hybridfree/eevblog-posts huggingface dataset:
Power rating of flourescent ballasts? - Page 1
Forum section: electronics / beginners

author: ivan747
author_rank: Super Contributor
timestamp: August 19, 2016, 06:01:03 pm
content: Stupid question here. Where does the current rating for a fluorescent tube ballast comes from?If I have a ballast that claims to be 21W, and I place a 39W lamp, for example, what will happen?-Will the ballast burn out?-Will the ballast limit the current to the lamp? (I've learned that flouros are like LEDs in the sense that you need some current limiting for them not to auto destroy. And that limiting comes from an inductor in the ballast)I'm specifically trying to figure out if I can switch a T5 bulb for a T5 high output bulb, the fixture has 21W marked on it, as well as the tube it came with. Of course, I could mod it with a different ballast if necessary but I'd rather keep it cheap (component level upgrades, perhaps), this is a very cheapskate project I'm working on.Thanks !

author: SeanB
author_rank: Super Contributor
timestamp: August 19, 2016, 06:25:54 pm
content: If it is a magnetic ballast it is simply a choke, which limits the current in the tube by it's reactance. In the USA it gets a little more difficult as most ballasts there are actually an autotransformer with a inductive ballast, so that you have a high enough voltage to strike the tube, then the current is limited by the ballast inductance.But in all cases the current is roughly constant, and almost independant of the lamp type, as most flourescent lamps tend to want to keep a constant terminal voltage when struck of around 70- 130VAC, depending on lamp type, temperature and age.With electronic ballasts the operation is similar, but many also incorporate sensing of lamp voltage and current, so might not start the higher power lamp, or it will switcvh off after a few seconds.

author: ivan747
author_rank: Super Contributor
timestamp: August 19, 2016, 08:19:03 pm
content: So, if I understand correctly, power should be roughly limited by the ballast if it is not an electronic ballast. Also I will not get as much power as I should with a high output lamp but no damage will be done to the ballast.Sent from my iPhone using Tapatalk
Power Sources and Load Switches (nRF52840 DBK) - Page 1
Forum section: electronics / beginners

author: Nikos A.
author_rank: Regular Contributor
timestamp: March 11, 2020, 07:06:48 am
content: Hi everyone,I am looking the schematic of the nRF52840 development board (PCA10056). I am a bit confused with the "Power sources and switches section" on sheet 7/7. The board can be supplied either from the V5V domain, Li-Ion battery or external power supply. The documentation, section 8.3.2 (it is attached) sais that "The power sources are routed through a set of load switches, which is controlled by logic to give the correct priority of the power sources".I can see how the prioritization works with the logic gates... Actually, I do not understand how the configuration with the load switches works. It looks like the signal VSUPPLY is assigned the signal from the corresponding power source (which be either VREG, VBAT or VEXT). It would make sense to me if VSUPPLY was connected to the output and power sources to the input of the load switches because the power flows from the input to the output of the internal FET.You can both the schematic and documentation attached.Thanks in advance

author: Nikos A.
author_rank: Regular Contributor
timestamp: April 30, 2020, 08:16:45 am
content: Anyone??
Power supplies - Page 1
Forum section: electronics / beginners

author: haggy38
author_rank: Contributor
timestamp: July 19, 2012, 04:05:23 am
content: Hi guys,I would like to hear opinions from you regarding this power supply which i´m interested:Tektronix PWS218590-192 W PowerWide voltage/current rangesPrecise 10 mV / 10 mA resolutionLow noise, linear regulationDual-function display shows voltage & current meter readouts or limitsProtection and lockout functions help prevent circuit damageLarge, bright readoutsDirect-entry keypad16 setup memory locations3 Year Warranty
power supplies in series or Paralell? - Page 1
Forum section: electronics / beginners

author: Dmeads
author_rank: Regular Contributor
timestamp: November 14, 2019, 09:04:17 pm
content: Hi!I have a question about hooking up power supplies. I am building an H bridge inverter.I am borrowing power supplies from my school to test it.the gate drivers are isolated on the Hbridge side and have a separate ground for the logic supply.The logic supply is coming from an arduino/battery set up (so isolated). The power supplies are the grounded through the electronics to mains ground.I will attatch the positive end of the power supplies to the different inputs. 12V to driver and 40V to H bridge.the negative inputs will be attatched to the ground of the isolated side of the gate driver. (see pic)My question is, will this not blow up my power supplies? I dont want it to harm them because I have messed with a similar set up and the power supplies went all wonky like they were shorting each other out or something.thanks.

author: soldar
author_rank: Super Contributor
timestamp: November 14, 2019, 09:30:03 pm
content: You draw two black boxes so it is impossible to say. If everything is correct then everything is correct. If not, not.

author: Dmeads
author_rank: Regular Contributor
timestamp: November 14, 2019, 09:37:10 pm
content: gate driver is UCC21222 from TI and using IRFZ44N mosfets

author: soldar
author_rank: Super Contributor
timestamp: November 15, 2019, 12:33:37 am
content: Yeah, that's not gonna work. You would need two separate floating 12 V PSU or a high side bootstrap driver.I see that is taken directly from a TI application example. Maybe I am mistaken but I cannot see how it can work.Sorry, didn't pay enough attention. It IS a bootstrap. And It says it right there. I wasn't paying attention.Well, It should work.I would test it with no load and with the PSUs current seriously limited so it will not blow anything up. Check that you are getting the on and off times right and very especially that both are not on simultaneously as that would cause shoot-through from the 40 V PSU.I have not studied the IC in detail. Are you absolutely certain it cannot enable both transistors at the same time? Because that would short circuit the 40 V PSU.What PSU was overloaded?Do you understand well how it is supposed to work?I designed and built a very similar circuit but with gates so it was foolproof. Look at the waveforms. It is crucial that you have dead time between one switching off and the other switching on or you will have shoot through.

