D180 Installation - Power sources

[cfiidon]

This question concerns how to provide power to the D180 during different scenarios.

I have designed my electrical system to have two busses: 1) Main buss
and 2) Combination avionics/endurance buss.  The avionics buss is powered through a switch and diode coming from the main buss or thru an endurance buss switch directly from the battery.

Now my dilemma:  I would like the D180 to be alive during engine start (to monitor EMS parameters), so I need to power it without the avionics switch on.  One option is to isolate the EFIS from the avionics buss with a rectifier diode array (it would then powered from the main buss OR avionics buss).

The D180 installation manual page 4-3 pin 15 shows an external backup power input.  If I connected this to the main buss, would the D180 come on immediately, or does power need to be applied to the master power input first?  Alternatively, should I perhaps power the main power from the master buss and the alternate power from the avionics/endurance buss?

In summary:

Option 1: Isolate the EFIS using diode rectifier array on main power input
Option 2: Power the EFIS from the main buss with alternate power from the endurance buss

If it makes any difference, I do have the backup battery option.

Don

 

[bmarvel]

Don:

You have another option.  Just start the engine and then flip on the avionics bus.  There is nothing you can do to harm the engine during a few seconds at idle power anyway.    

Bill Marvel

 

[cfiidon]

Thanks Bill. That is one option I've considered. How long does it take the D180 to "start up"?

 

[dynonsupport]

It's 6-8 seconds for a D10/D100 series unit to boot up.

Also note that the D180 is designed to be on during engine start, so that you can watch oil pressure.

 

[cfiidon]

SO I've made a decision unless someone in the know tells me NO!

The main power input will be connected to the main buss and of course will be on at engine start.

The alternate power input will be connected to my endurance buss.

Once I wire and power everything up I'll be able to see if it behaves as I think it will.  I assume that should I switch off the main buss the unit will switch to internal battery and give me 30 seconds to say OKAY before it powers down.

When I kick on the endurance buss the same thing should happen,  I'll have to acknowledge or it shuts down.