reccommend a tilt/level sensor?

Hi - I’ve been looking through various sensor wikis and other places trying to find the type of sensor I need. I have a gimble type rig (http://roypardi.com/gimble/IMG_2803.JPG) and to have an ‘auto-centering’ function I am thinking that 1 or 2 sensors (depending on type used) to determine when the rings are level would be the way to go.

I’ve used the “ball in a can” type tilt sensor before but that won’t work here. Basically I need to determine when the rings are level, so something analogue is probably what I need.

Anyone have a type/model/supplier that they would recommend?

thanks!

–Roy

Analog tilt sensors are expensive, accelerometers are cheap (Freescale MMA7360 e.g.) An accelerometer will tell you where the gravity vector is pointing and, as long as things are relatively still, you can calibrate to "level" ahead of time then see how far off the accelerometer's gravity estimate is from that.

Thanks! I see that Sparkfun sells those with a breakout board and I found a tutorial here: http://itp.nyu.edu/physcomp/sensors/Reports/MMA7260Q

--Roy

Another possibility: put slot sensors, like one of these

on the outer rings, 90 degrees from the pivot axes, and put vanes on the inner rings, so you can sense when they're lined up.

Ran

Wow - hadn’t considered anything like that. Thanks for the “out of the box” solution! Those are so cheap. Would work for the outer ring easily. The inner ring - less so, but another couple of dangling wires - (I’ve got 4 motors on the rig now) - won’t make much difference.

Mr. Trickpony in another thread (http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1233339782) referred to this cheap tilt sensor:

http://www.sharp-world.com/products/device/lineup/data/pdf/datasheet/gp1s036hez_e.pdf

Digikey doesn't seem to have in stock though:
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=425-1961-5-ND

Hey thanks - that looks like a cool sensor. I like the Cleaning Instructions

Cleaning instructions
The device shall not be washed with washing material, for there is possibility to remain washing material in
internal space of this transmissive type photointerrupter.

I would NEVER wash it!! (I haven't washed my right hand since shaking hands with Elvis in 1977) :slight_smile:

Mr. Trickpony in another thread (http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1233339782) referred to this cheap tilt sensor:

Index: SHARP Electronic Components...

I don't think that's going to work for this application because that tilt sensor is very coarse. It's basically a sealed photointerrupter with a little ball inside that moves around and breaks the light beam, so there's no way it'll tell you the difference between level and 10 degrees off.

The whole thing is potentially fraught - accelerometers can work, unless there’s a lot of vibration, and anyway, sines work against you.
If you’ve got, say 10 bits over a +/-2g range, 1 degree of tilt from the horizontal represents only about 4 counts, which could easily be lost in noise. ( (1024 /4) * sin (1))