A customisable, illuminated craft project inspired by the classic neon signs of the past.
BUILD TIME: 1 HOUR
DIFFICULTY RATING: BEGINNER
Neon signage hit the world stage at the 1910 Paris Motor Show. Claims of displays before this time have been discredited. The display was made up of two tubes, twelve metres long, showing a bright red light. Paris was the first city to begin using neon signs, and in 1923, they arrived in the United States. By the end of the 1920s, neon signs had become a common sight.
Neon signage is made with thin tubes of glass, with a coating inside the tube of different chemical mixtures of phosphor, which give different colours. The air in the tube is replaced with the noble gas Neon, and a very high voltage is applied to each end. This high voltage ‘excites’ the neon, which fires off electrons that hit the phosphor and make it emit light. That’s the very simplified version, but we didn’t come here to deliver chemistry lessons, fun though that is.
It wasn’t long before people started making neon signs with different sections that lit up one after another. Like a flip book, this created the impression of movement. A wheel on a picture of a car at a car dealership, for example, can be made to look like it is spinning. It was also common to have the letters of a business name light up one after another. Our circuit won’t do that, because only one stage can light at a time and the previous stages will turn off, but we can still make moving signs.
Neon signs started to lose popularity in the 1980s, and are now rare. Developments in other technologies pushed neon to the sidelines for both visual and economic reasons, but neon signs remained popular in certain places and certain industries. They are now making a return as decorative indoor signage, often using more modern technology to produce something looking similar to traditional neon lights, but on a smaller scale. You can even get LED strips that look like neon tubes.
For our build, neon tubes are just the inspiration. We’re going to use coloured paper, LEDs, and cardboard to make our sign. We’re going to drive it with some recycled circuitry that we’ve used previously, with modifications to suit the new use. You’ll also need a shoebox to mount the whole thing in.
INSTRUCTIONS AND ADVICE
We encourage you to read all the way to the end of the article before you build. Not only will you then have a better feel for the overall picture as you build, but we sometimes discuss options or alternatives that you will need to have decided on. You will need some basic hand tools for most builds. Small long-nosed pliers and flush-cut side cutters meant for electronics are the main ones. Materials like tape or glue are mentioned in the steps, too. We always produce a tools and materials list if you have to go shopping, but anything that is lying around in most homes is just stated in the steps.
As always with Kids' Basics, we're building on a solderless breadboard. We avoid soldering to make Kids' Basics accessible to more people, but having an adult around can still be helpful. You won't need any particular skills besides being able to identify components at a basic level, and even then, we help as you go along. If, for example, you don't already know what a resistor is, you'll probably be able to work it out from the photos and description in each step.
We do provide a schematic or circuit diagram but this is just helpful if you already know how to read one. Don’t stress if you have never learned, but take the chance to compare the digital image of the breadboard layout (which we call a 'Fritzing' after the company that makes the software) to the schematic and see if you can work some things out. You can make this project from the Fritzing and photos alone. You might also like to check out our Breadboarding Basics from Issue 15.
There is a “How It Works” section after the build, but you don’t need to understand it to get a working build. We have a “Where to next” section as well if you want to modify, expand, or alter your build, but again, it’s not essential.
|TOOLS & MATERIALS* (SEE TEXT FOR DETAILS)
|Shoe Box or Gift Box
|Hot Melt Glue Gun and Glue
TOOLS & MATERIALS* (SEE TEXT FOR DETAILS)
* These are in addition to things that can be found in most homes
|1 x Solderless Breadboard
|1 x Pack of Breadboard Wire Links
|5 x Plug-to-plug Jumper Leads *
|5 x 150Ω Resistors *
|R6 to R10
|4 x 1kΩ Resistors *
|R2 to R5
|1 x 47kΩ Resistor *
|1 x 100nF Capacitor *
|1 x 2.2μF Electrolytic Capacitor *
|1 x 100μF Electrolytic Capacitor *
|4 x BC337 NPN Transistors
|Q1 to Q4
|1 x NE555 Timer IC
|1 x CD4017 Decade Counter IC
|9 x White High-Brightness LEDs %
|LED1 to LEDx %
|1m Light Duty Speaker Wire
|4 x AA Batteries
|1 x 4AA Battery Holder
* Quantity required, may only be sold in packs. # We use MKTs but other types of the same value will work. % Quantity varies depending on your artwork.
The Craft Build:
We’re doing things a bit differently this month. We’re building the craft first, because what you do here will cause changes in how you do the electronics. We’ll have two types of signs. One has a ‘moving’ section and a section that stays lit all the time, while the other is entirely animated. The electronics will work for both, and you can build both or choose one or the other. We’re only going to show the steps for one type, because to build the other, you just leave a couple of steps out.