author: Dmeads
author_rank: Regular Contributor
timestamp: November 15, 2019, 03:26:21 am
content: Ya the IC has programmable dead time (makes sure inputs never overlap) which I will use. I will try with no load and PSU current limited. thanks.
Power Supply (Riden RD6018) and electronic load tester show different voltages? - Page 1
Forum section: electronics / beginners

author: sofakng
author_rank: Regular Contributor
timestamp: September 14, 2021, 03:58:37 pm
content: This is an extremely beginner question, but I'm using a Riden RD6018 PSU and I've connected a electronic load tester (West Mountain Radio CBA IV).I've set the PSU to 5V (V-SET) and 18A max (I-SET). I'm running the load tester at 15A.The PSU displays "4.99V" and "15.07A" but the load tester is showing 4.65V.Why doesn't the PSU show the same voltage as the load tester? They are connected using high quality banana plugs and Anderson PowerPole connectors (12 AWG) and the cable is only 2 feet in length.

author: BILLPOD
author_rank: Frequent Contributor
timestamp: September 14, 2021, 05:06:09 pm
content: Good Morning Sofakng,I suggest you check the voltages and currents on both yourdevices with a known to be accurate multimeter. Then you willknow which is giving you false information.

author: Caliaxy
author_rank: Frequent Contributor
timestamp: September 14, 2021, 05:25:16 pm
content: Quote from: sofakng on September 14, 2021, 03:58:37 pmBecause at such a high current the cable resistance is not negligible. According to Ohm’s law (R=U/I), your cables have about 0.023 ohms, each of them dropping the voltage with about 170mV (assuming they are identical and the two meters are accurate).

author: TimFox
author_rank: Super Contributor
timestamp: September 14, 2021, 05:31:23 pm
content: The displayed voltages at that current imply a resistance of 0.0226 ohms (ignoring the more important question of the calibration accuracy of both voltmeters at source and load).AWG 12 wire itself has about 1.6 ohm per 1000 ft, so your 4 feet of wire would amount to 0.0064 ohms of that, but it is very hard to estimate contact resistance in series with the wires.As stated above, take a reasonable voltmeter and measure the voltage directly at the power supply output terminals, and then at the load input terminals to see how much drop you actually have. A 3.5 digit meter will have aresolutionof 1 or 10 mV when reading 5 V (which corresponds to < 0.001 ohms at 15 A) even if the accuracy of the voltmeter is worse than that.

author: sofakng
author_rank: Regular Contributor
timestamp: September 14, 2021, 08:01:21 pm
content: Thank you so much for the help everybody!I've tested using my multimeter (Fluke 87V, not calibrated though in a long time) and the voltage drop is correct. Both devices (PSU and load tester) are displaying the correct voltage.Why is there more voltage drop with more current?5V @ 5A is showing 4.91v5V @ 15A is showing 4.71v

author: james_s
author_rank: Super Contributor
timestamp: September 14, 2021, 08:58:37 pm
content: Quote from: sofakng on September 14, 2021, 08:01:21 pmhttps://en.wikipedia.org/wiki/Ohm's_lawThis really should be one of the very first most basic fundamental things you learn when getting into electronics. You simply must know Ohms law like the back of your hand or you're going to struggle constantly.
power supply - Page 1
Forum section: electronics / beginners

author: Michael1990
author_rank: Newbie
timestamp: January 27, 2015, 08:53:24 am
content: Hi guys,I want to made power supply but i need a components for power supply designer by 18 to 250 Vac in and 5 Vdc to 400 mA output!can you help me?

author: Psi
author_rank: Super Contributor
timestamp: January 27, 2015, 09:54:15 am
content: 18 to 250 Vac is a VERY wide input range

author: newtothis
author_rank: Contributor
timestamp: January 27, 2015, 09:54:44 am
content: Hi,I'm myself pretty new to Electronics - but I think your question is within my scope to answer.Most phonechargers takes in 100-240V Ac, and gives a 5V, 1A DC output (this will be given on the label), and the current can be limited/reduced with addition of a resistor. couldn't this simple setup not satify your requirement?

author: Michael1990
author_rank: Newbie
timestamp: January 27, 2015, 10:46:24 am
content: Thanks!Ok i think it's better , input range between 110-245 V and output between 5 V and 400 mAplease help me now.....

author: cs.dk
author_rank: Unknown
timestamp: January 27, 2015, 11:06:20 am
content: As newtothis said, a simple wall-wart phone-charger would do the job. No need to over-engineer things.I don't understand, what you mean by this sentense; "output between 5 V and 400 mA"?

author: Dave
author_rank: Super Contributor
timestamp: January 27, 2015, 09:53:25 pm
content: Quote from: cs.dk on January 27, 2015, 11:06:20 amNot worded perfectly, I'll give you that, but still very clear what he wants to achieve:a 5V DC power supply capable of delivering 400mA.If you want to engineer your own switching power supply (I can see why someone would want to do that, as opposed to hacking a crappy wall-wart), I suggest you look into off-line SMPS chips (look at he product catalogs of manufacturers like Power Integratons, ON Semiconductor, NXP, ST Microelectronics and Texas Instruments). Look at the datasheets, they will give you all the information you need to design a good circuit.

