Electronics question

[az]

Disregard this, read post below (Sorry KvH )

AZ

[KvHagedorn]

There are such things made for car stereo displays, but I wouldn't know where to get them. Maybe you could find an old used one?

[az]

OK, I have a momentary pushbutton. I need to use this to switch a 12VDC power line open or closed, not for as long as the button is pressed, to switch between on and off with every push of the button.

I've thought about using relays, but ordinary relays won't stay closed on power loss, and ordinary bistable relays need two different polarities to be switched back and forth. So what are my options?

Thank you

AZ

[Jon P. Inghram]

You could use a stack of rotary switches.

[az]

What I want to do is essentially the way it is done with ATX power supplies: They switch on by closing a contact momentarily, and they power down by pushing that button again. How is this done?

AZ

[Jon P. Inghram]

Actuate the bistable relays with a flip-flop that's triggered by the push button?

[Greebe]

a 3PDT (or 4PDT) switch will do what you want... only real issue is that the input will not be grounded between throws and thus will cause a small amount of arcy sparky when switched. I know of a few specialized switches made for the audio industry that make ground connection before making the disired output connection to eliminate the popping but don't know off hand where to get... also don't believe you would find in an all inclusive switch todo what you want (grounding the amp output would be BAD)

You could make a relay logic switch box todo this but IMO would be a waste

[az]

Thanks greebe, I had the idea with the 3PDT switch too, but for aesthetical reasons would really like to have a pushbutton, and the pushbuttons I want are only available as temporary pushbuttons, not as pushbutton-style SPST switches.

JPI, could you elaborate on the FlipFlop idea? I can solder a bit, and I'm not stupid, but I've never done anything with electronics before, so please explain or, better even, give a circuit diagram of how to build a flip-flop and how to wire the relay to it.

Thank you both

AZ

[gt40]

why are you concerned about losing power?
if this is for automotive, you would only loose power if the battery was disconnected.
If it is a concern than the circuit Jon suggested would do the trick, except if you did loose power you may have to press the button twice to change the state of the relays.
A flip-flop is a logic circuit that changes state everytime the input cycles from logic 0 to logic one.
I'll see what I can dig up for you as a circuit before Monday, as I' off for a dinner engagement tonight.

And there should be plenty of push-on push off switches available.
Have you looked at digikey.com (I beleive they have a German supply depot)

[az]

gt40, this is essentially the power switch for a headphone amp. I want to use a pushbutton, mainly because it looks good and doesn't cost an arm and a leg. I could get push-on push-off switches, but those would cost lots more (especially considering shipping, as the place I'm ordering the rest from doesn't stock them).

So I would need something that lets me emulate an SPST with a momentary pushbutton, and jon suggested a bistable relay (which I thought of, too, but which need different polarities for switching on and off) and a flip-flop to provide these different polarities (I guess that's what he wanted to use it for). But since I'm a total n00b, I need a bit more direction than just this

AZ

[az]

Oh, about "losing power": I meant that an ordinary, monostable relay would revert to its rest state once I take the finger off the pushbutton, which wouldn't be very useful for me

AZ

[Jon P. Inghram]

There's a flip-flop circuit here that might work or be easily modified to work, and uses normal relays. I couldn't tell ya how to adjust it to work with all the relays like you want (besides feeding the output from that relay to the main switching ones, which sounds really kludgy,) but it looks like it's more or less what you'd need if you want to stay away from a push button on/off switch.

[az]

I only need one relay controlled by one momentary pushbutton (so that the whole contraption works like an ordinary SPST switch)

I'll have a look at your link now.

AZ

[Greebe]

simple enough... a simple on/off pushbutton switch activating a 3PDT relay or a SPDT and a DPDT relay. All needed to run it would be whatever PS needed to drive it (12v typical ~100ma)

[bsdgeek]

Off Topic:

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Originally posted by Jon P. Inghram
Actuate the bistable relays with a flip-flop that's triggered by the push button?

When you don't know jack about what's being said here, this is quite a funny sentence.

Sorry, I wish I could contribute something useful to the discussion.

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