ghostriver
New Member
Howdy,
Now that I have a Dynon EFIS and EMS I have installed an external power plug. I searched around for info on this with regards to the correct wiring. On the external plug the short + pin is jumped to the large + pin and this supplies power to the contactor to join the external power to the battery cable after the battery contactor. This is from the Cessna electrical diagram for a C 172 1969-1975. This should provide power to the starter using the ignition switch contactor wire for starting. To provide power to charge the battery and power the Dynon instruments I believe the Master should be on and a good battery charger plugged in through the external power plug. The problem is to ensure reverse polarity protection. Questions that someone might be able to answer are: What diode (in series) would be used from the short + pin to the contactor for reverse polarity protection? Another solution I saw was a 2 amp fuse and diode between the – pin and the short + pin (on the receptacle side), the idea being that the fuse would blow if one used the wrong polarity. I have been unable to find out what diodes to use.
Bob
Now that I have a Dynon EFIS and EMS I have installed an external power plug. I searched around for info on this with regards to the correct wiring. On the external plug the short + pin is jumped to the large + pin and this supplies power to the contactor to join the external power to the battery cable after the battery contactor. This is from the Cessna electrical diagram for a C 172 1969-1975. This should provide power to the starter using the ignition switch contactor wire for starting. To provide power to charge the battery and power the Dynon instruments I believe the Master should be on and a good battery charger plugged in through the external power plug. The problem is to ensure reverse polarity protection. Questions that someone might be able to answer are: What diode (in series) would be used from the short + pin to the contactor for reverse polarity protection? Another solution I saw was a 2 amp fuse and diode between the – pin and the short + pin (on the receptacle side), the idea being that the fuse would blow if one used the wrong polarity. I have been unable to find out what diodes to use.
Bob