Passive RFID pressure sensor?

[dknguyen]

THis is a huge longshot, but I was wondering if anyone knew of any possibilities. Are there any short range wireless pressure (or contact or similar sensors) that are passive wireless like wireless RFID? I have some big foam-filled RC monster truck tires and was wondering if I could use them as impact/ground contact sensors by means of a sensor stick inside the tire along with the foam. Problem is they spin and I can't get a wire into them.

Anyone know of anything? A short range low-power (or passive transmission)RFID sensor for measuring pressure or contact?

I suppose I could stick a small battery into them, but obviously it's preferred to have just the primary robot batteries.

I suppose a possibility is a RFID reader that doesn't send out RF (so it doesn't energize the tag) where the tag would instead be powered momentarily by a piezo of some type whenever there is an impact, or be continuously powered via the rotation of the wheels (somehow?). I guess that would count as an active RFID system. Forever flaslight concept? heh. I'm not sure.

 

[justDIY]

how about measuring the suspension travel instead? I'd think you'll get all sorts of weird measurements from a pressure sensor placed in a tire filled with a solid, varying with the location of the sensor relative to the ground at time of impact.

an optical or resistive encoder measuring travel on the (presumably) independent suspension parts for each wheel should give you some idea of the force of impact.

 

[dknguyen]

There is no suspension...
https://i34.photobucket.com/albums/d133/run2jeepn/DSCF1844.jpg
Rather the spine twists. There is no verical suspension.

Yeah I was thinking a pressure tube would be too hard to find and that a resistive bend sensor wrapped around the foam would be better. The reason behind all this is to allow the robot to allow for tactile touch without interferring with obstacles it can actually climb over. The wheels are the first thing to touch any obstacle. I still need to get the signal out of the wheel somehow.