Bench Power Supply (PSU) tutorial

[@garygarland9366]

I just picked one up and it acted differently than i expected, this helped, THANK YOU!

[@brucemccready682]

Very good video. Just bought a similar one with no instructions included and could not understand what to do with the current knob. You explained it very well thank you so much for the help.

[@SteveH-TN]

Thanks for sharing this excellent video; you explained several topics that I have been interested in learning more about. Earlier today I ordered a Longwei 3010KDS switching power supply from Amazon. I am building a home electronics lab, with Raspberry Pi, Arduino Uno, breadboards to experiment with for Amateur Radio and Model Railroading. I am 74 years old and retired USAF. Unfortunately I am recovering from 2 Strokes and my fine motor skills aren’t what they used to be. I recently got a Headband Magnifier so I can see where the holes on the breadboard & the leads on the components go. Getting old is proving to be a challenge to say the least. Thanks to you and others here on KZbin providing tutorials and advice. I am not giving up ❤❤❤

[@ErvPlecter]

you're very and most welcome ! I still plan to get my HAM license one day, and happy to hear about your home / DIY electronics lab. Sending strength for recovery. Challenges are the best rehab and physical therapy, cerebral plasticity exists at all age and your brain will grow new connections, based on exercising. Take it easy but to the long run. Or track, even for model trains (PS : my flight instructor is 76 !)

[@friedmule5403]

I like your video, greatly explained! May I add that the power supply is also a very important test instrument. It's perfect to test how your project is handling low power, high power, power usage it does also help to show how much an unknown component is needing to operate and other things.

[@MrSamoDude]

Thinking of getting one of these myself, I had a few questions that were all solved by your excellent video. Thanks

[@ErvPlecter]

+Richard Samson thank you, happy to hear it's helpful to many people. Really a must have tool.

[@cbic9806]

The best info on a supply so far that I've found

[@AnthonyFrancisJones]

Excellent - always seems counterintuitive to short a supply to set a constant current reading! When buying a PSU (especially second hand) I would check this function before connecting it to your valuable circuit. Internal relays and switches can stick and cause all sorts of problems. We have all seen power supplies that have needed repair over the years when they should be the reliable bit!

[@dashaB-sl4pu]

I've just bought one and this video is a great help for setting the amperage question, cheers

[@ErvPlecter]

thanks for the positive comment and glad it helped you out !

[@dashaB-sl4pu]

@@ErvPlecter It has made it very easy to follow and adjust as required, many thanks again

[@techtinkerin]

Thanks very helpful, it made me realise that my cheap power supply is not capable of this as it just beeps and cuts off. Time to go shopping 🙂👍

[@P3nguinDarknes5]

I wonder how many people thought, "oh THAT'S what the CC knob is for!?" and then immediately performed the short to set it to 1A. Thanks, Erv!

[@ErvPlecter]

So true :-)

[@dudeinthesea]

just starting out in electronics. your video helped a lot. thank you

[@shvideo1]

Thank you for taking the time to share this excellent information in detail. Really appreciated.

[@ErvPlecter]

Thanks for the comment david, much apreciated too and glad it helped you

[@timpayne8004]

Thanks. I could not figure out how to change the current limits!

[@ErvPlecter]

Tim Payne you're welcome happy to help!

[@rozero123459gnh]

Excellent video. Thank you for making it! Very concise, very informative.

[@ErvPlecter]

+ro luna thank you !

[@johngonsalves5268]

More thanks from Santa Rosa, CA

[@ErvPlecter]

thank you

[@octarapribadi]

your explanation is very good. thank you.

[@theguydudety]

Ok I'm interested for the purpose of electro plating, thank you for explaining it

[@theguydudety]

Looking now to see if you have a video on it I like how you explained it

[@danielmarzinotto6188]

Thank you for the video. NOW i finally understood it.

[@astorina]

long but very helpfull for me in the end, so thx a lot from brussels (belgium).

[@samshltn]

I have one of these. I'm struggling to understand how to set the current limit. When I follow the instructions that start at 5:22 , I don't get the same results. I turn the voltage and current dials to zero. I short the two terminals. Both displays read zero. Now when I increase the voltage even very slowly by the tiniest amount, the device beeps and cuts out. The 'current' screen shows something similar to 'ERR'. There is no opportunity to fine-tune, the device just cuts out. Now I've also noticed that with some very careful adjustment, I can get the voltage display to read 'zero' and the current screen to read around 0.5. But again... turning the current dial makes no difference. Can someone help me understand what I'm doing wrong please?

