Daylight Visible Bike Light - Front/Rear Combo - 100 Lumens on 2 AA's

Step 3 Building overview & options

this is a fairly simple electronics project, but probably a bit much to be your first electronics project. i am assuming you already know how to solder, and that you understand how to use a proto-board, that you know how to identify electronic components. if not, there are tutorials on the web about how to use proto-boards and such.

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the simplest possible build is a rear-only blinker, but once you've got that far it is very easy to add the front light or other options also.

simplest: ultimate rear safety blinker with 3-watt blinking led, AA rechargeable batteries

- option 1: add 3-watt front headlight (two bike lights in one!)
- option 2: front blinker instead of headlight, or front blinker/headlight toggle
- option 3: change to alkaline batteries
- option 4: support both alkaline and rechargeable batteries
- option 5: change to AAA batteries

you can pick and choose any options you want!

i built mine with a front blinker and support for both rechargeable and alkaline batteries, and i'll point out the places where other options differ in the steps.

the parts list tells you which parts you need for each option, and refer to the schematic as well, eliminating any parts that you don't need for the light you are building. in the schematic, D1, LED2, R3 and R4 may not be needed depending on your options.

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front headlight or front blinker?

this is personal preference. blinkers are a lot more effective for getting you noticed, on the other hand a headlight has obvious advantage if you want to bike somewhere without streetlights. it is a trivial circuit change to have either one, or to add a switch to have both. in the circuit diagram, you wire point A to C to have a headlight, and A to B to have a front blinker. use an SPDT on-off-on switch and then you can have either one and turn off the front too. i built the the front blinker but i may try switching to see how i like them - the front blinker is so bright everything reflective in front of you for 100 yards will blink back at you, you may find that annoying.

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the REAL simplest project: if you get stuck, maybe just scrap the electronics and have a super-bright non-blinking light? all you need then is a switch and battery, and use maybe a 1-ohm resistor to save battery life.