circuit seperation

[fruitfly]

I am building a gyro with a 2stroke engine and would like to run the hobbs meter off the regulator rectifier circuit without power backfeeding from the battery when the power switch is on. The way it is now, the hobbs meter runs as soon as the battery switch is turned on, which could be a problem if I where to leave the switch on.I was wondering if I could put a diode between the battery bus and the regulator circuit and run the hobbs meter off the regulator,would it be possible to have the meter run only when the engine is running?

 

[Capt. Geoffrey Thorpe]

The diode would have to carry the maximum of the charging current, plus you will get a voltage drop across the diode which will require a regulator adjustment to get the battery to charge properly.

Do you have a real alternator or are you using lighting coils on the magneto (similar to Rotax)? Power the Hobbs directly from the lighting coils (need rectification, voltage limiting)?

 

[flyingron]

Don't need much voltage regulation for the Hobbs. They'll take anything from 10 to 80V. You do need DC.

 

[fruitfly]

I am using a rotax 503, the lighting coil puts out 70v ac. I am using a rectifier/regulator to get 14vdc. The hobbs meter I have takes 14vdc. I have seen hobbs meters that run on 120vac but I don,t know if 70v would make it run right.