Introduction: Mini Dual Color Rotary Beacon Warning Light

About: Arduino and Robotics Nerd, and alumni of FIRST Robotics Team 5683 (Go R.A.V.E.!). Blinking LEDs with Arduino is still one of my favorite pastimes even after years of doing it.

In this Instructable, we will be creating a mini beacon light. You know, one of those old-fashioned spinning lights that they used to put on construction equipment before LEDs got big? Yeah. One of those. This one will be relatively simple, and small, but I'm hoping it will be fun to use with Arduino systems or as a party light or something. Maybe even as a real beacon on a vehicle? Who knows. In this project it will be powered through USB or barrel jack (5V-9V, 9V works best), but it can be modified to use a rechargeable battery as well.

Estimated time to complete: 2-4 hours

Special Skills used: Soldering, Hot Glueing, Painting

Level of difficulty: 4/10, beginner to intermediate

Total cost: If recycled, $0. Otherwise, $20 or less (likely a lot less, but depends on your area)

Why am I making this? Well, I had a bunch of parts left over from some of my previous projects and abandoned endeavors, and the urge to create something with them. I also had LEDs, and together these are the basis for a great project. In truth, I designed this project specifically because I was bored and tired of working on another project, so this is sort of a break for me.

Since I am blatantly misusing a drinking cup as a housing and a headphone jack as a rotating slipring for power transfer, and maybe some other things depending on how I fiddle with technicalities (don't we all love doing that?) I've decided to enter this in the Creative Misuse contest. If you like this project, please leave a vote!

By the way, if you guys like what I do here on Instructables and want to help me make more cool stuff, check out my new website. I have a whole ton of affiliate links to Gearbest for 3D printers and the like, and when I reach a milestone amount of funds from those I will be holding a massive giveaway with a 3D printer and some other cool stuff. So yeah, help me share the news, and thanks for all your continued support!

Step 1: Gathering Materials

I say this every time, and I'll say it again. Always have everything you need before starting a project, so that things don't end up half-finished due to missing parts.

This project was built entirely from left over, misused and recycled components.

You will need:

1x Mini DC Gear Motor (a faster spinning one will work better, mine is really slow)

2x SPST switch

6x 3mm LED, clear lens is best (any 2 colors, I used green and yellow/orange)

6x 5mm LED, clear lens is best (same colors as 3mm)

1x old USB cable (that you don't need or want)

1x 3.5mm 3-pole headphone jack (both male and female ends)

1x barrel jack (female, mine is the standard jack used by Arduinos)

1x clear plastic or glass cup (a clear Solo cup will do, but I used a glass cup)

Jumper Wires

Tinfoil (or silver spraypaint)

Cardboard (both corrugated and the thin cereal box-type card)

Acrylic Paint (any color, I used gloss black)


Hot Glue Gun

Soldering Iron

Multimeter? (Not essential but nice anyway, I had to use it for troubleshooting)

USB wall adapter (1 amp or more) or a 5V-9V supply with a barrel jack


Wire Cutters/Snips


X-acto Knife


Step 2: Cardboard

Cardboard... What would I do without it? But for those of you who know how tired I get of using cardboard, I have good news! I bought a 3D printer, which is currently being shipped, so y'all can expect to see a lot more projects a lot more frequently with much better quality coming along pretty soon!

Now where were we? Ah, yes. The cardboard.

Step 1: Trace & Cut:

Take your cup, and put it upside down on your corrugated cardboard. Trace the opening twice.

Now, cut out the two identical circles.

On one of the circles, mark a line.

Step 2: Thinner Cardboard:

Now, take your thin cardboard, and lay it out flat.

Trace two parallel lines 1.5 inches apart.

Take the circle with the mark, and starting with the mark at one edge of the thin cardboard, roll it along one of your lines until the mark has made a full revolution. Mark this point.

Cut out the strip you just created. If you wrap it around one of your circles, it should almost touch at both ends. Mine has a gap because carboard physics are strange.

Step 3: Smaller Thinner Cardboard:

Cut out 3 identical rectangles of cardboard 1.5 by 1.25 inches in size.

Step 4: Hot Glue & Foil:

First, glue the long cardboard strip to one of the circles. The face of the circle should be flush with the edge of the cardboard, this is the base of our beacon light.

Now, take the three small rectangles. Bend them into a curved shape, then glue them together so that they form the basis of a 3-sided reflector.

If you are using tinfoil, now is a good time to glue it to the reflector. Otherwise, take it outside and spraypaint it silver.

Now we can start mounting components!

Step 3: Mounting Components

This is a relatively short step, we're just going to glue some things before we start soldering.

Step 1: Motor Mount

Take your second cardboard circle, and do your best to find the center.

Cut a hole in the center, then glue your motor in place. Be careful not to clog your gears!

Step 2: DC Jack

On the base, cut a square hole for the barrel jack.

Insert the barrel jack in place, then gue it in. Make sure you can access the wires.

Okay, now we can move on to soldering stuff!

Step 4: Electronics

Whoopee, I have another chance to try not to burn my fingers! I honesly dislike soldering because my current iron is too massive for the little things I tend to do (it's an 80 watt iron) but it's the only quality iron I could find for a decent price. Whatever.

Above is the Wiring Diagram. You may attempt to follow that, or you can follow along here. Note that while following the diagram, there is an error with the LED section. Hover over the box for an explanation.

