DIY USB electronic load

PCB Prototype for $2(Any Color): jlcpcb.com
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USB load ali.pub/31lezi
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IRFZ44 ali.pub/31lf64
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LM358 ali.pub/31lf30
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600pcs resistors ali.pub/31lexr
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My laboratory equipment
Laboratory power supply ali.pub/2tmanr
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Multimeter 1 ali.pub/2tm7hm
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Multimeter 2 ali.pub/2tm7xk
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Multimeter 3 ali.pub/2tmcks
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Multimeter 4 ali.pub/2tm9qb
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Current clamp ali.pub/2tm9yo
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Capacitance and inductance meter ali.pub/2tm945
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Universal Signal Generator ali.pub/2tmgij
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Oscilloscope ali.pub/2tmb1d
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Transistor tester ali.pub/2tma7t
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Thermometer ali.pub/2tm8sa
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Frequency meter ali.pub/2tmigc
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Electronic load ali.pub/2tmagy
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Intelligent Chip Tester ali.pub/2tmicu
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Soldering Iron ali.pub/2tmbm6
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Microscope
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[@ashbe77]

I love how your projects are a mixture of technology functionality and high quality content.

[@wernerpeter9706]

Unfortunately, the prototype shown does not seem to be identical to the circuit and layout. My setup starts to work at over 6 volts, which is rarely achieved by normal USB :-) A look at the datasheets of the components used explains: The MOSFET IRFZ44 has a gate threshold between 2 and 4 volts. That means, that he starts to switch between 2 and 4 volts at some point. From now on, the conductivity (source/drain) increases with the voltage at the gate until the MOSFET is fully turned on. My exemplar starts at 3.8 volts. The OPAMP LM358 is not a rail-to-rail type. Its output voltage swing is +/- 1.5 volts of input voltage. This means that e.g. at +8 volts input the output is +6.5 volts (same as negative voltages). My LM358 delivers at 5 volts maximum 3.6 volts at the output, and there is still a 1k resistor between output and gate --> that's not enough for my IRFZ44. My solutions: With a rail-to-rail OPAMP (output voltage is much closer to the input voltage) like the MCP602 or LMC6482, the circuit works up to about 4.2 volts. Eventually, the resistance R6 to the gate of the MOSFET must be reduced. 1k is very high, 20-50 ohms are enough and do not have such a strong voltagedrop to drive the gate. Alternatively use the IRLZ44 as MOSFET. Its gate threshold is between 1 and 2 volts with very similar power levels. Thus, the test setup worked well below 4 volts.

[@DanielStingBR]

I changed de mosfet by a 30n06L, that is logical level, but, only if 8V it works, even changing R6 by a 10Ohms one.... I think that the chips are bad... Your are fake ...

[@wernerpeter9706]

@@DanielStingBR Your FQP30N06L is listed in datasheet with a Gate Threshold of 1 to 2.5 volts. That should work. Have you ever measured the real gate voltage from your setup? At what voltage does the MOSFET start switching, at what voltage it is fully turned on and what really arrives at the gate? Remember, the worst case scenario is that the LM358 can only provide +1.5 to +3.5 volts from the USB (+5V) input voltage. Without measurements on the circuit you can not say "fake". At first, my setup did not work until I measured it and compared the component tolerances with the measured values.

[@klave8511]

The On Semi data sheet for the LM358 says the input range extends to the negative rail, seeing as the inputs common mode voltage should never exceed 5/27 x 2.5 v= 0.46v the op amp is correctly selected for this job. It also works down to 3v. The only drawback I can see is that the fan current is not passed through the sense resistor so it is not controlled but this is constant for a fixed voltage and the current is measured separately anyway. This is a good design. A thermal shutdown may be a nice addition for safety, maybe a 100k NTC thermistor in parallel with R3 to reduce current when it gets hot, put the thermistor against the heat sink.

[@cipher-1]

Why donot change design for use a BJT transistor?