[@ErvPlecter]

I can't speak for all bench PSU models, however, you should probably put your current know a little higher first place before you start increasing the voltage with the probes shorted and watch the current increase. Current at zero might trigger a fault mode. It's possible also that your PSU isn't designed to make the voltage drop when excess of current is detected by the current limiter and that you get an error instead (first time I would hear about this, usually you are proposed to adjust your current knob).

[@samshltn]

@@ErvPlecter Wow... thanks for that fast reply. With your help I've managed to work it out. Because I would probably forget if I didn't write it down, I've written myself a guide which I'll paste here in case it helps someone else figure out how their particular model works: (With the caveat that 'your results may vary', and 'always read the manual'!): 1) Ensure that the power is turned off. 2) Turn the current (left-most) dial to the 9'o'clock position. This represents a cut-off of about around 1.5A. 3) Turn the next dial (the 'clicking' voltage selector) to 0-15. This connects the remaining two dials. 4) Turn the remaining two voltage dials to zero. 5) Turn the power on. All displays should read zero. The unit beeps twice. 6) With banana plugs, leads, and crocodile clips, short the -ve and +ve terminals. This should not cause any change in the displays, nor any beeping. 7) Gradually turn the 'fine' voltage dial clockwise. The current display should increase to around 1.5A at around the 10 or 11'o'clock position. This is approximately the current that the 'current' dial was turned to in step 2. Then a slight further turn of the 'fine' voltage dial should cause the supply to cut out, accompanied by beeping and 'ERRR' on the current display. The limit is now limited to around 1.5A. Fine-tune the cut-out by gently turning the current dial to make the unit cut out at the appropriate level. 8) For reference: 1.2A is the minimum limit on the dial - turned all the way to the left. 2A is around the 1'o'clock position. 2.5A is at around 3'o'clock. 3A is the maximum output - turned all the way to the right. Thanks again for your reply!

[@ErvPlecter]

@@samshltn that's perfect. You got it right, the goal is indeed to build up a "scale" of current on your knob and get used to put the current limit where it's acceptable, like when turning on a board for the first time, you estimate it needs like 150mA, you give it 200-300 but not 2A, safely increase the voltage, check used current etc. Good job

[@patprop74]

Thanks for the video help, I bought one of them and I didn't know how to set the current and I would not of thought of clipping my leads together to do so.

[@ErvPlecter]

very welcome and glad it helped another user !

[@patprop74]

Maybe there one more thing you can help me out with, In C.C I never see the a change in numbers, always stays at 00.0 is this normal? best example is, and I might not be doing this right, I made a 12V battery pack from 10 1.2v ni mh and I wanted to charge the pack with it, when I plug it the Volts start at 12.5 then after a few mins it slowly drops down to 11.1 but the Amps never change, always at 00.0. Any idea's ?

[@ErvPlecter]

nimh are charged at about 1.4V per cell. You'll see the current increase then, and that where you have to limit it. Safe factor is to charge at about 1/5th of the capacity. NiMH do accept to be charged at the capacity for a quick charge but A) you need a smart / delta peak charger to detect the end of the charge B) it will reduce the number of cycles of the battery. Beware of non-smart aka "overnight" chargers which charge at like 1/8th or even less but will never stop charging. The charging current is so small it will not damage the battery at first but leaving the cells in charge like that forever will kill the chemicals.

[@patprop74]

I doubt this power supply is smart in anyway lol, id been 45mins and the voltage has dropped from 12.5 to 10.4V it keeps dropping by 0.1 every couple of minutes or so ( on the power supply) So basically your saying charging this power pack I made on my bench top power supply is a bad idea .

[@ErvPlecter]

a PSU isn't a smart charger. You need to read about battery charging and delta peak. If the voltage has now dropped to 10V, you're possible *far* below the delta peak and all your cells might be damaged. PSU can be used to do slow charging of niMH and niCD, but also lead batteries (the easiest)

[@JROrg2009]

Also keep in mind that most LED's will also have something like a 1K or more resistor in series with their positive lead to also limit the current running through or that the LED can draw, thus keeping the LED from being destroyed. You might want to take that resistor into consideration when setting your current limit.

