Mindboards

I want to build a segway, but I don't want to spend a ton on tilt sensors. I know that the Wii Nunchuk has a 3-axis accelerometer in it, and I know that it can be used with the NXT. Is an acclerometer enough? Or should I get a Wii Motion+ too? It has a 3-axis gyro.

Thanks.

I once tried to build a segway only with a wii Nunchuk but i failed. Possible though that i just wasn't good enough.

most segways use a gyro instead of an accelerometer. From my point of view a gyro is mathematically much easier to handle for this inversed pendulum what a segway actually is (just integrate the gyro values over time, and you'll get the turned angle).
Gyro drift might be a problem for analog gyros, but accelerometer noise is also an issue.
I would recommend to purchase an i2c gyro - (this http://xgl.minfinity.com/ seems to be excellent! )
or try to use the integrated gyro of an android smartphone if you want to take these efforts (IIRC it directly returnes the tilt / inclination value) ...
;)

Maybe you missed the part where I said I don't want to spend a lot?

I'd be really interested to see you use a wii motion plus

Maybe i'll try it, too, if i find the time...

inxt-generation wrote:Maybe you missed the part where I said I don't want to spend a lot?

no, I never miss anything -
but who knows, maybe you already got an android smartphone?
;)

(and I'm really curious how you will handle an accelerometer mathematically...) :P

You need a gyro, not an accelerometer. Perhaps with some super good algorithm you could use an accel, but I don't think it's ever been done on an NXT segway.

The Wii Motion Plus is great, but there is a huge delay in the readings (about 40ms compared to the HiTechnic Gyro). See the attached graph for a visual.
I recommend the dIMU by Dexter Industries. While it seems a little expensive, it's a 3 axis gyro, as well as a 3 axis accelerometer. The HT Gyro, and the CruizCore are both only 1 axis gyros.

If I'm gonna spend that much, then I'm gonna get this: http://www.pololu.com/catalog/product/1268 But, I literally cannot spend that much.

Does the delay make that much of a difference?

40 ms while trying to balance is huge! It might be possible to make it work, but I certainly wouldn't hold my breath.

I don't have access to a 'Droid, but I can can get to an iPhone 4S. Would it be possible to use that? Or would the BlueTooth delay be too much?