[simpits-tech] Momentary Toggle switches

[Jims Parambus Account]

Rick,

You have just described the principle behind the early electronic
ignition systems for car engines that still used points in their
distributor.
What it also covers is points switching for model railways.
It is commonly referenced as "CD" (capacitor discharge), and
yes it should work for you as long as you do not get relay bounce.
This little problem can be easily cured by a capacitor and resistor
in series across the relay contacts that will effectively "quench"
any spark caused by bounces.
You will need to experiment with the size capacitor that you use for
the main relay call-and-hold circuit. You need the relay to hold
ON for the time that the electronics connected to it see it as a
keystroke. Remember that some I/O devices scan the inputs so the
sopftware needs enough time to see the relay contacts closed for
at least one look during the scan period. Check the specs and
method of input detection of the interface you intend to use.

BTW, the switch needs to be a single-pole change-over with spring
bias to one position.

Jim.

-----Original Message-----
From: simpits-tech-bounces at simpits.org
[mailto:simpits-tech-bounces at simpits.org] On Behalf Of Rick Davis
Sent: 03 June 2008 22:39
To: Simulator Cockpit tech list
Subject: [simpits-tech] Momentary Toggle switches

Gene,

I was looking at a post on the site awhile back about tearing apart toggle 
switches (so they would still work like a real switch, but could be used for

a single keystroke (using a keyboard card))

Weak eyes and big mitts make that a challenging proposition for me. Has 
something different developed since then?

I was thinking (rare function for me) that you could wire a small 5 volt 
relay to a regular toggle switch. When you close the switch, it would 
discharge a voltage from a very small capaitor to the relay. One which would

hold only enough juice to click it once and all over. Then when you turn the

switch off (being SPDT) it would connect the capacitor to a supply voltage 
to charge it up for the next run. I guess you'd have to have a seperate cap 
for each position, but they are pennies a jar.

Any of this make any sense or can I just buy something like that at Radio 
Shack?

Rick


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Thanks!