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Lab Power Supply - The Lost Current
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radoczi94:
@xavier60:
I found this: http://www.electronics-lab.com/project/voltmeter-ammeter-lcd-panel/
Is the type of the MOSFET critical, or it's interchangeable with another types?
How about a negative reference for the CV and a positive for CC?

@Audioguru
The oldest version I found of this schematic, is in a polish magazine (ELEKTROinzert) from '96. I tought, it is a good one, but turned out to be a transistor graveyard.
xavier60:

--- Quote from: radoczi94 on August 05, 2018, 09:03:10 am ---@xavier60:
I found this: http://www.electronics-lab.com/project/voltmeter-ammeter-lcd-panel/
Is the type of the MOSFET critical, or it's interchangeable with another types?
How about a negative reference for the CV and a positive for CC?

@Audioguru
The oldest version I found of this schematic, is in a polish magazine (ELEKTROinzert) from '96. I tought, it is a good one, but turned out to be a transistor graveyard.

--- End quote ---
MOSFETs can be substituted in many situations except in very fast switching applications where the MOSFETs switching and conduction losses have been carefully match to the job.
There would be many parts that would happily switch a fan. I tend to use whatever I already have in stock even if it's massively over-sized for the job but still switches reasonably quickly. I would use an IRLML0030 because I already have some. Its current rating is much higher and although it is rated at 30v instead of 50v, there should be only 12v present anyway. Both parts are dirt cheap on ebay.

You could use a negative reference for the CV and a positive for CC. Because I don't expect that you are going for 20 amps output and if you use a 10 milliohm shunt also, R1 can be increased to over 50K which wont load the CC Pot much anyway.
xavier60:
I have been assuming that the Pots are 10K because my blue ones are 10K.
Audioguru:

--- Quote from: xavier60 on August 04, 2018, 10:52:54 pm ---I found the discussion here, http://www.electronics-lab.com/linear-lab-power-supply-digital-meter/. Does someone have a link to the schematic?

Is this it? https://www.instructables.com/id/Superb-Lab-Power-Supply/

--- End quote ---
The Instructables uses the Chinese kit that is a copy of the original old Greek kit that has many parts overloaded, is not reliable and has poor performance. I am surprised that the Instructable author never tested the maximum output voltage and max current which will be much less than its 30VDC/3A rating.

Here is my latest schematic and parts list that work well:
radoczi94:
I saw those chinese kits all around ebay, with a red soldermask, and a single SPT. They were too good to be true.

Alright, I just bought a few mosfets, transistors and opamps to experiment with. I think I will try 2 or 3 schematics and then decide, wich one gets into the design state. Then, the cad will be started, but for now, release, the magic smoke! Will bring some news and experiences. :popcorn:
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