An Electronic Chute Timer

   This chute timer uses two 555 timer chips and a few discrete parts.  The
first timer sets the 12-second delay time by a 1-megohm fixed resistor or a
1-megohm trimpot. When the output of that chip goes to the second chip, the
second chip's output times the MOSFET gate's On time.  One second is enough
time to burn an ignitor.  More time is needed to run a chute-deploying motor.
The schematic of the circuit.
   The launch switch must ground pin 2 of the first timer momentarily ONLY.
The delay starts right after the switch OPENS.
The trigger wire trips the switch.
   When the rocket starts up the guide rod, the trigger wire first closes the
microswitch (copper finger) and then it will open when past the trigger wire.
The circuit on a prototype board.
   This is not the most elegant configuration, but one which was made using
all old spare or new Radio Shack parts.
  (2) 555s (older TTL, NOT newer CMOS)
      1 meg ohm
      100K ohm
  (2) 10K ohm
      330 ohm
  (2) 10 mfd elec
  (3) .01 mfd
      LED
      NTE 2395 MOSFET
   The MOSFET is shown here before it is wired in so that the rest of the
circuit can be seen.  If a heat sink is placed under the MOSFET, it can be
used to drive an electric motor for mechanical chute deployment, such as for
water rockets, or a camera. In which case the 100K resistor needs to be
changed so that the motor operates for the right amount of time.  The 100K
resistor allows one second to burn an ignitor.  A 1 meg ohm resistor would
allow 12 seconds to operate a motor.