Another EE question - - grounding

On Tuesday, April 30, 2013 6:47:47 AM UTC-4, wrote:
Using three batteries, I have three "-" battery wires running to a negative terminal strip all "jumped on the terminal input side. Is it also best to ground the "-" terminal strip to the largest metal mass in the glider such as the elevator/aileron yoke?



Thanks.



Ben

Ben,

'Grounding' the minus wires to metal structures was (and still is in some cases) used as a way of saving wire and reducing circuit resistance. Back in the day when most electronics devices were built on metal chassis, it made a lot of sense to eliminate half the wiring by using the chassis itself as the 'return' portion of the circuit. However, this practice has no relevance in modern gliders, as there is very little metal anyway, and what metal there is is not usually located conveniently.

The very best way of handling multiple battery setups is to use a twisted-pair cable from each battery to a common location, where the minus/return wires should be tied together to the minus side of the power distribution bus.. The plus and minus wires from each battery should be sized the same, as any electrons going out of a particular battery must come back to the battery via the minus wire. In general, the larger the wire size, the better off you are (up to the point where wire size/weight/flexibility become an issue, of course). The twisted-pair technique is a very effective way of suppressing RF noise problems, and twisted-pair cables can be fabricated very easily using regular wire and a cordless drill (a good twisted-pair cable will consume about twice the wire for a given length though).

Hope this helps,

Frank (TA)