Also, anyone who knows anything about electronics will likely be puzzled by my use of a series circuit with no resistors while pumping 9V through LEDs not rated for more than 5V. Why in the world would I do that??

TL;DR I tried a parallel circuit in several variations with resistors and... nothing worked. The motor would spin, but the LEDs never lit.

I chalked this up to the motor drawing all the current away from the LEDs (indeed, I had a reading of 0.12 V when I checked the LEDs to see if power was flowing, and that's while drawing power from a 9V supply!) The only way I was able to make the circuit work well was with the LEDs in series with the motor, without resistors. The motor acts as a automatic variable resistor, so any voltage between 9V and 5V will work fine, the only real difference is the motor speed. I decided not to push it above 9V because I might risk frying LEDs, as they do get a little bit brighter with every jump up in power.

As to how it will work, we have a single power switch which turns it on and off, a second switch to change the color, and the rest is history. The interesting bit is the use of the 3.5mm jack as a slipring; I needed a way to transfer power through a rotational joint and I found it was perfect for this! If I really wanted, I could even integrate an Arduino and use Neopixels, becuase there are already 3 lines on the jack. How's that for perfection?

Step 1: Power Supply:

Cut off the non-USB end of your USB cord. Strip the power and ground wires (you can use your multimeter to determine which these are)

Solder together the positive wire from the USB to the positive (center pin) wire from the barrel jack.

Likewise, solder the negatives together.

Step 2: Switches and Motors:

Solder the positive wires from the power supply(s) to the center pin of one of your switches.

Solder one of the wires from your motor to either side pin on this switch.

Solder the other motor wire to the center pin of your second switch.

Step 3: LEDs:

Solder your LEDs together in "trees". Each tree should have a 3mm and a 5mm LED of the same color in parallel, and you should have 6 trees total.

Now, glue the trees to your reflector. You should have a green tree and a yellow tree on each side. If you used tinfoil, make sure nothing is touching the LEDs other than your glue.

Solder all of the short legs together. This is your cathode, or negative as I'll refer to it.

Solder all of the long legs of the yellow LEDs together. Do the same for the green, but do not connect the two colors.

Now, solder each of the 3 sets (green, yellow, negative) to your male 3.5mm jack.

Step 4: The other end:

This is where I had to use my multimeter. I used it to run continuity checks through the 3.5mm jack to find which pin was which. You should probably do the same, just to make sure.

After I determined the pins, I soldered wires of the appropriate color to the female 3.5mm jack. I made sure these wires were long enough to run from the top of the cup, down the inner wall and still had a couple inches to spare.

Now, solder the negative wire from the feamle 3.5mm jack to the negative wire(s) from the power supply(s).

Solder the green and yellow wires each to their own side pin of the second switch.


Uninsulated connections are dangerous as a fire hazard and present an irritating problem that will fry your power supplies and components if they touch. Fix the problem before it happens!

Step 5: Glue:

Now, remember that small gap on the base from 2 steps ago? Glue your first switch there.

If your second switch will fit, glue it there as well. If not, cut a new slot in the side and glue the switch in place.

Cut a slot for your USB cable, and thread it through from the inside to the out.

Now, you can slot the piece with the motor down into the base. Push it down until there is at least a 1/4 inch lip of the thin cardboard sticking up on all sides, then glue it in place, as level as possible.

Now we can move on to the final assembly!

Step 5: Final Assembly

Now, this is the tricky part.

Step 1: Centering:

Take your relfector piece (which should now have the LEDs glued down and the 3.5mm jack soldered on) and carefully attempt to glue it in as centered a position as possible on the motor.

After the glue dries, thread any of the excess wire on the 3.5mm jack down the center of the refector.

The trickiest part is this: you must now glue the 3.5 mm jack as close to center of the reflector's rotational axis as is humanly possible so it won't "wobble" as it spins. I found the easiest way to do that is to find the center while the motor is on, and then turn off the motor to glue it.

Step 2: Final bits:

Now all that is left to do for wiring is plug in the lights. Slot the 3.5mm jack together, and viola! Give this a test run while holding the jack in place (to keep the wires from tangling).

Now, test fit this inside the cup. If your cup is shorter, like mine, it will fit perfectly with a teeny little bit of space at the top. If this is the case, put a glob of hot glue on top of the jack and the wires, and put the cup in place so that the glue cements the jack and wires in position, unable to rotate and get tangled up.

If your cup is too tall, just use a small nut or standoff as a spacer in between the jack and the top of the cup, and then do the same as above. The wire shouldn't be a problem, that's what the extra couple of inches are for.

Once the jack is glued to the cup, glue the cup firmly to the base of the light.

Step 3: Paint!

Now, paint the base whatever color(s) you desire. I went for a simple, professional-looking gloss black.

And done!

Step 6: The Grande Finale!

So, after a few speedbumps, this project came out nearly perfectly. My only complaint is that the motor doesn't spin faster, but hey, I don't want to give anyone seizures either.

If you like this, please don't forget to give it a vote and perhaps consider making it a favorite!

If you have questions or comments, I will always reply no matter how stupid you think it sounds, so post it below!

And last but not least, if you made one, I really want to see how it turns out, so click that "I made it" and post a photo or two!

As always, these are the projects of Dangerously Explosive, his lifelong mission, "To boldly build what you want to build, and more!"

You can find the rest of my projects here.

Creative Misuse Contest

Participated in the
Creative Misuse Contest