author: Michael1990
author_rank: Newbie
timestamp: January 28, 2015, 09:28:54 am
content: Thanks for your helps !I think it's good by di-152-3-w-ultra-wide-range-input-power in this site : ac-dc.power.com

author: Timmay
author_rank: Contributor
timestamp: January 28, 2015, 10:19:45 am
content: Quote from: Michael1990 on January 28, 2015, 09:28:54 amLink to the actual product. No one wants to sort through an entire webpage to find what you are talking about, nor can we give an opinion on it.
Power supply - Page 1
Forum section: electronics / beginners

author: daniel123
author_rank: Regular Contributor
timestamp: April 25, 2016, 09:47:21 pm
content: Does anyone have instructions on how to make a variable power supply. If you do I cant read schematics yet so I would need a picture of the board and step by step pictures.Thanks Daniel

author: ZeTeX
author_rank: Frequent Contributor
timestamp: April 25, 2016, 10:17:55 pm
content: Learn schematics, it will take you a week max if you have passion for electronics.You cant build circuits without the ability to read and draw schematics, but it is easy as sitting on a chair.Also, what do you want from your psu? what voltage range? what current range? linear? switch mode?

author: SewingYard
author_rank: Contributor
timestamp: April 25, 2016, 10:21:08 pm
content: I'm not great at schematics but I put the following board together quite easily after playing with it on the breadboard first:https://electrosome.com/variable-power-supply-lm317-voltage-regulator/First get a transformer and learn how to make a full wave bridge rectifier with itNext learn about the LM317 (don't forget the heat sink) then connect the two fragments together.I'm a real newbie so maybe someone else knows how to do it better but this was my take on doing it as a complete beginner.

author: danadak
author_rank: Super Contributor
timestamp: April 25, 2016, 11:17:41 pm
content: Being new to electronics the most important element to learn is personalsafety when working with electricity, especially line rated voltages that comeout of your wall socket.Google and Youtube electricity/electrical safety and read/watch. This is a partof all EE and Tech training in the first lab classes they take.You mention in anotehr post you do not learn reading. The world is largelysplit into visual and audible learners. So the toughest thing is quickly figureout how you learn. That can be tested for by specialists. Maybe your schoolwould provide that. The reason I discuss this is most learning in the electronicsworld is in a huge body of written books, application notes, papers.I began reading electrical stuff at 11, and still read almost every day something, evenif it is only a paragraph or two. Thats what worked for me, I am a visual learner.Initially much of my reading I did not understand, but bits and pieces became lodgedin my memory, and over time relationships between the pieces began to develop.Regards, Dana.
Power supply advice - Page 1
Forum section: electronics / beginners

author: circuitman2000
author_rank: Newbie
timestamp: November 07, 2015, 12:18:31 pm
content: Hi everyone,I'm new to putting power supplies together, so I just want to check if I'm using the right practice...I need a 12V power supply with 1 Amp for a solenoid...Please see the image attached of my schematic and tell me if I'm on the right track,please note that I haven't filled in the variable resistors set values because I don't know what they need to be yet...Thanks in advance

author: Paul Price
author_rank: Super Contributor
timestamp: November 07, 2015, 03:31:02 pm
content: If you are just driving one solenoid, you would only need a 7812 regulator a single-diode half-wave rectifier and a much smaller filter cap before the 7812 and on the 7812 output pins. In other words you are using too many parts. You could probably get by with just a half-wave rectifier diode and a series resistor to the solenoid with no regulator at all and a smaller filter cap following the diode.

author: Kleinstein
author_rank: Super Contributor
timestamp: November 07, 2015, 04:27:45 pm
content: The bridge rectifier is ok for a 1 A power level - just a singel diode would need a larger capacitor.For the regulator a single regulator is enough. Either a LM317 with two resistors or a 7812 regulator. In both cases there should be small caps (e.g. 100-330 nF) on both sides of the regulator to grround.

author: Ian.M
author_rank: Super Contributor
timestamp: November 07, 2015, 05:14:56 pm
content: Most solenoid applications aren't that voltage sensitive and would tolerate +/- 20%. If the unregulated supply at C1 with the solenoid connected is between 10 and 14V, don't bother with the regulator, just fit a 1.25A fuse before the bridge. The regulator will need to drop about 3V so will need a heatsink. If the unreg voltage is much greater than 15V that will need to be a large heatsink and it may be simpler/cheaper to change the transformer or add an off-the-shelf SMPSU to get 12V directly.
Power Supply and IEC 320 Switch Wiring - Page 1
Forum section: electronics / beginners

author: cereyanli
author_rank: Newbie
timestamp: February 05, 2016, 01:04:41 pm
content: HelloI am a newbie so please bear with me and I will appreciate if you could shade some light on the topic.Yes I have searched in the internet about the topic but could not find a convincing answer and as this involves mains I would like to make sure I get this right.I am building a Eurorack Modular Synthesizer MDF housingI have Meanwell T-60B power supply and I would like to use IEC 320 Switch to help me to switch on/off its powerI am in Switzerland and this is the colour codes for plugs L (brown), put N (blue) and PE (yellow-green).I bought this cheap switch ( see attachment ) and they have 3 pins on switch side ( all examples that I found in the internet have 4 pins )Can somebody show me the proper way to wire them ( my main question is IEC Switch )

author: PTR_1275
author_rank: Frequent Contributor
timestamp: February 05, 2016, 02:17:52 pm
content: Do you have a multimeter you can check the switch with? Does it have a on / off light?Normally the different colour pin is neutral (left pin in the photo you posted), the middle pin is active to your load (Meanwell power supply) and the other end pin is the supply (from mains input)Make sure you bell it out with your multimeter to make sure, 240v isn't friendly if you get it wrong.
Power supply and short circuit protection. - Page 1
Forum section: electronics / beginners

author: jack
author_rank: Newbie
timestamp: September 05, 2010, 12:15:20 am
content: Hi,We have a simple power supply on our bench at Uni, 9V 1A AC, and a switch that wont turn on if attached to a short circuit. My google-fu isn't getting me any closer to a circuit diagram on how to build this switch, can someone point me in the right direction?Cheers.

