Hi all new to forum also like to say hi, I apologize in advance if this is in wrong section I'm new to electronics, and still learning the ropes of the basics so without doubt its laughable pleas be kind I'm new and learning this is my first project because every good enthusiast has a power supply, you say just buy one, yes I could and it would of been cheaper but I would not have close to the amount of amps output and I'm not learning

Ive built a power supply using computer supply,
So I've got a solid 3,5,12v output of 25a ea

I have also boost and buck converter board so I've got 10a adjustable between 1v to 36v I've removed the cc and cv trimpots both measured at 200,000 ohms, why I removed them is I want pot switches on front panel for ease of adjustment

The CC is 200,000 ohms
The CV is 200,000 ohms

I want to ad in a extra pot for fine tuning of the CV I can't figure it out I think I need to go lower number in ohms but how much is there a work around for this was thinking about 70% slower or what ever they are normally would be in commercially made power supplies, would this mean around 60,000-70,000 ohms for fine tune on CV

Please be kind I'm learning
Thank you to everyone in advance that can help

 

Welcome to AAC!

Would you by any chance have the circuit schematics? This would be a great help in providing you with proper advice.

 

 

Ths is the buck and boost convert in question there's no schematic it's getting powered directly from the computer power supply

All I've done is removed the trim pots from the board to ad in potentiometer on the front face panel for ease of use and want to ad in a fine or slow tune voltage option to accompany the cv 200,000 ohm potentiometer which matches the boards original 200,000 ohm blue trimpot I hope I'm right to do that I figured if that's the value I should replicate the original value for cc and cc

many thanks sorry no schematics

 

You will have to do some reverse engineering on your own.
Look at the bottom side of the PCB and see if the part number of the controller is visible.
I suspect that they are using LTC1625CS.

Next, you have to try and trace how the two pots are wired.
Are they wired as a potential divider (all three terminals go to different places) or are they wired as a variable resistor (the centre pin is connected to one other pin of the pot).

Next, see if you can find which pin on the LTC1625 the pot is connected.

 

 

I just realized the part number in first image is incorrect I apologize for any confusion this has made the first board with number is not correct sorry

 

Now that I can see the connections on the CV pot, it is wired as a variable resistor.
Take the resistance of the pot. Insert a fine control pot in series with the original pot, with a value of 10% of the original pot.

 

Already I see a challenge which is asking for "pot switches" to put on the front panel. Do you want continuously variable potentiometers OR do you want switches to choose preset voltages?
Next question is about the devices that you removed. They could be the board mounted 25 turn adjustable ones, or they could be the ones that turn about 200 degrees from minimum to maximum.
AND, no matter what, it is most likely that you need to have the same end to end resistance to make the circuit function correctly.
Sticking in a different resistance without understanding how that will affect the circuit is not a good choice.
Also, what output voltage range did the pots you removed cover?

 

Sorry everyone for late replies yes it's a variable trim pot part no 204 in both cc and CV measures at 200,000 ohms so I'd make the fine tune voltage pot 10% of original value which would be 20,000 ohms if I did my math correct ?

Hi sorry I've already got continuous fixed 3,5,12v out from the power supply but I also wanted and needed a continual varied output 1v to 36v or close to that which would be a separate circuit, I will how ever be feeding 12v from the fixed circuit to the variable circuit

My end goal here I already have cc a CV sorted trying to figure what Resistence value I'd need for potentiometer to run in line with course voltage so I can slow it right down for fine tuning

Thank you to everyone help was amazing and insanely fast help too I'm impressed once I've got it together I'll have to post up photos of my handy work for criticism so I can learn from mistakes so I can excel maybe one day I'll be good enough to help others aswell

 

CC fine adjust is trickier because I cannot locate an example circuit diagram for it.
By the way, do you understand that you cannot regulate both current and voltage simultaneously?
CC and CV controls are limits. The power supply is always on CC or CV, but not both at the same time. The PSU will be in CC or CV mode whichever limit is reached first.

