Plasma - wiring question
 

I have a couple of questions on the Plasma Wiring;

The manual says "when connecting power supply, route the positive lead to a 5A pullable breaker and then to battery plus terminal, bypassing any electircal bus or master solenoid"

Q. Is there any problems with wiring it to the Battery Bus (always hot) or must it go via a CB?

Q. Input connector; Pin number 6 is for the Tach signal, I have the Vans IE VTACHGEN 2 attached to the engine tach drive which will be wired to the GRT/EIS. I asssume this overrides any necessity to wire to the Plasma Tach signal as well.

Q; Output connector; Unless you are using a key switch (which I am not) it looks like this is optional, not sure about variable timing though, am I correct ?

The battery bus will NOT be "hot" if the master solenoid fails, or if the battery voltage falls too low. In both of those cases, the battery would still most likely have enough current to power the ignition.

Wiring should be
a) battery + terminal to
b) 5a CB to
c) On/off toggle switch (you can probably use the old Mag switch, but you'll have to rotate it 180 degrees so that "Up" is "On") to
d) Plasma control box

Yes, although a second digital tach signal is nice. I don't know if the Van's unit is digital or analog - a digital unit will be more accurate. If you bought your unit new and recently, the signal should be 10v - but if you bought an older, used unit it may only output 5v. Klaus will upgrade the unit for free to 10v if you have one of the older units.

If not using a key switch, do not connect this wire (if you were, you would not use the toggle switch and there would always be power directly from the battery to the control unit, interrupted by the key switch signal). Unless you are racing, do not tinker with the variable timing - period. You could hurt your engine!

Plasma
 

Thanks for that Bill,

Doesn't "battery bus" usually imply a direct, always-hot connection to the battery?

mcb

No, only when the battery switch is on. But if you have an electrical problem and need to turn the battery switch off, you would still want your ignition to work. Arguably, if the battery is the problem it might be a moot point. But Klaus offers a schematic for a backup battery which you can switch to in case of a complete electrical failure; the backup does not even need to be very large as the ignition does not draw a lot and it only needs to last as long as it takes for you to land at the nearest airport (you wouldn't really continue on if your main electrical system failed, would you?).

I think there is a terminology difference here. I am using the same designations as Nuckolls:

• "Main bus" is connected to the battery through a contactor, relay, or other electromechanical device. It is only powered when the associated master switch is closed.
• "Battery bus" is connected directly to the battery, is always powered , and is not switched in any way.

mcb

Wiring Schemes Differ
 

If you are using any of Bob Nuckolls' wiring schemes from "The Aeroelectric Connection", as many do, the battery bus is connected directly to the battery positive terminal and does not go through the battery contactor.

You can connect the Plasma to the battery bus through either a pullable breaker or fuse. Either will work just fine.

Fair enough - I'm not sure most planes have a "battery bus" in that sense, so I assumed the reference was to the Master bus.

For those wishing to wire it to the Master bus (so they don't inadvertently kill the ship's battery after shutdown) the backup battery is a good scheme. Just put it in line using a diode so it won't try to power the ship's bus, and you're good to go if the master dies.