Ignition voltage

[Rocketjunkie]

You can do it with a single battery. All that's needed is for the long wire to carry enough current to drive the relay coil. Battery goes by the pad.
Connect from +12V to a NO contact of the relay. Connect the other contact through the igniter to -12V. Run a wire from +12V to your launch button then back to the to the top of the relay coil. Connect the other end of the coil to -12V. I made the switch removable for a safety. Keep switch with you. Plug in and it's ready to fire.
This is what I used for the 1000' controller for this static test.

 

[Voyager1]

You can do it with a single battery. All that's needed is for the long wire to carry enough current to drive the relay coil. Battery goes by the pad.
Connect from +12V to a NO contact of the relay. Connect the other contact through the igniter to -12V. Run a wire from +12V to your launch button then back to the to the top of the relay coil. Connect the other end of the coil to -12V. I made the switch removable for a safety. Keep switch with you. Plug in and it's ready to fire.
This is what I used for the 1000' controller for this static test.

Without a relay driver circuit at the pad end, you will need to confirm what the minimum relay activation voltage is. If the voltage drop over the long switch cable is such that it reduces the relay switch voltage to below its threshold voltage, then this simple technique might be unreliable. Choose a relay that has a low coil activation voltage and use a heavy duty field cable.

 

[Tractionengines]

The relays are all SSR's

Do NOT use SSRs unless you have a lot of experience with them and take precautions. SSRs have 2 big issues.

1) When you apply power to the line input. The DV/DT (change in voltage per change in time) can false trigger them for a fraction of a second. [ Even with both sides of the control signal grounded.]

2) They ALL have leakage current. This is a small amount of current that flows out of the device even in the off state.

If your familiar with the above, carry on. If not don't learn on this project.

 

[Rocketjunkie]

Without a relay driver circuit at the pad end, you will need to confirm what the minimum relay activation voltage is. If the voltage drop over the long switch cable is such that it reduces the relay switch voltage to below its threshold voltage, then this simple technique might be unreliable. Choose a relay that has a low coil activation voltage and use a heavy duty field cable.

The coil only uses about 50 ma. I used the cheapest wire I could get - 18 gauge speaker wire. The relay is a 6V coil. The system is for a single motor, not clusters. The battery is 12V sealed lead-acid.