[@ErvPlecter]

Joseph Rotello total non sense.The huge majority of LEDs do not have any resistor provided with it, no idea where this is coming from. A very few of low power leds (5mm) are pre resistored for being used on 12V on cars, or as power on lights on older equipments that were using 12, 24, or 48V bulbs. That's very specific though.

[@TaiViinikka]

I have a few hundred LEDs of various colours and intended applications. I think I have

[@JROrg2009]

Non-sense ? Then you won't be designing anything I or others use. What I meant was that bare / naked LED's almost always have in the circuit they are used in, a current-limiting resistor found in series with one LED lead. Perhaps 90% of all LED-is-used circuits have such a resistor. Of course, most all LED's do not come with such a resistor as part of the LED package, and yes, some LED's may not require one, all depending on the circuit need and design.

[@horus2779]

Little help.. Minileaf power supply Hi , I'm learning about electricity so I'm new to power supplies from what I've seen I should be able to set a voltage and amperage before I connect a load, I can set the voltage and it's displayed on the screen but the amperage will not display, the amperage selection does not work either , it will not display the amperage when not connected to a load, once a load is connected The display shows but generally I think you are suppose to be able to select a amperage limit before you apply a load. You can not select a amperage limit before a load is connected Once a load is connected the amperage dial does not allow you to choose a limit either. I tested it on a led light with amperage turned all the way down but it still went over the limit.

[@ErvPlecter]

Some newer power supplies have a disconnect button to allow voltage and amps settings. This model sets the max current by shorting it as demonstrated. You can't expect current to flow if a load isn't connected.

[@moeshickenyay]

Thanks, had to watch it a few times for it sink in but it really helped, Great video tutorial.

[@emostorm7]

wow, you are very knowledgeable sir!

[@robc8468]

Prices have come way down on bench power supplies as of 2017 the ebay range is about $40-$60 USD for 0-30 volt 5Amp many are including free shipping. In that range most are switching circuit which are lighter maybe a bit more HF noise. Analog units with the big transformer are still in the $60-$80 + range. Build quality varies a lot between similar looking units so try to find a tear down review for the model number and brand before purchase. I would assume the power supply is a switching design unless the product description specifically mentions linear. Both designs have pros and cons.

[@GeekBoy03]

You got to watch out on those cheapies. An electrical engineer shows us when turning those cheapies off, there is a power spike which can fry your device you are prototyping.

[@abijeetrs6522]

GeekBoy03 can you post the link?

[@robc8468]

@@GeekBoy03 I am well aware of the start up and shut down regulation issues seems. I would never leave a device connected to any power supply when powering up the PSU up OR shutting it down. I suppose if you wanted more insurance a big electrolytic capacitor across the output terminals would soak up a spike. I really doubt a $60 or $80 supply would be any better.. I this is a giant concern maybe something $300 to $600 range would address the spike issue.

[@slurryz]

Also very new to electronics and have a question: At 8:40 you have the LED hooked up again and have the current limit set to 1.0A. You increase voltage until current reaches 1.0A, and voltage ends up at 3.4V; the LED turns on bright and thus this is effectively a ~3.4 watt LED, yes? Wouldn't increasing the voltage above 3.4V require less current to dissipate the same power? Why does the voltage not go up past 3.4V when you adjust the knob?

[@ErvPlecter]

The voltage locks where the current meets the limit. It follows the voltage current curve of the led. See my other video on led forward voltage measurement for details.

[@the-ok-stuff]

can i power up my tp link router with (9V/0.85A rating) a DC power supply? (I tried doing it but the voltage reading on the power supply drops as soon as I make the connections)

[@ErvPlecter]

sure, that will work just perfect. Indeed your stock PSU is probably broken

[@the-ok-stuff]

@@ErvPlecter Thank you for the reply! Just to recheck, Constant Voltage mode is good enough for it, right?

