Help with accelerometer.

In labVIEW, we are trying to put our accelerometer into our robot program, but we are not sure where that should be what wires connecting where and such… Can anyone give us a little help or a push in the right direction? sorry for low clarification >.<

we also need help finding an aceleramitor devref

You should look in the senor manual on the competition manual. As to making it work in the program we don’t know. Our problem is that the measurement is returned in volts per gravity of acceleration. What is that and how do you convert it to linear measurement?

Ok, here is a push in the right direction:

To connect up the boards: Use the standard 3 wire servo cable and solder the male (pin end) direct into the accelerometer board… The edge of the board is ground or the black wire…(Check the drawing for the board to make sure!!!) You will need three cables if you want all three axis… Use a low wattage solder iron and be careful…

Now, just plug them into the AtoD inputs on the analog board… One each for X-Y-Z for a total of 3 AtoD channels. The cable will plug directly into the 3 wire input on the AtoD sidecar with out any modification. Make sure you check orientation of the connector when you plug it in.

This is also true for the rate gyro… one for rate and the 2nd for temperature

To use the data, you should filter the data, then integrate the accelerations over time to find velocity in X or Y… This can also give you the direction of travel…

The accelerometer output is about 1.5V steady state and ± .3 volt per G up to a max of 3g ie: moving forward (X+) at 1g you would get 1.5v +.3 v = 1.8volts, moving in reverse (X-), it would be 1.5v - .3v or 1.2volts… see the data sheet for precise information.

see: http://www.glenbrook.k12.il.us/gbssci/phys/Class/1DKin/U1L1e.html
and: http://www.math.ucdavis.edu/~hass//Calculus/HTAC/excerpts/node25.html
http://www.glenbrook.k12.il.us/gbssci/phys/Class/1DKin/U1L1d.html

see the data sheet on the First web site…

http://www.usfirst.org/uploadedFiles/2009%20Sensor%20Manual%20Rev%20B.pdf

http://www.usfirst.org/uploadedFiles/AD22305%20Carrier%20r0.1.pdf

http://www.usfirst.org/uploadedFiles/ADXL335%20Carrier.pdf

tom lafleur
mentor team 812
The Preuss School at UCSD

Of course, X, Y and Z each need to go to their OWN Analog inputs (you will thus use three analog inputs for all three axes). That means that the other end of the PWM cables you soldered in almost certainly needs to be reconfigured.

We mean in programing not in electrics we have the electrics figured out

OK, step zero would be to wire it up correctly. I guess you have this done already.

Next would be to use programming to simply read the value and display it. Pick one axis for now.

With the robot standing still, you’ll get a voltage (I think 2.5 volts, but look it up). Accelerating the robot in one direction will make that voltage go up, in the other direction it will go down.

To find out what voltage it will give in a 1 gravity field, turn the robot (or the sensor!) on its side, you’ll be able to read the change in value. If what I mean isn’t clear to you, let me know.

OK, once you can read the voltage and its changes, convert that to an acceleration in, say, meters per second per second. (m/s2).

Now to convert that to a motion reading: Let’s say you measure exactly one meter/sec2 acceleration, for exactly one second. After that one second, the robot is moving at a speed of 1 meter per second. I’ll leave it to you to figure out how far it went, but it is less than 1 meter.

But, step 1 is reading inthe analog voltage(s) and converting it to an acceleration value.

Have fun.