Re: [CAD_CAM_EDM_DRO] Re: Encoder circuits for parallel port hookup?

Hi:

>>>> What I am looking for is the circuit diagrams that show how to hook
> up
>> an optical encoder to the parallel port (I a

No signal filters are usually necessary, you hook the A and B quadrature
up to the pins on
the printer port directly, and you have to hook the signal gound to pin 25.
Thats it. Mach3 can read
up to 7 of these if you have enough pins, but when reading from a printer
port, your limited to the nyquist
frequency of the program reading it in terms of speed. In Mach3's case, at
25Khz mode, you are limited to
about 12500 pulses per second on the encoder, howver, Windows being Windows,
I recommend a 10000
pulse limit and 20000 in 45Khz mode.

I have seen some DOS software that wil read faster though, and it is
possible for a Windows DRO program to
do up to 50000 per seconjd from an encoder if it doesn't have to do motor
movements and such to limit
the interrupt time. I have letters from several that have encoders hooked
up as semi-closed loop correctors
and they seem to work well within those limits. Personally, I haven't had
time to hook up my linear scales to Windows yet,
but intend to do so next month to put closed loop corrections into the code
base for Mach3 anyway..

Marris has a post recently on the gecko group about hooking an encoder
directly to a motor to make it follow the encoder
with very simple circuitry as well...

Thanks,
Art
www.artofcnc.ca

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