1. Home
  2. General Robotics Forum
  3. Dealing with leakage current

Dealing with leakage current

I have some 2-wire sensors that I need to plug into a PLC (Opto22 UltimateI/O). Apparently the leakage current on the sensors is too much for the PLC to deal with so I need to calculate a bleeder resistor value. I thought I did it correctly but it's not doing the job. Here are the specs:

Sensor:

1 mA leakage current

PLC input:

24VDC source 15k input resistance 10VDC minimum turn-on voltage 3VDC maximum turn-off voltage

Based on some formulas I came across on the web (buried in an Omron spec sheet) I came up with a bleeder resistor value of 30k or less. This is based on the following formula (from the spec sheet):

R
Reply to
Joel Moore
Loading thread data ...

Reply to
Joe Turner

"Joe Turner" wrote in news:jpG2b.20339$ snipped-for-privacy@twister.southeast.rr.com:

Sorry for not responding earlier. It was a crazy week and we managed to get it working so I never checked back here.

Yes, you're right. The resistor is placed in parallel with the PLC input. For some reason I was picturing the sensor as being wired directly across the two terminals of the PLC.

We wound up getting advice from the PLC manufacturer on this (Opto22). They basically just had a rule of thumb for this type of problem that works but unfortunately it didn't explain why my original calcs were wrong.

Joel Moore

Reply to
Joel Moore

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.