[@ErvPlecter]

@@the-ok-stuff yes it is, correct. Just set your current limit slightly above the ratings of the stock power supply, like 1A and check

[@jimsinnovations2737]

can i use like multi meter tips/cables so i can be able to get to a specific component? thank you man, just got one of these today, not this same one but similar, i got everything i need now for my repairs

[@ErvPlecter]

You can ideed "probe voltage" to a part with multimeter probes! Glad you like the video and found it useful

[@jimsinnovations2737]

@@ErvPlecter thank you for the prompt reply, i subbed to im about to do some repairs on some computer parts, thanks again

[@jasonbrown467]

so is the constant current and constant voltage aspect of these psu's more of a safety limitation for the sake of your things you are testing? i am still confused, but i am getting closer. i have a tiny 12agm battery in front of me connected to my 30v10a psu and i am starting to see the light i think, mainly because how you worded a few things it kinda clicked for me a bit

[@ErvPlecter]

yes, the current limitation is used so that if something goes wrong, you can't inject too much current

[@rutubombasaway4982]

Thank you for the tutorial. I really appreciate it!

[@ErvPlecter]

very welcome, glad you liked it

[@frozenprakash]

Volt x Amps = Power (in Watts) So you are basically limiting the wattage, i hope if wattage is displayed like Volt and amps would be more useful.

[@clorifeto]

Thank you! You helped me out to configure my PSU. :)

[@ErvPlecter]

Rafael Vega you're very welcome

[@dzabakwesi2213]

Thanks for the video and the knowledge sir. Please is this dc power supply linear or smps?

[@ErvPlecter]

this one was "linear" with transformer. Most of the newer models are now SMPS

[@dzabakwesi2213]

@@ErvPlecter thanks for the response but which type(Linear or SMPS) will you recommend based on your experience so i could know which one to go for as a beginner thanks.

[@shmendrix]

I have a dc motor 7.2 V, each time I connect to the bench power supply, the current indicator turns on and it’s not working. With another power supply (simple one, 7.2V- 2.4 Amp, it works good but stop working after 20 min, and with batteries it’s working normally) The motor was taken from small electric screwdriver. Do you have any idea what’s going on?

[@ErvPlecter]

not enough current available on your PSU, start current is too high (expected for hi torque motors like in portable screwdrivers)

[@ErvPlecter]

@SoldierDDR: the spark doesn't mean there's a lot of current, but the voltage is high enough to generate that spark even at 500 mA. If the meters on the PSU show .5 A when shorted (regardless of the voltage) then it's working just fine and is limiting the current. With a pure short, voltage should actually drop close to zero while amps remain limited to the set limit.

[@sreekumarUSA]

Please let me know from where you got those red and white test prod clips, I'd like to get them. Here's my email address. [e-mail]. Thank you for your power supply unit educational tutorial.

[@ivanirizarry3758]

Ervin Plecter hj b 1

[@joeydubbs763]

Thank you!!! Thank you my friend, what a pain in the ass trying to find a tutorial to explain this goddamn thing. Perfect breakdown, thank you.

[@ronaldpalomino2532]

pain in the ass? jajaja +

[@dinabraganca9659]

do you still have this psu? I really need help reconnecting one that didn't have its front panel plugs marked.

[@ErvPlecter]

Sadly, i gave it to a friend

i like your note, it is very important to know the side of the current, because before seeing your video i thought that the regulator of current it was for outing current, but here it shows the current's comsuption, does it?. Sorry for my bad English.

[@nin5129]

Great job explaining. Very useful. Thanks

[@FPChris]

So short circuiting is how you put it into the mode to set the voltage and current limits?

[@ErvPlecter]

Current limit only

[@charlesklein7232]

it has a red display can the color be changed or is it all ways dsiplaying in red? i would like white. do they make them with changeable display colors?

[@nodriveasusephotos8019]

can you get one where whatever you set the voltage it is exactly that, also to the current. in other words not setting limits but setting exactly the voltage or ampage that does not change regardless of load or impedance. so for a high power l.e.d. set at 3 volts 20ma or 30 volts 2ma which does not change. complete control!

[@ErvPlecter]

+Alan Wolstenholme you have that sort of control but keep in mind a specific load will impose you the voltage/current bias point. A LED is typical for this, defining a current will make the voltage drop or increase to the corresponding zone of the current / voltage relationship of the semiconductor

[@nodriveasusephotos8019]

i just want to find a way of doing an experiment to found out for example if a 12 volt 10 amp bulb will light at the same brightness if a 24 volt 5 amp supply is connected to it-obviously massive current limiting but just in theory-think i might be able to achieve this with batteries due to internal resistance current limiting-any thoughts?

[@nodriveasusephotos8019]

you missed the point never mind. i want 10,000 volts limited current, will it shock the same? there is a thing called skin effect..

