How to make an LED light up for a second or two with a button press, regardless of how long the button is pressed?

I am looking to make a prop gun that just need to have a small flash for the sake of actors to know when the gun was "fired". 

I was hoping there is some way to make a small analog circuit to do what I need, and that is this:

I need an LED to light up for a second or two, then turn off. The lights need to turn off, regardless if the button is still being depressed or not. If the light needs to go off again, then the button would need to be release and repressed.

Thanks for the time! 

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iceng2 months ago

Click the pic to see the whole image..

LM555Gun.GIF

+1. I like the high pass network, in between the button and the 555's trigger input on pin 2. It guarantees the the amount of time pin 2 spends lower than 1/3 Vcc is very short.

+1

rickharris2 months ago

For the sake of those who might want to get into microprocessors.

For £1.88 in the Uk you can buy a Picaxe 08 microprocessor. Of course the picaxe can be used again for many things.

https://www.instructables.com/id/Lets-Program-a-PI...

Add a push button and an LED as in the diagram bellow - click for full size.

The programme is simple - NOTE Start and Flash are labels and have a colon after them

Start:

if pin3=1 then goto flash

goto start

flash:

high 4

wait 2

low 4

wait 2

goto start

This checks the input pin (pin 3) to see if it is high, the `10K resistor makes sure the input is connected to 0 volts(low) if the button is not pressed.

When the button is detected the picaxe flashes the LED on for 2 sec then turns it off and returns to waiting to see if the button is pressed again.

08qqq.jpg
DoctorWoo (author)  rickharris2 months ago

I actually was going to do this all with a micro-controller right out the gate! But, due to size and cost, I want to try and keep it as cheap as possible.

This is some nice info for when I dip into picaxe, though, to thank you!

Your welcome - Actually the picaxe 08 is an 8 pin chip like the 555 timer BUT you don't need bulky capacitors - so it could be smaller.

mind you will need to buy a one off programming cable.

Jack A Lopez2 months ago

This kind of sounds like a job for a 555 timer, wired as monostable multivibrator.

https://en.wikipedia.org/wiki/Monostable

Or maybe not. I seem to recall that for this trick to actually work, the trigger pulse had to have a duration shorter than the output pulse.

https://www.instructables.com/howto/monostable/

Of course, I kind of have to mention the 555 timer IC, because, like almost everybody has some those in his or her parts collection.

I'm trying to think if there is some way to make that circuit work better, by using more than one 555 timer, because very often the people who have one 555 timer, also have two or more of them.

https://www.instructables.com/answers/What-could-I...

I guess 555s are like roaches that way. If you see one of them, there are probably several others nearby, also inside your house somewhere.

;-)

DoctorWoo (author)  Jack A Lopez2 months ago

Thanks for the info!

An yeah...555 timers tend to live in packs. I bought 10 about 5 years ago, and I have about 40 in my stock now. Can't complain too much! They are handy.