Switching question.

[BMF Effects]

I've racked my brain and I think I know that I can only do this one way but I wanted to throw this out there in case I missed a possibilty.

I need to switched between three electrolytics. My target values are 2.2uF (Less), 4.7uF (Stock) and 10uF (More). Because of space limitations a rotary switch is not an option. What I've arrived at is using a DPDT on/off/on with a a 2.2uF, another 2.2uF and a 10uF which would yield -

4.4uF in the up position (Stock)
2.2uF in the middle position (Less)
12uF in the down position (More)

Is there any way I can wire this to yield -

2.2uF in the up postion
4.4uF in the middle position
12uF in the the down position

I'd like the middle postion to be the Stock setting but I don't think it's possible with a toggle. Have I overlooked anything? Thanks.

[db]

Can you arrange it with two caps in series e.g. 2 4.7uFs in series gives 2.3uF, but short one out and you've got 4.7uF.  Just a thought.

[BMF Effects]

Can you arrange it with two caps in series e.g. 2 4.7uFs in series gives 2.3uF, but short one out and you've got 4.7uF.  Just a thought.

That thought crossed my mind but I don't think you can wire the caps to be one set series and one set parallel and share a common cap.

[R.G.]

Can one terminal of the caps be grounded?

That is, are you switching signal through these in series or using them as a shunt to ground?

[BMF Effects]

Can one terminal of the caps be grounded?

That is, are you switching signal through these in series or using them as a shunt to ground?

Signal is being switched through them.

[BMF Effects]

Would it be easier or possible to figure out a way to mount the caps on the circuit board and use the switch to change the values that way? Did that idea even make any sense?

[db]

I don't think there is a way to do what you want with the DPDT.  The problem is that you want the middle (switch off) position to provide 4.7uF and then by connecting one pole, provide 2.2uF.  I can't see a way of connecting 2 points in a network of capacitors to reduce the overall capacitance.  Which ever whay you look at it, this can only ever increase overall capacitance.

I do hope I'm wrong though, as it would be really good to see a clever idea to solve this.  I think the general problem here is : how to turn a DPDT into a SP3T.

My suggestion, however unhelpful, would be to get a SP3T.  This would be just as compact and would give you exactly what you need.

[Seljer]

and get you prettymuch the exact values

but for available capacitor values try
2.2 for the top left one
10 for the bottom left one
4.7 and 3.3 in parallel for the right one

and it should give you 2.2, 4.8 and 12.2

[DocHeavy]

This is a little messy but.....