converting switches to triggers (was: trigger inputs on toys)

[media at mail1.nai.net]

At 12:00 AM -0400 04/29/98, Chris ('the Hex') wrote:

>This is probably a blatant newbie question, but I think it may help not only
>me but a lot of newcomers who've done some noodling but don't have a strong
>EE background (or a even a weak one :-/ ).  Is there a common circuit or
>method for converting a switch -- just an open or closed junction, like the
>buttons on the
>toys being described in the previous post -- to a trigger input?  I imagine
>this is a common mod, but I've not yet come across a simple explanation of
>how it works.  Any takers?  If there are good references for this sort of
>thing that I should be looking in, you could just post the names of these
>books to the list...

Yes, there is a common circuit that does this and it is called an
"S-Trigger converter."   I've built so many for myself and other people I
could probably build one in my sleep.  In fact, if I wasn't so busy and
behind on my email, I would be building a group of four of them (one with a
pulse stretcher for a Vortex) for a friend of mine with my new Weller WTCPT
right now.

Anyway, there should be some nicely illustrated ones up at Music Machines
at hyperreal.com and on several Moog related sites.  This is a lousy ascii
one I keep on my hard drive for when I answer this question every two
months:

>here's from the sept. 89 issue of electronic musician, p70:
>
>
>                                                    S-trig out
>                                          ----------| |--------
>      Gate        10k                    /                    |
>	[v-------/\/\/\---------+-------| 2N3904             ---
>        |                       |        v                   ///
>        |                       -        |
>        |              1N4148   A        |
>        |                       |        |
>       ---                     ---      ---
>       ///                     ///      ///
>
>
>and here's another one from the paia kit, pretty much similar to the above:
>
>
>                                                    S-trig out
>                                              RadioShack #274-201
>                                            1-gnd, 2-voltage (5~15v;0v active)
>                                          ----------| |--------
>      Gate (0v;5v active)                /                    |
>	[v------------------------------| 2N3391             ---
>        |                                v                   ///
>        |                                |
>        |                                |
>        |                                |
>       ---                              ---
>       ///                              ///
>
>
>------- End of Forwarded Message
>
>Right, you can do it with an NPN transistor and a 10K resistor... (or
>47K or whatever you have at hand...)
>
>one end of resistor to gate signal, other end to base of transistor.
>Emitter of transistor to ground of incoming gate signal, and ground of
>Mini' S-trig input. Collector of transistor to S-trig signal input.

PEACE OUT :)
MARK