dcooper33
Lifetime Supporting Member + Moderator
Hi guys,
I'm wondering if this is possible. I have a machine with two different 3600 count encoders wired into a 1771-VHSC plugged into a PLC 5/40e processor. First encoder is for "machine position" and it goes to counter 1 on the VHSC. The rollover point is 3599 counts, but there is also a shaft-mounted flag and a prox which "resets" the count every machine cycle. The second encoder monitors a turret which makes a complete cycle every 6 machine cycles. It goes to counter 2 on the card and it also has a flag and a rollover point of 3599 counts. The values for the card are BTR'd into two separate integers for each value, a MSD and LSD, so for instance 3516 counts or 351.6 degrees would be read as MSD 3 and LSD 516 at N7:103 and 104 respectively.
We have issues with this machine on power outages or maintenance shutdowns if the machine is not brought to the "zero" position of both encoders before power is turned off or lost, because both encoder values will zero wherever the machine happens to be whenever power is cycled, so we have timing issues until both encoder flags come around and reset everything.
What I'm wanting to do is move the values for each encoder into "safe storage" integer values continuously while machine is running. Then use a first pass bit to move the stored values back into the BTR destinations for the counter values. Would this work, or would the stored values be overwritten by a "zero" value from the encoders on power-up? I was hoping someone here had done something similar so I would have an idea if this could work before I implemented it on the machine.
Thanks for reading and replying!
Cheers,
Dustin
I'm wondering if this is possible. I have a machine with two different 3600 count encoders wired into a 1771-VHSC plugged into a PLC 5/40e processor. First encoder is for "machine position" and it goes to counter 1 on the VHSC. The rollover point is 3599 counts, but there is also a shaft-mounted flag and a prox which "resets" the count every machine cycle. The second encoder monitors a turret which makes a complete cycle every 6 machine cycles. It goes to counter 2 on the card and it also has a flag and a rollover point of 3599 counts. The values for the card are BTR'd into two separate integers for each value, a MSD and LSD, so for instance 3516 counts or 351.6 degrees would be read as MSD 3 and LSD 516 at N7:103 and 104 respectively.
We have issues with this machine on power outages or maintenance shutdowns if the machine is not brought to the "zero" position of both encoders before power is turned off or lost, because both encoder values will zero wherever the machine happens to be whenever power is cycled, so we have timing issues until both encoder flags come around and reset everything.
What I'm wanting to do is move the values for each encoder into "safe storage" integer values continuously while machine is running. Then use a first pass bit to move the stored values back into the BTR destinations for the counter values. Would this work, or would the stored values be overwritten by a "zero" value from the encoders on power-up? I was hoping someone here had done something similar so I would have an idea if this could work before I implemented it on the machine.
Thanks for reading and replying!
Cheers,
Dustin