Jee Labs Talk

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1. raalst
   

   Hi all,

   I was blown away by Jean-Claude's blogs. very impressive and a LOT of good info on sensors.

   I have recently been playing with optical mouses. a lowly logitech RX250. it contains an ADNS5020 optical chip. this chip is a 16x16 pixel optical camera. it can be read out with some I2C-ish protocol. you can read out the actual picture it sees or the displacements it detects.

   playing with a few lenses I got it to read a few dots off a paper a few centimeters away. it's own lens is focussed on the surface right under the mouse.

   Why do I post that here ? (drumroll....)

   It might be very usable as a read-out of the electra and gas meter. it can probably measure how much of that disk is rolling along underneath it, eliminating the problem with the stopped disk. It MIGHT even be usable to recognize numbers, but just detecting movement of the lowest digit of the meter would also do the trick.

   No. it's not entirely my idea. just the part of using it to read the meters.

   there is a lot of stuff out there on hacking optical mice, e.g. http://www.bidouille.org/hack/mousecam/index.en.php and this (autonomous flight with 7 optical mice!) http://infoscience.epfl.ch/record/140575/files/emav09optipilotweb.pdf

   Posted 05/04/2010 20:16:27

2. jcw
   

   Great idea, this could be a major improvement over IR reflection measurements. I know of two different meters with digits which I can't read out right now (old water meter and the "PEGUS" city central heating system in Utrecht) because they don't have LEDs or mirrors. And if digit detection works, the resolution would be 10x more accurate than the mirror trick.

   Would a specific mouse be the best way to go with this? A while back, I saw this part at DigiKey:

   There must be a lot more uses for these sensors (CNC linear positioning system?). Fascinating links, no time to dive in further right now, unfortunately ;(

   Would love to hear it if you make some progress with this.

   Posted 05/04/2010 21:48:00

3. raalst
   

   about the lineair positioning, I'm not entirely sure that absolute positioning is feasible, but maybe with a combination of displacement measurements with some recognizable markers. at a resolution of about 800 dpi it should be able to indicate at least 0.1 mm (0.03mm actually) Idea with potential, although I recently bought 3 10-euro digital calipers (schuifmaat) for such purpose.

   specific mouses, I used the logitech RX250, the cheapest in the shop. datasheets of a whole range of chips mostly at www.avago.com. That digiKey chip would do nicely and is a middle-of-the-road model. it is just that (broken) mouses can probably be scavenged from shops.

   I just glued webcam optics to the mouse PCB . it seems to react when I move paper in front of it at about 5 cm. it also sees the window at 4 meters. but reaction is fairly jerky.

   Posted 07/04/2010 16:44:38

4. raalst
   

   on absolute positioning I found this link for future reference. this guy used the sensor for positioning into the micrometers (or so he says)! one of the problems with Internet that everything interesting seem to have been done already..

   Posted 07/04/2010 19:48:30

5. jcw
   

   > one of the problems with Internet that everything interesting seem to have been done already..

   Nah. There's always more. Besides - it's not about who did what, it's about where it leads us all :)

   Thx for the link (with the new syntax rules, you need to place <>'s around a URL to make it active - edited).

   Posted 07/04/2010 20:18:47

6. raalst
   

   Just now I succesfully laid the converted mouse on the water meter and after some tweaking had the mouse moving over my laptop screen in sync with the rotation of the LSB digit. Nice ! unfortunately the video I made from it was too dark to show.

   Posted 07/04/2010 21:32:11

7. jcw
   

   Wow - that sounds very promising, congrats!

   Posted 07/04/2010 23:53:15

8. jcw
   

   Here's another link someone emailed me about, with info and code for dealing with that mouse sensor:

   Yesterday, I wanted to try something out with the ADNS-2610, but then I realized that it needs an image of the target object in sharp focus. I didn't have a proper lens to try this, so I stopped going there. To use "the rodent approach" for the electricity meter, we're going to need a way to focus on the counter digit behind the clear plastic window, which is probably about 1 cm away, and which will differ from meter to meter.

   I wouldn't know how to create such a little focusing system, especially one that others could easily replicate. Suggestions welcome.

   Posted 12/05/2010 11:26:38

9. raalst
   

   sorry, forgot to mention : I ripped apart a small/old webcam. these have a plastic holder right above their chip, often with an adjustable lense (you focus it by turning the lens up/down in it's grooved holder). So, check if you can focus the lens by turning before ripping it apart. some hot glue and you have a lens system over the ADNS2610...

   Thanks for the link. I knew it, but others may not. it's yet another very useful capability of this mouse chip.

   I wanted to apologize for having been away for a week, but then I saw the timestamp on your post ;-)

   Posted 12/05/2010 12:20:17

10. jcw
    

    > I wanted to apologize for having been away for a week, but then I saw the timestamp on your post ;-)

    Haha. You mean people who visit this forum are not allowed to skip class, eh? Intriguing concept! ;)

    Posted 12/05/2010 13:06:37

11. raalst
    

    I just re-read the old posts and both the link and the webcam hack were already mentioned above. It must have been a good vacation. As you say : Onwards !

    Posted 12/05/2010 13:13:27