[@Ozzy3333333]

That is the exact same schematic as the DYI 150W load I got on ebay 6 years ago. I found out that loading certain dcdc adapters, it would oscillate. I fixed it buy changing C2 = 0.1uF.

[@electroniquepassion]

Thank

[@willyrivero470]

Excellent video! This reminds me. Can you make a video to make a good cellular phone charger? Something capable of around 3 amps at least for charging the new cellular phones. Thanks!

[@f.m.a5928]

Good job. Could you plz make the load for testing 9v,12v,24v adopters .I had purchased them looking at ratings on it but on actual load they are not working.

[@williamvaughan1218]

Love your videos and your English is very good.

[@HYTMUAE]

The circuit diagram photo does NOT match Ur circuit made in this Video?!!

[@MFEeee]

Love your channel

[@arrowstheorem1881]

JLPCB seems to be China owned. Will they use the PCB design and replicate in China if any product sells?

[@sumitchaudhary8489]

Thanks for this very useful circuit

[@prashanthb6521]

Thanks for this project.

[@electronic7979]

Excellent project 👍 very useful

[@nitinsingh-hb7mt]

my prototype is working but amps dont change it is always working on its maximum capacity only thing different that i have used is .2ohm 5w shunt resistor and a 10uf 50v capacitor please help

[@Khalilkhan6120]

Can i use 2 z44 in perallel because single one get so hot

[@MCsCreations]

Fantastic work, man! Really nice! 😃

[@khalidaldalalah3403]

Hi, i tried this circuit. I don't have tl431 so i used voltage divider potentiometer with 20kihm resistor. And i don't have 0.1ohm so i used 1ohm resistor. I got at 5V current between 100mA and 1.2A. I couldn't make it less or higher. Q1: I'm wondering what part should i change to reach 2A at 5V? I tried 5 parallel 1ohm resistor to get 0.2ohm but still same. Q2: why there is a feedback resistor (220kohm) to the op amp? Usually these current control circuit don't have this feedback. Q3: the tl431 u used it in a strange way not in the datasheet, i guess in this way some voltage goes to 6kohm resistor and the rest to the capacitor to make tl431 have certain voltage, but if the supply voltage changed the the reference will two!!! It like voltage divider. What is the use of it here?

[@abdelhakimallal3753]

nice and useful thanks

[@TristarCollections]

Followed the schematic shown but it didnt work..i wonder if the prototype and the schematic are the same...

[@goosenp]

Could you please explain why there is a capacitor (C2) in the circuit?

[@amkp40technology]

Nice video

[@mukhammadfaisal9735]

can you make short protection for lab power supply diy

[@ulhasrane3656]

Download aechive @t schematic does not match with your prototype since your proto has variable mutiturn resistor of (100k ) which is not ther in schematic as well as in layout file at above link. Please provide updated pcb file

[@sumitchaudhary8489]

Please make a charger of 58.8volt for a 52 volt 40 ah lithium ion battery pack, or convert my 48 volt lead acid ebike charger to 58.8v lithium charger thanks in advance

[@hadypranoto2329]

If i use 2w shunt resistor how much current i can get?

[@ocayaro]

Love KASYAN!

[@imtaufiqmehedi]

Which resistor i can use alternate of SMD R050

[@Edmorbus]

Good job

[@imtaufiqmehedi]

Which resistor i can use alternate of SMD R050??? Please reply me, only for SMS R050 my circuit is pending, R050 is not available in my area

[@jagdishsingh9997]

You can use 0.1ohm 5w big resistors

[@imtaufiqmehedi]

@@jagdishsingh9997 after 1 yr i've received this answer. Anyway, thank you very much

[@Happiness50057]

Super video

[@DanielStingBR]

it seems to be diferent from the prototype, it didn't work voltage less than 8V, what is the trimpot on the prototype? The voltage reference only start to stabilize in 2,5 volts over 8v. Any clue?

[@wernerpeter9706]

Please read my comment to solve the problem.

