Re: [CAD_CAM_EDM_DRO] Re: Proper size of capacitors for transient suppression?

jmkasunich wrote:

>If you want to connect this encoder you need four wires. There
>are three ways to do it:
>
>1) use 4 individual wires (perhaps loosely twisted inside an
>overall jacket
>
>2) use 2 tightly twisted pairs, with + and - in one pair and
>A and B in the other pair.
>
>3) use 2 tightly twisted pairs, with + and A (or B) in one pair
>and - and B (or A) in the other pair.
>
>Number 3 is the best choice. The single ended outputs of the
>encoder generate signals on A and B that are relative to the
>negative supply (and the positive supply, since + and - are
>almost certainly bypassed to each other). Likewise, the single
>ended inputs at the other end of the cable measure the signal
>with respect to the negative (and positive) supply. So twisting
>each signal wire with one of the power supply wires is the best
>thing to do.
>
>

Or, you can use 3 twisted pairs, putting both power on one pair, and each
signal (A and B) in its own pair, with an additional ground wire as the
other wire in the pair. This has the advantage of now running 3 ground
(negative power, if you must) wires to the encoder. If the signal levels
are referenced to the ground (- power) terminal of the encoder, there will
be less noise voltage on this pin at the far end of the wire (although,
depending on the reason for the noise, it may be much better, or not
much better). 3 conductors will have lower impedance and resistance,
but if the problem is magnetic coupling, it won't help much at all.

Jon