PSAS/ Lv2RocketReadyRelay

RocketReady Relay (RRR) board

RRR board as of August 4th, 2005

Overview: This is a launch tower relay board that has been hacked to observe the umbilical cord. Usually, the umbilical cord provides shore power. But right before launch, shore power is turned off, and the RRR looks for a 5V signal from the rocket via the umbilical cord. If:

  1. Shore power has been off for at least 1 second
  2. The rocketready signal (on the umbilical cord) then goes high for 1 second

... then the RRR turns on the rocketready relay which allows the LTC/LTR to actually fire the igniter. If rocketready goes low, or shore power comes on, then the rocketready relay is turned off.

The reasoning behind this system is that we want the FlightComputer on the rocket to be able to directly abort the launch without having to rely on a wireless link.

Hardware Notes

The RRR board uses the same PCB as the Launch Tower Relay (LTR) board. Only one relay is used, and the rest of the board is hacked up for the RRR board. See the latest schematic for more details.

Firmware Notes

Based on PicCore. See the README file in c/firmware/rrr which can be seen at

Project Notes

08/04/2005 Replaced 6A SPDT relay with 12A SPST relay. Cut traces which would have shorted after relay change. Soldered ground strap on. removed 1k resister that shouldn't have been there. Bulked up the power traces a bit.
07/09/2005 Reworked the RRR board again. Added pull down resistors, 1uF ceramic caps, removed manual armed switch
03/23/2004 Reworked RRR with surfacemount components. Documented schematic.
09/21/2003 Hacked board to make it work in BRD. Eventually, it actually worked.