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Asked — Edited
Resolved Resolved by Rich!

Connecting Sensors In Parallel.

One person on the forum at least said that he hooked all of his PIR sensors to one port and it worked great. What OTHER sensors can I connect to the same ports to save on ports? will it work with the Ultrasonic, IR and other similar sensors?




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It depends how you define "worked". The thing with connecting more than one sensor to one port is you will have no idea which sensor is giving the readings or even if the reading is of just one sensor or a combination of all sensors.

The other problem is connecting things in parallel but if both sensors are giving readings. For instance, let's take the IR sensor connected to the analogue port. They receive 5v from the VCC and report back a voltage on the signal. You will not get a true reading from the sensors.

Push buttons or bump switches would work ok if they are only needed for detection of a bump but wouldn't work for direction of a bump unless you multiplexed them using resistors and set up the software to recognise which switch reports what voltage coming back.
@MovieMaker Good question! I would say, if your sensor gives only a high/low value, much like a switch which is either on or off you can probably wire several up in parallel for a digital input. (PLEASE, Consider the voltage level of your sensors though, simple switches should be fine, sensors that provide a voltage level output would likely need some resistors at the very least.)

What you would end up with is a an ON signal or a 1 for any of the sensors that is tripped. If you have a ring of touch sensors and want to know if the robot has bumped into something, that would work. If you want to know if the bump came from the front, right, left and so on it would not work in parallel on a digital line. You could multiplexe them with resisters and connect them to an AD line.

PIR sensors I believe give a high/low state of 5 volts. It would make sense that you could parallel these (but again you might need some resisters and diodes to protect against shorts and feedback) because the output is either on or off, motion or no motion.

Most ultrasonic sensors like the ones in the EZ-B kit provide a variable feedback, these you would not want parallel connect to the same port.

IR sensors, some give a high/low output like some IR line following sensors. Some of the SHARP IR sensors can be connected to a digital line and will give a high/low at a short range even though they are better suited and I would say designed for AD ports so they can provide a variable distance reading. If you use them for only a digital high/low readings you can parallel them.

Does that help answer you question?
Both of you gave me good answers. But since Rich was first, I will give him credit.

Thank You both for your answers.

I was thinking in terms of using just the PIR in Parallel to know if someone is in the same room.

Then, I guess the others should be individually hooked up.