[@DanielStingBR]

@@wernerpeter9706 I can't see any comment of Werner... :( where is it?

[@DanielStingBR]

Hi, please... I didn't found the solution..:(

[@wernerpeter9706]

@@DanielStingBR apparently my longer comments are filtered out :-( - are only displayed to me

[@wernerpeter9706]

1) The MOSFET IRFZ44 has a gate threshold between 2 and 4 volts. That means, that he starts to switch between 2 and 4 volts at some point. From now on, the conductivity (source/drain) increases with the voltage at the gate until the MOSFET is fully turned on. My exemplar starts at 3.8 volts.

[@DanielStingBR]

Hi, can you help me? how can I use a 10k pot in place of 5k?

[@SKElectronics]

yes u can

[@conductionband4712]

hi . please anyone can help me on this problem : i assemble the circuit but its not work until the input voltage reach 6 volt and above. i tried to change the R9 with smaller ohm range like 0.1 ohm but still not succeed. i simulate it in proteus and also in proteus its still need 5.8 volt for input. Any help ?

[@cipher-1]

This Mosfets need around 5 to 7 volts gate to source to work correctly

[@mazengomaa27]

What if I don't have a USB tester Can I use my multimeter instead

[@pavelbires]

For the voltage yes, but not for current, the leads have too much resistance.

[@davestech6357]

Put a .1ohm or .01ohm resistor in series to the load and measure millivolts across it to get current.

[@batticha462]

1:13 "On one harsh winter evening I simply had nothing to do ......". Poor Russian girl hahahahah :)

[@imtaufiqmehedi]

Sir please give me alternate of R050, which diode i can use instead of R050?

[@davestech6357]

R050 is a .05 ohm resistor not a diode.

[@imtaufiqmehedi]

Which resistor i can use alternate of SMD R050

[@BilalSatellite]

Use multimeter amp copper jumpre

[@BilalSatellite]

Otherwise .1 ohm 2 resistors use parallel

[@farmuelangel6342]

Dear Sir the circuit is not working although to my surprise the circuit was working only if I left he mosfet without a heatsink!!!!!!!!!!!!!!! Ahhhhhhhhhhh this is very odd because the mosfet was burning nasty drowning current from the source (usb load) but when I put a heatshink on it then it draws zero current..!!!!!!!!!!!!!!!!!!!!! Amazing!!!! The heatsink is not making any short circuit with the rest of the circuit. Well the conclusion is this : The circuit is good for a thermal stove. !!!! I could use a fan without a heatsink but the fet is still burning badly when it draws the current.!!!!! I haven't seen this in my life before as an electronic engineering that I am. I will try to isolate the heatsink completely and then I will post again. ! Very strange indeed. I will compel it very soon. I need holy water.

[@farmuelangel6342]

It doesn't' work either...No response from the creator!!!!!!!!!!!!!!!!!!!!!! An answer please????

[@mrgreenswelding2853]

What program do i use to open the .lay file?

[@KasyanTV]

sprint layout

[@imtaufiqmehedi]

Sir, can I use 5k pot?

[@davestech6357]

Yes 5k 10k 100k would work also.

[@FantaBH]

yaiiiiiiii 100th like is my only my , forever my .

[@SnipeR-02]

Old voice... just the old voice.. please?

[@stinkycheese804]

This is all ridiculous. You ended up spending multiple hours and times as much money as just buying some very low cost, ready made tester. Even if you happened to have all the parts, as salvage rather than paying regular market prices for, it is a colossal waste of time to reinvent the wheel. Also your PCB design was ridiculous. Terrible waste of solder. If your traces are too thin to support the current, stop wasting so much solder and leave more copper on the PCB instead of etching an excessive amount away, plus there was no need to make it so small if that was the problem with having enough copper. Plus the design is terrible for lack of mechanical fortitude where the USB connector meets the PCB, apparently relying only on the solder joints for something meant to be manipulated with that mass? There is no good reason to build this and several reasons not to.

[@electronicsio2554]

Nice video