Picture of DIY Bicycle Turn Signals

Living in a city, I use my bike as means of transit, riding from home to work, work to studio, errands, etc. When I ride at night, I am often concerned if other vehicles/people on the road can see my hand signals when I am about to turn. To make my night rides safer, I decided to build a turn signal system for my bike!

The following instructable will go over how to use a 555 timer to flash an array of LEDs, and how to mount LEDs in an acrylic panel, and cast it in resin.
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Step 1: Materials

Picture of Materials
You will need the following materials and tools to embark on this project.


The circuit
(1X) 555 timer - (Radioshack #276-1718)
(1X) 4.7 uF capacitor - (Radioshack #272-1024)
(1X) 100K resistor - (Radioshack #271-1347)
(1X) 10K resistor - (Radioshack #271-1335)
(1X) 220 Ohm Resistor - (Radioshack #271-1313)
(2X) tactile switches - (Radioshack #275-002)
(1X) proto board - (Radioshack #276-170)
(1X) single core wire - (Radioshack #278-1221)
(1X) 9v battery clip - (Radioshack #276-1718)
(1X) SPST switch - (Radioshack #270-324)
(30X) LEDs - (Radioshack #55050630)
(1X) solder - (Radioshack #64-013)
In this project I use a water-tight method of encapsulating circuits in polyester casting resin. This way I am able to ride in the all weather conditions, and still use the turn signals.

Turn signal and circuit housing
acrylic panel
pipe clamp, from the hardware store, slightly larger than the diameter of your bike seat's stem.
bike handlebar wrap
zip ties

Tools used:
soldering iron
glue gun
utility knife
angle grinder/palm sander
laser cutter

Step 2: Assembling your flash timing circuit.

Picture of Assembling your flash timing circuit.
After you have gathered your materials, assembly begins!

Please reference the attached fritzing file for the construction of your circuit.

You want to mount the 555 Timer IC so it straddles the center of your proto board. Solder into place.

Tater Zoid4 months ago

Okay, I am inspired to create my own turn signals. I'll let you know when I am finished. How are your bike trailer lights coming along?

audreyobscura (author)  Tater Zoid4 months ago


I am going to publish that project soon - it turned into an LED strip explosion. The project's done but I just need to finish the documentation :)

It turned out great.

EugeneL18 months ago

This is awesome. Beyond my abilities at the moment, but will definitely try it. Have a drawer full of dead bike lights to scavenge from.

This is beyond my skills, but wow, does it ever have commercial potential. Your design and functionality are excellent, and as a year-round bike commuter, I'd gladly pay for this add on. If it could be installed on my bike and powered from the dynamo hub, that would be perfect. I can see it as a built-in option on new bikes, too. It's fantastic.
Here is the complete unit wired up.
13, 7:37 AM.jpg
Here is the circuitboard I hooked it up with one LED and it just shines bright no flash. I'm going to go through the bill of materials and see if I missed something. Thank you for your help
13, 4:45 PM.jpg
I finished mine thank you for posting this. Are the blinkers to blink on and off like a car does? Or is my thumb going to have to do all that work. This was the funniest project I did in a long time. The instructions were FANTASTIC
audreyobscura (author)  markgrecowork1 year ago
The 555 timer will make them blink. Post a picture!
cdell11 year ago
That's cool!
ginnpc2 years ago
this is possible the most simple tutorial with a project like this that i've seen in a long time
matt3922 years ago
Wow - amazing Instructable! Great work
redtraceur2 years ago
Congrats the best documented instructable i've seen in a loooogn time definitely im trying this on weekend.
you are right! this is one of the best instructables IMHO.not just the idea,but also the explanation,details and documentation!
audreyobscura (author)  redtraceur2 years ago
my pipe clamp just snapped off, i recommend smooshing it into the resin once it gels. that way it is embedded in the body.
baltika2 years ago
Excellent idea! For an alternate build, I'd like to use a car's turn signal relay and some form of pre-manufactured lights. A car's turn signal relay also clicks to remind you that it's engaged, i.e. "a blinker is flashing." While perhaps not ideal for a bike, a car's 12 Volt electrical power system could also be used for other things like a car horn. A turn signal relay and horn should be pretty cheap at an auto wrecker.
Wally_Z2 years ago
Nice project, but I would have used an Arduino instead of a 555 timer IC.
mrmerino2 years ago
4 feet of heatshrink: $1.29. Just sayin'.
agis682 years ago
the idea is good but theese nude joins and hanging wires scares me...please gather all these cables and use some isolated tape in joins!
That's neat! The one thing that jumps out at me that I would do differently is spacing - your arrows are really close together and as such I could see some drivers mistaking it for just another blinkey (though the arrow shape helps avoid this confusion). Since my bike has a rack, I would consider mounting the blinker arrows on either side of my rack.

I also think it might be a good idea to try stepping it up a notch to also create a stop light indicator (perhaps if one can figure out a way to connect a switch to the brake levers) as well as switch all the signal lights to red so that they are more in line with what other vehicles on the road tend to have (I've noticed amber lights tend to be more-so for the sides of cars as well as the front, though there may be exceptions).

On a completely different note, how bright are these signal lights? Are they visible during the day, and how do they compare in brightness at night to automotive signal lights?
Very good idea, clearly explained. Congratulations. Sadly Belgian law forbids using them on bicycles. Lawmakers here drive cars...
Very nice project. Some small nits to pick as suggestions for improving it, or for others following it.

1. Switches are meant to be mounted to something. The ones you chose are PCB mount switches. They don't hold up well hanging by wires or held in place by tape. With your casting skills, I'm sure a switch mounted on a small piece of perf-board could be cast into a piece for the same spot.

2. Solder is not a secure mechanical connection between wires. It is an electrical connection only.

3. Although it is hard to tell from the photo alone, it looks like you used solid hook-up wire for the long runs to the handlebars. Stranded wire would be better as it is more flexible. Solid wire will break after repeated flexing, such as turning handlebars.

4. Use of multi-conductor wire instead of individual wires to the handlebar switches would make a neater, and less likely to get snagged on something, installation. Even small two-conductor wire, such as speaker wire, would be an improvement. Wire ties and following brake/shift cable housings is a good place to run wires on a bike.

5. Wire-to-wire splices in the middle of wires should be avoided. Make them extra long in the first place and trim to length at the end. If they must be made, make them secure by twisting the wire together to make a mechanical connection first, then solder. Insulate with shrink tubing. Tape unravels.

6. Laser cut acrylic? The same thing could be done with a drill press a lot easier. More people will have access to that. A scrap piece of that perf-board would make a nice template for drilling.

7. The on-off switch could be eliminated. The circuit only needs to be on when the turn is being signalled. The brake lever switches on the handlebar should be all you need. It might mean separate circuits for each side, but they do make a dual-555 chip. Instead of the switch between the LEDs and the timer, switch the power to the timer for the direction you want.

8. I'd integrate the 9v battery into the unit, instead of wire-tieing it to the bike somewhere. One less set of wires sticking out.
vinslet2 years ago
Why not buy an extra mountable reflector, take the reflector off of the mount, drill a small hole in your led casing and mount the case to the reflector.
I added an image to show what I meant for the mount.
This is a great idea ! although instead of using resin, I would simply cut a few more triangles out of acrylic With holes for the leds to sit in, Then place a clear piece over it without holes to waterproof it all (This way you could attach them with bolts or machine screws, So if anything breaks you can fix it.
rimar20002 years ago
Congrats, Audrey, this is a interesting and useful project!