quote from: Ed.Kloonk on December 19, 2019, 11:17:15 amIf you don't need it to go below 1.2V, I believe you could use a slightly different version with a "single supply" or "rail-to-rail" op-amp.I think I would try a LM358 with 0V and 12V for its supply.Edit: Or the TL071 shown on the other version.I'm not so sure you need a negative supply rail.

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: December 19, 2019, 02:21:12 pm
content: Quote from: MarkF on December 19, 2019, 12:46:06 pmNice. Thanks.

author: David Hess
author_rank: Super Contributor
timestamp: December 19, 2019, 05:53:02 pm
content: Another way to make an adjustable current and voltage regulator without an operational amplifier is shown below.

author: not1xor1
author_rank: Frequent Contributor
timestamp: December 20, 2019, 06:33:11 am
content: Quote from: glinjik on December 19, 2019, 09:30:49 amI'm sorry, but that circuit (I'm referring to the overall one, not just the fan control) just doesn't make any sense. It looks like a random assemblage of electronic components.

author: glinjik
author_rank: Regular Contributor
timestamp: December 20, 2019, 10:28:12 am
content: thankyou for you reply but could you explain your point? ie constructivly point out problems errorsQuote from: not1xor1 on December 20, 2019, 06:33:11 amthe cicuit is a well know one its all ove the intenet im trying to adapt it to suit me i keep changing things and all is working so far all the parts are recovered for old stuff except bd140, 2n3055, and bd140 oh and the volt monitor, my next problem is restricting the voltage to fan contol i put in a zener 12v but its getting vey hot is the wattage to low? or is there a better way to achive 12v it needs to come from the rectifier so it wont disrupt any other part of the circuit and when the circuit is switched off the fan will keep running untill components are cool that is indicated by the led and the i can switch off the mains input

author: MarkF
author_rank: Super Contributor
timestamp: December 20, 2019, 03:01:48 pm
content: Quote from: not1xor1 on December 20, 2019, 06:33:11 amRight, the OP introduced some errors into the last few versions.Here is what I think it should be IHO (with a few unnecessary components removed).

author: george.b
author_rank: Frequent Contributor
timestamp: December 20, 2019, 03:02:41 pm
content: Quote from: glinjik on December 20, 2019, 10:28:12 amWhy don't you check your Zener diode's datasheet? Then you'll have your answer.QuoteYes. Use a 7812, or use a transistor as a buffer for the Zener.

author: glinjik
author_rank: Regular Contributor
timestamp: December 20, 2019, 03:19:23 pm
content: Why don't you check your Zener diode's datasheet? Then you'll have your answer.that indeed would be a great idea.....but im using recovered parts and there are no markings on the zener i obviously checked its voltage but thats all i can go on other than its physical sizei like the little circuit but i dont have the parts so what i think is il put in a lm715 circuit with a fixed voltage (i have lm315'si did move the zener to just restrict the voltage to the fan but its still getting to hot like i can smell itmy problem is i live off the beaten track a bit and getting parts is a lot of trouble so i take apart junk to recover what i can but thank you for your answer all the various opinions are greatly apprieciated the fan control circuit works well no parts over heating apart from the zener the whole circuit can push 3 amps no problems just this little fan control that doing me in

author: glinjik
author_rank: Regular Contributor
timestamp: December 20, 2019, 04:33:15 pm
content: Well here is my latest incarnation fo your enjoyment i know its a bit odd adding a 317 just to regulate voltage to a fan circuit but it will work i only using what i have here so this is my solution now to build the last part circuit board is getting crowded bu here goes...

author: glinjik
author_rank: Regular Contributor
timestamp: December 20, 2019, 07:45:44 pm
content: update the lm317 works great but i think still too much current coming in i wonder if i can add a resister befor 317 to restrict the current i fan only needs 0.15A and bd140 is getting hot as well 317 both need heatsinks

author: glinjik
author_rank: Regular Contributor
timestamp: December 20, 2019, 08:43:58 pm
content: well looks like i found my own answer to this question due to not having the parts availabe or volt regu;ator i think the answer is a secondary transformer i have plenty of 12v trabsformers so im looking at tomorow to redraw scematic to include a secondery transformer with output straight to the fan control circuit 12v transformer only puts out 1a at most should solve the problem

author: george.b
author_rank: Frequent Contributor
timestamp: December 21, 2019, 01:24:01 am
content: Quote from: glinjik on December 20, 2019, 03:19:23 pmFair enough. Well, the glass body Zeners you usually find on stuff will be 1W, tops. 500mW are also common.

author: MarkF
author_rank: Super Contributor
timestamp: December 21, 2019, 02:57:01 am
content: Quote from: glinjik on December 20, 2019, 04:33:15 pmYou have diode D6 in the wrong place. No current will flow to the 2N3055 transistors where it is.

author: glinjik
author_rank: Regular Contributor
timestamp: December 21, 2019, 05:34:48 am
content: thank you for your reply please explain why d6 prevents current flowing and if it is wht am i getting 3 amps (when i crank it up) on the emmiters of 2n3055? here is the original drawing well i doubt its original but its where i got it

author: not1xor1
author_rank: Frequent Contributor
timestamp: December 21, 2019, 06:31:58 am
content: Quote from: MarkF on December 20, 2019, 03:01:48 pmthat circuit still doesn't make any sense. Both voltage regulation and current limit are really bad.You can get similar results with just a potentiometer in parallel to a shunt regulator (e.g. TL431) plus a darlington to provide enough current for the power transistors.And I' can't see any reason for not using just a BJT between the base and emitter of the power transistors.Much better results might be achieved by several LM317 in parallel with ballast resistors (see the datasheet).

