Introduction: Automatic Bicycle Handlebar End Lights

About: I'm a husband and a father and I make stuff.

This Instructable will teach you step-by-step how to integrate automatically illuminating LED's into the ends of your bicycle's handlebars.

The lights operate using a reed switch and magnet so very little permanent modification of the stock handlebars is required. The only irreversible alteration required for this project is holes for the lights drilled into the handlebar end plugs. This modification can be done to any bicycle in an afternoon using only basic hand and power tools. If you decide to do this modification to your bike please take some pictures and I will post them here.

There are two main groups of people who I think could benefit from these lights. The first group is comprised of anyone who owns a bicycle. Much like books are great for people who can read, and cars are purchased most frequently by people who can drive; these lights are perfect for the bicycle owners of the world.

The second group of people who could benefit from these lights would be people who do not own bicycles. I know what you are thinking, "Without a bicycle where would they put the lights?" I thought of that too. The best solution I could come up with is that people in this second group should buy bicycles and join the popular kids in group one. As writer Iris Murdoch once wrote, "The bicycle is the most civilized conveyance known to man. Other forms of transport grow daily more nightmarish. Only the bicycle remains pure in heart."

The scope of this instructable is limited to bicycles with mountain bike style handlebars. This system could be easily adapted for road style "dropped" bars or even motorcycles but in an effort to maintain focus; those areas will not be explored in this guide.

Table of Contents

Intro- Project Overview and Table of Contents
Step 1- Parts List
Step 2- Parts Detail
Step 3- Inspiration and Development Background Information
Step 4- Design and Component Overview
Step 5- Circuit Construction
Step 6- Circuit Instalation
Step 7- FAQ's
Step 8- Bicycle Quotes
Step 9- Alternate Trigger Design and Other Information

The next step contains a full parts list.

Step 1: Parts List

Step 1 is a list of what you will need to make a set of these lights for your bicycle. If you are not sure about a part you see listed here, check step 2 for additional details.

Note: This project uses tools that can be harmful if proper safety procedures are not followed. Please be safe.

Parts and Quantities

1) Bicycle or at least the handlebars from a bicycle. (1)
2) Reed Switch (1)
3) LED's (2)
4) Button Cell Batteries (2)
5) 14 to 24 gauge Speaker Wire (approximately 5 feet)
6) Rare Earth Magnet (1)
7) Steel washer (1)
8) Car Washing Sponge (1)
9) Resistor (1)
10) Gloves (1 pair)

Tools and Supplies:

A) Soldering iron
B) Electrical solder
C) Electrical tape
D) Wire strippers
E) Drill
F) Drill bit

The next step contains additional information about the parts listed above.

Step 2: Parts Continued...

This step contains additional notes about the parts and supplies listed in step 1. If you read this and still do not understand something about the parts required please let me know.

1) A bicycle with flat or semi-flat handlebars will make following my instructions easier but flat bars are not required.

2) The reed switch is the hardest part to source locally. I used Mouser part# 816-RI-01CAA but any normally open reed switch should work. I suggest buying multiple switches because they break easily. There are millions of other fun projects you can make with the leftovers. This is one item where buying local may not your best option. The local electronics place where I live wanted about $8.50 per switch; I got 10 of them shipped to my door from Mouser for $12.

3) For LED's I used some generic 5mm diffused yellows from a Radio Shack LED multi-pack. Any LED's will work, although some colors may not be street legal in all areas. Blue and white LED's also have higher voltage requirements that must be taken into account if you choose to use them.

4) I used [!-You_ll-be-Surprised.../ Kipkay's 12V Battery Hack] to get some cheap button cell batteries. For standard LED's you need to provide at least 3V so any two 1.5V batteries run in series will work.

5) To connect the components I used some old speaker wire I had laying around the house. Any 14 to 24 gauge multi-strand wire will work.

6) I found a 4 pack of neodymium disc magnets in the craft section at Wal-Mart. I also found a nice selection of earth magnets at Northern Tool. If all else fails, the internet is full of websites selling this type of magnets. You can try different sizes and shapes but the magnets I used are disc shaped, about 1/2 inch in diameter and less than 1/8 inch thick.

7) The washer is used to secure the magnet to the glove. Make sure the washer you choose is ferrous (attracted to magnets) and in this case smaller and flatter is better.

8) A piece of sponge is used to hold the delicate glass reed switch in position and prevent damage from the vibrations inside the handlebars.

9) The resistor value will be determined by what batteries and LED's you use. I recommend the calculator at to determine resistor values for your specific application. If you are unsure about using the calculator in the link, a 47 ohm resistor is pretty safe for most applications.