author: PeterG
author_rank: Frequent Contributor
timestamp: September 05, 2010, 12:31:22 am
content: What type of switch is it?

author: jack
author_rank: Newbie
timestamp: September 05, 2010, 12:39:42 am
content: Okay, so the switch is more like a box with two terminals to grab power from, two push-button switches and two LED's. Pushing the red switch will allow power to flow and illuminate a green LED while pushing the black switch will stop it. If however a short circuit is connected to the terminals then a red LED will light up and the box will make a sort of buzz/vibration and no current will flow into your circuit.Cheers.

author: PeterG
author_rank: Frequent Contributor
timestamp: September 05, 2010, 01:37:38 am
content: From what your saying, the box contains a current limiting circuit of some kind. If you google it you will find many examples.

author: NiHaoMike
author_rank: Super Contributor
timestamp: September 05, 2010, 04:23:09 am
content: It's just a circuit breaker.

author: jack
author_rank: Newbie
timestamp: September 06, 2010, 02:03:34 pm
content: Great, thanks guys. I've found some stuff showing me what I need to do to get this working.
power supply and smoothing capacitor calculations - Page 1
Forum section: electronics / beginners

author: Simon
author_rank: Unknown
timestamp: March 23, 2018, 05:56:00 pm
content: Yes it's assignment time again and that means I am reading my module material a second timeSo cut a long story short attached is the lesson. I cannot see any calculation given that allows me to calculate the average load voltage without knowing the load current and to know the load current I need to know the load voltage. So yes I have become a dog chasing my own tail.I hoped the example on page 20 (Q2) solved on page 23 would shed some light on the matter but it seems they too are dogs chasing their own tails as "x"is solved by a formula that has "x"in it and my result of that using MS mathematica is that x=0.....

author: Simon
author_rank: Unknown
timestamp: March 23, 2018, 05:59:10 pm
content: Correction Vrpp is 7.46 I had entered the calculation wrongly. But is there a simpler way ?

author: Jwillis
author_rank: Super Contributor
timestamp: March 23, 2018, 11:19:18 pm
content: Although some would say that this is over simplified ,it works.Because the calculated values will never match the standard values ,a very high degree of accuracy is irreverent. I use the 70% rule as that the capacitor supplies current to the load approximately 70% of the cycle .C = capacitance in farads, I = current in amps, ?V = peak-to-peak ripple voltage, F = ripple freq in hZSo putting it together we get C = 0.7 * I /(?V * F) for example for 4 amp at 40volt C=0.7*4/40*120=0.000583 Farads =583uFOf course this is for zero load.Unless you know what your load in ohms is you can't really calculate the ripple under load.

author: Simon
author_rank: Unknown
timestamp: March 24, 2018, 08:28:07 am
content: Well I did my calculations and came up with sensible numbers which are not expected to match the simulation results as I understand that the math presented in the module uses approximations.

author: fourtytwo42
author_rank: Super Contributor
timestamp: March 24, 2018, 10:34:46 am
content: There seems to be an awfull lot of maths in that paper! For a lifetime I have used C = (IT)/V or any juxtopision to get at the unknown where V is the p-p ripple voltage, I the load current and T the time between charge pulses.Maybe if I think about it your problem is related to knowing I for a specific load resistance as I depends upon V that is in turn dependant upon IGenerally I resolve that issue by guestimating an initial I if needed however most times I is fixed in a specification somewhere rather than the load being a specified R.

author: Simon
author_rank: Unknown
timestamp: March 24, 2018, 10:48:58 am
content: It's a classical case of being asked to solve something no one bothers to solve. as pointed out it can be approximated to an RC circuit and and a calculation made for C in terms of discharge voltage over one cycle. You always end up over calculating C and then rounding it to the nearest E6 value so the ripple can never be more than estimated. Oh well I suppose they need some excuse to pass the dumb students that simply need to change the numbers in the example to solve the assignment.
Power supply - another current decimal point - Page 1
Forum section: electronics / beginners

author: Jane
author_rank: Frequent Contributor
timestamp: July 27, 2018, 07:10:54 am
content: I use , 3010d power supply e.g.https://www.eevblog.com/forum/testgear/yihua-10a-lab-power-supply-review-and-fixing/It works OK but I would need more decimal points of current - now it has only ONE decimal points.How much difficult would it be to add another decimal point - so I would have TWO decimal points?Or is it possible to add Analog type current meter panel?

author: sokoloff
author_rank: Super Contributor
timestamp: July 27, 2018, 09:05:27 am
content: Why not just patch an ammeter inline with the output?You can get a decent handheld DMM for $10 on Amazon. Patch that inline.

