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Subject: VMS startup problem.


>
> I like the idea of the small 12 volt battery... is there no way to use a
> single switch though?

To prevent the voltage drop-out problem on the VM 1000, you could use a 12
Volt SPDT relay (P&B or Bosch) and wire accordingly (12 volt aircraft)

(from starter switch)----------------------(voltage while
cranking)-----------> Pin #86
(from ground
bus)-------------------------------------------------------------------->
Pin # 85
(from 12volt battery source*)-------------(fused
7.5amp)---------------------> Pin #87
(to 12 volt input on VM 1000
DPU)----------------------------------------------> Pin #30
NOT
USED------------------------------------------------------------------------
-----> Pin #87a

* needs to be a source that doesn't drop out while cranking; pick it up at
the battery or on the hot side of the master solenoid.

Install a 1amp diode on each of the power input wires going to the VM1000
DPU (bands facing the DPU).

This circuit would allow normal operation while master is on or while
running.  When starting, you are activating this relay which is continuing
power supply to the DPU while cranking.  The relay only operates while
cranking.

Kirk Hammersmith
Lancair Avionics
(541) 923-2244





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