Is there a toggle switch like this?

[Onion Ring Modulator]

Here's what I want to do: have 3 different capacitor choices to the same single connection on a PCB. The switch would be three position, and would connect 1 of the three capacitors to the pcb via wiring depending on the toggle position. I've been staring at a 4PDT for 30 minutes now and I don't think that's my solution, but is there even a solution?

Thanks!

[EBK]

A SP3T* or a SPDT (ON-OFF-ON) would work.

*Sometimes called a DPDT (ON-ON-ON)

[EBK]

For the ON-OFF-ON switch, you would wire up your lowest cap value and use the switch to parallel different cap values with it in the ON positions. 

The ON-ON-ON switch is the better option if the switch position for each value is important.

[Mark Hammer]

1) What value-range of caps are we talking about?  Is this in the nanofarads, hundreds of uf, or what?

2) When I want a choice of 3 different capacitance values, I use an on-off-on SPDT toggle.  I can use the smallest value as the "default" on the board and use the toggle to add in other caps in parallel to arrive at each of two large values.  Alternatively, depending on the values needed, I use two caps in series, and the same toggle either leaves them in series or bridges the one or the other.

For example, a 100pf and 150pf cap in series yields 60pf.  Leave them as is and you have 60pf.  Flick the switch to bridge the 150pf and you now bump the resulting capacitance up to 100pf.  Flick the switch in the other direction to bridge the 100pf, and the resulting capacitance is now 150pf.  An easy way to change the delay range of many chorus pedals.

Works like a charm, but the math can be tricky.  The available standard values of capacitors may not always work in one's favour, in which case adding caps in parallel makes a better choice.

Note that a cap left "hanging" (one end unterminated) can often produce an audible pop when it is once again connected.  The two-caps-in-series solution avoids that because both caps are always connected.  Switch-popping of caps in parallel can be avoided by having each of the secondary added caps in series with a 1M resistor.  The switch is then used to bridge that 1M resistor to make a given additional cap "active".

[PRR]

You are already in the realm of rotary switches (or long slide switches). Yes, Mark's technique does work, but what if you want four choices? (Or two?)

[ElectricDruid]

For the ON-OFF-ON switch, you would wire up your lowest cap value and use the switch to parallel different cap values with it in the ON positions. 

The ON-ON-ON switch is the better option if the switch position for each value is important.

+1 agree. If you don't care about having the options "in order", you can do it with a ON-OFF-ON SPDT. If you want full control over what value goes in which switch position, you need the DPDT ON-ON-ON type.

If you want to go beyond three options, Paul is right and you're probably into rotary switches.

[Mark Hammer]

You are already in the realm of rotary switches (or long slide switches). Yes, Mark's technique does work, but what if you want four choices? (Or two?)

Two can certainly be done with an SPST switch, using either method I described.

Four CAN require a rotary switch, but a pair of toggles can also accomplish the same number of >3 choices in less space.  There is perhaps more to remember (this switch has to be up and this one down), but simpler in many ways than installing a rotary switch.

And of course, there is always the dipswitch option.

[EBK]

More details on the DPDT ON-ON-ON version:
https://smallbear-electronics.mybigcommerce.com/dpdt-on-on-on-solder-term/

To wire such a switch as SP3T, you just do this:

[Onion Ring Modulator]

Awesome! thanks for all the replies and ideas.

To clarify, what I'm thinking of doing is trying to put in place both tone mods mentioned in the build doc for the Aion Klon, just in the interest of overkill. So, a choice of 3n9, 6n8, or 8n2 on C14.

[ElectricDruid]

Awesome! thanks for all the replies and ideas.

To clarify, what I'm thinking of doing is trying to put in place both tone mods mentioned in the build doc for the Aion Klon, just in the interest of overkill. So, a choice of 3n9, 6n8, or 8n2 on C14.

Ok, so the ON-OFF-ON SPDT option would be to use a 3n9 for the off position in the centre, with an additional 2n7 on one lug and either 3n9 or 4n7 on the other lug.

3n9+2n7=6n6, definitely close enough - within 3%, very good for caps.

3n9+3n9=7n8, or 3n9+4n7=8n6. Bear in mind these values are probably +/-10%, so 7n8 could be as high as 8n6, and 8n6 could be as low as 7n7. If you got really choosy, you could select caps to give exactly the values you're after - I'm just giving you the "average" based on the marked cap value.