author: ArthurDent
author_rank: Super Contributor
timestamp: July 27, 2018, 12:31:49 pm
content: I have a different 30V10A digital display P.S., the Longwei K-3010D which is a smaller physical size SMPS and it isn't a bad supply for the money but I found that the supply I have does drift with time so if I set it to 15.0VDC with a load, a few minutes later it may have drifted to around 14.8VDC. Probably the one decimal point meters are more than adequate for the design of these cheaper supplies.If you're just interested in what the current is at a moment in time, the suggestion of using a DMM inline with the output is a good way to go. If I want more resolution and stability I use a much better (and expensive) supply like this one.
Power supply battery charging - Page 1
Forum section: electronics / beginners

author: Shutterdial
author_rank: Newbie
timestamp: March 16, 2017, 06:15:55 pm
content: I have a gw instek 3060d. If i use this to charge a battery shpuld i use a diode in between or will it be ok to charge it without?

author: james_s
author_rank: Super Contributor
timestamp: March 16, 2017, 06:25:45 pm
content: It should be fine without, although it may be worthwhile to include anyway in case the power is lost. I don't know how that power supply is designed but some of them don't like having the output driven by another source.
Power supply board issues - need help to understand electric schema  - Page 1
Forum section: electronics / beginners

author: vladc77
author_rank: Regular Contributor
timestamp: September 03, 2024, 07:30:53 am
content: I need help understanding how voltage is provided for the power supply board connector - CN5 con on the electric schema. The power board supply is not working correctly for CN-5. I hope someone may be able to help a beginner. Thank you in advance!According to the attached electric schema "Schema-PSBoard_01.png", the CN5 connector should have the voltage values listed below but it gets incorrect voltage:CN5pin1 gets +12v from IC401pin8 | On test it gets +12.3v which is closeCN5pin2 gets +5.6v from C411 | On test it gets +12.3vCN5pin3 gets -12v from IC401pin4 | On test it gets 0vCN5pin4: GND | On test it gets 0vCN5pin5 gets +15v from ZD403 | On test it gets -12.2vCN5pin6 should be AC power | On test it gets -12.2v, no AC powerHowever, according to the attached "PCB-Trace-View.png" diagram CN-5pin1 (+12v) and CN-5pin2 (+5.6v) are directly connected to one trace that is IC401p8 (+12v). There is no trace from C411 to CN-5pin2 to deliver 5.6v. These two pins are directly connected. How CN-5pin2 can have (+5.6v)?According to the PCB-Trace-View.png diagram - CN5pin3 is not connected to IC401pin4 but to the ground. How CN5pin3 can get -12v?The same with CN5pin5 (+15v), it is traced on PCB Trace view directly to IC401pin4 (-12v) and no connection to ZD403. How CN5pin3 can get +12v?I cannot identify what is damaged. I need help to understand how the voltage described in the electric schema "Schema-PSBoard_01.png" is delivered because looking at "PCB-Trace-View.png" does not match what is in the electric schema. I already removed all transistors for testing, most caps, and some diodes and they all seem to be OK. The caps are not 100% perfect but were working fine before. So, I do not know what else to check. Thank you!

author: Gyro
author_rank: Super Contributor
timestamp: September 03, 2024, 08:49:41 am
content: Isn't this a double post ofhttps://www.eevblog.com/forum/repair/power-supply-board-damage-reversed-polarity-on-two-cons/?... Where you were receiving assistance from MathWizard.

author: Gyro
author_rank: Super Contributor
timestamp: September 03, 2024, 09:35:36 am
content: It just looks a bit bad when you already have a member helping you with the PSU there, especially when you are referencing CN-5 voltages in that thread too.It's generally a good idea to keep stuff together to provide context, eg. what you did to cause the problem.

author: vladc77
author_rank: Regular Contributor
timestamp: September 03, 2024, 10:07:58 am
content: Gyro, I moved it to the Beginners board.
Power supply build help! - Page 1
Forum section: electronics / beginners

author: Gabriel
author_rank: Regular Contributor
timestamp: June 24, 2017, 02:23:22 am
content: Hi All,I have created a power supply with the DPS3212 from bang good. It was a great success apart from the fact that I missed the part in the manual that specified that the input voltage must be 1.1 times the output voltage. So naturally, I ordered a 12V 15A power supply to get it working! After I assembled it I found out that this was that case and the ma voltage that I could get out of it was 12.16V (I tweaked the power supply to output 13.16V). Since I have tried to look for a 36V power supply with a high current rating but I have found nothing (The max input voltage for the module is 40V). I was wondering if anyone had any ideas how to go about this. I have considered using a boost converter to boost the voltage but also have not found anything with a high current rating. I have included a couple of photos of the power supply so you can see the insides if that helps!

author: Teledog
author_rank: Regular Contributor
timestamp: June 24, 2017, 03:21:04 am
content: Bang Good has 36V power supplies/SMPS units.That DPS unit is basically a regulator - with a fancy display, not a power supply, per se.Not sure why you would use a 12V supply to start with, if you want more than that out.A boost converter would be horribly inefficient and noisy.
Power supply connection proofing - Page 1
Forum section: electronics / beginners

author: AndrewA
author_rank: Newbie
timestamp: July 13, 2014, 12:34:28 am
content: Good morningI have recently become involved in a project where a microcontroller was going to switch number of sequential outputs from one or two inputs.we are using Picaxe 08M2 and 14M2chips for the project.Anyway, the question of the power supply came up, and I suggested we use a DC socket on the board (our own homebrew design, which works remarkably well on the bench) to supply power. The ideas guy came back and said no, he wanted a screw terminal type unit.I thought I might place a bridge rectifier on the power supply input to proof the power supply correction against incorrect hook up.So my question is: Will that work, or do I need to try something different?Any thoughts?

