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@@OmarElmasry1 Thanks, I'm glad you enjoyed it!

github.com/Dominik-Workshop/Electronic_load/tree/master/pcb/pcb_main

@@dominikworkshop6007 THANKS !!!!

Thank you!!!

Hello! The LM4140 was chosen for its outstanding stability, particularly due to its low temperature coefficient. Since the DAC's output depends on the supply voltage, ensuring a very stable reference voltage is crucial for consistent performance. The DAC needs to operate within a supply voltage range of 2.7V to 5.5V, which necessitates using a voltage divider to limit the output voltage range, as you correctly observed. The reason for setting the output voltage range to 0-217mV is that this reference voltage is compared with the voltage across the 0.1 ohm shunt resistor. When the reference voltage on the non-inverting input of the U1 amplifier reaches 217mV, the corresponding current through the shunt resistor would be 2.17A (for one power stage, there are 4 of these in parralel). Hope it clears things up, and that I understood your question correctly.

@@dominikworkshop6007 That is exactly what I meant and thanks for the reply. I've done some simulations and with your explanation and the schematic provided (and some information from SW) I will use a very similar mosfet gate control. Your projects are brilliant, keep up the good work.

Yes, the 5V regulators are currently used as voltage references for the op-amps. However, this is not the most optimal design choice. Using a dedicated voltage reference like the TL431 could provide better precision and stability. After replacing the P-MOSFET with a BJT, the output has shown stability even under heavy loads. More details on this change can be found in the README file on the GitHub repository. While I haven't precisely measured the output voltage drop at a 2A load, I estimate it to be less than 10mV. As demonstrated in the video at the 5:39 mark, there's no noticeable drop in output voltage even at a 3A load.

10 mV is very good as with common l317 and simple design it can drift (at least in my case) about 180 mV or something in both ways which is quite annoying while charging LiPo batteries 🙄 I have to monitor the current all the time...

@@samuelgift6889 I'm glad to hear that!!!

@@eboy536 Thank you!

@@stanislawi.4610 Thank you!

Thank you!

Thank you!

Thank you!

Można zrobić wielokanałowy z możliwością łączenia szeregowo, ale tak jak piszesz, controll board by to zwierał. Rozwiązać to można by było stosując izolator I2C do przetwornika ADC, i mieć połączenie między płytkami tylko przez I2C. (zasilanie ADC też nie może być brane z controll boarda oczywiście)

Thank you!!!

Thank you! When the voltage on the P-channel MOSFET's gate decreases, it starts conducting, thus increasing the output voltage.

Thank you! What exactly do you want me to explain in more details? What probelms do you have?

Thank you! I might do that in the future. It is very likely that there will appear some documentation on the github repository.

Thank you!!!

Thank you!

It can limit the output current, but it's designed so that it's should survive a short on the output.

Thank you!!! I don't have to calibrate each mosfet seperately. The op-amps ensure that the current is very evenly distributed. I used 4 resistors to sum the voltage on shunts, but it turned out unnecesary (maybe except for when there could be some hardware failure), because the op-amps are so precise, that the voltage on shunts is pretty much identical. Hope I managed to clear this out.

Thank you, I'm glad you like it. The op-amps are powered with 15V coming from the emitter of T2.

Is it possible to add the floating ground part to this circuit?@@dominikworkshop6007

@@siedshojaat4473I'm sorry, I don't understand your question.

The floating ground is used in the laboratory power supply to parallel the sources or create negative voltages@@dominikworkshop6007

@@siedshojaat4473 The output of this power supply is galvanically isolated from mains earth, so it is possible to for example, connect other power supply in series with this one

They can be just a generic medium power transistors. You could use bc639

Thank you, I'm glad you like it! It is indeed a good feeling to build something yourself, but there is always something you wish to improve. Now I'm working on a second version of a linear power supply which hopefully will be more professional and easier to recreate.

Thank you! Having a PCB made is very easy. There is a gerber file on my repository (link in the description). You just have to upload it to a PCB manufacturer, like JLCPCB, and order it.

@@dominikworkshop6007 Thank you. I´ll try it.

@@dominikworkshop6007The PCB is ordered now, we just have to wait until it arrives. What program is used to upload the code? I can't find the list of components, maybe I don't have the right programs. Sorry for the questions, I'm a beginner, thank you very much

@@marecek19891989 I used platformio to upload the code. There are many tutorials on RUclips. There is a pdf with full schematic on my repository. You could also open this project in Eagle to be able to inspect what goes where more easily. Let me know how this project is going for you!

@@dominikworkshop6007 Hi, my project has progressed. The PCB arrived from China looks very good. I am ordering components, but it is very difficult here in Slovakia. I can't buy measuring resistors :( where did you get them? Thank you

There is a gerber file on my github repository. There were no major PCB changes, and this gerber file is the most recent version of the main PCB.

Yes, they can be replaced with 0,5 ohm resistors, but that would mean more power loss on these resistors, unless the maximum current is reduced. They can certainly be replaced with other types of resistor, but I suggest ensuring that they have low thermal coefficient.

Thank you, and good luck with your build!

Thank you, I'm glad to hear that!

You are right, thank you for pointing it out. I haven't used the input trigger yet, and there is an error in defines.hh, where I defined this pin to pin 3, instead of A7. The two pins I know can work as external interrupts were used for the ENCODER_A and ENCODER_BUTTON signals. I'm not sure if I will be able to configure the A7 input as external interrupt, but in that situation I planned to just check the state of this pin frequently, and act accordingly. I know it's not perfect, but the uC used in this load has some limitations. If I were to make a V2 of this project, I would probably base it on some STM32 uC.

@@dominikworkshop6007 Maybe the PB3 pin can be used on the current system, which is still unused. It's a keyboard spare pin and MOSI too. And there is PCINT3 attached.

Thank you! That sounds like a great solution (ignoring the immense weight I can only imagine it had xD)! I wander how it reacted when the output voltage changed rapidly, especially when it goes up. I guess that the motor-controlled variac didn't adjust very fast (or did it?). I see that this problem would be ocurring especially in the constant current mode, when the load rapidly decreases. Or maybe it's not a big deal and the power supply handled it well?

Thank you!

Thank you!!!

Thank you!!!

It would still be 8A.

Thank you! I get your point, though that would make this project a little bit more expensive.

Thank you!!! :D

Nope.

Może w przyszłości kiedy będę mieć wiecej czasu o tym pomyślę ;)

@@dominikworkshop6007 spoko dzięki za odpowiedź 👍

The measurements are on github repository: github.com/Dominik-Workshop/Linear_power_supply/blob/main/measurements.pdf