THCAD via 7i96-7i94D mode 2 mpg encoder input

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27 May 2020 01:24 - 27 May 2020 11:48 #169027 by microsprintbuilder
I am using a 7i84D in mode 2 as a remote card for a WIRE EDM project. I need to read the voltage to adjust the feed rate. I have a THCAD-300 connected to the spark box voltage and it outputs a square wave signal confirmed by an oscilloscope and reading hal scope reading 7i84 encoder 0 A phase. without a B phase the count will not work. I've tried several commands to change the counter mode to 1 like std encoders to ignore phase B. Is this option not available? Is there another way to achieve this. I have hooked up an mpg wheel and can see a count so the card is working. The card layout is 7i96 with 7i73 pendant on serial and 7i85 on the 7i96 expansion port with the 7i84D on its serial.
Thanks in advance
:)
Last edit: 27 May 2020 11:48 by microsprintbuilder.

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27 May 2020 01:50 #169030 by PCW
Do you mean 7I84D?

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27 May 2020 11:36 - 27 May 2020 11:49 #169115 by microsprintbuilder
Yes , I’ll edit that. In the end I guess I need a velocity, not a count to feed into my comp I’ve made to slow or speed up the feed rate.
Last edit: 27 May 2020 11:49 by microsprintbuilder.

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27 May 2020 15:15 #169133 by PCW
Yeah, the 7I84 encoder counter is really just meant for MPG usage so does not have the
fancy velocity estimation hardware that a normal encoder has. It would be better to wire
the THCAD to a standard encoder input.

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27 May 2020 15:48 #169135 by microsprintbuilder
That would require adding a long cable from the spark box to the control box. This something I was trying to avoid. Could I instead measure the voltage via the analog inputs use a voltage divider? Max voltage would be 160 DC.

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27 May 2020 17:25 #169138 by PCW
Is the 160V common close to ground potential?
Is it + 160V?

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27 May 2020 20:37 #169152 by microsprintbuilder
yes, if you mean its DC positive.

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27 May 2020 22:59 #169164 by PCW
OK then you should be able to read that with the 7I84/7I84D

A 75K 1% resistor in series the input should give you
about 160V full scale

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28 May 2020 07:40 #169201 by rodw

PCW wrote: Yeah, the 7I84 encoder counter is really just meant for MPG usage so does not have the
fancy velocity estimation hardware that a normal encoder has. It would be better to wire
the THCAD to a standard encoder input.


So Peter what card should we add to a 7i76e if we want to run encoders?

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28 May 2020 11:28 - 28 May 2020 11:29 #169216 by microsprintbuilder
as turns out this will not work as the reference ground is insulated from the switched ground. I’m back to using the thcad. see attached
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Last edit: 28 May 2020 11:29 by microsprintbuilder.

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