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pinout help for my salvaged ir sensor/photo diode from mouse.? Answered

i have salvaged ir emitter sensor pair from an old optical mouse. ir led glows fine on testing with mutimeter but the sensor part has 3 legs and i have always worked with 2 leged photodiodes .

what is this specifically called?
how can i know its pinout by testing with multimeter?

Tags:ir

8 Replies

user
Jack A Lopez (author)2013-12-25

If it is the old kind of mouse, the kind with a ball and two slotted wheel optical encoders inside,  the photosensor with three terminals is a actually two phototransistors with their collectors tied together.

Anyway I have done this trick before, and I even uploaded some pictures of this, about a year ago, here:

picture of mouse wheel optical encoder
https://www.instructables.com/file/FW3FJUNH6MF2Y3N/?size=ORIGINAL

circuit diagram
https://www.instructables.com/file/F556408H6MF2Y3F/?size=ORIGINAL

In the diagram, it looks like I am powering the IR LED with a 5V supply in series with a 1K resistor, and I am using only one of the two IR phototransistors in that package.  I have this phototransistor drawn using the symbol for NPN transistor, but with no base.  Its collector is connected to +5V, and its emitter is connected to a 22K resistor, and the other side of the 22K resistor is connected to ground.  

The 22K resistor seemed to be good match to my phototransistor's change in resistance from light to dark.  The voltage at the emitter should be high (closer to +5V) when in light, low (closer to 0V) when in shadow. 

If I remember correctly, that little three-terminal plastic package had two phototransistors in it, with their collectors connected to a common pin, and the emitters connected to the other two pins.

If you want a better picture, or diagram of this, of my phototransistor, I still have that junk around here somewhere, and I could re-examine it to see if it really is wired the way I remember it was.

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user
Atul009 (author)Jack A Lopez2014-01-03

Yeah i'll be glad to see some images, I actually just want the pinout

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Jack A Lopez (author)Atul0092014-01-03

Both phototransistors have their collectors tied together and connected to the center pin.  The remaining two pins are the respective emitters of each phototransistor.   I took a closer picture of my dual-phototransistor, and edited it to draw a little diagram on it.  Link to the full-sized picture here:
https://www.instructables.com/file/FF0I8O3HPZLKCQW/?size=ORIGINAL

This is the same board as that other picture,
https://www.instructables.com/file/FW3FJUNH6MF2Y3N/?size=ORIGINAL
but with the slotted wheel and beige mouse plastic out of the way, so you can see what the phototransistor looks like, basically a little black(but transparent to infrared) plastic box with 3 pins. 

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TaynaraO (author)Jack A Lopez2015-10-26

I need to control my stepper motor through the encoder. I am using the encoder of an old mouse, but there is no specification of this component.

I measured the tensions and currents of the phototransistor in the mouse circuit. And then, I I calculated the value of the resistor that will be connected at the collector of this component.

The problem is when I am testing these components (IR LED and phototransistor) on the breadboard: the voltage and current are not the same measures the mouse circuit.

My concern is damage the components.

Do have another solution?

I need to know the stepper motor position. I opted for mouse encoder, but it's something wrong.

Maybe you can help.

Thanks

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user
FernandaL12 (author)TaynaraO2017-01-13

Hey, TaynaraO, Did u get any answer for ur problem?

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user
Josehf Murchison (author)2013-12-24

The IR sensor is a photo transistor with a base or like the pic I am posting.

To find out set your meter for continuity and apply a current to the diode, move your meter probes from leg to leg until you get a reading, that is a photo transistor and the red probe of your meter is collector the black is emitter all are NPN.

A transistor tester works on these.

If you don't get a reading from your meter or transistor tester the side that faces the IR LED is the front and it should be hooked up like the pic.

see my Instructable:  https://www.instructables.com/id/Photo-Components-Testing/

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user

I need to control my stepper motor through the encoder. I am using the encoder of an old mouse, but there is no specification of this component.

I measured the tensions and currents of the phototransistor in the mouse circuit. And then, I I calculated the value of the resistor that will be connected at the collector of this component.

The problem is when I am testing these components (IR LED and phototransistor) on the breadboard: the voltage and current are not the same measures the mouse circuit.

My concern is damage the components.

Do have another solution?

I need to know the stepper motor position. I opted for mouse encoder, but it's something wrong.

Maybe you can help.

Thanks

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user

That is a PIC of some kind and it may be a onetime program, read only, or locked IC.

What are the markings?

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