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Re: PNP Inductive Sensor
Yes NPN outputs are a lot easier and preferred. But if you really need to use the PNP device you have two main problems that need to be addressed.
1. The device you quoted requires 12 volt power and the DSC only supplies 5 volts.. You need to wire a separate 12 volt circuit to power it.
2. The output from the device you want to use is active high with 12 volt logic. You will need some method of getting the input to the right voltage. An opto-isolator is the method normally used in industry. But you may also be able to use a resistor divider network to drop the output voltage to 5 volts. The lower leg of the divider should also act to pull the I/O low when your output is not on.
I would try a resistor network with about 350 ohms between the output of your sensor and the input of the DSC, and then another approximately 250 ohm resistor between the DSC input and ground. I have not tested this, but I think it should get you in the input range you need and limit your signal current to 20 or so milliamps. Any one else see a mistake here?
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04-03-2013, 12:33
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