Hi, I am going to use a 5V encoder of 600 pulses. The signal it gives me is a pulse train of 5V and it goes to a driver that is 25 metres far away from the encoder. The cable of the encoder goes close to some power cables and all the cables are shielded. I don't have any experience in such long distances and I would like to know if I could have problems with electric noise, and how to avoid it. Thanks a lot.
You will have trouble, use a RS232 line driver near the encoder to change the signal levels and a reciever at the other end to change them back.
Hi, Haritztolete. I hope you haven't purchased your encoder yet. If you haven't, look for one that gives you a line driver output. You can then set up a line receiver at the other end of the twisted pair line, and change the signal back into standard digital logic. A standard open collector output will be a noise nightmare at 25 meters, no matter what the pullup resistor.
A line driver/line receiver setup will provide quite a bit of immunity from noise, because the noise is equally coupled into the both sides of the differential pair if you use twisted pair wire. The difference between the two voltages will still be the same, and that's what determines the logic level.
However, you also have to worry about sufficient energy being inductively coupled into the signal lines to cause damage to the line driver or line receiver. You really should arrange for different routing of signal and power lines as a matter of course, shielded or not.
Trust me on this one. There are few things more dispiriting, or more likely to evaporate your and others' trust in your electronics expertise, than creating solutions that kind of work or break down at random.
Please post back if you have any questions.
Good luck Chris
use twisted pair cable (eg one pair from a cat-5 cable) and put a optocoupler and suitable resistor on the far end.
Bye. Jasen
Greetings, I am not an electronics expert by any means, just a rank beginner. But in the last year I have been using encoders for some custom applications and have learned quite a bit about them. Nearly all this knowledge came from US Digital. Their website is USDigital .com. I think. Anyway, they sell a device for connecting encoders to long wire runs. The prices are from $11 to $34 for these cable drivers. Here's the link:
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