Introduction: Pocket Sized Industrial LED Sign

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 project, we will be building a small LED sign from some scrap aluminum sheeting, modeling wire, and some basic circuit components I recycled from old toys and such. The idea is a layered sign built in such a way that the LEDs give a sort of underglow to the display and the edges of the sign. It will be powered by a rechargeable 3.5v Lipo battery, and will utilize 3 LEDs, operated by a simple slide switch.

I built this specifically as a contest entry, so please don't forget to vote!

Originally, I wasn’t making a sign. I was experimenting with trying to cut some slip-ring components for another Instructable I am currently working on. Short story shorter, I failed entirely on all accounts. I had a bunch of scrap metal and some modeling wire left over, but not enough to be useful for much. I got the idea for the sign when I took three lengths of leftover modeling wire and twisted them together to form steel cable. Of course, I had no idea what the steel cable would be useful for, but I was frustrated and somewhat bored, so I went ahead and made it anyway. Seeing the result, I thought it would make a good border for an “Industrial” style picture frame. And then I saw the contests here on Instructables and had the brilliant idea to make a mini LED sign instead, using some of the scrap metal I had laying in front of me.

Anyway, follow along, and let’s see where this will take us.

Step 1: Gathering Materials

It is always good practice to have all the required materials before starting a project.

All of my materials are bits of scrap or recycled components, so my project cost is sitting at a nice pretty $0. Factor in the original material costs, and you would be looking at a grand total of about $15, so this is a very cheap project.

You will need:

3x LEDs (any color, rated for anything between 2 and 3 volts)

1x 200 Ohm resistor

1x small SPDT slide switch

1x 3.5v 150-180 mAh Lithium-Polymer flat cell battery (and a corresponding charger)

1x connector for the battery charger

4x M3 hex spacer rods (about 0.5 inch tall)

4x short M3 screws (that fit the hex spacer rods)

4x long M3 screws (that also fit the hex spacers)

8x M3 nuts (which fit the long screws)

About 6 Feet of steel modeling wire, roughly 24 gauge

0.5 mm aluminum sheeting


Power Drill

Soldering Iron


Snips/wire cutters


Hot Glue Gun

(Optional) Gorilla Glue Gel

Step 2: Sheet Metal and Steel Cables

Sheet Metal is an incredibly useful and versatile material, even in scrap form. I find that a strong pair of scissors is enough to cut through my 0.5 mm aluminum, which is handy because I don’t like using saws and angle grinders on small pieces where my hand is more likely to get in the way.

I made my sign with dimensions 3.5 x 3 inches, but if you have a large bit of scrap and/or want a bigger size, you can change this with little effect on the rest of the project.


Step 1: Cutting

With a ruler and a writing utensil of your choice, mark out the dimensions for your sign, in my case 3.5 x 3 inches.

On each side around the perimeter of the box you just drew, add a ¼ inch tab.

Cut along the lines to get your sign, leaving the tabs attached.

Step 2: Bending and Marking

Fold over the tabs to a nice 90° angle using pliers, leaving the edges slightly rounded. The markings from Step 1 should be on the inside of the box you just formed.

On the inside of the box, mark a point in each corner to drill through for the screws.

Step 3: Drilling and Cables

At each of the 4 corners, drill through the marked points, using a drill bit about the same width as your screws, in my case 7/64” (3mm).

Cut the modeling wire into 3 strips 2 feet long.

Line up the ends and twist them together using pliers.

Stick one of the twisted ends into the drill’s chuck, and hold the other end firmly with a pair of pliers while carefully running the drill at a slow speed. This forms the steel cable.

Step 4: Screws and Borders

Insert the 4 short screws into the holes you drilled, and screw the hex spacers onto the back. Leave a gap between the front of the metal and the head of the screw for the cable to slot into.

Bend the cable around the screws, forming a border around the edge of the sign. Twist the two ends together at the middle of the top to tension the cable and straighten the sides.

Give the hex spacers a few twists to tighten the screws against the cable.

Now you can move on to create a design for your sign!

Step 3: The Displayed Design

This is the part where you create the part of the sign that makes it interesting: the design. In this sign, we will use a two-layer method: a 'negative' cutout of the design, overlaid by a slightly raised 'positive' cutout.


Step 1: A Negative Design

On a piece of paper, mark out the design you want your sign to have. Keep it simple; you will need to cut it out of the metal by hand. I originally intended to do my signature lightning bolt, but after some contemplation on the difficulty I decided to simplify it to the well-known Radiation Hazard symbol. Cut out your design and trace it on the front of the box.

Remove the paper, and use your drill to put some holes in the middle of the design so you can start cutting it out. You basically want to leave intact everything except the design.

