Amiga Mouse Original Tank Mouse Optical sensor Faulty Help please.

[darkage]

logically these should be in pairs.  One IR emitter and One IR receiver.

Im not sure what brand / model, but you should do a keyword search like

rectangular LED infrared emitter and IR receiver diode

Examples

http://bit.ly/2kM9QIS

http://bit.ly/2joFg7x

You will need to check the circuit diagram to see if you need to replace the emitter or receiver.  I think this is the schematic

http://pavouk.org/hw/en_amigamouse.html

Theres an upgrade to laser mouse for the original - http://amigastore.eu/en/559-laser-upgrade-for-amiga-mice.html

Edit - You might get better hits if you use the keyword 'phototransistor'

Example - http://bit.ly/2jx71Gj

Hard to find out what the original brand is.  You will probably need to check datasheets and do some calculations based on the circuit given to check that the phototransistor is within spec.    Or maybe just try one with a narrow beam like 30 degrees perhaps  ?

[darkage]

Not sure how old the mouse is (if the original tank mouse)

Heres an old diagram example - http://www.ianstedman.co.uk/Amiga/amiga_hacks/Amiga_mouse_repair/amiga_mouse_repair.html

Do both sides look the same?  One should be a IR LED Diode (Emitter) and I would guess the other side is photo transistor (receiver)    kind of like a LDR but different package but I would say they would use photo transistors as they are more senstive.

[darkage]

Hi Pat,  

The last schematic Ive posted clearly shows a phototransistor, for receiver

http://www.ianstedman.co.uk/Amiga/am...se_repair.html

The first schematic I posted, doesnt look like it has the correct symbols even for a photo diode.  ie. no arrows on one set of diodes

Edit - You could just buy a pair to make sure its the same wavelength.    It should be a NPN phototransistor for Rx, going by the last diagram.  I assume slightly newer models should be the same before the new looking ones.     It's not voltage that matters so much, its more about getting the one with the right current charactors as per the original ones.

https://www.sparkfun.com/products/241

[darkage]

I know. But I never saw a transistor with two legs. Have you?

A Transistor is basically a switch.   Base is the light senstive material in lieu of a 3rd pin.   The amount of light dictates how much current should pass between collector and emitter.  Therefore just 2 pins.
Symbol is the same as in my last schematic.

[darkage]

Not exactly the same.  Photodiodes and phototransistors have different characteristics.

Phototransistor is more senstive than a Photodiode and is the symbol that is shown in the circuit diagram.

[darkage]

OK thats a Tank mouse with a LM339 ic.  

Heres a very good discussion that covers same topics.

http://www.atari-forum.com/viewtopic.php?t=20207#p177259

Someone else on that discussion has picked up that the first diagram is wrong with the strange double diode symbol as well.  They also suggest phototransistor is a more appropriate setup

[darkage]

Official name is 'Phototransistor side looker (looking) package'

I would measure exact package dimensions plus pin width (measured from center pin to center pin) with a digital caliper and then try to match one up with same physical dimensions and supports IR.

List of phototransistor side looking package -

Rs Components (free shipping - no minimum order amount) http://bit.ly/2kOG95B

Element14 - http://bit.ly/2klZTRl

Ordering from Rs Components is cheap, probably worth to get at least 2 different brands to try.   maybe honeywell or osram.   Check acceptable angle, it should be something sensible and not too wide.  Maybe 50 degrees or lower

Edit - You will probably need to get a matching pair, so grab a IR LED (emitter) side looking package as well.  Same brand / operating specs.

Note - Only if your certain that the fault is with the optical sensor.   There could be issues on other parts of the board / cable.

[darkage]

Problem Sorted  ?
The load on the IR Reciever was to low (Original Design) which was 670 Ohms.
Now modified to 2.7K ohms as per Pavel Ruzicka's Circuit.
I have changed all 5 Resistors to this standard.

Thanks for all your help.
Ray

Odd.   Was the board worked on before ?   Im not sure if Pavel's schematic would be 100% correct, best way would be to check another untouched tank mouse for values.  Or maybe your mouse was built on a friday afternoon in the factory and someone put in the wrong values.  Or maybe overtime as the optical sensor ages it might become less senstive and a load change has done some magic.

Happy its working now

[darkage]

A larger resistive load will make it more sensitive.  

Theory here, key point towards the end.  

http://learn.parallax.com/tutorials/robot/shield-bot/robotics-board-education-shield-arduino/chapter-6-light-sensitive-11

If its the original resistors in there from the factory, the phototransistor may be breakingdown with age and is drifting out of spec  ? See how you go, if it happens again then look at the sensors.