relay that stays closed until power removed?

You want a latching relay. The latching function can be done with a set of contacts on the relay that parallel the contacts of the "Do Not Push" switch or you could use the "Do Not Push" switch to trigger an SCR which operates the relay. Either method will keep the relay energized until power is removed.

John

A SPST NO switch and a latch. You can use a flip-flop for the latch, then if you really want to geek it up, you could put a NC magnetic reed switch behind the (aluminum) panel somewhere so that you could reset it with a little pocket magnet. :-)

I'm pretty sure you can make a latch with a couple of cross-coupled transistors or even gates as well.

Have Fun! Rich

(view with a fixed-width font)

o o | | | relay coil | | push-button _ | | --- / \ | .------o o------o-----( K )---------| | | \_/ | | | | | | | | | | .-------||------' | | | | relay contacts | | .----------------' | | | | __ /| | 'o-| | | '-------||----------o-|__| | \| (created by AACircuit v1.28.6 beta 04/19/05

Use an ordinary 12 V, double pole relay. Wire the push button in parallel with one set of contacts and the other set of contacts in series with the siren. When the button is pressed, both sets of contacts close. One set is "sustaining" and keeps the relay energized once the push button is released. The other contacts power the siren. When power is removed, the relay coil releases the contacts, so when power is subsequently applied, the siren stays off. Lather, rinse, repeat.

Kind of like this.

/ / ,---O O---------------, | | | | | | +-----||||----, ,---+ | | | UUUUUUU | | | '--------------O O----' \ \

But with another normally-open switch on the relay for the horn on a separate circuit loop.

I'd want to include something that would automatically cut the power at some point later. sci.electronics.design had posted a nice circuit for that some time back:

Approximately, for a 30 second blast.

Jon

"Greg Russell"

Then use a cheap push switch and resistor of say 1000 ohms from anode to gate to pulse it into conduction.

A C106D1 would be suitable.

.... Phil

this one's simpler than the others have been making it seem. you need an ordinary 12V automotive relay

just wire the relay coil and the horn in parallel so that when the horn is powered so is the relay.

then wire the button and the realay contacts in parallel so that that either can conduct power to the horn.

T 10A ----- fuse +----o o---+----o\o-----+ | | | | | ----- | _- | --- | _- | . (30) +----o : o---+ (87) . 12V | : . battery | : . (85) +-----[/]----+ (86) . | | ----- | | --- | | | +---{HORN}---+------------+

the numbers shown will match the numbers impressed in the base of many automotive relays

Any push button switch that is strong enough to run the horn will suit. (contacts rated 3A or more)

won't the SCR shut down when the horn contacts open?

Hell, I'm not familiar with all the basic electronic component names; I'm just learning, and need some help please.

I want to create an electronic joke for a friend's shop trainer: a push button on the console of the trainer will be labeled "Do Not Push". If someone chooses to push it, an electric horn will sound until the 12v battery source is disconnected.

What type of switch or relay is it that will close and sound the horn when the button is pushed, but will stay closed when the button is released, then open when the power source is disconnected?

Don't forget the most important part of your plan. What if he doesn't push it?

exactly..

Jamie

"Geoff" schreef in bericht news:Xns9F0AEFC717080Geoff@88.198.244.100...

Technically it fits perfectly. Practically I doubt whether any of the ideas provided will do for the OP. He needs a a OPSS relay or an SSR. Does he know what they are and how to connect them? Can he read the schematics? As long as the OP does not react on the provided stuff there is no need to provide more info.

petrus bitbyter

On Tue, 21 Jun 2011 14:55:44 +0200, petrus bitbyter wrote in

Well, I'm trying to understand everything that's been presented. I won't have access to the horn information (amperage) until July 5.

I didn't mean for the discussion to erupt into a fight with name-calling etc.

I'm sorry for that, even though it's not my fault. I tend to run and hide when things like that happen.

Phil A. is a good pro audio EE with some mental health issues t. Listen to what he says about audio, but don't mind his vituperation--he can't help it.

Cheers

Phil Hobbs

"Greg Russell" schreef in bericht news: snipped-for-privacy@mid.individual.net...

"I'm sorry for that, even though it's not my fault. I tend to run and hide when things like that happen."

You should not. We live in an insane world after all and the internet does not filter most of the patients. (Not even me :) So stick at the facts concerning your question and disregard the rest.

Though to be able to give any more help, we need some more information. Like the amperage of the horn for example. Are you able to read electronic schematics? If you can't it's no use to provide one without at least some extensive explanation.

petrus bitbyter

Good point. No point in having a booby trap if you don't have a booby.

Then you label it, 'DO NOT PUSH THIS BUTTON!!!'