Relay question

Jim Brain brain at
Fri Nov 28 16:02:10 CST 2014

On 11/28/2014 3:21 PM, Chris Elmquist wrote:
> On Friday (11/28/2014 at 12:23PM -0800), Chuck Guzis wrote:
>> On 11/27/2014 11:23 PM, Jim Brain wrote:
>> I'm trying to wrap my mind around the problem.  Does this describe it?
>> You want a push-on push-off circuit using only mechanical relays.
>> Am I reading you correctly?
> How 'bout this,
> They show a 24V supply and relay coil but I see no reason a 12V supply
> and coil couldn't be substituted.
> The RC network is there to basically give you "opposite polarity" each
> time you press the button.  It's charged to roughly the supply voltage
> when the relay is unenergized and when you press the button, dumps that
> into the coil to pull in the relay.
> Then, while the relay is energized, the RC network decays to close to
> 0V and so when you press the button again, it pulls the topside of the
> relay coil to 0V, dropping out the relay.
> The RC network is the memory part of your "D flip-flop" :-)
> You will need a DPDT relay though so that the other set of contacts can
> control your load.
> Chris
I looked it it, but it doesn't seem to support the 3rd state (do nothing).


Jim Brain
brain at

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