Constant swich into momentary.

All frequent questions on switching: true or not true bypass, transistor-based or mechanical.
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Reintz
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Joined: 20 Jun 2010, 17:56
Location: Estonia

Post by Reintz »

Can someone please suggest a circuit that would convert constant switching into momentary switching.
I need this with my diy amp/pod footswitch. I'm using a 3PDT footswitch where first contacts switch amp channel, second contacts turn footswitch LED on/off and I need the third contacts to switch my pocket POD's presets up and down, but for that I need a momentary connection.
Pocket POD footswitch mod can be found here: http://joekataldo.com/blog/pocketpodfootswitchmod/61
I'm going to power the footswitch from a 9VDC supply. So I'm hoping to power the constant to momentary circuit by that aswell.
I have had no luck finding a relay that would do that.
All ideas appreciated.

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The G
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Post by The G »

My understanding is that you have a 2-channel amp and you want to press the footswitch to change the channels on the amp and on the Pocket POD - first push, channel 2 + Pocket POD next patch, second push channel 1 + Pocket POD previous patch.
If that's right, I think you need two monostables like in CD4098, one triggered on the positive edge and the other one on the negative edge. Each monostable will connect in parallel to one the Pocket down or up buttons through a relay or a transistor or - this is really not checked - even directly through resistors.

Reintz
Posts: 5
Joined: 20 Jun 2010, 17:56
Location: Estonia

Post by Reintz »

ggedamed wrote:My understanding is that you have a 2-channel amp and you want to press the footswitch to change the channels on the amp and on the Pocket POD - first push, channel 2 + Pocket POD next patch, second push channel 1 + Pocket POD previous patch.
Yes, you got it right.
Thanks for the idea.

Reintz
Posts: 5
Joined: 20 Jun 2010, 17:56
Location: Estonia

Post by Reintz »

Ok, this is what I came up with. CD4538 switching a relay through a transistor.
Image

I just put the circuit together on a breadboard and ran into a problem. When I engage the constant switch (S1) the cd4538 gives out a momentary pulse just like I want it do. But when I disengage the switch it gives out a momentary pulse again. And that's something I don't want. I only need an output pulse when I engage the switch. :slap:

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