Use the snips to carefully remove the design, essentially creating a 'negative'.

Step 2: A Positive Design

On another piece of metal, trace your design again. Add to the design a few metal tabs about 1/4 inch wide and 1 inch long.

Cut out the design, leaving it and the tabs intact.

Bend the tabs back, and then bend them out again 1/4 inch down, forming an "L" on the back of the design.

Step 3: Gluing

Slot the positive design onto the negative design, so the tabs are on the underside of the box and the design in front.

Glue the tabs in place with either hot glue or gorilla glue, making sure the positive is directly aligned above the negative.

Now we can move on to create the circuit!

Step 4: The Circuits!

Here we will create and mount the circuit that make this glow. It is essentially 3 LEDs in parallel, connected by a resistor (to avoid frying them) to a switch which can turn the power on and off, and to the ground lead of the battery. The LED circuit (including the switch), is wired in parallel to a charging port, so we can charge the battery when needed, without affecting operation.


Step 1: Plating

First, cut out two identical rectangles of scrap metal, with dimensions just a little bigger than that of the front of the sign.

Then, on one of these, mark where to put the holes in the corners for the screws. This is done by putting the front of the sign on top and tracing the edges of the hex spacers.

Drill through these points with the appropriate sized bit, and then use this as a template to mark and drill holes on the second rectangle.

Step 2: LEDs

On one of the two rectangles, mark three points for the LEDs to go. I would recommend placing them strategically under the largest bits of the design, in my case the three sectors of the radiation symbol.

Drill through these points with a 5mm drill bit.

Insert the LEDs into the holes, and glue them in place on the backside.

Solder all of the Cathodes (short legs) together to for a common Cathode.

Preferably with a different color wire, solder all of the Anodes (long legs) together to form a common Anode.

Cut off any extra space at the end of the legs of the LEDs.

Step 3: Battery, Switch and Charging Port

On the other rectangle, glue down the switch, charging port connector, and battery. The switch and charging port should be accessible from the side.

Solder wires from the positive red wire of the battery to the positive side of the charging port and a side pin of the switch. You can tell which side of the charging port is positive by plugging in the charger and using a multimeter.

Solder 2 wires to the black ground wire of the battery, soldering one to the negative side of the charging port and leaving one unconnected for later.

Solder the 200 ohm resistor to the center pin of the switch.

Isolate all connections (aside from those to the switch and charging port) with electrical tape to avoid shorts.

Step 4: Union!

Carefully solder the unconnected lead of the resistor to the common Anode on the LEDs. You can use a short spacer wire if needed. Also, you may want to insulate the resistor to be safe and avoid shorting.

Solder the remaining unconnected Ground wire to the common Cathode on the LEDs.

Test the circuit by flipping on the switch. I found mine quite enlightening... :-P

Now that our lights work, let's move on to final assembly!

Step 5: Final Assembly

And now, we will put the whole thing together to make our wonderful sign complete!


Step 1: Screws

Take the long screws, and slot them through the "bottom" plate with the battery and switch.

Screw two nuts onto each of the screws, letting them sit loosely in the center for now.

Slot the "top" plate with the LEDs onto the screws, letting it sit loosely as well.

Step 2: The Design Meets the Circuit

Align the hex spacers with the four long screws, and tighten the screws until they will turn no more.

Now, tighten the first set of nuts against the plate with the LEDs, sandwiching it against the hex spacers.

Tighten the last set of nuts in the opposite direction, pushing the plate with the battery against the heads of the screws.

If you think that the screws are too long, you can carefully cut them down with a hacksaw and a vice. Be careful not to make them too short!

Step 3: A Safety Precaution

Bend over the corners of the two plates with pliers, so that they no longer protrude outwards, but rather inwards.

Although this sign is pocket-sized, I wouldn't recommend actually trying to put it in your pockets due to the open-air circuit and the metal edges.

Step 4: Admire your work!

Turn this thing on, put it on your desk, and admire your handiwork!

Step 6: Results

For a scrap build with minimal parts and tools, I'm actually quite proud of my little radiation hazard sign. I really like the way it glows out the edges, too. The next step is to do this with better equipment, i.e. a laser engraver and a 3D printer, and integrate an Arduino so that it can double as a light switch, timer, or anything else conceivable. I challenge you out there to take this design and make it your own, and show me you know how to DIY! I hope to see many variations of this in the comments below, from all you lovely people clicking the "I Made It!" button.

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.

Oh, and don't forget to vote!

Questions, comments, suggestions, I want to hear them all in the comments section below!

Happy Making!


Trash to Treasure

Participated in the
Trash to Treasure

Pocket-Sized Contest

Participated in the
Pocket-Sized Contest

Epilog Challenge 9

Participated in the
Epilog Challenge 9