Switching a relay?

[HighFidelityGuy]

My friend has a guitar wah-wah pedal that he wants modifying to have a separate DC input (currently uses battery) and a "true bypass" switch.
After researching the true bypass part I've found that this is usually done with a DPDT switch. I've decided that it would be better to use a DPDT relay to get a slightly cleaner signal.

After pondering the issue for a while I've come up with this basic design for the relay and power input:




The relay in the schematic is SPDT because the software I used didn't have DPDT. Just ignore that bit. The main two bit's I'm unsure on is where to wire the switch in the 5V line and whether or not to use a separate input cap for each reg. I've put a switch under each place I thought it could go. So which place would be best for the switch and should I use two separate input caps? Or is the whole schematic a steaming turd? Please bare in mind that designing electronics circuits is not my forté, so I welcome any suggestions.

Cheers.

[Trickie_Dickie]

The input cap is fine as it is.

I'd put the switch between the cap and the diode.

[Reid Malenfant]

Looks fine to me Dave One capacitor feeding both regulators should be fine as long as they are within a few inches of each other. I'd put the switch on the positive line between the output capacitor & the diode

[Reid Malenfant]

So that's doubly told you then!

[HighFidelityGuy]

Thanks chaps!
Thinking about it a bit more that actually makes a lot of sense as if I but the switch before the cap it will probably stop the relay from actuating instantly due to the charge stored in the cap.

Now for my next two questions:

I got the value for the input cap (0.22uF) from the 7805 data sheet but I've just noticed that the 7809 data sheet recommends 0.33uF. So seen as I'll be connecting two regs, what input cap value do you recommend?

Secondly, would you recommend that I add any additional components to soften the switching in the circuit to prevent any pops? I think I've seen this done before but I can't remember how or for what application.

Cheers.

[Reid Malenfant]

Anything up to 1uf or more won't do any harm.

As your using a seperate regulator for the relay, any interference can't make it's way back into the other circuit, i think you have it covered

[HighFidelityGuy]

Thanks Mark,

I'll stick 1uF on the schematic for now but I'll have to see how much space there is in the case. I'm planning on using a film cap on the input. I think I read somewhere that the caps after the regs are best being tantalum's. Is that correct or would film or ceramic caps caps be better? I think THIS is the wah-wah pedal's schematic if that helps.

Here's my updated schematic:



Cheers.