10) I use Mechanix brand gloves available at any auto parts store. I tore up a ligament in the back of my right hand in a bike crash this spring and it took months to heal. A pair of gloves would have prevented that damage. Now I wear gloves any time I am on my bike.

B) Be sure you have electrical solder and not plumbing solder. They look about the same but function very differently.

F) Drill bit size will depend on what LED's you chose. You want the LED to fit snuggly in the hole made by the bit.

The next step covers the origin of the idea and a little bit of the background on the developement process.

Step 3: The Idea...

The ball began rolling on this project after a crash on a local multi-use path resulted in my bike losing one of the handlebar end plugs. With the plug missing I was able to see how much prime real estate went unused inside a set of bicycle handlebars. I began brainstorming ideas for using this space to add function and maybe even some style to my bike.

The limitations I set for what the modification could be were simple:

~Must fit inside the existing handlebars.
~Must be stealth while the bike is parked to avoid theft and vandalism problems.
~Must be removable if I get tired of it.
~Must not interfere with normal handlebar operation.
~Must be reliable and user serviceable.
~Must perform some function to improve the cycling experience.

I had a lot of ideas, but some off them were too far out there and others I just did not have the time/parts to do right now.

Here are a few highlights from the brainstorming process:

~> Bar-end Flame Throwing Device- Besides the likelihood of this modification being illegal, it really was not very practical either.

~> Electrified Security Handlebars- Basically the bars would act as a taser to would-be bike thieves. This is really pretty do-able but the likelihood of self-electrocution got it marked off the list.

~> Automated Bicycle Alarm- I am still considering this idea of a loud audible alarm housed in the handlebars that would be triggered if someone molests my bike while it is locked up. The small size and easy availability of piezo buzzers makes this one a strong candidate for getting built in the future so stay tuned.

~> Handlebar Radio- Some music while I am cruising the local greenway would be nice but external speakers are somewhat impractical and an easy theft/vandalism target.

~> Integrated Handlebar USB Charger- basically a Minty Boost shoved into the handlebars. I decided this did not "improve the cycling experience" and it was scratched from the list.

Finally, I decided I should start with something simple to get a feel for working inside the constraints of a small metal tube. Lights seemed easy enough. While researching for the build I found a company called XRL already makes and sells lighted handlebar plugs. I looked at the pictures of their product and saw an issue I felt I could improve upon. XRL's plugs have manual toggle switches that must be turned off and on individually. I already have 3 lights to turn on before I ride and I did not want to up that number to 5. I decided I could improve upon the commercial design by making my lights automatically illuminate when you get on the bike and go off as soon as you let go of the handlebars.

Very nice.

Warning: The next step contains educational content.

Step 4: Form and Function...

To begin, gather all your materials.

The only part that will be difficult to source locally is the reed switch. I have 3 options for electrical components where I live: 1) Radio Shack; does not sell reed switches. 2) The local electronics place; wanted $8+ a piece for reed switches. 3) Mouser; shipped 10 reed switches to my door for about $12.

Once you have begged, borrowed, or stolen all the parts on the list you are ready to start building.

But wait...

A contractor does not start framing a house without first looking at the blueprints...
A doctor will not put your arm in a cast without looking at an x-ray...
So we too are going to take a few moments to learn a little bit about what we are making, and how it works before we begin building it.

This page contains some pictures demonstrating the features and functions of the unit. These pictures are worth at least 1000 words.

The next step covers the construction of the circuit.

Step 5: Circuit Construction...

This page covers the construction of the electrical circuit outside of the bicycle.

I built the unit to be triggered by the right hand grip because I use my left hand to signal when I ride in traffic. For this reason my instructions are written as left side and right side indicating the sides of the handlebars as they appear when you are sitting on the bicycle's saddle.

1) Cut a piece of speaker wire long enough to extend all the way through the handlebars. This will be the power lead for the right LED.

2) Solder the right LED onto one end of wire you just cut making sure to pay close attention to which is the positive and negative lead.

3) Cut another piece of wire about 8 inches long and solder the left LED onto one end. Again, pay attention to the polarity of the leads.

4) Stack your batteries so they are in series.

5) Take a 6 inch piece of wire with the ends stripped about a quarter inch and put 1 wire against the top and bottom of your battery stack. Make sure the negative wire is not touching the side of the battery as the sides are positive and will cause a short.