Alternatively use the DPDT ON-ON-ON option, and pick any three caps you like. It's easier from a user's point of view but a bit more complicated and expensive parts-wise. And, as mentioned, given the tolerances, it doesn't necessarily give you better values. What it does do is allow you to put them in a logical order, if that matters (How twitchy is your OCD?!?).

[duck_arse]

(How twitchy is your OCD?!?).

twitchy enough that I'd have to add - there is two patterns of on-on-on switch. you need to check the specs on the switch in hand.

[ElectricDruid]

(How twitchy is your OCD?!?).

twitchy enough that I'd have to add - there is two patterns of on-on-on switch. you need to check the specs on the switch in hand.

"Always read the datasheet"?

Famously good advice, rarely taken

[Onion Ring Modulator]

Awesome! thanks for all the replies and ideas.

To clarify, what I'm thinking of doing is trying to put in place both tone mods mentioned in the build doc for the Aion Klon, just in the interest of overkill. So, a choice of 3n9, 6n8, or 8n2 on C14.

Ok, so the ON-OFF-ON SPDT option would be to use a 3n9 for the off position in the centre, with an additional 2n7 on one lug and either 3n9 or 4n7 on the other lug.

3n9+2n7=6n6, definitely close enough - within 3%, very good for caps.

3n9+3n9=7n8, or 3n9+4n7=8n6. Bear in mind these values are probably +/-10%, so 7n8 could be as high as 8n6, and 8n6 could be as low as 7n7. If you got really choosy, you could select caps to give exactly the values you're after - I'm just giving you the "average" based on the marked cap value.

Alternatively use the DPDT ON-ON-ON option, and pick any three caps you like. It's easier from a user's point of view but a bit more complicated and expensive parts-wise. And, as mentioned, given the tolerances, it doesn't necessarily give you better values. What it does do is allow you to put them in a logical order, if that matters (How twitchy is your OCD?!?).

Thank you kindly! i was just getting ready to do all this math and then decided to check my thread first. My OCD says they should be in order of value, top to bottom.

[iainpunk]

(How twitchy is your OCD?!?).

twitchy enough that I'd have to add - there is two patterns of on-on-on switch. you need to check the specs on the switch in hand.

"Always read the datasheet"?

Famously good advice, rarely taken

datasheets on switches can be notoriously be lacking in an actual description of which contacts are 'on' in which position.
especially if youre nor buying big brand switches.

cheers

[Ben N]

twitchy enough that I'd have to add - there is two patterns of on-on-on switch. you need to check the specs on the switch in hand.
...
datasheets on switches can be notoriously be lacking in an actual description of which contacts are 'on' in which position.
especially if youre nor buying big brand switches.

Or you could just map it out with a continuity tester. But never assume.

[anotherjim]

Toggle switches can be easy to understand. At least 0n-Off, On-On and On-Off-On are.
The middle lug is the common contact.
A switched contact is made to the common contact on the *opposite* side the toggle lever is pointing.

An On-On-On can go its own way. Mechanically it might have both outer contacts sprung to make the common when the lever is centre and break the opposite contact when the level moves over.

What we do is clip the DMM on and see what contacts make or break by measuring resistance and make our own drawing. Even if we "know" the layout do it to prove it's a good switch.

As the project is OCD, you will have to work out your cap combination values to within +/- 10pF or it won't be any good and you won't sleep at night worrying about it.

[Ben N]

Never mind. Mis-post.

[iainpunk]

twitchy enough that I'd have to add - there is two patterns of on-on-on switch. you need to check the specs on the switch in hand.
...
datasheets on switches can be notoriously be lacking in an actual description of which contacts are 'on' in which position.
especially if youre nor buying big brand switches.

Or you could just map it out with a continuity tester. But never assume.

2 things, this forum is supposed to be politics free, and projection much?

cheers

[Ben N]

Hah! I didn't even notice the political symbol. I'll change it to something less provocative.

[Onion Ring Modulator]

As the project is OCD, you will have to work out your cap combination values to within +/- 10pF or it won't be any good and you won't sleep at night worrying about it.

I'll have to create a spread sheet with all the capacitor values I have and then a formula that will tell me which combination to use to create any new value. I'll also have to make sure to account for the extra enclosure space involved in possibly having a switch that has, like, 10 capacitors hanging off of it.