[@arifryo6823]

I bought one like this and i do like you did. I turn the amp in 500ma, and voltage is0, then i connected the led, i turn the voltage up like yours, until max, and the led survive, i pull the plug and the voltage is 25 like yours, but when i hook it up again like you did, the led is dead, i think my psu isnt fast response ..am i buying a bad psu?

[@ChrisSmith-wm7lz]

Great video and very well explained. Where did you get your leads to connect to a circuit.

[@pesti_ja1]

Great tutorial but how do you un-set the current limiter? Just reset it to maximum? Thanks.

[@ErvPlecter]

yes set to the max

[@ImprEcr]

Nice... In good clear voice.

[@galagatron5319]

How do you know what amps to set it on. I bought a bunch of electronics that I haven't played with yet. Whatever I decide to make, how do I know the amp setting? Thanks.

[@ErvPlecter]

the video explains how to set the max current limit

[@ErvPlecter]

the current limit depends of the device you're powering, I can't guess, it totally depends on what it is

[@galagatron5319]

@@ErvPlecter thank you for your quick reply. I bought a bunch of things. A bluetooth circuit, relays, a timer, etc. I was wondering because I have a power supply getting shipped and I want to play with it by hooking up some stuff to it. I know how to set the amps thanks to your awesome video but like say if I have a strip of led that I snagged from some old junk that doesn't have amp numbers on it or say I have a few things that don't say amps but volts. Is there a way to figure it out using a formula or do I wing it or do you have a video that helps a noob such as I that I can watch. Thanks again!

[@galagatron5319]

BTW, your homade power supply is cool as hell.

[@neil8288]

great video! Now I know how to much better use my power supply...

[@ErvPlecter]

you're very welcome, glad to help !

[@bhargavtreevedimmt]

thanj you verry much sir for this video it is verry usefull for me to understanding about the use of power supply. .. .

[@bzqp2]

What's the name of these connectors? None of the banana plugs I have at hand fit these. And why do they unscrew? How do you use them? :o

[@ErvPlecter]

@@bzqp2 they are standard banana plug. Doubles a screw-on for bare wires like speaker cabinets

[@Theeslickness]

Quick question: I want to test high amps and volts on a PSU. The limits are 30V 10A. I'm going to be testing a motor setup that uses a constant 25.2v, just like a 6-cell LiPo battery. I plan on pushing the amps almost to 10A. So the question is: will the PSU try to maintain 25.2V until it passes 10A? I have a feeling that none of these cheap PSU can achieve anything close to 10A at 25v.

[@photonic_induction2633]

if it goes over 10 amps then the voltage is gona drop soo lets sey ur puling 9.99amps it vil keep the voltage at 25.2v but if you go over10amp lets sey 10.1 amps the voltage will drop :)

[@mariaangelessalvador1516]

Thank you. It has been very useful to me.

[@2bit661]

if you don't mind. what country are you in? what is the mains electricity?

[@ErvPlecter]

France ! Mains = household AC current, 240v here.

[@2bit661]

@@ErvPlecter thank you

[@Rebel12Lz]

Thanks man, really helped me out :)

[@VAlien79]

my current CC light is on and wont turn off ? displays all show zero, fan is running ..tuning the knobs does not effect readout of the display? any idea this unit is only a few weeks old.

[@ErvPlecter]

from what you say your PSU is in short circuit (therefore voltage drops to zero and amps to the limit set by the current knob). Or it's dead.

[@justiceecheonwu8145]

thanks so much...but can u make a video of a linear power supply...

[@ErvPlecter]

regulated bench PSU exist both as SMPS and linear. Operating them is stritcly identical (voltage regulation, current regulation / limitation)

[@ErvPlecter]

@Loco: the voltage is limited by setting it with the right knobs.

[@longjohncrypto688]

Thanks for a great video!

[@ErvPlecter]

very welcome and glad if it helped you !

[@mussaali1696]

Well done to make this program

[@saarike]

Great video! Clear and informative. Thanks!

[@Paradox3627505]

Thanks for the explanation. I was about to return my PSU until I saw this video. I wonder why the digital display isn't carried out to 0.000 (3 digits behind the decimal point). Isn't, for example 0 to 9mA, common current magnitudes to work? I would like to see them as well.

