power loss when starting

[sas11]

I have just installed a plc (12vdc) om my homebuilt aircfaft. everytime I start the engine. my plc goes dead. I have tried a new battery but that did not help. Is there anything someone could suggest to keep my plc up when I am starting up? Thanks for any advise

[TimWilborne]

What PLC are you using? What are the LEDs showing?

[Ken Moore]

Quick quess, power spike, bad grounding, bad isolation, noise, etc... Does the PLC come back after the engine is running? Does it only work when the engine is off? Everytime you fire a spark plug, you are creating a potential noise source.

[PdL]

Are you sure the power isn't interupted by the starting circuit when the engine starts ? Same happens in a car with the radio etc when starting the engine... I would use a separate battery circuit for the PLC.

[Clay B.]

This would be my thought as well. Do you have a dedicated circuit for the PLC? If the circuit runs thru the solenoid then you are going to have problems. I would suggest you have a power circuit that only feeds the PLC from the battery.

[OkiePC]

I know nothing about airplanes, but... In a car, the cranking of the starter may drop the battery voltage significantly, so a hot wire straight to the battery may not fix the problem. You would need a separate battery to keep it at full voltage during starting if this is your problem. If you want it to charge from the normal charging circuit, there are probably isolators that would handle that, only allowing the main battery to be used for starting, while still charging them both. Edited February 7, 2008 by OkiePC

[cHud]

Just wire it straight from the battery with short circuit protection some where inbetween. If you wire a radio this way it keeps going even when you start the car so I doubt he will have problems at startup Edited February 13, 2008 by cHud