Re: Noisy Accelerometer
 

I haven't gotten any data on bad accelerometer or gyro boards yet (but that doesn't mean that there is none to be had). I'd be very interested in discovering what the failure mode is. If you are willing, we could chase it down when you get a chance.

Re: Noisy Accelerometer
 

The accelerometer chip itself might be broken due to mishandling. They're not particularly robust; dropping the board from table height can be enough to do permanent damage to the sensor.

Re: Noisy Accelerometer
 

Our team was having the exact same problem, so we had an ME come in to suggest a filter. He hooked it up to his personal oscilliscope, and the graph looked beautiful compared to the noisy Labview graph. I doubt that that the boards are all broken or that the manual was wrong, he suggested using a simple IR filter:

remsignal = 0.05*newsignal + .95*remsignal

This worked well for us and the noise was drastically reduced. You can use a formula node in Labview to do this and it is quite easy.

Re: Noisy Accelerometer
 

Note: I'm a system programmer, not an EE...just know enough to be dangerous.

I attached an oscilloscope to the accelerometer last night, and it showed a swing of +/- 200 mV at the beginning of the sample and then stabilizes. I'm not sure what to make of it. Maybe I need to change the sample rate.

I dislike the idea of putting something like this

remsignal = 0.05*newsignal + .95*remsignal

As the real acceleration would, I believe, be swamped out by the damping of the noise.

Re: Noisy Accelerometer
 

I'm the head programmer of team 701, and i have spend almost all hours for a week on the KOP '09 Accelerometer. Now after all the effort I am getting position from it, now accumulator, no DMA, no filtering, no averaging. A side from some drift, that i believe i can fix as soon as i find a better method for zeroing. IT WORKS

Re: Noisy Accelerometer
 

Do you think you could lend the rest of us a hand? I'd be interested in knowing what all you went through to get it working.

But, congrats! That's more than a lot of us can say right now about our accelerometers :-)

Re: Noisy Accelerometer
 

Just an update. Took the accelerometer into work, and had an EE take a look at it. Bottom line is that on the bench, it works just fine. So it's probably noise coming from the bot. Not exactly sure what to do to identify the source of the noise, but will try some things.

Re: Noisy Accelerometer
 

Someone else suggested taking this out of the equation and using a chip with a digital interface - I think they were right.

Here's a relatively good priced 3-axis accelerometer from Sparkfun:
http://www.sparkfun.com/commerce/pro...oducts_id=8791

It has an I2C interface, and here's the best part - a 192 sample ring buffer. It can sample on its own at a fixed speed, and has a line you can connect to a digital I/O port to act as an interrupt when the buffer is 1/2 or 3/4 full. You then can read all the acceleration data, pre-filtered, into your own code and run integration and analysis. It even gives 11-bit data, and is temperature calibrated.