Servo timer for water rocket

I start build water rocket. For that i need parachute and electronic for release them (like this https://www.youtube.com/watch?v=UnwP3YXOn-I). I want build similar on the ne555 but im beginner. I want regulate time for servo start with potentiometer.

Tarien said:

servo

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Please confirm whether you really want to use a servo. It is possible although additional circuits are needed to drive the servo.

BradtheRad said:

Please confirm whether you really want to use a servo. .

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I want use standard 9g tower pro servo

Have you used a servo? If not, then consider operating a motor (or solenoid) instead. That is likely to be an easier way to deploy a parachute.

A servo is sophisticated. It's ideal for operating something many times while an aircraft is flying. However the parachute is operated only once. A motor is simpler and cheaper for that purpose.

A 555 timer IC is a practical method, to wait a few seconds into the launch, then turn on the motor which deploys the parachute.

BradtheRad said:

A 555 timer IC is a practical method, to wait a few seconds into the launch, then turn on the motor which deploys the parachute.

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Ok, but do you maybe know any easy schematic to build that?

Tarien said:

Ok, but do you maybe know any easy schematic to build that?

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To design a timer circuit, you need to figure out how you'll begin a timing interval. At first thought we might think it is the easiest way, to set a 10 second interval, flip a switch and launch the rocket. Simple, right? However suppose launch is held up for 11 seconds? The parachute deploys before launch. Not exactly how NASA does things.

The timing interval should begin automatically at launch.

You also need to decide whether this is to be the only electronic circuit on board. It will determine where you install a master power switch, as well as where you put a device to begin the timing interval.

For tons of circuits using the 555 IC, see this website:

**broken link removed**

As explained the first problem is trggering the timer at launch time. What I fancy is a torch with a LED in it which PWMed. The reception of the PWM keeps the timer reset. So when the missile is launched it gets out of the PWM light beam, so the timer starts.
Now as for the servo, seems a lot of technology to open a parachute. This is an idea I played with in 1959, and it worked for me. Basically it to use the melting property of very fine gauge wire. So what I did was to carve a notch in the wooden end of a matchstick. Two pins were used to hold an elastic band and the matchstick was hooked on to it. Two more pins were driven in beyond the chemical end of the matchstick. One end of a very fine wire was soldered to one pin, the wire was wrapped around the chemical end, the free end pulled tight , so tensioning the elastic band, then soldered to the remaining pin. So it looked like an X with the match stick in the centre. passing a high current would ignite the match head and fuse the wire , so the match stick took off like a flare.
You have the elastic band holding the chute cover on, so tether it with some very fine copper wire into which you feed a high DC current to fuse the wire, so releasing the cover.
Frank

i finally done build this on two ne555 thanks for help