[@ErvPlecter]

it's a cheap PSU, so current measurement doesn't have such a nice resolution. If you need to measure a small current, the best is to use an amp meter.

[@dzabakwesi2213]

Please sir what is the name and the model of this power supply thanks?

[@ErvPlecter]

video description

[@biometrix1000]

thanks Erv.....it all helps

[@horacioricardodrut6645]

Hi, nice video. Do you happen to have the schematics for the one you built yourself? Thks. Rgds

[@JTKhopefuls]

What does it mean if current value is not displaying when rotating switch?

[@ErvPlecter]

Current is showing on display only when flowing

[@RYU47376]

my unit amp bottoms out at 2 amp for some reason, and the voltge is 5v-47v....

[@ChrisSmith-wm7lz]

L o. As I'm learning at home and not getting classroom tuition, when you say that the amps displayed is the amp the circuit is drawing, would that ampage drawn be the ampage through the whole circuit. So let's say I have a pcb hooked up to 12vdc and the ampage displayed is 251mamps,is that 251mamps through the entire circuit.

[@hariharanramamurthy9946]

can you say difference between psu and programmable psu

[@chahrameftah5413]

hi what the unit of Current density ? is it A or MA? i have Dc power supply 60V - 3A model. and i want to connect it to a reinforced concrete so the bar act as cathode and a mesh on the concrete act as Anode. i want to apply a current density of 0.8 A/m2 .. Do i have to multiply this number by the Steel Area to get the current density at the DC power?? if the steel area is 0.01m2 therefore i = 0.008 amps. i think it is very small number!! can you help please as soon as you read my comment. thank you

[@ErvPlecter]

Chahra Meftah : current density is current per area unit. Current can be expressed in amps or mAmps. You don't apply a current density. Current density is the result of applying a current to a certain surface.

[@chahrameftah5413]

@ Erv Plecter Thank you for your reply

[@chahrameftah5413]

***** another last question please! say i want to apply a current density of 0.7 A/m2 to a bar with surface area equal to 0.01 m2 .. so the current is should set at the DC supplier should be 0.7 * 0.01 that give me 7 ma. is that right?

[@johnheaton6705]

Great video, clear ond concise - thanks

[@fernandolozano9898]

Why does one need to short the terminals to set the maximum current?

[@ErvPlecter]

to force current being drawn while adjusting the limit

[@bhargavtreevedimmt]

good morning sir, sir i have one maxx dc power supply for mobile repairing when i connect the phone to the power supply and switch on the mobile device i found that current meter is fluctuating from 30 to 50 constantaly in every device so please tell me what is the problame

[@ErvPlecter]

it's probably because it's is charging the battery, which can be with pulsed current at some steps of the charge curve

[@3dvisiongamer213]

Thank you, I now have a better understanding of this very overweight, very beige metal box I have.

[@3dvisiongamer213]

I may just have to paint mine.

[@ErvPlecter]

put a sticker on it !

[@mauricepetit9986]

Thanks for the great video.I would have a question to ask you if you don't mind.It may seems to be a stupid question, but I'm just learning electronics, and almost every videos about benchtop dc power supply, they always mention to adjust your voltage to the desire setting and then after, you adjust the current. I have 2 dc power supply on my bench and when I try to adjust the voltage, I have to turn the current knob a bit before I'm able to get a voltage display. Is that normal, or if there's something wrong I'm doing or there's a problem with the power supply??My name is Maurice Petit and I'm from Ontario, Canada.

[@ErvPlecter]

Hi Maurice, you need to have some minimum current allowed before your PSU can output voltage. While the PSU current limitation is intended to put a real limit to it, most of the time, you'll leave your current limit high enough to power your device, like 1A. You don't need to have the current limit down all the time, only when you want to insure the current won't go above a certain limit, like when powering a device for the first time.

[@mauricepetit9986]

Wow !!!! Thank you very much for answering to my question and also to have responded quickly like that. So, if I'm mostly working right now with transistors and leds circuits, should I set my current to one amp, or should I set it up lower? Is this why, in your video, you shorted both leads of the power supply to set up your current?

[@ErvPlecter]

Your current limit depends on the "safe" factor of your electronics. You first need some insight about the current use of your circuit and set the limit in the same area. For instance, when I first test or debug a new MCU board that uses 70 mA with no sound and no led attached, I first jump start it on the 100mA range of the PSU so that, if something goes wrong, I can't get above this.