6) Carefully wrap the batteries and wires with electrical tape. You need to pull the tape snug to ensure good wire contact. I recommend wrapping tape around the ends of the batteries to hold the wires down first, then a second piece of tape around the circumference of the batteries to hold them in alignment. This is a quick and dirty method of securing the batteries. If you know a better method of securing the batteries inside the handlebars please let me know in the comments section and I will update this step.

7) Solder the resistor to the end of the negative battery wire. Unlike the LED's, the resistor can be attached either way so just pick an end and solder it up.

Now you should have 4 electrical parts of the project sitting on your workbench. These parts are the left LED assembly, right LED assembly, battery assembly, and a lone reed switch.

8) Take both LED assemblies and locate the positive wires. Solder both positive wires to one end of the reed switch. Keep in mind that for ease of assembly the left LED wire will need to run back along the length of the reed switch. This wire can be soldered backwards.

9) Next you can solder both negative wires from the LED's to the open end of the resistor you soldered to the negative battery wire in step 7.

10) Solder the positive battery wire to the open end of the reed switch.

11) Now you should be able to test your circuit. Take your magnet and pass it near the reed switch. If the lights come on, skip to step 13. If the lights do not come on or will not stay on proceed to step 12.

12) If your lights failed to illuminate in step 11 you need to do a little troubleshooting. It is best to start at one end of the circuit and work backwards until you find the problem. The first place I would check is the battery connections. If they are okay, check the polarity of the LED's to make sure they are not backwards. Finally, you can check the connectivity of your solder joints and the function of the reed switch with an electronic multi-meter. Fortunately this circuit uses a minimal number of parts so troubleshooting is not too bad.

13) Congratulations! If the test worked, you have completed the hardest part of the project and you are just moments away from bike-light completion. The final steps in the assembly process do not require soldering so go ahead and unplug your soldering iron if you have not already.

14) Tape the reed switch to a piece of car washing sponge that is shaped like a cylendar. Size will vary because of differences in handlebars but it should be roughly 1 inch in diameter and about 2 inches long. This sponge will hold the delicate glass switch in place inside the handlebars. You may want to test fit the sponge prior to attaching the reed switch to ensure it is the correct size. If you cut the sponge too big it will be difficult to insert, and if you cut it too small it will not stay in place. One car washing sponge can be cut to make many of these cylendars. You can try several different sizes and shapes until you find one that works well for your application.

15) Pull the plugs out of the ends of your bicycle's handlebars. They should just pop straight out but I have been known to use a bit of persuasion from a small screwdriver if they are not cooperative.

16) Select a drill bit that is the same diameter as the LED's you chose. Carefully drill a hole with your selected bit in the center of each of the plugs you took from the bike. You can test fit the LED's that you have just wired up but do not fully install them into the plugs yet.

The next step will cover the actual installation of the light assembly on the bike.

Step 6: Installing the Circuit Into the Handlebars...

Installing the circuit you just built into the handlebars is not complicated but you must be gentle to avoid damage to the delicate solder joints. The process I used is detailed below but I encourage you to modify the directions to best fit your specific application.

1) It is a good idea to test your lights and make sure they work one last time before you begin the installation. Troubleshooting after installation means pulling everything back out and can be a real headache.

2) With both bar plugs removed from the bike, carefully feed a scrap piece of wire in from the left until it comes out the right end of the handlebars. This will be used to pull the wires for the left LED back through the handlebars. The bike can be laid on its side allowing gravity to assist in feeding the wire through.

3) Attach the pulling wire you just ran through the handlebars to the wires of the left LED. You will be removing this connection later so do not go crazy with it; a small piece of tape will work fine.

4) Slowly and carefully begin pulling the wire you just attached to the left LED assembly back out the right end of the handlebars.

5) Before the left LED clears that end of the bar you will probably need to feed the battery assembly into the right end of the handlebars. I used a large screwdriver to gently push the batteries in as I pulled the wires through from the other end.

6) Once the left LED clears the end of the handlebars you can detach the pulling wire. Gently push the left LED into the hole you made in the left bar plug. Once the left LED is securely fit into the plug you can feed any excess wire gently back into the handlebar and reinstall the plug.

7) Test the lights like you did before. If there is a problem, go back and check all your connections.

One side down, one to go!

8) With the left half of the handlebars complete, it is time to install and position the reed switch. Rotate the piece of sponge so that the reed switch is facing up. Gently insert the reed switch assembly into the handlebar end and push it in far enough that the switch is centered under the right hand grip. I used a large screwdriver to get the switch positioned in just the right place. Take your time and get it exactly where you want it. If the switch is not at the top of the bars, or is to far off to either side of the grip it may not trigger reliably.

9) Test again. You do not want to get finished with the entire installation only to realize a wire came loose.

