circuit design help: momentary switch activates/cancels electronic switch

Here is the application:

I have a momentary switch. When I press it, I want to switch something on (light bulb) and have it stay on even though momentary switch was released. maybe 500 mA draw.

When I press it again, it turns the light bulb off. How do I do this? This is in a 12VDC circuit.

Thanks!

Reply to
matthewuw
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Do you particularly want to use that switch or would you be prepared to swap it for a push-on/push-off momentary action one?

Ken

Reply to
Ken Taylor

Will in the end, I need a circuit to do this. But I do want to learn. What I asked for is actually only part of the functionality, but I see it as a building block to start with and was hoping I might figure the rest out on my own.

Reply to
matthewuw

Well a push-on push-off switch isn't really momentary. It feels like a momentary switch, but doesn't function like one. I have to use a momentary switch, no option because or existing hardware.

Reply to
matthewuw

Well a push-on push-off switch isn't really momentary. It feels like a momentary switch, but doesn't function like one. I have to use a momentary switch, no option because of existing hardware.

Reply to
matthewuw

There are a number of ways to do this. Do you want to learn, or are you just interested in having a circuit that will do it?

Ed

Reply to
ehsjr

See "TogggleFlopAncient.pdf" on the S.E.D/Schematics page of my website.

...Jim Thompson

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|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
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Reply to
Jim Thompson

This should do it.

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There are many circuits for a 'toggle' or flip-flop, but that's the simplest/cheapest I know of.

--
Terry Pinnell
Hobbyist, West Sussex, UK
Reply to
Terry Pinnell

Did you simulate that?

Reply to
Fred Bloggs

"matthewuw" wrote in news:1129097288.402163.260420 @o13g2000cwo.googlegroups.com:

I've tried this and it works. Simple and cheap. Sub in a 12vdc supply and a

12v relay.

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Reply to
Ken Moffett

You can use a miniature SCR bistable: View in a fixed-width font such as Courier.

. . 12V . | . +--------------+--+----+--------------+-----+ . | | | | | | . | +-------------|--------------------------+ . | | | | | | | | . | | | | | +-----+ | | . [10M] [1K] | [1K] | | | | | . | | | | | | -|-----|-----|--- . | | | | | | | | | | | . | | | | | | | \\ COM NC | . | 0.0022 | | | |< - | / | . +---||---|--------+--| ^ | \\ | . | | | |\\ | | / | . | | | 2N2907| | | | NO | . | | | | | -|------------|-- . | | [100K] [3.3K] | | | . | | | | +-----+ | . | | | | | | . | +-----+--||---|--------------+ | . | | 100U 16V | | | . | | non- | | | . | | polar | | | . | | | | | . | | | | | . o | SCR1 | SCR2 | | . -| SW --- | --- | . o \\ /-+-[1K]-||-[1K]-+--\\ / LAMP . | --- | | | --- | . | NTE5400| | | | | NTE5400 | . | | | | | | | . | |[10K] [3.3K] [10K] | | . | | | | | | | . | | | | | | | . +--------+--+----------+----------+---+------------+ . | . --- . /// .

Reply to
Fred Bloggs

Should be: View in a fixed-width font such as Courier.

. . 12V . | . +--------------+--+----+--------------+-----+ . | | | | | | . | +-------------|--------------------------+ . | | | | | | | | . | | | | | +-----+ | | . [10M] [1K] | [1K] | | | | | . | | | | | | -|-----|-----|--- . | | | | | | | | | | | . | | | | | | | \\ COM NC | . | 0.0022 | | | |< - | / | . +---||---|--------+--| ^ | \\ | . | | | |\\ | | / | . | | | 2N2907| | | | NO | . | | | | | -|------------|-- . | | [100K] [3.3K] | | | . | | | | +-----+ | . | | | | | | . [470] +-----+--||---|--------------+ | . | | 100U 16V | | | . | | non- | | | . | | polar | | | . | | | | | . | | | | | . o | SCR1 | SCR2 | | . -| SW --- | --- | . o \\ /-+-[1K]-||-[1K]-+--\\ / LAMP . | --- | | | --- | . | NTE5400| | | | | NTE5400 | . | | | | | | | . | |[10K] [3.3K] [10K] | | . | | | | | | | . | | | | | | | . +--------+--+----------+----------+---+------------+ . | . --- . /// .