[@mauricepetit9986]

Thank you very much for answering my questions and keep up with your very good videos. It is very appreciated.

[@zt64]

I just got a power supply that looks exactly like the one shown in this video. I was able to change current and voltage but around 5 - 10 volts I can hear a hissing sound coming from either a capacitor or a fan. I looked inside but could not tell any possible capacitors. Any idea?

[@duncanng3]

Will the LED be burnt if you set the voltage to maximum and the current limitation knob to maximum?

[@dannuttle9005]

Assuming that you don't have an LED that can withstand whatever the maximum voltage and current your power supply can produce, then yes. (Short answer: Oh hell yes.)

[@davidjames9935]

Can these type of lab PSUs be used as battery chargers and if so, is there anything "special" that has to be done? Any special precautions that need to be taken? What if the battery remains connected and the PSU is off might that harm the PSU? Also, can a resistor be used to set the current limit or does it have to be a very low ohm short?

[@ErvPlecter]

+David James the only battery i would let it charge is lead battery as it's constant current with no real time limit. Ni-MH don't like to be overcharged, unless you charge them at 1/20 or 1/10th of their capacity (mAh). Those should use a delta peak charger which detect the end of the charge. Overnight charger charge with constant current with no time limit and that generally ruin the cells (anode) if longer than 8 hrs (reason why they are called overnight). Li-ion use a VERY special charging profile mixing constant voltage and constant current and only specific chargers must be used for those. Same for lipo.

[@davidjames9935]

***** Ok assuming I am using flooded lead acid batteries such as a 6V golf cart battery, what precautions do I need to take? Can I just set it to 3A max in current limiting mode and then when it reaches a certain voltage, switch it over to constant voltage mode and let it top off? Also you didn't answer my question if the current limit can be set using a resistor instead of shorting the leads. Is it a good idea of extra safety or will the PSU protect itself even without it and even at a voltage higher than a fraction of 1 (such as 5 or 10 volts)?

[@ErvPlecter]

+David James The way I recall doing it is : - Set the charging current limit by turning the current knob while applying a short circuit on the PSU with 1-2V - Set the voltage of the PSU at the proper battery voltage (the charging voltage which is > than the nominal voltage. A 12V battery is charged at something like 13.5, check your datasheet). - finally plug the battery. The current will jump at the charging current and the voltage will drop to what the battery voltage is currently. Progressively the injected current will make the battery voltage climb. You need to monitor this and stop once the charging voltage is reached. You can use a voltmeter on the battery to determine with accuracy if you've reached the charged point

[@willm350]

I got a 60v 5 amp model and when i shorted it out to set the current limit to 4 amps like you did in the video it sparked and now I cant adjust the output current, it just stays at 120 volts. I just requested a return if they wont return it could it possibly just be a fuse that popped? Or maybe something else that would be easy to fix? Thanks for your time this is my first PSU

[@ErvPlecter]

On which voltage was that when you shorted it ? By definition, voltage should drop and current would just ramp up to the the limit. Now if it was set to high voltage (like 20+) when you set the current you could have blown a fuse. There are several inside in general

[@willm350]

***** Thanks for the reply, ya if your saying 20+v is high voltage i wont tell you what i had it at lol. I'm going to see if they take it back but if not im not going to push the issue and I'll open it up and see if its just a fuse. Thanks again!

[@ErvPlecter]

willm350 happy to help. If you had cranked it close to the max, it's possible that the current limitation module didn't have time to trigger, as that's a lot of voltage to take down, and a lot of amps too. So to prevent a major failure, the fuse blew. You should be able to find those inside. Good luck

[@jemsncrystals]

My bench power supply has max output volts to 17V And 2A Im trying to charge a 12V car batt lead acid When i connect the psu to batt the psu drops to 11.5 V??? And fluctuating (11.1V-12v) And amp fluctuate (0.00 to 2.99) What is wrong here?

[@ErvPlecter]

The battery will impose its voltage until it gets enough current and it will keep charging. Basically you have to set your voltage to de target one, limit the amps to the max charge current of your battery (usually on lead acid, discharge current / 10 or 20) and plug

[@jemsncrystals]

@@ErvPlecter yea, i had hoped that too. Its a puny 2 A max 12V power supply. The ones for mobile repair things. Yea i might need a bgger power supply that can output atleast 10Amps. Thanks.

