Conclusion

I hope you find the model rocket ignition system schematics useful, even if you don’t build my exact board. Of course, you can edit my board in Copper Connection if you want to make adjustments. Although I encourage you to include a programmed microcontroller for safety features, you can still get the power benefits of locating the battery near the launchpad from even a brainless home-etched version of this project.

Video

Here is a brief example of the rocket ignition system being shown off:

Potential Improvements

The new device is better than my original fancy rocket launch controller. However, now that I have built and used it, here are some changes I will keep in the mind for the next revision.

  1. A current-limiting resistor (say 1 kilohm) could be added between IC1 and the Go pin to limit current if someone uses both the microcontroller and a button connected directly to Go. That would be an unusual setup, and IC1 can handle the shorted pin, but nevertheless an added resistor would make the solution more robust.
  2. A diode between the interlock output and everything but the relay coil would allow the interlock switch to be single pole. This might save some money and provide a wider variety of choices of keyed switches.
  3. An optocoupler could be placed before the launch and arm switch inputs to provide circuit isolation and input protection.
  4. A double ring socket (TRRS) instead of a single ring (TRS) would allow the remote control to draw power.
  5. The circuit board and igniter connections share a power source, which can reset the microcontroller during launch if the battery voltage drops too much. By adding an additional connection and a diode after D1, a spare battery (say a 9V) can provide backup to the circuit board.
  6. The quantity of LEDs and blink states can be somewhat confusing. A microcontroller with more pins could support an LCD for better information. This would be a significant change.

Suggestions?

I would love hearing from you if you implement your own version of this relay-based model rocket ignition system. Or, even if you just have comments, questions, and ideas for improvements.