author: Fank1
author_rank: Regular Contributor
timestamp: July 13, 2014, 12:48:38 am
content: Even a single diode can provide reverse polarity protection.

author: tautech
author_rank: Super Contributor
timestamp: July 13, 2014, 12:57:06 am
content: I have seen a reverse biased diode across power rails used for wrong polarity protection.I'm not sure if it would be quick enough for a micro??Probably if put on the supply side of the main supply caps could rely on surge to the caps allowing it to conduct quickly.UF diode could be used.Or a crowbar reverse polarity protection.Either creates a dead short until the magic smoke escapes.

author: mariush
author_rank: Super Contributor
timestamp: July 13, 2014, 02:35:28 am
content: There's also reverse voltage protection using p channel mosfet

author: AndrewA
author_rank: Newbie
timestamp: July 14, 2014, 08:11:25 am
content: Thanks guys.I think I'll put a diode in the power supply circuit on the positive supply side, probably a 1N4004, seeing as the whole circuit draws less than half an amp.Thanks for the assist.
Power supply controlled by microcontroller and powered by USB - Page 1
Forum section: electronics / beginners

author: Fowflux
author_rank: Newbie
timestamp: February 18, 2016, 06:42:37 pm
content: For a project I want to build a simple dual power supply that can be controlled through a microcontroller.It should be powered by USB (so 5V), but should be able to provide voltages in the -20V through 20V range. To be more exact I want two outputs: one that ranges from 0V to around 20V, and another one that ranges from -20V to 0V. As said before, the output should be controlled digitally. It doesn't have to deliver much current (like 100mA max).I have no real experience with powering electronics so I came here for some help. I had a few ideas to tackle this problem and would like to get some feedback if these ideas would work, or if there are some better ways to solve this problem.The first problem is to be able to create around +20V and -20V from the 5V provided by the USB.My first thought was to use a linear regulator (or maybe a DC-DC converter?) to boost the 5V to +20V which shouldn't be that hard I think. However a problem arises when I want to create the -20V from the supplied 5V, does anyone have a suggestion how I could do this?The second problem is how to make the output controllable from 0V to +/-20V. To solve this I have two possible solutions: using a (non)inverting amplifier circuit, where the opamps are powered by the +/-20V that were created by the previous paragraph, and the input is provided by the microcontroller (through PWM and a low pass filter to create an analog signal). So by adjusting the PWM DUT I can control the output of the non-inverting (supplied by +20V) and the inverting (supplied by -20V) circuit.Another possible option I found would be using a digitally controlled potentiometer to adjust the voltage in some sort of circuit, but these are pretty inaccurate by my understanding?So the main question is how to create the +/-20V and if my proposed way of controlling is going to work.Thanks in advance!Gr, Fowflux

author: mstoer
author_rank: Contributor
timestamp: February 18, 2016, 07:17:40 pm
content: I think you might be demanding a bit much of the USB port. The standard is 500mA for USB 2.0 and you want that to supply not only your outputs, but all your control electronics.
Power Supply design - Page 1
Forum section: electronics / beginners

author: IvoS
author_rank: Frequent Contributor
timestamp: September 09, 2013, 11:51:15 pm
content: Attached is a schematic of power supply from older Pioneer cd player. I understand all of it except the connection of D5 to upper secondary (lead # 3 and 4) windings. Specifically the D5 connected through a set of 3 parallel resistors 1k5 each to secondary winding lead #4. I know those resistors are current limit for zener diode. But why did they hooked it up lead #4?Can someone explain to me what kind of trick is that? Would the lead #3 of the secondary be another negative potential increased by the output voltage of the secondary winding #3&4 to the D5 anode potential?

author: ElectroIrradiator
author_rank: Frequent Contributor
timestamp: September 10, 2013, 07:15:05 am
content: Fairly easy to understand. One connection for the 3/4 secondary AC voltage is for some reason needed to float at -19V below chassis, which is what D6 ensures. The other connection will then vary around -19V, depending on the exact 3/4 secondary voltage. Why this is needed will have to be discovered in the full schematic for the CD player.R1, R2 and R3 are the Zener current limiting resistors, as you say, and my suspicion is they used three in parallel to reduce the amount of power each resistor needs to dissipate. Doing things this way may save the designers from having to use a 'proper' 500 ohm power resistor.

author: Andy Watson
author_rank: Super Contributor
timestamp: September 10, 2013, 10:58:18 am
content: Quote from: ElectroIrradiator on September 10, 2013, 07:15:05 amMy money's on a vacuum fluorescent display. Winding 3-4 provides the heater which is also the cathode and biased at -19V by D5 etc..

author: IvoS
author_rank: Frequent Contributor
timestamp: September 10, 2013, 06:39:24 pm
content: OK. Yes, this CDP has fluorescent display. I would never figured it out. Thanks guys.The zener diode heats up like a bitch. It's a small diode, my guess is 500mW zener. The PCB underneath the diode is brown-ish/black already, from the heat stress. I wanted to put same voltage zener diode with around 1W power loss, but the problem is I couldn't find one in 19V. What can I do, or what can I use to decrease the heat of the diode? Can 2 zeners in parallel be used?

