I'm a beginner at building electronic circuits and this started as me working on a small project and just kind of went off on the mental tangent of no return.

How to connect multiple potentiometers in series taking each potentiometer's value into account and still be able to use the entire assembly as a potentiometer and NOT a rheostat.

Having four different potentiometers of different values 10k, 20k, 30k, and 40k.

The minimum wiper resistance is 0R and the maximum is the combined value of 100kR (tolerances notwithstanding of course).

Attached is what I came up with, I only have one pot from a kit or I would try it out.

Mentally walking through it I think I got it nailed but, I'm in California, and as everyone know Californians aren't "all there" to begin with.

So two things I'm asking is:

1) Am in the ballpark or do I need to rethink my thinking?

2) Is there a valid reason why someone would want to do this? Only reason I can think of someone doing this is for a variable voltage divider/ladder with multiple variable rungs, but can't imagine why anyone would want to pull all their hair trying to make adjustments.

TIA,
Mike

 

The reason someone might want to put two trim pots in series would be when one desires course and fine adjustment. In such a case the pots would have widely different values such as 10:1 or 20:1 ratios. Three pots in series would provide no benefit.

In your particular example, the trim pots set the maximum voltage at the wiper of the potentiometer. Since the accuracy on the setting of the wiper is no better than 10%, there is no need for multiple trim pots.

 

Thank you for the reply.

I understand that there is no need for multiple pots, as I said it's merely a mental exercise on my part wondering if I at least (in theory) have the wiring correct.

Although if I were to have coarse and fine adjustments wouldn't it be handled with a rheostat and a potentiometer and not multiple potentiometers? As I said I'm a beginner and using even just two pots seems the reference on the voltage divider (which is what a pot basically is) of the first pot would be lost.

Effectively (I think) what I'm doing in the diagram is converting 4 of the pots to rheostats and using only the last pot as a pot, but I'm also thinking that as a voltage divider my thinking may be flawed cause the high/low references of the divider is only taken into account in the last pot and not the previous four?

Only way I can think to resolve this would be by throwing static resistor into the mix (in parallel?) for it to have any real meaning.

Mike