Close

Functional tire

A project log for No battery NFC air pressure sensor

Measure tire or ball pressure with your smartphone

captmcallisterCaptMcAllister 11/06/2015 at 03:470 Comments

ovember 5, 2015: Just in time for the end of biking season, I have a sensor tag inside a tire and I can read the pressure quite accurately. To put the tag in the tire, I first coated the PCB in epoxy and I also put a dab of epoxy between the antenna and the PCB. Epoxying the antenna on takes stress off the solder joints which were previously the only mechanical connection between the antenna and PCB. Encapsulating the rest of the components in epoxy is how I'm trying to ensure they won't break off when the tire is rolling. I was careful not to epoxy the pressure port on the sensor shut!

Then I cut a hole in a bike tube that was the size of the PCB. Only the pressure sensor really needs to be aligned with the hole, but I thought it would be less stressful on the PCB if the entire board got to rest inside the tire.

After that, I adhered the antenna to another piece of rubber cut from a different tire tube.

Then I used rubber cement to adhere the patch to the tube, being careful to align the PCB to the hole in the tire. This was kind of a pain, because the patch was hard to get to lie down flat. I should have used some clamps, but it worked out ok in the end. I didn't even notice any leaks when I inflated the tube.

I put the tube back in a tire and pumped it up and took some data. I can't believe the R-squared value on this!

So I think that's pretty much it in terms of proof of concept. It works! The next steps will be to finish a demonstration app and to get some miles on this tire to see how well the patch survives being ridden on. This has been a neat project so far. I think it might work better in a ball or other inflatable where it wouldn't be ridden on. Maybe I shouldn't sell it short though - I haven't tried to ride on it yet.

Discussions