[@ErvPlecter]

@@jemsncrystals you can set the current limit to the max, it will just take longer to charge, but lead acid don't like high charge current anyways

[@alicemcfly2011]

Tu es le best💖😘😍😊

[@severalmalfunctions]

If I have a charger that outputs 3V and with a max current of 500mA, can I connect a 3V LED directly to it? In other words, even if the charger is a 500mA charger it'll just output the 30mA I need for my LED or will it burn the LED?

[@TaiViinikka]

You will put the LED into overcurrent and cook it. LEDs do not limit their own consumption.

[@sara78130]

Can I use that for Ecu Programer?

[@mrawesome6239]

Hello What’s the one your using in the video called and which ones do you recommend available in the uk under £100

[@hadeelatta7986]

hi sir i have some proplem here and i hope you can help me i got one of these power supply and i have experiment that's requrird constsnt current at 2.7 A but when i connect my DC power it give me a max, current of 1.8 A and max (constant voltage) of 28.9 V , i tried to set the current but when i do the steps and try to connect it again it just the same old current can you help me please 😭

[@ErvPlecter]

hi, it's no brainer, you can't output 2.7A with a 1.8A source.

[@hadeelatta7986]

oh i get that, but why the Dc have unstable amp i mean i want 0.89 amp constant and its just keep go up and then down

[@int0x13]

Hello, good explanation, i bet you are from Quebec?C'est quoi une biscotte dans ta boite a composants?!

[@ErvPlecter]

presque, je suis de France ;-) La Nano Biscotte est une carte son pour sabre laser d'entrée de gamme.

[@int0x13]

***** Mince alors comment tu as un si parfait accent, tu dois être expatrié? Je suis tombé sur ta vidéo car j'ai pas trouvé une seule vidéo en français qui explique comment se servir d'une alim de labo...dingue

so, i have a question, when you connect a mobile for feeding it, does the current display show you the value of current that is being consumed?

[@ErvPlecter]

+Arreglos Informáticos : that's correct. However, it will probably show only the current used for charging, not what the device is using itself.

[@kilgoretrout4461]

Thanks, this was helpful.

[@sudheervelavoor]

How can I use bench powersupply to find short in laptop or mobile pcb. I found there is a short , but when i connect to power supply , it goes to over current protection

[@zaperfan]

Great tutorial thanks for posting

[@joshzotz7445]

Excellent information.

[@jimmywester1000]

Anyone got a fix for the current display not working ? Thanks

[@kurk1701a]

Ervin Plecter, question can you switch off the power supply at the power point? and will it hurt it?

[@ErvPlecter]

not recommended. I always either remove the banana plug or turn the voltage down before switching it off. I tend to always remove the positive banana plug in any case once the voltage is at zero.

[@madpinoy5683]

Hello Irv. I've seen 15V 2A PSU's on eBay. Will those work, too?

[@ErvPlecter]

A bit limited for LED testing. I'd rather get a 30V / 3A or 18V / 2.5A

[@madpinoy5683]

Ahh. So anything 18V or higher and more than 2A would be ideal, then?

[@georgimiller3355]

Hello I have the same tool. But my current display isn't working. What happened?

[@xila8861]

+Erv Plecter Where can i find a very good 240V capable bench power supply ,and which one do you suggest ?

[@ErvPlecter]

you'll find those on amazon UK. If you're after a professional bench PSU, I suggest you look at the ones sold at Farnell, Maplin, or Mouser, depending on your location.

[@xila8861]

i'm looking for a begginer one, and to be honest i like this one you're using now but i cant see its name to look for it .the heat sinker looks really great and shows that this one you have is well build .i wish if you can provide me with the brand name ,thankyou also for communecating and helping me out by giving these tips .

[@Saidavali.123]

Sir I have one beetech 3002 model rps dc power supply. But isn't on when switched on. Please give suggestions

[@geraldshields4720]

@Erv Plecter Is it possible to purchase a tri output power supply for about $50 - $70 dollars?

[@titaniumdiveknife]

Subscribed. Very pleasant fellow.

[@MrGeekGamer]

I tried to follow this and I blew up my LED when I tried to disconnect and reconnect the power supply at 25V.

[@j3s0n]

At least you didn't die

[@MrAtheHun]

Thank you very much that was very helpful.