SparkFun Forums

[Yes0]

I've got this accelerometer hooked up to an Arduino, as shown here. I get readings for all three axises, but the problem is they don't seem accurate - they fluctuate from around 375-550, even when the accelerometer isn't moving at all. I do have .1 uF caps in between the accelerometer outputs and the Arduino. Has anyone else had this problem?

Thanks!

[leon_heller]

Those analogue output accelerometers don't work very well on breakout boards, I've found, the long connections cause the ADC to pick up too much noise. I didn't have any problems when I mounted the accelerometer chip very close to the ADC inputs of the AVR I was using.

Why have you put capacitors in series with the outputs?

[Yes0]

Oi, the wires are pretty long between the accelerometer and breadboard. Would cutting down that size work?

I thought capacitors would help even out the output?

[leon_heller]

You need direct connections between the accelerometer outputs and the ADC input, as on the diagram in your link.

[Yes0]

Alright, I'll have to solder new wires onto the breakout board and will post back if I still have the problem.

Thanks!

[Yes0]

Awesome, this seems to be working better now. When sitting still, the data is always clustered within 20 units of each other. But I'm still a little confused by it - when I move it along one axis the data changes, but it seems kind of random in how it changes. Sometimes it drops a hundred units, other times it gains a hundred units. When I stop moving it, it'll go a couple dozen units back towards the original resting reading, but it doesn't actually return there. Is this normal? Should I just be testing for a change in readings, and then watch for when the readings stabilize to determine when I'm moving and when I've stopped?

Thank you!

[leon_heller]

You can't move it smoothly enough by hand to get stable readings, to check it properly you need some way of clamping it in one position. You can then check the values, rotate it slightly, clamp it, and check the values again, while it is stationary.

[Yes0]

Oh, I see. Why is that, that the acceleration would be different at different rotational positions? Because of the force of gravity, acting at different angles?

[leon_heller]

I just don't think you can hold it without jiggling it about.