Internet PLC Forum

General => Technical support => Topic started by: can on January 11, 2011, 08:50:00 AM

Title: HSC
Post by: can on January 11, 2011, 08:50:00 AM

Hi. Encountered a strange problem again. I'm using MD888 to control 2 motors via inverter using setdac. The motors encoders are connected to the inverter and pin 3,4 is connected to first inverter and pin 5,6 is connected to second inverter. Whenever I run motor 1, the HSC 2 is increasing / decreasing randomly while HSC 1 is normal. What can be the cause? grounding issues again?

Thanks.

Title: Re:HSC
Post by: support on January 11, 2011, 09:45:20 AM

Why are the HSC inputs connected to the inverter? Are these inverter providing encoder feedback signal to the PLC? What kind of signal level is the PLC getting from the inverter?

The PLC HSC is only reporting what it receives on its inputs. If it is counting up and down randomly it means it is receiving pulses from its input pins. Did you try the enhanced quadrature method?

Title: Re:HSC
Post by: can on January 11, 2011, 10:26:06 AM

Yes. The inverter is providing encoder feedback. The encoder feedback goes through a ULN2003A pin 1, 2, 8 and pin 15,16 is connected to MD888 input 5,6. Pin 8 is connected to power supply 0VDC. First scan has setsystem 4,3. Anything wrong with the setup? The wire from inverter to ULN to PLC is not shielded. Any issues with that? Should not be an issue since input 3,4 is ok, right? Thanks.

Title: Re:HSC
Post by: support on January 11, 2011, 01:38:53 PM

Why don't you switch the input 5,6 with that of 3,4 and see if the problem shift from 5,6 to 3,4. If it does it means your encoder is sending pulses for whatever reason.

Title: Re:HSC
Post by: can on January 16, 2011, 08:41:12 AM

ok. problem solved. ULN2003A is faulty. Thanks.