Hi,
Really hoping someone can help here. A tiny bit of background is that I'm historically a software guy. I have really been enjoying the Pi and GertBoard and have a temp sensor, button and LED working and logging with Python etc. But I'm trying something new. Essentially from work I salvaged some broken mice. Mainly to get at the buttons, resistors and LED's which has saved me a few pounds. But in one I found something interesting.
In this one mouse, the click wheel motion (scrolling) is detected by prongs coming off the axle that cross an IR TX/RX pair. Every time the beam is broken a scroll is registered. Anyway, neither of these have any serial numbers or identifying marks. How would I go about working out how to use them?
1 has 2 pins, the other 3. I would assume that the TX is the 2 pin one (also it's clear) and simply is on when connected. This would mean that the RX is the other one (black). Seeings as there are 3 pins and this has to detect scrolling forward and backward, I would assume that the RX actually has two receivers and 1 pin is power and the other 2 are outs for each of the receivers indicating direction of scroll on which ever one is broken first. (I'm not actually bothered with testing for direction, yet, just want to get something working) I would assume that when there is no scrolling both transmit on and when each breaks, the outs drop to 0 in turn ... or vice versa. However all of this is complete guess work as like I said I've no idea on part numbers.
As it happens, I do also have a borrowed DMM but have no experience with it apart from getting a 3.3V reading on the GertBoard. Has anyone got any suggestions on how to start, or even some tutorials I can read? The very first thing that I'm aware of is the need to add resistors to any circuit I create on both the RX and TX sides so as not to blow the components... but with no identifying marks I don't know what resistor values to use... I would guess that I can work these things out with the help of the DMM... but how is beyond me at present.
Any help would be much appreciated!
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shippwreck
- Posts: 4
- Joined: Wed Nov 21, 2012 7:32 pm
Re: IR TX/RX beam break help
Your mouse has an infrared LED (TX) and a dual photodiode sensor (RX) hence the 3 legs.
Unfortunately photodiodes require amplification to work to convert signals into digital TTL output this is all done by the main black IC on the board.
If you're lucky you maybe able to power the mouse and tap into one of the pins on the IC to get the RAW output but that's a big if.
If you're in need of a IR beam breaker for some project then you might want to check out the Vellemen kits at Maplin or online for other IR circuits.
Richard S.
Unfortunately photodiodes require amplification to work to convert signals into digital TTL output this is all done by the main black IC on the board.
If you're lucky you maybe able to power the mouse and tap into one of the pins on the IC to get the RAW output but that's a big if.
If you're in need of a IR beam breaker for some project then you might want to check out the Vellemen kits at Maplin or online for other IR circuits.
Richard S.