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Automation, sensing and robotics • Re: Wiring multiple photoelectric sensors to RPI 4

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Ok then it is exactly what you specify on the first post.

My problem is that the output of the sensor is suppose to be a NPN transistor because the PNP will be PM-U25P.

This mean that the sensor only pull the signal to gnd. it can't have any voltage on the output unless you add a pull-up resistor.
opto_npn.jpg
Collector on transistor only put the signal low.
So to get voltage on the output obviously you need to have something that put the line high.

According to PM-U25 part there is no resistor added to the circuit so the only thing is the transistor output which pull low or let the output open.

Normally I use 4k7 pull up resistor to get the correct response on open collector. That resistor is connected to 3.3V for a raspberry Pi.

So how do you get a voltage on the sensor if you didn't put any resistor and it is not connected to anything except is connected to the voltmeter?

Could you fill the table I asked you to do. I just don't want you to burn your Pi with an invalid assumption. Something don't make sense.

In theory the output doesn't need a resistor divider but just a 3.3V pull-up, something around 4k7 to 47K.

Statistics: Posted by danjperron — Mon Mar 18, 2024 5:05 pm



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