 

Oh ok sorry I was under the impression all I'm doing is moving them off the board and running them externally so I don't have to open the box up to change the volts cv, so I can do it at the front so instead of using pots on board any time I want to change voltage out just relocate them to front panel

So this is not simply the case?, have to excuse my ignorance being new I thought it would be as simple as that I got the idea from watching many diy power supplies on youtube with the power source being a old computer power supply and a boost and buck converter (stepup and stepdown)

 

I found this sheet for the original adjustable trim pots that have installed in this board in this circuit, so the circuit is made I'm just relocating the pots

 

I found this aswell different sort of board much smaller in amps ability but exactly same of what I wanted to achieve being new to electronics I wasn't 100% sure on values for the pots to have the full sweep just like blue trim pots did

 

Look at the PCB trace for the CV pot.
The centre and bottom pins are joined. Hence you really only need to bring out two wires to your front panel course and fine control pots.

Don’t use the same blue trimmer pots for the front panel.
You want to use large panel mount pots with 1/4” shafts so that you can mount a proper knob on it.

I will post some pictures much later.

 

Thank you thought so, so you think 10% of the original value @ 200kohm would be good for fine voltage value I think that 5kohm maths is a weak point.which has to change quick lol

Or would I be best to build my own simple circuit instead of this prebuilt unit,

I added a YouTube link which I hope is ok this honestly looks a lot less complicated both are good for 10amps out I just want some that's heavy duty and will survive years of use in automotive industry side and my personal PCB projects learning to tinker with things

 

Hi all new to forum also like to say hi, I apologize in advance if this is in wrong section I'm new to electronics, and still learning the ropes of the basics so without doubt its laughable pleas be kind I'm new and learning this is my first project because every good enthusiast has a power supply, you say just buy one, yes I could and it would of been cheaper but I would not have close to the amount of amps output and I'm not learning

Ive built a power supply using computer supply,
So I've got a solid 3,5,12v output of 25a ea

I have also boost and buck converter board so I've got 10a adjustable between 1v to 36v I've removed the cc and cv trimpots both measured at 200,000 ohms, why I removed them is I want pot switches on front panel for ease of adjustment

The CC is 200,000 ohms
The CV is 200,000 ohms

I want to ad in a extra pot for fine tuning of the CV I can't figure it out I think I need to go lower number in ohms but how much is there a work around for this was thinking about 70% slower or what ever they are normally would be in commercially made power supplies, would this mean around 60,000-70,000 ohms for fine tune on CV

Please be kind I'm learning
Thank you to everyone in advance that can help

Upload the schematic of your power supply. Only then we can try to help you on this. But from your description above, if you need to add extra POT Resistors, surely it will be lower in Ohm each but your circuit will have to be modified surely.

 

Welcome to AAC!

Would you by any chance have the circuit schematics? This would be a great help in providing you with proper advice.

Exactly.!!!!

 

Exactly.!!!!

If you look at read clearly I'm making a diy lab supply that's using a computer power supply
Which I've taken the fixed 3,5,12v from as they have those 3 fixed voltage out on computer power supply and for the variable side I've added in a boost buck converter as pictured also with correct model number which also takes it power from 12v rail the power supply is not of issue or question I'm a newbie even I'm question this all I wanted to do was figure out how much lower value the pot / variable resistor had to go as I wanted to ad in a fine tune for voltage unsure what this has to do with power supply not even in th same ball park atm

I've relocated the cc and cv from trim pots to linear pot of same value they both work fantastic just wanted to ask about fine voltage and what value, is there a method to figure out a magix number or is it trail and era a user has already given solid answer

I am simply just only removing the PCB or breadboard variable resistors and matching those values with another 2 variable resistor with approx 6 inch wire between the boost buck converter and the 2 panel mount pots or variable resistors as per diagram shows nothing to with the boards power supply

Also stated I can not get the schematic of this boost buck converter it's a Chinese Ali express job, please look at schematic provides using a similar buck boost converter that's running same as me cc cv with added fv exactly I intend too

 

I found this aswell different sort of board much smaller in amps ability but exactly same of what I wanted to achieve being new to electronics I wasn't 100% sure on values for the pots to have the full sweep just like blue trim pots didView attachment 291034

I found this diagram exactly what I've done and intend to do the board they have used is a 3a the buck boost converter board I'm using is a 10a with cooling buck boost converter
I was going to ad a FV to the CV exactly as shown

My post all it asked for was there a way to workout magic value to slow the rate done enough when I turn pot it's usefull for fine voltage or fine tuning the course voltage the CV value is 200k ohms so what ohms would be suitable for fv or is it trail and error