Transforming Soft Touch SPST into bypass?

[phector2004]

Hi everyone,

I'm getting my summer builds all ready, and have two momentary SPST stompswitches I'd like to make some use of. I'm thinking of doing momentary bypass...

Is there any small bypass circuit I can use with an SPST? How can I design something of the sort to fit into a small space? (~ 1" x 1")

I'm thinking I could send 9V to an N-FET's gate to pass the clean signal to the output while doing the same to a P-FET to stop the modulated signal from reaching the output...

[Hides-His-Eyes]

If current isn't an issue, G6A-234P or derivatives

The trouble with latching footswitches is that they work with non-latching relays that have an inherent current cost to them (only when the pedal is on, but you're talking a considerable amount)

[phector2004]

Of course!

I've never dealt with relays before, and assumed they were all latching. I don't use batteries any more and I doubt the 15-20mA it draws will cause any problems

Any good links on implementing relays? Or is it as simple as putting 9V --> switch --> coil --> ground?

Thanks for the suggestion!

[3080]

Hi everyone,

I'm getting my summer builds all ready, and have two momentary SPST stompswitches I'd like to make some use of. I'm thinking of doing momentary bypass...

Is there any small bypass circuit I can use with an SPST? How can I design something of the sort to fit into a small space? (~ 1" x 1")

I'm thinking I could send 9V to an N-FET's gate to pass the clean signal to the output while doing the same to a P-FET to stop the modulated signal from reaching the output...

Look at the schematic here: http://www.freestompboxes.org/viewtopic.php?f=1&t=10945 (bottom, left part of the schem)
There is the "bypass" circuit. U13 is 4024.
You could connect the 4024's 12 pin with R1 from here: http://geofex.com/FX_images/relay%20true%20bypass%20with%20Boss-Ibanez.gif (R1=1M, C1=4n7, D1=1N400x)

... by this you can control a non-latching DPDT relay with a momentary switch for true-bypass!  

[3080]

the first link again: http://bit.ly/jawW9O

[phector2004]

Got it the first time  

It seems overcomplicated, though... I've already got a 3PDT, I just want a momentary bypass using the SPST switches I accidentally ordered

** EDIT: not bypass... a momentary ON switch **

[cpm]

SPST is just a open/closed connection. you have to figure how to use that in your circuit, but you wont get a proper (true) bypass with that.
Can be used to disable oscillation on a tremolo, push the feedback in a delay, etc

however, the simplicity of an SPST is what i like about them, i guess they are less prone to mechanical fail than a more complex latching dpdt or 3pdt. Smallest (true) bypass i can think is a latching relay and a PIC for control (plus a 5v regulator, and probably 1 or 2 transistors to drive the relay). All that could be reduced to a 1x1" size

[Hides-His-Eyes]

Of course!

I've never dealt with relays before, and assumed they were all latching. I don't use batteries any more and I doubt the 15-20mA it draws will cause any problems

Any good links on implementing relays? Or is it as simple as putting 9V --> switch --> coil --> ground?

Thanks for the suggestion!

I've used the following arrangement for stereo TB in a different pedal; just be aware of the funky pinout of the switches themselves on the relays I recommended.

[phector2004]

Thanks!

I'll try it out when I get my hands on a relay

[Hides-His-Eyes]

be aware if you're only using one then one of the coils should be replaced by an appropriate resistor to get approx 5V across a 5V relay (signal relays seem to come mostly in 5v or 12v)