Twisted Pairs

Hi,

I was talking to someone yesterday who was using a 10' twisted pair,
sheilded cable for his encoder. He had used one pair for channels A
and B, the other for +5VDC and ground. He called to say things
weren't working very well.

I suggested one pair be channel A and +5VDC, the other channel B and
ground. He rewired it and called back to say everything was now
running very well.

The moral of the story is only one wire of a twisted pair should
carry a signal; the other wire should be ground or supply. Otherwise
cross-talk will get you.

This is true also if twisted pairs are used for step and direction,
limit switches or any other I/O use. It can be the cause of many
mysterious malfunctions.

Mariss