recovery timer

[iamthemik]

im planning on making a circuit using a 555 timer that would set off ejection charges/stages or whatever i need it to do. i could just buy a timer from perfectflite but thats not too fun now is it. id rather do it myself.

problem is that i have very little experiance with electronics.
what i want the timer to do is this:
-the timer only starts after a g switch is closed for a certain time (one second?)
-once enabled, the timer would wait 10 seconds and then set off a charge or something.

does anyone have a schematic for it? i found a bunch of examples but they didnt have the 1 second safety delay for the g-switch.

(the time values are just estimates, il tweak the resistor and capacitor values so i get the right delay)

thanks to anyone that can help!

 

[GL-P]

once enabled, the timer would wait 10 seconds and then set off a charge or something.

Wouldn't you want the delay to be variable for different rockets?

Do some google searches. I hope someone with more experience with chime in

 

[gerbs4me]

I seen somewhere a schematic of the timer you talking about, sorry I don't have the link

 

[edwardw]

Search the forum for '555 Timer' I'm sure you will come up with something.

I have to say though, the Perfectflite timers are worth it. I've built my own timer (I used to be an electrical engineer), and I couldn't build what they sold for my time and expense. And if it happens to malfunction - you can take it back and get a new one...not the case with your own.

Edward

 

[wwattles]

Richard Nakka has a schematic and instructions on his site, using a 556 (2 555's). It also has a link to a 555-based timer near the top.

richard nakka's timer

WW

 

[iamthemik]

thanks for the link!

Wouldn't you want the delay to be variable for different rockets?

im probably ganna put a few jumpers or something so i can change the delay. i havnnt worked it out completely yet.

 

[Hospital_Rocket]

For the one second delay, you would probably be best off with a 556 dual timer. It is essentially 2 555 timers in one package.

Make the first one a one shot or monostable multivibrator. at launch you could have the g switch trigger the monostable for a programmable delay and use the output to trigger a second monostable usingf the second timer to handle the final action. You would need 4 resistors, 2 capacitors, and the IC itself. keep in mind a 555 has a very low current sink so you would probably need to buffer it with a small transistor . Something in a TO-220 case would suffice for every conceiveable need. You also need a G-switch, IC Socket, perfboard, and some misc hardware. The entire circuit could be built on 2 14pin IC sockets.

Wirewrap would e real convenient way to do this...

Just for the record, you are up to about $15 in parts and I'm not includding the battery.