Reply to
Fred Bloggs

No, but maybe I'll have a crack at it when I get some time. Meanwhile, I've put together this scan from my original source: "Elektor 302 Circuits", ~1985

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which explains its working.

And I'm pretty sure I breadboarded it successfully a decade or two ago.

--
Terry Pinnell
Hobbyist, West Sussex, UK
Reply to
Terry Pinnell

Okay, thanks for all the replies. Sorry to change things up on you...but like I said early on, this is a learning experience for me. It has occured to me that I don't want to worry about contact bounce and that in reality, this will fit my application much better if there are 2 momentary switches. pressing one of them turns the system on and pressing the other turns the system off. i can probably adapt this setup somehow from some of the provided circuits, so I will look into it. this might actually simplify the circuit too i would think. THANKS!

Reply to
matthewuw

Here is a less parts intensive version of the same thing, consumes about

50uA in the off state: View in a fixed-width font such as Courier.

. . 12V . | . +-------------+-----+--------+-----+ . | | | | | . | o | | | . | -| SW | | | . | o | +----+ | . | | | | | | . | +------+ | | -|-----|--------- . | | | | | | | | | . | [10M] === | | | \\ COM | . | | 0.022U | - | / | . | -+- | | ^ | \\ | . | /// | | | | / | . | | [1.5K]| | | NO | . | [820] | | -|------------|-- . [100K] | | | | | . | | | +----+ | . | | | | | . +--------+--------||---|-----+--------+ | . | | 10U 16V | | | . | | non- | | | . | | polar | | | . [100K] | | | | . | | | | | . | SCR1| | SCR2 | | . | --- | --- | . | \\ /-+-[1K]-||-[1K]-+--\\ / LAMP . | --- | | | --- | . | NTE5400| | | | | NTE5400 | . | 2N5060 | | | | | 2N5060 | . | |[10K] [270] [10K] | | . | | | | | | | . | | | | | | | . +--------+--+----------+----------+---+------------+ . | . --- . /// .

Reply to
Fred Bloggs

Thanks- I think I recall that article now, clever.

Reply to
Fred Bloggs

A little before my time, but those were the days...toggle on release.

Reply to
Fred Bloggs

Ken Moffett wrote in news:Xns96EE4ED95F5AEqwerty@24.94.170.94:

I looked back at the circuit again and noted something they had left out. The relay in their circuit was a 12vdc for the 24v supply. So for a 12v supply you would choose a 5vdc or 6vdc DPDT relay. The resistance of R1, R2, and relay's coil would all be approximately equal.

Reply to
Ken Moffett

How much simpler can you get than the circuits posted? Have you tried any of them yet?

Hey, how about an even simpler approach: a single toggle switch? No buttons, no electronics. AC or DC power supply in at one side, and out of the other to whatever you want to control. Its explanation is as follows: when you switch it one way, the circuit is powered on. When you switch it the other way, the circuit is powered off again. Very reliable, parts easily obtained. What's more, it has another advantage over a button-based approach: the status of the circuit is always visibly obvious (providing the two switch positions have been marked accordingly, e.g. 'On' and 'Off' or whatever.) This advantage over buttons applies even if the load has failed somehow (lamp filament burned out, motor stalled, etc).

--
Terry Pinnell
Hobbyist, West Sussex, UK
Reply to
Terry Pinnell

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This is the standard way to do it: (View in a fixed-pitch font like
Courier)
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Reply to
John Fields

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