10) Once you are satisfied with the placement of the reed switch, install the right LED in the same way you installed the left LED. Be gentle as you feed any excess wire back into the handlebar because you do not want to disturb the placement of the reed switch assembly.

11) Now you need to test it again, but you already knew that.

Almost there!

12A) You will need to find the correct position to install the magnet on the glove. Do this by putting on the right handed glove and gripping the handlebars like you do while riding. Make a mental note of what area of the palm of the glove is closest to the reed switch you installed earlier inside the handlebars.

12B) If you wish to use this system without gloves, skip to Page 9 of this Instructable for glove-less trigger instructions.

13) Without removing the glove, slide the metal washer inside the glove's palm area. Try to get it close to where you think the magnet needs to go to be in position to trigger the reed switch.

14) Put the neodymium magnet on the outside palm of the glove and you will feel it stick to the washer on the inside of the glove. You can adjust the position by pulling the magnet away from the washer slightly and sliding it around until you find a position that is both comfortable and efficient for triggering the lights.

15) Neodymium magnets can oxidize so a quick spray with some sealant or a coat of nail polish will keep the magnet from getting rusty.

16) Once you are satisfied with the position of the magnet for maximum hand comfort and triggering ability you are done!

After you build it- If you have any tips, tricks, suggestions, or improvements for this instructable I would love to hear them. Please use the comments section or send me a private message and I will gladly add your tips and credit you for your ideas.

The next step contains FAQ's about the device.

Step 7: FAQ's...

Q- I can not find any reed switches, what can I do?
A- Many online vendors ship worldwide. If you do not have a credit card I sugest you call the suppliers directly to discuss alternate payment options.

Q- I do not wear gloves when I ride, can I still use this system?
A- See Page 9 of this Instructable for an alternate trigger that does not require gloves. -OR- See next question.

Q- Can I use a regular on-off switch if I do not want to mess with all the magnet stuff?
A- Yes, the commercial design for lighted bar ends does use standard switches if you want to check them out here for ideas.

Q- Can I mount the lights facing forward if I do not like them pointing off to the sides?
A- Sure, you will need to come up with a way to mount the LED's so they point foward though.

Q- How much does it cost to build a set of these lights?
A- Even if you had to buy gloves, the LED's, a magnet, a reed switch, and some wire it should not cost more than $25USD. I paid $12 for 10 reed switches and a couple resistors from Mouser, $3 for a 4 pack of magnets from Wal-Mart, $3 for a multi-pack of LED's from Radio Shack, and I used wire and gloves I had laying around my house.

Q- I do not know how to solder, will you build a set of lights for me?
A- I would consider it. Send me a private message if you are seriously interested in having one built. Keep in mind that my time is worth money and although materials are only about $25, the price tag for having one built and shipped would be closer to three times that amount. I am consider offering just the parts for sale as a kit that you could buy and assemble.

Q- Is it street legal?
A- You should check your local laws. Personally, I am far more afraid of being run over by cars than I am of being ticketed by the police. If you use certain type of lights, such as flashing red or blue lights, you are increasing the risk of drawing unwanted police attention.

Q- How long do the batteries last?
A- The answer depends on what batteries you use.

Q- Can I install these lights on my _ _ _ _ _?
A- If you have space to mount the lights and batteries and can get a magnet close enough to trigger the reed switch, this system can be installed almost anywhere.

Q- Your instructions did not tell me to wear safety goggles and I accidentally soldered the reed switch to my eyeball. It really hurts.
A- At this point a handlebar mounting is out of the question but a magnet mounted to your eyelid can probably still be used to trigger the switch.

Q- Can I make the lights blink or strobe?
A- Substitute blinking LED's for a simple blink. For a side to side strobe effect I imagine you could use the sink-or-source ability of an astable 555 circuit to create a square wave that would strobe the LED's back and forward. That is well beyond the scope of this project and you would need to enlist the help of someone more knowledgeable about circuit design.

Q- How can I remove the lights if I get tired of them?
A- Just reverse the installation instructions. Pop the handlebar plugs out and remove the LED's from the holes they were mounted in. Pull the whole mess of wiring out through the right side of the handlebars. You can reinstall the old plugs with the holes in them or buy inexpensive replacements at your local bike shop.

Q- I made a bicycle related Instructable, will you link to it?
A- Sure, post a link in the comments section. If it is awesome enough I will add a link somewhere in my Instructable as well.

The next step contains some quotes about bicycles.

Step 8: Bicycle Quotes...

