Re: hooking up an open collector?

Greetings,
Mitch Berkson wrote:


Ack! Resister is 10K (measured & replaced with another one, also measured). I've tried everything I can think of. If I pull the output wire, I get +5v on the input as I would expect. When I put the output wire back I get either 0.03V or 0.40V, neither of which is enough to pull the TTL high :(
Just as a sanity check, here's my setup:
+5 --+------------------+ sensor +5v/orange wire | 10K resistor | +--- output from sensor (brown wire) | | --+------+-----------+ input to PIC
GND ---------------------+ sensor gnd/blue wire
I've tried two different sensors & get the exact same results with both. The frustrating thing is everything else is working great.
Any additional thoughts much appreciated!
--
Kyle A. York
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Most open collector circuits recommend 2.2K or so as a pullup. Look at how voltage comparators are used and you will see examples of this. But it almost sounds like your PIC terminal is configured as an output! This will hose up anything you are trying.
Cheers!
Chip Shults My robotics, space and CGI web page - http://home.cfl.rr.com/aichip
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Greetings,
Sir Charles W. Shults III wrote:

Thanks. The 10K resistor comes from the following statement in a note that came with the the motor: ``Honeywell recommends 10K pull-up to +5V for driving TTL gates.'' I'll try the 2.2K resistor through.
Also, I made my measurements with a multimeter and without the PIC attached figuring the more variables I could eliminate the better.
--
Kyle A. York
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There is also the chance that something is blown. Like your driver.
Cheers!
Chip Shults My robotics, space and CGI web page - http://home.cfl.rr.com/aichip
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