DroidCycle: Motherboard Schematic

Image of moduleI 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.

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100V LED Buck driver

driver board with test LEDs
Here the driver is seen powering a string of 8 white LEDs in series for a total forward voltage of 27.2V from a 30V input at 15mA.

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.

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