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Help with timer Circuit

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Ronin055

New Member
Hi everyone ! Im obvoiusly new here, but I need some help with a project and after reading through your forums you seem to be the best place to get this help.

What Im doing is working on a project with my paintball group. Specifically were making a device that will spray paint on persons who trigger it.

Currently were using a pair of nine volt batteries to trigger a sprinkler valve that is pressurized with a low volume of air. The result is that the air forces paint out of another cylinder and onto unwitting players.

My problem is this. The cylinoid on the sprinkler valve is in essence an electro magnet that pulls the switch stays open and drains the battery for no reason.

Run time on the device is about 4 seconds to spray the paint, and after that I need it to shut off power from the battery.

So the circut that I need is one that will : when activated, allow the circuit to run for 5 seconds and then shut off power from the battery.

Do you guys have any ideas that could help me?


Thanks for your time.
 

MikeMl

Well-Known Member
Most Helpful Member
What activates it in the first place?
 

Ronin055

New Member
The positive circuit is interupted by a removable nonconductive material. So when the player hits the tripwire, the non conductive is pulled free and the power circuit closes.
 

protoadv

Banned
What your looking for is a monostable multivibrator, a simple 555 will do. Tons of circuits on the web. Have the 555 drive a 2n3904 that drives the coil.

Hope this helps.
 

Ronin055

New Member
Thanks. So the 555 chip, Ive read that you have to program those. Is that the case with this application as well?

Currently(this week) my simple solution has been to use a couple of capacitors to drive the switch. Its extremely low tech.

Now what you describing would be to have the 555 chip run a transistor. So when the power is turned on, it will only run for a few seconds and then shut itself down.

Am I understanding this correctly?
 

protoadv

Banned
You don't program a 555. The timing is setup by the resistors and capacitors you choose. Just search google for 555 monostable.

The output would drive the base of an 2n3904 through a 470 ohm resistor. Emitter would go to ground and the collector would go to the relay. Make sure you put in reverse diode protection across the relay.

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MrDEB

Well-Known Member
could just go with an RC circuit

here is a link to a very simple relay / RC circuit.
about 1/2 way down the page it shows a circuit.
I think a 300K resistor and a 22uf cap will get you the 4-5 seconds you want.
PIR Sensors - Electronics
just get a 9volt relay and caculate the base resistor depending on the relay load.
 
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