Any prints from the Beta team?

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sorry for the late reply, off topic: I just replaced my windows XP with LUBUNTU, it is a crazy learning curve but totally worth it!

When I suggested this I was doing a quick search on digikey:

Product Index > Sensors, Transducers > Magnetic Sensors - Hall Effect, Digital Switch, Linear, Compass (ICs)


I use digikey for small orders, yes it is more expensive but they have amazing stock and the website is very organized. Once I find my parts, if they are too $$ you can cross reference on www.findchips.com for cheaper competitors.

[edit] Wrong link here, but it was a digikey link to a magnetic Hall sensor. I lost the link but since the following sensor is better, you can find it if you are curious!

- Hysterisis error is from temperature cycling (not magnetic hysterisis)
- symmetry error only applies if you are flipping the magnetic field polarity during operation.
-ratiometric error is also irrelevant since your supply voltage is fixed.
- Linear sensitivity seems like it will be the only relevant error, and it is only ±1.5%

1.5% is still too high in my opinion though... but this is a $2.31 chip.


Diodes Inc sensor looks better:
http://www.diodes.com/datasheets/AH49E.pdf

the linearity of span is 0.7% which is better than the allegro. I think that this if the chip I would try! In this rare case I think the through-hole version is better since you can easily manipulate its orientation to fit the field on the sense magnet. (maybe eventually make a circuit board for it. Be sure to have it on the opposite side of the mirror driving coil!

How to use it:

Ive never done this before, but I would start by looking how a magnet could be connected to the mirror axis, and then look how the sensor would need to be placed to have that field move in such a way that the sense would see it.

You might need to do a bit of reading and look at some diagrams on how to use these sensors.

After the system is set up with glue or tape, you would then run the thing to see what kind of an output you get! Then feed that to an amplifier to get your proportional feedback signal, and send it back to your main amplifier.

From there youll have to use the Zieglar Nichols method to figure out the PID values.

http://en.wikipedia.org/wiki/Ziegler...Nichols_method


I know it may seem like quite a bit of work, but I have a feeling it would be worth it if you are having significant accuracy problems. At the very very worst case, you develop it for the pro version and then open source the circuit so I can copy it and add it to my peachy

good luck and dont be shy to shoot me a line if you guys get stuck.


-UD