potentiometer Questions

[electrocub]

I am building a schematic I found on the internet and it calls for a 5K potentiometer. The symbol that is on the schematic shows the typical pot with cw and ccw like this.

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ccw | cw
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I understand cw to be clockwise and ccw to be counterclockwise. I am using Eagle to design the board and the pot symbol that I am using shows a typical pot symbol with an arrow on the right side pointing to the center like below.


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| <-----
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I put the symbol in the circuit with the arrow pointing to the left corresponding with cw in the circuit design. Is this correct?

Also once I get the pot locked in the value that want it to stay in, I have been using ca glue and kicker to glue the pot where it is at to lock it in.
Is this ok? It seems that the pot value wanders in value either way and I would like it to stay at one value.

Thanks

 

[Torben]

There are a few different things you can do.

You could measure the resistance from the wiper to each side lug of the pot and then replace the pot with matching resistors, but this only works if you can come up with a resistor combination that is close enough to what you need to work.

You could also use a multiturn trim pot, which provides much greater accuracy than a regular pot, to set the initial value and then put a dab of nail polish (I'm not kidding) on the shaft to hold it in place. Nail polish is fairly easy to remove if you have to adjust later on, and it looks absolutely fabulous.


Regards,

Torben

 

[crutschow]

The CW and CCW pin positions are determined by the pot design. If you want the circuit to change in a particular way when changing the pot (CW increases gain, for example) then you need to layout the board with this in mind. The symbol on the schematic may not be sufficient to properly orient the pot on the PCB for that purpose.