Has anybody been able to find a data sheet for the provided accelerometer? (besides the one page spec sheet FIRST posted, http://www2.usfirst.org/2005comp/Specs/TI_Accelerometer.pdf). I’ve tried searching TI’s site and google to no avail so far.
That’s strange, I couldn’t even find the datasheet in the Texas Instruments website, using both code numbers (from the guidelines or the section 5 doc).
The accelerometer data sheet mentions a ‘cross axis sensitivity error’ of 3%, which suggests it must be more than single axis. One single axis accelerometer would be next to useless for nav purposes, unless your robot is going to move in 1D only.
Just because the accelerometer has a sensitivity to acceleration in another axis doesn’t mean it measures that other axis. Most likely it is a byproduct of the way the sensor is designed. There is only one signal pin, which leads me to beleive it is only a single axis.
Thanks for the sheet Mike. It’s not nearly as detailed as I’d had hoped, and I still have hope there is a more detailed one floating around somewhere, but this is certainly better then the single sheet FIRST had.
Check out www.klixon.com. This is the actual manufacturer of the device and has more info. There is also a document titled " Accelerometers and How They Work". It is a good tutorial and gives some clues as to use of this device. My estimate is that the two Hall Sensors giving rotational data from the BOT directional movement along with the data from the accelerometer could be used for BOT navigation. Dave Lavery mentioned PID in the kickoff presentation while he was demoing the robots. Do a search on the term or acronym PID relating it to robotics and you will find some links for connecting these sensors. I have just glanced at the software listed in the manual (has lots of nav stuff imbedded). There is a specific module named “PID.C”. So take it from there. Best wishes for the season! Larry U.
I have a TI sensors and controls rep coming in this morning. I will ask him about any more info he can get me.
I would like to point out however drawing posted at FIRST is typical of what I get from them normally for pressure transducers and pressure switches.
Pete
The drawing is a mechanical layout only. We need electrical specifications, pinout information, et cetera.
There is a minimal amount of electrical information on the drawing. The pinout is shown on the drawing in the upper left hand corner. A bit of electrical characteristics are on the far right.
With that data, one has enough information to hook it up and start using it. I would like a full datasheet, though.
Spoke with the TI sensors rep this morning. Showed him what we had. He said he would get some one in touch with me by close of business tommorrow.
That’s great!
Pete, did the representative contact you?
Has anyone figured out where to buy some more?
Joe the rep didn’t get back to me yet. I’ll be out of town on business until Saturday. Don’t know when I can bug him about the info prior to the 24th. Hopefully the info is sitting in my Inbox when I get back.
Pete
When we were putting together our accelerometer, we noticed that the positive line was BLACK, while the negative was RED. Did other people notice this? Or was ours just assembled wrong? If you didn’t check, then do so, so as not to risk breaking something.
Again, did anyone else see this, or are we all crazy, or did TI do ours wrong?
TobyHi,
The BLACK and RED wires on our plug are definitely switched. Sooo, the RED wire should be connected to COMMON (0V) and the BLACK wire should be connected to VCC (5V). The WHITE wire is the signal wire.
Using an oscope, we oriented the accelerometer so that the sensing axis was perpendicular to gravity. The voltage is about 2.7V (spec sheet says 2.5V). We then laid it down flat into gravity. The voltage changed by exactly 1V. The spec sheet reads 1V/g.
Regards,
ChuckB
Yes, it’s marked on the datasheet FIRST provided. The wires are marked on the device as 1, 2, 3, and the signal, Vcc, Gnd are labeled on the datasheet.
The color mis-match really throws you off doesn’t it?
I have to admit though, I prefer a 2-axis accelerometer.