When man invented the bicycle he reached the peak of his attainments. Here was a machine of precision and balance for the convenience of man. And (unlike subsequent inventions for man's convenience) the more he used it, the fitter his body became. Here, for once, was a product of man's brain that was entirely beneficial to those who used it, and of no harm or irritation to others. Progress should have stopped when man invented the bicycle. ~Elizabeth West

When I see an adult on a bicycle, I do not despair for the future of the human race. ~H.G. Wells

For instance, the bicycle is the most efficient machine ever created: Converting calories into gas, a bicycle gets the equivalent of three thousand miles per gallon. ~Bill Strickland

The bicycle will accomplish more for women's sensible dress than all the reform movements that have ever been waged. ~Author Unknown (circa 1895)

The bicycle is just as good company as most husbands and, when it gets old and shabby, a woman can dispose of it and get a new one without shocking the entire community. ~Ann Strong

Melancholy is incompatible with bicycling. ~James E. Starrs

The bicycle had, and still has, a humane, almost classical moderation in the kind of pleasure it offers. It is the kind of machine that a Hellenistic Greek might have invented and ridden. It does no violence to our normal reactions: It does not pretend to free us from our normal environment. ~J.B. Jackson

Get a bicycle. You will not regret it if you live. ~Mark Twain

After your first day of cycling, one dream is inevitable. A memory of motion lingers in the muscles of your legs, and round and round they seem to go. You ride through Dreamland on wonderful dream bicycles that change and grow. ~H.G. Wells

It is by riding a bicycle that you learn the contours of a country best, since you have to sweat up the hills and coast down them. Thus you remember them as they actually are, while in a motor car only a high hill impresses you, and you have no such accurate remembrance of country you have driven through as you gain by riding a bicycle. ~Ernest Hemingway

Nothing compares to the simple pleasure of a bike ride. ~John F. Kennedy

Consider a man riding a bicycle. Whoever he is, we can say three things about him. We know he got on the bicycle and started to move. We know that at some point he will stop and get off. Most important of all, we know that if at any point between the beginning and the end of his journey he stops moving and does not get off the bicycle he will fall off it. That is a metaphor for the journey through life of any living thing, and I think of any society of living things. ~William Golding

All above quotes were taken from The Quote Garden.

Step 9: Other Stuff...


I designed the layout of this instructable to encourage the use of gloves while riding.

I feel that gloves are second only to helmets as vital cycling safety equipment. In reality, I know most people do not and will not wear gloves when they ride so I came up with an alternate triggering device that does not require the use of gloves.

The alternate design uses a ring with a magnet mounted on the palm side. If you intend to use this device you may need to position the reed switch inside the handlebar rotated slightly more forward than you would for use with the glove. The basic idea is to get the reed switch as close to the magnet as possible. I recomend building the ring before installing the switch to ensure correct positioning.


1) Magnet, same as glove method
2) 25 Cent Novelty Ring
3) J-B Weld

To begin, obtain a ring that fits your hand and you do not mind ruining. I used some rings from the 25 cent vending machines at the front of the local K-Mart but any ring you have laying around will work.

Next, prepare the J-B Weld according to label directions. You only need to mix enough to mount the magnet to the ring.

You'll use the cold weld to attach the magnet to the palm side of the ring. You want the magnet to be positioned so you can grip the bars comfortably with the magnet attached so shape the cold weld accordingly.

Allow the cold weld to set overnight and your trigger ring is complete.

The neat thing about brain injuries is that they only happen once. Please wear a helmet when you ride your bike.

Thank you for viewing my Instructable! If you liked it please vote for it in the Instructables Universal Laser Cutter Contest.

Some other bicycle projects still in the development process in my workshop include:

Automated Bicycle Pedal LED'sto compliment my bar end lights.

Build a Bicycle Alarm for under $5

and eventually,

How to stuff LED's into every aperture of a bicycle

The last one is tongue in cheek becasue I have 2 existing bike/LED instructables and more on the way. My wife calls my commuter bike the "The Christmas Tree" because of all the lights I have strapped to it.

I'd like to thank...

~> My wife for putting up with me and pretending to care about all my silly inventions.

~> Earth Traverse Bike Shop for donating several sets of bar end plugs for prototyping. If you are in the Knoxville area you should stop by and check these guys out. They have always treated me right and I have no reservations about recommending them.

~> Finally, I'd like to close this instructable with a sincere thanks to everyone who makes this site what it is. I am frequently inspired by things I see here, and I hope my instructables might inspire others as well.

In the movie Field of Dreams, Shoeless Joe Jackson once said, "If you build it, he will come", I'd like to add to that, "if you teach him how to build it, that's"