Bicycle Tail Light With Brake Light




About: Jack of all trades, master of a few.

Photo #1 is the Tail Light operating. Photo #2 is the Brake Light operating.

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Step 1: ​This Is the Tail/Brake Light.

The box is from an old Laptop power supply that burned out. I had to crack it open to get the guts out so the only way to hold the two parts together would be to glue or tape it. I used electrical tape so it's easy to get apart if I need to work on it. I used a bracket from an old drapery bar that's riveted to the cargo rack. You could also use an angle bracket

The LEDs are from Ebay. They can be used with 3 volts - 12 volts

Step 2: Photos of the Brake Switch and Power Supply

Photo #1 is the switch. It's just a strip of flexible plastic from a paint pail bent in half. The contacts are brass plated paper fasteners as in photo #3. Being brass plated, it's easy to solder wires to them. Two of the LED red wires are connected together separate from the other LEDs for the Tail Light and share the ground with the other LEDs. Photo #4 is the wiring diagram.

I used a RC Plane wheel stop on the cable (photo #5) to press against the plastic when the rear brake is engaged, also from Ebay. It takes a little trial and error to get the tension adjusted to work correctly. You want the Brake Light to come on before the pads contact the rim enough to slow the wheel down but not too soon.

Photo #2 is the power supply also from Ebay. This uses 3 18650 Lithium Ion batteries that can come from an old laptop battery but you can use a USB power bank or a battery box for AA batteries.

The Tail/Brake Light and Headlight are all running on 12 volts.

1 Person Made This Project!


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4 Discussions


1 year ago

being that close to the wheel, have you had any trouble with the contacts getting dirty and not functioning properly?

1 reply

Reply 1 year ago

To be honest, I haven't even taken this bike out on the road yet. It's an ebike that I've been working on for a couple months. I got everything done a few weeks ago and then the weather got cold. Really cold, like below zero F.

I believe there won't be a problem though because the switch is out in the open and will be easy to clean off. The contacts are bright brass so dirt and rain should fall right off.

There are rear brake lights for sale on ebay that use a similar idea for the switch but the're enclosed in a plastic housing. I think those could hold water and dirt and that might cause the switch to fail.

The switch I made cost next to nothing so replacing it wouldn't be a big deal if it did fail.