author: not1xor1
author_rank: Frequent Contributor
timestamp: December 21, 2019, 06:48:23 am
content: Quote from: MarkF on December 21, 2019, 02:57:01 amBTW if the diode (in glinjik schematic) were correctly polarized it would not withstand currents greater than 1A (and would be useless).

author: glinjik
author_rank: Regular Contributor
timestamp: December 21, 2019, 06:59:40 am
content: im thinking that diode is not serving any purpose at all i might remove it and check results but the volt control and currnt control work very smoothly with no problems even shorting the output across a 15w resistor getts good results although i only tried that for a few seconds to see what amperage i could achive the only problem is getting 12 volts to the fan circuit and keeping the current low without using a transistor other than a lm317 or a volt regulator at the moment the lm317 and bd140 are getting too hot thinking of putting in a secondary transformer to achive the 12v low current power 4 is the latest as of now

author: MarkF
author_rank: Super Contributor
timestamp: December 21, 2019, 11:54:26 am
content: Quote from: glinjik on December 21, 2019, 05:34:48 amI believe D6 is intended for over-voltage protection on the output (i.e. The device being powered has a voltage on its power rails that is higher than this circuit is set for). It is only working for you because I suspect your wiring does not match the circuit diagram.Your last circuit -- WRONGHow does the current go backward through the diode, D6, to the 2N3055?NO collector current!Your first circuit (Reply #7) -- RIGHT

author: MarkF
author_rank: Super Contributor
timestamp: December 21, 2019, 12:10:29 pm
content: Quote from: not1xor1 on December 21, 2019, 06:31:58 amI think this WHOLE design is poor.I am working on a circuit where I was trying to limit the current by limiting the base current.It worked. But NOT very well.New design:

author: glinjik
author_rank: Regular Contributor
timestamp: December 21, 2019, 01:50:05 pm
content: I believe D6 is intended for over-voltage protection on the output (i.e. The device being powered has a voltage on its power rails that is higher than this circuit is set for). It is only working for you because I suspect your wiring does not match the circuit diagramthank you yes you are correct my drawing is in error it is actually wired correctly, i have removed the whole fan control circuit and the volt limiting 317 im looking for a way to control the in a different way i think the best and simplest way is in the following diagram although i dont have a bd139 i do have a great big igbt so im going to try than instead report back at next version

author: glinjik
author_rank: Regular Contributor
timestamp: December 22, 2019, 11:21:06 am
content: hi so my power pupply parts woes this morning got a knock at the door and a friend rought me this sack to see if i needed anything when i opened it woww its like early christmas maybe il find a fixed 12v volt regulator an awfull lot of transistors and big caps looks like computer power supplies or industrial power supplies, its nice to have friends of course im keeping the lot

author: glinjik
author_rank: Regular Contributor
timestamp: December 23, 2019, 10:24:25 pm
content: after my windfall of components i finally finished the power supply its stable and functions well ive added heat sinks where i can tomorow i will put it in its case tomorow and do a few pics of the final product of course i will mod it at some point and add a amp meter im looking for a 0-5 a meter for now it will do hares the final scheme i know not perfect but im only a buiginer so thats my excuse merry christmas to you all in the wesern world here its not chrstmas till 6 jan but new year is the same

author: george.b
author_rank: Frequent Contributor
timestamp: December 24, 2019, 01:57:25 am
content: Something's missing from your MOSFET's drain, no?

author: glinjik
author_rank: Regular Contributor
timestamp: December 24, 2019, 07:03:59 am
content: Quote from: george.b on December 24, 2019, 01:57:25 amwell spotted an error an the ctr/c ctr/v ni miltisim, paint,save asmery xmas

author: glinjik
author_rank: Regular Contributor
timestamp: December 30, 2019, 07:07:18 pm
content: happy new year to allso carrying on with the development of my basic power supply the fan control i added is not as good as i hoped the transforer suffers when the fan kicks in and it is very difficuly to adjust tried different thermistors 2k 5k 10k 15k 47k got a whole bunch from my scrap power supplies so whilst i was hunting i had a look inside some old security cameras and found what i thought were 12v transformers turns out they are 19v with a volt regulator at 12v so i thought hm maybe i can rebuild is into a basic power supply and run the fan from that as A secondry transformer then i came across a fan control board the model is 3bs00383xxgp ver 1 so i installed a 15k thermister attached it to my rebuilt power supply and sems to work really well il do a schematic in tie bt for now some pics of just this part

author: glinjik
author_rank: Regular Contributor
timestamp: December 30, 2019, 07:15:07 pm
content: although this seems ok fan runs very quiet i think i would like it to turn off compleatley so im thinking remove the resistor highlighted in pic and put in a trimmer pot any thougts?

author: glinjik
author_rank: Regular Contributor
timestamp: December 30, 2019, 07:39:37 pm
content: this is what the fan power supply is ased on except i used bridge rectifier instead of 1n4007 1000uf cap is a820uf 200v lm7812 is a kp142ен8б that seems to be a russian equivalent of lm317? and the 1uf cap i stck in a 100uf 100v the small heatsink is enough to keep the volt reg cool it puts out a steady 11.81v the fan is 0.12A

author: alex-sh
author_rank: Regular Contributor
timestamp: January 14, 2020, 08:53:26 am
content: Quote from: EEVblog on December 17, 2019, 11:10:17 amSo what happened? These never went to production