Tuesday, July 24, 2007

Handlebar "Remote" for LED Bike Light

Changing modes and using the high-beam was awkward using the switches mounted on the original LED bikelight box, so I added a "remote" within easy reach of my thumb. This will make the high-beam more useful when approaching treacherous areas of paths that require more light but are exactly the places where you don't want to take your hands off the handlebars.

This uses a "rocker" navigation switch to change modes, pushing it switches on the high beam. The mode-up and down buttons are simply wired in in parallel with the existing mode rocker switch, however the high-beam was a bit trickier and uses a BD681 darlington pair transitor to "pull" the control signal to the BuckPuck to ground. This has the same effect as the existing NC push-button switch.

This was necessary because all three switches on the navigation switch share a common wire, the Picaxe software and circuit is expecting the switches to provide +5v, so it was easier to make the high-beam use a transistor to cut-out the control signal than rework the remainder of the circuit to pull the Picaxe pins to ground when the switches are pushed. If I was building this again, using ground as the common wire would be much simpler.

There was enough room on the existing pcb to solder in the transistor, resistor and wires from the navigation switch. That's one advantage of using proto-board over a printed pcb.

One further mod would be to have a capacitor attached to the BD681 some how so that a single push holds the high-beam on for say 5 seconds, but I couldn't figure out how to get that to work. Alternatively, putting in a flip-flop to toggle the high-beam on/off would work too, but there was definitely not enough space on the pcb for that option.

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