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

[Rushey]

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?

 

[BobK]

What are you connecting to the input and output when they blow? Have you tried the same power and load with the original pots installed?

If you set the replacement pot to 1/2 it's rotation, it should not be able to blow anything no matter how you connect it.

Bob

 

[kellys_eye]

The pin connection on the blue multi-turn potentiometer is NOT the same as that of the board mounted preset. The 'tapped' connection is usually the centre pin on the board mounted preset but is usually the BOTTOM (nearest the base) of the multi-turn potentiometer.

Show us exactly how you connected them.

 

[Rushey]

What are you connecting to the input and output when they blow? Have you tried the same power and load with the original pots installed?

If you set the replacement pot to 1/2 it's rotation, it should not be able to blow anything no matter how you connect it.

Bob

Thanks for the reply Bob.

When the unit arrives I test it with a 12v supply and just a multi meter and its fine. Then I replace the volt and current pots and with no load the same test it works for a while then it drops to the nominal voltage to between 2v and 5V and on one occasion blow a capacitor.

 

[Rushey]

The pin connection on the blue multi-turn potentiometer is NOT the same as that of the board mounted preset. The 'tapped' connection is usually the centre pin on the board mounted preset but is usually the BOTTOM (nearest the base) of the multi-turn potentiometer.

Show us exactly how you connected them.

Again thanks for the reply,

I am aware that the blue multi turn has a different pin set up and did allow for this.

Thanks

Rob

 

[davenn]

Thanks for the reply Bob.

When the unit arrives I test it with a 12v supply and just a multi meter and its fine. Then I replace the volt and current pots and with no load the same test it works for a while then it drops to the nominal voltage to between 2v and 5V and on one occasion blow a capacitor.

so obviously you are still doing something wrong

please do as @kellys_eye asked and show us exactly how you have wired them..... PHOTOS, not drawings ( top and bottom side of your board)

Again thanks for the reply,

I am aware that the blue multi turn has a different pin set up and did allow for this.

Thanks

Rob

so you are aware that you are also using a single turn pot for one of the multi turn pots ?

why?

Dave

 

[kellys_eye]

Are you using the correct VALUE pots?

 

[BobK]

@kellys_eye :

always make sure I match the resistance value of the original

Bob

 

[kellys_eye]

@kellys_eye :



Bob

Yes, but it's easy to misread the coding on those presets - just double-checking.

 

[Alec_t]

It's possible that the inductance of lengthy wires to the pots is causing circuit instability/oscillation and consequent overheating of components.

 

[Rushey]

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 Alec 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.

Thanks Again

 

[davenn]

and not mixing multi turn and single turn (I have only tried both types in pairs) and wiring the pots in the same orientation

you photo shows that you are mixing multi and single turn pots
so is your photo not correct ?

 

[kellys_eye]

An actual picture of the board(s) you are using, how you've soldered to them and the wiring/arrangement of the potentiometers would make a HUGE difference to how we can respond to this problem.

 

[Rushey]

you photo shows that you are mixing multi and single turn pots
so is your photo not correct ?

The picture is only an illustration of what I was trying to do with the different components I have used as per my narrative.

 

[Rushey]

An actual picture of the board(s) you are using, how you've soldered to them and the wiring/arrangement of the potentiometers would make a HUGE difference to how we can respond to this problem.

Hi Kellys Eye

I have unsoldered it now but I have attached a view of the actual board front and back and a illustration of exactly what I tried to do.

Thanks for your help and understanding.

 

[(*steve*)]

Were the original multi-turn trimpots 200k?

 

[Rushey]

Were the original multi-turn trimpots 200k?

Yes they were W204

 

[davenn]

The picture is only an illustration of what I was trying to do with the different components I have used as per my narrative.

then please don't do that in future … it caused several of us to be confused about what you were saying

always post your own pix so we know exactly what you are talking about …. otherwise it just wastes peoples time

 

[davenn]

I have unsoldered it now but I have attached a view of the actual board front and back and a illustration of exactly what I tried to do.

and now again, you have shown the wrong type of pots !

if you are going to show us what you are doing …. YOU MUST show us exactly what you are doing
That pix gives us zero idea of if you have wired up correctly whatever pots you are actually using

PLEASE SHOW US PHOTOS OF YOUR ACTUAL CONSTRUCTION


You want people to help you, you have to do you part in supplying the real info