author: Zero999
author_rank: Super Contributor
timestamp: September 10, 2013, 06:57:38 pm
content: You're better off putting two zeners in series as parallel connection is unreliable.A higher powered zener can be made using the TL431 and a transistor, see figure 24 of the data sheet.http://www.ti.com/lit/ds/symlink/tl431.pdf
Power Supply Design - Page 1
Forum section: electronics / beginners

author: slowaudio
author_rank: Contributor
timestamp: April 04, 2014, 06:53:58 pm
content: Are there any good resources for power supply design? I've found a few, but I don't think I'm doing something right. The TI Webbench application wasn't really getting the results I'd like.What I need is a power supply that takes 120AC in and then a few output rails +/-15V, 5V, and 3V3. I'd like a linear regulator for the +/- 15 (low noise audio application) and I'm open to other suggestions for regulators for the other rails. They're going to power a micro and some digital peripherals, and to be honest I don't know what the best solution might be.

author: madires
author_rank: Super Contributor
timestamp: April 04, 2014, 07:02:23 pm
content: How much current do you need for each rail?

author: slowaudio
author_rank: Contributor
timestamp: April 04, 2014, 07:05:57 pm
content: Not much, I would say maximum 300mA/ rail, and that's being very conservative. The +/-15 rail will just be powering a handful of opamps, nothing exotic. 5V rail will just be power a supply and some LEDs. 3V3 rail will just be powering a STM32F3 micro, which has a max current rating of 100mA.

author: Bored@Work
author_rank: Super Contributor
timestamp: April 04, 2014, 07:47:48 pm
content: Quote from: slowaudio on April 04, 2014, 06:53:58 pmLM2596 based SMPS modules. Approx. $1.50 on eBay for one.

author: mariush
author_rank: Super Contributor
timestamp: April 04, 2014, 07:56:45 pm
content: A transformer with center tap, preferrably larger than 24v ac , a bridge rectifier, a couple of capacitors, and LM317/LM337 to get stable +/-15vbefore the LM317, take the 15+v input and use a LM25** (cheap on ebay) regulator to get 5v .. or get a MC34063 and the parts needed to make it yourself.Use a 1117-33 linear regulator to get 3.3v 100mA from 5v (1117 only needs about 1.1v above 3.3v to output stable 3.3v)

author: slowaudio
author_rank: Contributor
timestamp: April 04, 2014, 07:57:16 pm
content: Is the noise not an issue??

author: slowaudio
author_rank: Contributor
timestamp: April 04, 2014, 08:12:53 pm
content: Quote from: mariush on April 04, 2014, 07:56:45 pmSo I'm familiar with the center tapped setup for the +/-15 rails and that seems really reasonable, and I've done a few power supplies before like that and I'm fairly comfortable with that.I'm just unsure about the switch-mode regulators. Is there anything that I need to be concerned with?

author: madires
author_rank: Super Contributor
timestamp: April 05, 2014, 10:24:35 am
content: Not really. Maybe replacing cheap caps with branded ones when you buy SMPS modules from ebay. If you're doing the circuit and PCB youself follow the datasheet. On noise problems add an ripple filter. And power the SMPS directly, don't place it behind a linear regulator.
Help With Power Supply Design - Page 1
Forum section: electronics / beginners

author: BitShard
author_rank: Contributor
timestamp: August 29, 2014, 11:07:38 am
content: Hi all,This is my first electronics design project in a few years, and first design of something on this scale. Basically, this is a power supply which I'm trying to design based off of Dave's uSupply, minus a few features, and add a few features, to tailor it more towards my requirements.What I think I'll do differently: Doesn't need to be so small, doesn't need to be battery powered, dual rail, doesn't need ultra low current senseSo far I've only completed preliminary requirements, bill of materials, and system diagram. Would you be able to point out any flaws, incompatibilities, or improvements?Thanks!QuoteQuoteSystem Diagram attached

author: Strada916
author_rank: Frequent Contributor
timestamp: August 29, 2014, 11:38:45 am
content: LT3080 has a bug where it stops working in some circumstances. Search LT3080 in this forum.

author: blackdog
author_rank: Frequent Contributor
timestamp: August 29, 2014, 11:39:27 am
content: Hi BitShard,Do not make biginners mistake's en put al your energy in designing the digital part! ;-)1eDesign the analog part, make sure its works OK, test it dynamic, you need a scoop, pulsgenerator enz.2eDC-DC converters are difficult and they push high frequenties in your analog circuits, it is difficult to screen them.3eA low noise PSU with DC-DC converters(high power), is extreemly difficult.4eNO, CPU in the voltage or controle loop!5eUse "real" opamps, not lm324Take a look at ADA4077 series.6eMake shure that you know what "Phase Margin" is, extreemly important to keep your design stable.If you insert an current sense IC, you make the phase margin worse, thats normal, but keep in mind when designing of the analog part.If you ignore it, the circuit will certainly generate when the current limit kicks in.Just 2 cent...Kind regarts,Blackdog

author: BitShard
author_rank: Contributor
timestamp: August 29, 2014, 02:41:04 pm
content: Thanks for your replies, I'll go check out the LT3080 bug.I'm fairly proficient with digital design (in terms of software and software/hardware interface) so I don't think that should be too much of a problem. The analog part is pretty much straight from Dave's uSupply, so it should work fairly well, though I would breadboard and test it, except I am currently lacking any lab equipment at all, so I'm trying to design it before I set up my labDC - DC converters would also help to avoid setting the thing on fire when it's dissipating 20W through the LT3080It shouldn't be too bad if I include a RC filter and possibly RF bead. It doesn't need to be ultra low noise, but it would be preferable to keep it as low noise as possible.The voltage control loop is governed by the voltage applied through the DAC into the set pin of the LT 3080Swapping the Op Amps shouldn't be that hard, I just chose those ones because Dave did.I'll go check those other out.I have no idea what that is. I'll ask my electronics professor to explain it to me on monday.Thanks for the feedback
Power supply design - Page 1
Forum section: electronics / beginners

