# trigger button?



## Aquayne (Sep 1, 2008)

I'm working on a midway game that launches soda bottles at a target. I need a button that will close and then open the circuit with one push. A regular momentary switch only opens the circuit when the button is released. I don't even know what to call it for a search.


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## mkozik1 (Sep 6, 2010)

Really easy project here http://www.spiderspreyground.com/howto/pill.html

Depending on the switch you use (no/nc) will depend on the action you get from it.


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## Aquayne (Sep 1, 2008)

That is a nice project but I still need the right kind of button. Most, like horn or doorbell are made so that when the button is pressed it closes the circuit. As long as you hold the button the circuit will stay energized. I need one that will on then off with the same push. So if the button is held down it will not keep the circuit energized. Think like a trigger. The button is pushed, the valve opens briefly then closes so that the "gun" will recharge and not drain the compressed air tank.


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## mkozik1 (Sep 6, 2010)

Ah!! My apologies then, I mis understood the need. I have never done one with a switch, just with a switch tied to a controller. Have to think on that one!


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## scarybill (Oct 7, 2012)

All I can think of is a timer relay or a controller. I know of no switches like that. You might contact AutomationDirect and see if they have something

http://www.automationdirect.com/adc/Home/Home


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## Hippofeet (Nov 26, 2012)

I'm assuming you want the switch to function a certain way to prevent loss of air, so that it just fires a short burst of air, and does not drain your tank/bottle/what have you.

May I ask what you are switching? Is it a solenoid? Or a solenoid/quick exhaust valve combination?

As Bill said, a controller or relay could be made to function that way, or you could make a nail board, which is a much more crude method, but would work just like you want. 

A knife switch which is center activated would be fairly easy, a piece of wood, a hinge, 2 nails and some wire, but not much better looking than a nail board, and it could pinch fingers.

Really, knowing a bit more would help me with ideas, but as for a simple, pre-made, one push on/off switch, unfortunately I know of no such animal. You mentioned "Midway" so I am thinking people and possibly kids behind the trigger, so some of my ideas are probably a no-go. 

hmmm.


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## Aquayne (Sep 1, 2008)

I'm working on a game where a pop bottle is slid down on a 1/2" pipe. The assembly is aimed at a target. A button is pushed that energizes a solenoid that allows a burst of air to fire the bottle. The air will quickly recharge and be ready for another shot. I saw one at a children's museum in Hickory NC. I intend to set up some no no dolls as targets. They are hinged in the middle to allow them to be knocked off without falling away.


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## Otaku (Dec 3, 2004)

Sounds like a one-shot timer is what you need. Easy to make with a 555 and a few other bits and pieces. Press the button and the timer fires for a preset length of time, then resets. Use the timer to operate a relay to power the solenoid. It sounds like a lot of layers, but its easy to do.


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## Aquayne (Sep 1, 2008)

Do I search for "one shot timer?


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## Aquayne (Sep 1, 2008)

Monostable PIC with 555?


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## mkozik1 (Sep 6, 2010)

Try this http://www.dummies.com/how-to/content/electronics-projects-how-to-make-a-oneshot-timer.html


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## Otaku (Dec 3, 2004)

That circuit will work. If you want to reduce the time down to say, 1 second, use a 100K resistor at R2. Replace the LED with a relay (use one with a fairly high coil resistance, around 150-200 ohms) so you don't pull too much current through the 555 chip.


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## Nutz (Feb 19, 2013)

Not sure if something like this switch would work http://www.colehersee.com/home/item/cat/59/59071/ But just in case.


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## Aquayne (Sep 1, 2008)

Thanks everybody. I would never be able to figure this out on my own.
Wayne


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## Aquayne (Sep 1, 2008)

I looked closely at the diagrams that emkozic1 linked to. The actual diagram is hard to see. Is it a 470K ohms resister that is replaced by the 100,000 resister?


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## Aquayne (Sep 1, 2008)

When I look for the parts I dont know what to get.

10 mf electrolytic capacitor but all are 30 volts or more. What should I get.


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## Otaku (Dec 3, 2004)

Yes, the 470K (R2) should be changed to a 100K resistor. A 1/4W will be fine. The 10uF cap at 30 volts is okay, too. I typically use 100uF 16 volt caps in timer circuits, but I usually build them for longer timing sequences than what you need here.

One thing about this circuit - the timer will not run out unless the button is pressed and released, which kind of defeats your intention. If you want to use this circuit, you'll need to use a normally-closed button switch as the trigger. When the ToT presses the button, the timer will run out and be reset when the button is released.

As an alternative:
Go to the site I linked below and look for Circuit 5. It's a one-second one-shot circuit and it will time out even if the button is held down. You would use a normally-open switch to trigger this circuit.
Make the following changes:
Replace R1 with a 100K resistor.
Replace the 1uF e-cap with a 10uF e-cap.
The 0.1uF cap is a disc (ceramic) type. Many are rated at 50 volts, this is not a problem.

Here's the link to the timer circuit site. Lots of good info here.
http://home.cogeco.ca/~rpaisley4/LM555.html


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## wandererrob (Aug 8, 2007)

Could a cheap, piezoelectric grill igniter work? Use the brief electrical pulse as a momentary trigger signal.


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## Aquayne (Sep 1, 2008)

Otaku,
Thanks a million. You sure share a lot with us less fortunate souls out here.

Wayne

PS Wandererrob, It would probably work once then I'd have to clean up all the ashes ;-)


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## Otaku (Dec 3, 2004)

No prob, Wayne, happy to help.
Almost forgot - in that one-shot circuit I linked to, Pin 4 on the 555 should be connected to V+ and Pin 5 should be connected to a 0.1uF cap, and then to ground. That's not shown in the Circuit 5 schematic.


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## Aquayne (Sep 1, 2008)

I have a plan. I can use a normally open electric valve on the air pressure reservoir and a normally closed electric valve on the launch tube. When the button is pressed the nc valve opens as the no valve closes. The valve at the tank will minimize the discharge of air loss.
When the button is released the launch valve will close and the tank valve opens to recharge the air pressure for another shot. The one shot circuite can be used for sound effects and flashing lights.


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## Joe_31st (Aug 20, 2013)

Just came across this post, and I had wanted the same thing. A trigger that resets it's self even if you held it down. I'll have to take a look at those circuits in the link. I have always wanted to tinker with those 555 integrated circuits. Now I have more reason to.


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