Machsupport Forum
Third party software and hardware support forums. => PoKeys => Topic started by: zbig1989 on July 26, 2016, 10:04:37 AM
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Hello.
I am trying to connect touch probe to PoKeys CNC board. In manual it says that "external pull-up resistor must be used".
So I draw my idea how to connect the probe and my question to us is, is that correct ?
(http://www.galerieallegro.pl/zdjecia/z782/7821780/big/1.jpg)
Image description:
5V - +5V from f.eg."Encoder connector"
Probe inuput - dedicated inputa in "Additional limit switches connector"
GND - ground
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Nobody connect touch probe to PoKeys CNC board ?????
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Don't have a PoKeys, but if it's calling for an external pull-up resistor that looks correct. I usually see a resistor value of 4.7k specified. I'm not sure how important the value is, though, as a pull-up resistor simply prevents a direct short when the switch is closed. In a circuit such as this, the Probe Input will sense a low (GND) when the switch is closed. When the switch is open, this point will sense the applied voltage (5V in this case) since the resistor is a relatively low value compared to infinite resistance of the open switch contact. Too high a value of the resistor could result in slightly less than applied voltage but it 10K vs. 4.7K shouldn't make much difference.
Bottom line, if the documentation calls for a specific value. Otherwise, a value in the range of 4.7 - 10K should work just fine. But your diagram is right on the money for this application.
Stephen "Highspeed" Kruse
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Thank you, for our anwser.
I connected touch probe to PoKeys board like on a picture and it works whery good.