author: MoighonFweeman
author_rank: Contributor
timestamp: April 04, 2015, 01:23:39 pm
content: I've almost finalized my design for an adjustable power supply, and I would really appreciate some feedback. I based this partially on Dave's design, but I've moved the current regulation portion of the circuit to after the load. This has the advantage of simplifying the circuit a bit, and also makes it so that the LM334 that provides the minimum load for the LT3080 can operate down to the minimum voltage output. Also, this makes it so that the current limiting circuit does not "take into account" the 1mA drawn by said LM334.The circuit uses two potentiometers, one to adjust the voltage across the load from 0 to 6 volts, and the other to adjust the current limit from 0 to 1 amps.I'd appreciate if someone could tell me:1. Whether this is safe for for the LT3080. I only ordered two, and those things are four bucks a pop, so I'd rather not let any magic smoke escape.2. What disadvantages or problems might arise from placing the current regulation portion where it is.Any other feedback would also be greatly appreciated.Edit: Whoops, I messed up the attachments somehow. The two are the same.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: April 04, 2015, 01:51:03 pm
content: So now the load has a floating ground, watch out if you plan on connecting it to anything else...

author: JohnnyBerg
author_rank: Frequent Contributor
timestamp: April 04, 2015, 02:17:17 pm
content: A somewhat unconventional design for a psu?As Alex said you have a floating ground now. You have 2 series elements, one to control the voltage and one to control the current. Why not use just one? Perhaps by replacing the LT3080 by a transistor and use a "classic" reference? You ony need 1 heatsink then, now you need 2.The feedback for the current will be unstable. It needs a capacitor from the output of the opamp, to its inverting input.edit: Why is R8 such a "high" value? At 1 Amp you loose 1 Watt there.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: April 04, 2015, 02:30:58 pm
content: Well, as long as the power jack is supplied by a transformer-isolated supply, it's probably OK, but just make sure the grounds are actually isolated from each other.It's just low-side sensing in a way. I guess seeing that "load" as a resistor floating around kind of aroused my suspicion.

author: MoighonFweeman
author_rank: Contributor
timestamp: April 05, 2015, 01:45:28 am
content: Quote from: JohnnyBerg on April 04, 2015, 02:17:17 pmWhat is this "classic" reference? I'll take a look at it.And I have a few 1R power resistors laying about, so I'd rather not go and purchase something special.And I'll add that capacitor. Could you explain it's purpose, though? Would it be to prevent oscillations?Quote from: Alex Eisenhut on April 04, 2015, 01:51:03 pmI won't be using this for anything serious, tinkering mostly. So I think as long as I take care to disconnect the actual ground from the load's floating ground, I should be fine.
Power Supply Design Information - Page 1
Forum section: electronics / beginners

author: Saitama
author_rank: Contributor
timestamp: May 25, 2020, 09:51:11 am
content: Hello! I posted this on other topic, but i think this belongs here.I have taken interest at designing bench power supplies, but they are not very reliable, so now I am looking for information on designing them. Do you have any suggestions on where should I start reading? Any form of info is fine.Thanks for reading my post

author: xavier60
author_rank: Super Contributor
timestamp: May 25, 2020, 12:34:24 pm
content: Almost all store bought linear PSUs use designs based on the HP/Harrison topology or sometime called "floating"In this thread, the opening poster has reverse engineered such a design.https://www.eevblog.com/forum/projects/help-with-how-this-psu-works/msg2897950/#msg2897950And where it all likely began,https://www.hpl.hp.com/hpjournal/pdfs/IssuePDFs/1962-07.pdfAs you likely have already discovered, there are many designs to be found on the internet that don't work properly.As one member has put it, "they have warts"The design I used in my last bench supply project actually evolved from one of these dysfunctional internet findings.https://www.eevblog.com/forum/projects/linear-lab-power-supply/375/

author: TimFox
author_rank: Super Contributor
timestamp: May 25, 2020, 03:12:19 pm
content: A very useful resource for designing the transformer, rectifier, and filter circuits for a linear power supply is the free software "PSUD2" available from Duncan.http://www.duncanamps.com/psud2/The user interface is a bit idiosyncratic, but it gives useful results on the power-up evolution, surge currents, capacitor ripple currents, ripple voltage, and output voltage under load. Note that the transformer is modeled from its no-load voltage and series resistance that limits the voltage under load, while manufacturers normally specify the voltage under load: you need to extrapolate the no-load voltage from that and whatever "regulation" spec the manufacturer has. The ripple current through the filter capacitors may be especially important when choosing components for a high-power system. When comparing specs on suitable electrolytic capacitors, naturally the maximum ripple current varies with physical size, and the choice may affect reliability.

author: TimFox
author_rank: Super Contributor
timestamp: May 27, 2020, 07:26:48 pm
content: A good reference for linear power supplies is the "Kepco Power Supply Handbook", which is not available online but can be purchased. For reliability on a supply that must operate over a wide range of output voltage from a fixed rectifier output, down to low output voltage at high current (maximum stress on the pass device), they invented a circuit that uses two transistors and a power resistor, reducing the dissipation on the transistors automatically (and getting the resistor real hot) in the worst case. I used one for an electromagnet, where the resistor was a nichrome coil wrapped around two ceramic pillars directly in the blast of a fan. Kepco linear supplies are damned-near bulletproof.