RE: [CAD_CAM_EDM_DRO] VFD control wiring question

I would think you could do this with a Voltage-to-frequency converter; check
out the National LM231; specs at http://www.national.com/ds/LM/LM231.pdf

There are other chips that could be used; I don't know if this one is the
best for this application, just found it in a very quick web search(to make
sure there really WERE such chips; I 'm getting' old and I'm not as sure of
things as I used to be.)

You'd need a circuit that could put out a square wave, with a frequency
proportional to the voltage in. You would have to wire it up so it put out
1 pulse per revolution, as I understand the Mach2 speed sensing.

Andy Wander
Verrex Corporation

-----Original Message-----
From: washcomp [mailto:jeff@...]
Sent: Saturday, March 06, 2004 1:22 PM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: [CAD_CAM_EDM_DRO] VFD control wiring question

First let me appologize - I'm posting this question to 3 groups, so
if you get it more than once, please resond on whichever you like.

I'm about to design the controls to an Omron G5+ (same as Yaskawa and
a few others) VFD for my Bridgeport (1 1/2 HP). I'm using MACH2 CNC
software.

There are (as in most VFD's) a bunch of contacts both in and out.
I think I've got the speed and direction control figured out, but I
understand that contacts can be used for E-Stop and other functions.

Which contacts into or out of the drive do you recommend using and
how would you impliment them.

Also, there is a setting to output the motor speed as analog voltage
(0-10 volts D.C.). Most of the circuits I've seen convert from PWM
to a voltage to control the drive. MACH2 has the ability to read a
sensor delivering pulses so that it knows what speed a spindle is
turning. Is there an easy way to go in the other direction and
convert the analog voltage to pulses so that this can be emulated and
fed back into MACH2 as speed (as if a rotary encoder was being used)?

Thanks,
Jeff



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