Apologies for my extended absence from the forum, time gets away too fast.
I have had the spindle encoder on my lathe fail and want to run an idea past the brains trust.
The spindle encoder is no longer outputting a z channel. I have tested all outputs on the board inside the encoder to eliminate the possibility of a damaged cable. The encoder was still connected to the acorn and the oscilloscope shows +5.003v on the power rail, perfect quadrature outputs on channels A and B but no output on Z. Constant low voltage and even using Z as a trigger for the scope to make sure I don’t miss the pulse, still nothing. Tested resistance to ground to make sure the signal isn’t earthed out and tested good. Safe to say that Z is MIA.
My main problem is that I have a few jobs to get out that need threads cut and threading won’t initiate without the z pulse. I have ordered a replacement encoder but being in rural Australia, I won’t see that for around a month which is an issue. As a bonus, a lot of my work is remanufacture of parts for much more than the parts cost purely due to excessive lead times
.The idea that I had was to desolder the Z terminals from the DB9 connector and solder on the signal wires of a 4 wire NPN proximity sensor that I have here and position the sensor over the rear of the main spindle where there is a 3/8 key way. The power will be piggy backed off the encoders supply in the DB9 so there are no power anomalies. The prox sensor only draws ~30ma so I doubt excessive current draw will be an issue. This will give me one rise and fall per revolution but the peak time will be rather large. I understand that this is not ideal but I am in a bind and hope it will be good enough. The threads required are fairly large (1.75mm & 16tpi single helix) so a slight deviation in the index time shouldn’t have too much of an effect. I am assuming that Acorn only uses a rising or falling trigger and hopefully won’t recognise the large on time while over the keyway.
The only other option I have available to me is an absolute encoder I have here. It is a 13 wire from memory but if I use the two Quadrature signals for A and B and then use the 180° signal for the index. This will give me exactly 180° on and off, not a pulse but if the Acorn only uses a rising or falling signal it should be ok.
Before I start tearing machines down and fabricating brackets etc, I thought I would check with people much smarter than me
I appreciate any input or other ideas.