This is looking pretty good guys... I've made some major progress.

I've finalized the software for the sensor/transmitter and have been running bench tests to find a good balance between how it operates and battery life. What I DON'T want is a system like what is currently on the market that only updates pressure info every 5 minutes, yet still can't make their battery last more than a year or two. Whoever is putting systems like this on the market is either using really old technology or they don't know how to write good software.

I have this sensor programmed to measure pressure and temperature every 3 seconds and then transmit every 30 seconds. This is a pretty busy schedule for a sensor but I'm only drawing 12.5 uA (microAmps) to do this. Figuring a coin cell battery rated at 550 mAh, my calculations are EASILY exceeding a 5 year battery life. If I lengthen the transmit interval to 60 seconds or go to a 1,000 mAh battery, I think I can get 10 years out of this sensor.

With that said, long battery life is just the icing on the cake. The actual cake is having a system that'll keep you safe. Gradual pressure loss in a tire is one thing, but a blowout at highway speeds is something different altogether... and this is what I'm focused on.

At the end of every measurement cycle (3 seconds) the sensor compares the new pressure with the last pressure measurement and if there's more than 6 psi difference it'll send an alert to the receiver to light up the dashboard LED. For this to work, the LED has to be bright enough to be noticed in all riding conditions, it has to be mounted within your field of view, and you better be ready to immediately get off the gas if you ever see it light up.

What do you guys think?

Is 3 seconds short enough to catch a catastrophic tire blowout?

Is 6 psi a reasonable pressure difference to check for?

Any other thoughts?




Here's the LCD display wired to the receiver; I think it's a fairly good match to the OEM LCD. There's no pretty pictures, cute graphics, or any other extraneous distraction. It's there to give you tire information clearly and quickly, nothing more.

I currently have it configured to show front tire pressure and temperature on the top row and rear on the bottom row. Psi and Fahrenheit are shown; kPa and Celsius will be available for our metric friends.

The LCD is shown with the backlight off. The little blue box with white wires coming out of it is a potentiometer connected to the backlight control. I'm currently looking into an ambient light sensor that will automatically adjust the backlight when it gets dark. I'll bet some people will want it lighter or darker than others so I plan to have a manual control present also.

I was initially concerned that the characters would be too small to see well but I don't think that's the case. If you see good enough to ride, you'll be able to hold this at arms length and read it quite easily.




After seeing how well this little sensor does at drawing small battery current, I'm ditching the idea of adding an LF controller to the system. I initially planned to add an LF controller for two purposes: 1) to shut down the sensor when the bike is parked and 2) to allow the rider to request a pressure reading before getting on the bike.

Reason number 1 is unnecessary; as it's turning out, the sensor should run continuously for more than 5 years and not need to be turned off.

Reason number 2 will be baked in; since the sensor will run continuously, I'll make the receiver continuously capture data even when the bike is turned off. When you turn the bike off, the display will shutdown but data will continue to be captured in the background. When you get up in the morning and turn the key on, that will turn the display on and show the most recent tire pressure.