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Please can I have some help with a boost/buck convertor? Answered

Hi

I want to use one of the cheap boost/buck convertor to increase and decrease variably my 12v power supply. I have now purchase and (bricked) 4 now as each time I remove the board bound pots and solder in ones I can mount on the front panel I must wire them incorrectly even though I mirror the pin set up. I have tried all types of pots single turn and multi-turn always make sure I match the resistance value of the original.

Please help, what is this rooky doing wrong?

Discussions

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Jack A Lopez

1 year ago

I still have not found a published circuit diagram for this gizmo, or even a data sheet for that little IC on the back, which appears to be named, "sh1215cs" or "shi215cs"?

However I have found that your power converter module is popular. There are lots of people discussing it. In fact I have even found anecdotal evidence that someone has done the mod you wanted to do, and changed out the pots on the board, with some panel mount ones. Here:

https://forum.banggood.com/forum-topic-280657.html

I mean, I think this is strong evidence the modification you want is not impossible.

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Rushey

1 year ago

Thanks for all your replies Guys


I am matching the resistance values, and not mixing multi turn and single turn (I have only tried both types in pairs) and wiring the pots in the same orientation. I think I goes wrong when I change the current pot, perhaps it is as someone has suggest the 6 inches of wire added to the circuit. It may be I am effecting the reference voltages on the boards. And it is true to say I can not find any boost/buck unites pre-wired with front panel pots and this may be why.

However photos attached as requested.


Thanks Again

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Jack A LopezRushey

Answer 1 year ago

Usually the voltage signals on these pots are DC, like defining a reference DC voltage level. Somewhere else in the circuit is a comparator that looks at that reference voltage and compares it to a voltage intimately related to the output voltage, or current, or whatever is being regulated.

For this reason, because the signals on the pots are DC, I would not expect long wires to make any difference, like they would for very high frequency AC.

You know, the actual DC resistance in a 15 or 30 cm length of copper wire, it is like tenths, or hundreths, of an ohm, which is tiny compared to the resistance seen in the pot itself, which is probably some number of kilo ohms.

In contrast, for AC signals, depending on frequency, long wires can look like inductance, or capacitance, or even like a transformer or an antenna. That's my explanation for why long wires sometimes mess with AC signals.

Of course, if you want some insight into what a particular pot is actually doing in your circuit, that will require discovering the circuit diagram, and pondering it.

Sometimes discovering the circuit diagram is a tedious matter of squinting at the board, and mapping out the connections on paper, for to see which wire goes where.

Sometimes discovering the circuit is much easier. In particular, it is much easier when the circuit diagram has already been published somewhere by someone.

Such is the case when the circuit being used on your board is the same as one of the example circuits, published in the data sheet for the IC that is doing the regulating.

In other words, in the fortunate case, you just look up the data sheet for that IC, and there's your circuit diagram, often on the bottom of the first page.

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iceng

1 year ago

Please take a very good picture of the back side traces if any.

Then a component side pic of the pots removed from the board.

Then I may be able to offer what you ask.. ( It is a two way street )

And more then drawing some lines ;-)

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iceng

1 year ago

Do you know how to use a VOM ?

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adhith94

1 year ago

Hello there...

Are you sure that your external potentiometer pins are conneted in the same way as that of the PCB mount potentiometer.

The only thing that you have to see is that the pins are soldered in the correct place. Usually in the PCB mount type the pins would be inscribed on the outer blue plastic case as 1, 2, 3

If your external pot when placed the rotary shaft upwards, are numbered from the left to right as 1, 2, 3

Make sure that you have soldered the pins in the correct order and it should work fine.