My primary transportation is an elBodaBoda electric assist cargo bike from Yuba bikes. It’s a great bike and a real car replacement with cargo and passenger capacity. The electric system comes with a tail light but no head light. It does however include an auxiliary power output that supplies 6V whenever the tail light (and control panel back light) is switched on. So I headed down to my local makerspace and quickly whipped up a headlight.
My ebike computer project was selected as a presentation for the “DIY Geek” series of lightning talks at the ARM Tech Conference this year. They were looking for people who had gotten their hands dirty using ARM Microcontrollers to give walk throughs on approaches and with a cortex M3 mbed at its heart and 2+ ARM processors on the android phone side, this project fit the bill. You can download a PDF of my presentation.
I want a featureful and easy to expand bike computer for my electric bicycle and I have a high performance computer with a great display that I carry around with me all the time so I am developing an Android accessory bike computer, the DroidCycle. I already have an “off the shelf” motor controller handling all of the high power electronics and I have developed my own LED driver module for driving the headlights and taillights from main battery power. For the Android interface and handling all the realtime sensor monitoring and control, I have selected the mbed LPC1768 because it has an available library for the ADK and the online compiler means that 1) I don’t have to waste any time setting up the toolchain myself and 2) I can work on my firmware in wherever I am in whatever tiny scraps of time I have.
My electric bike is my primary mode of transportation so I need to be able to ride it under all conditions and at night that means I need light, lots of light. It seems silly to me to have a separate battery to power the lights when I have this nice big battery for the motor and it would be one more thing to remember to charge. The hiccup comes from the fact that the bike battery is at 48V (with a soon to come upgrade to 80V) so a switching power supply is needed.