plc_user1973
Member
Greetings, this my first post to this forum so here it goes. I have a PLC from Triangle Research (T100MD888.) I have a wire drawn linear quadrature encoder connected to the PLC. The encoder has differential outputs and is place 50+ feet from the PLC. The PLC doesn't have differential inputs but is connected through a differential to open collecter unit.
The problem is: As with most people that use quad encoders my position data is not consistent with what is measured with a "tape" measure. At the end of a work day. The position data is not consistent to what it should be.
I am using this equipment to control the position of a sawmill carriage. The carriage holds the log at a position in relation to the sawblade. This is making me look very bad. I have exhausted what I feel is all means to correct the problem and the only thing I can think is the problem is the wire drawn encoder.
I believe the encoder itself is fine, but the spool and wire apparatus is what is in question.
The sawmill carriage moves at 6 in/sec and the encoder has a resolution of 500 pulses/in. Therefore 3kHz is being generated at the outputs of the encoder. This pulse rate is well within the 10 kHz response of the PLC.
I don't believe its a noise problem due to the differential out's and I also have tested the machine at rest and there is not problems with position data. To further see if it was noise, I connected the encoder outs to an interrupt channel with the machinery running but at rest and there was no accumation of interrupts being generated.
I feel that the acceleration of a "crashing" log against the fense of the machine which is monitored by the encoder is greater than the accerlation rate of the retraction spring of the encoder and it causes the wire to wrap around the spool in an inexact means, which could lead to positioning errors.
Can anyone give me some insite on this.
Thanks in advance.
Roger
The problem is: As with most people that use quad encoders my position data is not consistent with what is measured with a "tape" measure. At the end of a work day. The position data is not consistent to what it should be.
I am using this equipment to control the position of a sawmill carriage. The carriage holds the log at a position in relation to the sawblade. This is making me look very bad. I have exhausted what I feel is all means to correct the problem and the only thing I can think is the problem is the wire drawn encoder.
I believe the encoder itself is fine, but the spool and wire apparatus is what is in question.
The sawmill carriage moves at 6 in/sec and the encoder has a resolution of 500 pulses/in. Therefore 3kHz is being generated at the outputs of the encoder. This pulse rate is well within the 10 kHz response of the PLC.
I don't believe its a noise problem due to the differential out's and I also have tested the machine at rest and there is not problems with position data. To further see if it was noise, I connected the encoder outs to an interrupt channel with the machinery running but at rest and there was no accumation of interrupts being generated.
I feel that the acceleration of a "crashing" log against the fense of the machine which is monitored by the encoder is greater than the accerlation rate of the retraction spring of the encoder and it causes the wire to wrap around the spool in an inexact means, which could lead to positioning errors.
Can anyone give me some insite on this.
Thanks in advance.
Roger