pcbpnpsensor
I've got this component and I don't know how it works. I'd like to how how it works and how to wire it because i want to rebuilt the pcb and modify it a littlebit.
All I know is that it's a sensor for a motor to measure it.
It has 3 pins and I assume it has something to do with PNP.
The ATMEGA328P that the Arduino runs on (assuming an UNO or similar) has an input resistance of 100MΩ on the analogue inputs:
So, at a maximum of 5V, the current draw would be:
\$I = \frac{V}{R} = \frac{5}{100000000} = 0.00000005A = 50nA\$
Half level would be 2.5V, so 25nA, etc.
You might be able to use an optical flow sensor. If there is enough variation in the surface of the tape, it could tell you how much tape has dispensed. A way to test this quickly is to make a solid square out of the tape and see if an optical mouse works on it. There are Arduino libraries for some optical flow sensors too. The other two best ways would probably be an optical encoder along the rotating shaft or a potentiometer based encoder. You mentioned having trouble getting grip on the shaft, but I don't really understand what you mean by that. A variation on the encoder idea that would require a little more mechanical involvement would be to make two rollers that the tape is pulled between so they rotate. Then you could measure that rotation instead of the main shaft of the dispenser.
Best Answer
The chip looks like a hall effect sensor.
As the IR remote receivers in that package there is not only the sensor but also the appropriate circuitry to drive and read it. Two pins are probably power (\$V_{CC}\$ and ground) while the third is the output.
Looking at your PCB traces I'd make this guess:
And the guess agrees with Handoko's link. You can confirm this by powering the board and checking the voltage across pin 1 and 2, or following the traces and seeing where they connect to other components (that's what I did).
Pin 2 connects to a huge copper plane, these planes are usually connected to ground to provide shielding and to carry around the reference voltage.
Pin 1 is connected to a trace that wanders a lot, goes to a couple of connectors and to the microcontroller: no way that's the signal output, that must be \$V_{CC}\$.
Pin 3 finally seems to connect directly (and only) to a microcontroller pin: now that's your output. If you look closely you can even see the resistor shown in Handoko's link.
My pin order: refer to the last photo, pin 1 is at the bottom while pin 3 is the top one. Pin 2 is in the middle of course.
Addendum: to test it you do not need your motor, a hall effect sensor senses magnets: a fridge magnet or something similar is probably quite enough for it to work. You will need a multimeter or something to tell if the output is high or low. Please keep in mind that the sensor output might not be strong enough to directly drive a LED.