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Vintage threads from the first ten years

SPST Momentary Switch

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6/30/2000 1:42 AM
Ryan	SPST Momentary Switch Can anyone provide me with a lead to where I can find these switches (I'm looking for a style to what Mesa/Boogie uses for their momentary switches). I've looked everywhere without successs Again, any leads to these switches would be REALLY appreciated. Thanks! -Ryan

6/30/2000 3:40 AM
marrk	Ryan, If you are looking for the ones that switch channels, they are regular SPDT. If you mean momentary, where in/on the amp do they use them? Mark

6/30/2000 2:47 PM

Mark, I do mean the Momentary type... I'm building a footswitch with 4 switches, If I were to use normal SPST or SPDT (non momentary) I would have to turn one off and another on (or I would have 2 channels on my amp ON at the same time). The fix, use a latching CMOS driver (which requires you use momentary switches). The circut is based on the CMOS switching scheme Randall Aiken has got over on his site.
-Ryan

6/30/2000 3:23 PM

Randall's design is a good, straightforward one using good CMOS design practices.

However, if you're willing to live with some MML (that is, Mickey Mouse Logic 8-)

8-)

then there is an alternate solution for the footswitch logic. See "switching with the CD4053" at GEO. The 74C373 will latch one to eight momentary footswitches. It can actually be done with only the 373, but I stuck in an inverter chip in front to make for momentary switches to ground instead of momentary switches to +V.

If you're messing with this, you may also be interested in the "programmable FX switching system" also at GEO that lets you pre-program a number of patches of effects plus control the reverb/tremolo etc. on your amp as pre-set patches.

GEO also has a circuit for driving latching relays so you don't have to power the relay coil the whole time it's on.

7/1/2000 1:03 AM
Ryan	RG, I was actually planning on basing my "programmable switcher" (great idea BTW!) on the CD4053 chip as well as for my amp footswitching... but the question still remains, I can't find the momentary Stomp switches anywhere -Ryan

7/1/2000 2:41 AM

OK, here's a trick to do this.

All the switches commonly used as stomp switches are break-before-make switches. That means that the contact with the first throw is opened before the contact is made with the second throw, so there is a fractional moment in there where the pole is not connected to anything - completely open. If you tie the pole to a resistor to ground, and wire *both* the throws to V+, every time you click the switch, the pole is pulled to ground for a few milliseconds. Bingo - momentary stomp switch.

This is right out of Kevin O'Connor's "The Ultimate Tone", but I suspect it's a really old trick that he rediscovered.

You could also do a trick with CMOS XOR gates to get one pulse from an alternate action switch.

Mouser sells vandalism proof switches intended for vending machine, elevator, etc. use that are pretty robust. I believe that they are momentary as well.

Yell if this doesn't hit something useful.

7/1/2000 2:03 PM
Ryan	Wow! both GREAT ideas... I think I'll try both, although I think using some CMOS logic would be alot more fun. Thanks again! -Ryan

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