We recommend asking your adult to help you search the internet for neon signs, as inspiration for your own. Some signs have pictures, others are just shapes or patterns. For ours, we chose a basketball moving toward the hoop. The hoop is always lit, while the ball is repeated in four places across the sign, lit up one after the other. If your picture is all movement, you can just leave out the always lit part.
We are building the circuit for four frames of movement, like four pages in a flip book. If you want more, you’ll need to modify the circuit board. If you want less, you can leave some unconnected.
Black cardboard can often be bought from discount variety stores (dollar shops) in packets of A4 sheets, and the same goes for coloured paper. If you cannot get black cardboard that way, poster cardboard will work just fine too. You can use a shoebox to mount it but if you don’t have one, the dollar shop again comes to the rescue. Most have gift or craft boxes that will suit.
On a sheet of black card, use a graphite pencil, often called a lead pencil, to sketch out your design. Draw it in outline form so that in the next steps you can cut just the sections to be lit.
Have your adult help you cut the outline of the shape with a sharp knife. A craft knife or snap-blade utility knife works best. Make sure you have something under your work to cut on. We use a cutting mat, but scrap cardboard works well if it’s thick enough.
The centre of most shapes needs to be black to make the light look like tubes of neon. Use scissors to cut a thin, even amount from anything you’ve cut out of your cardboard. This way, when you put it back later, you should have a gap for the light to shine though.
Turn over your artwork, and glue on coloured paper wherever you can cut out shapes. You can use different colours for different shapes. You might have to cut quite thin pieces here, so be careful.
Cut strips of black card at least 30mm wide, and use hot melt glue to secure them in a way that divides the different sections of your picture. You need to create a separate ‘zone’ for each section of the picture. In other words, one for each different set of lights, so only that part of the picture is lit and the light doesn’t bleed to the parts beside it as the light ‘moves’.
Cut a hole in the lid of your box big enough for all the parts of the picture to show through. Glue the lid onto the back of the picture, making sure none of the coloured paper is covered. We need to build the electronics before we can go any further, so we’ll do the last craft steps in with that.
The Electronics Build:
We’re going to use the CD4017 decade counter that we’ve used previously in Kids’ Basics, and drive it with the familiar NE555 timer Integrated Circuit (IC). We’ll build this circuit for four outputs but you can have up to nine.
Place the breadboard in front of you with the outer red (+) rail away from you and the outer blue (-) rail closest to you.
Install the NE555 with its notch or dot for pin 1 facing left. Also, add the wire links which join the matching supply rails.
Install six wire links. Three of them are to join pin 6 of the NE555 to pin 2, one joins pin 8 to the upper red (+) rail, one joins pin 4 to the lower red (+) rail, and one joins pin 1 to the lower blue (-) rail.
Insert a 47kΩ resistor (yellow-purple-black-red- -brown) between pin 3 of the NE555, and the wire links joining pins 2 and 6. Also install a 2.2μF electrolytic capacitor with its negative (striped) leg on the lower blue (-) rail, and its other leg to pin 2 of the NE555.
Insert the CD4017 with its notch or pin 1 dot facing left. Add the four wire links, three above and one below. At the top, pin 16 connects to the upper red (+) rail, while pins 15 and 13 connect to the upper blue (-) rail. Pin 8 connects to the lower blue (-) rail.
Add the three wire links here to connect pin 3 of the NE555 to pin 14 of the CD4017. If they’re blending into the others in your eyes, there’s a new red link from pin 3 of the NE555, connecting to an orange link which crosses the gap in the breadboard, which connects to a white link to the CD4017.
Insert four 1kΩ resistors (brown-black-black-brown- -brown). Count carefully and follow the image, because the components that connect to these soon only just fit. There is a resistor from pin 3 of the CD4017 that goes the furthest to the left, one from pin 2 that goes a bit less to the left, one from pin 4 that goes a bit to the right and one from pin 7 that goes further right.
Place four BC337 or similar transistors so that their middle (base) legs line up with the resistors from step 7, and the flat faces are toward you. Every leg should be in its own row, none together. Add a wire link between the right-hand leg (emitter) of each, and the lower blue (-) rail.
Install four 150Ω (brown-green-black-black- -brown) resistors, from the upper red (+) rail to what are currently empty rows. You’ll see the ones we chose line up with the so-far unused legs of the transistors on the other side of the gap. Add one more 150Ω resistor at the far right, in the last empty row.
For the part of the artwork that is always lit, we’ll need more than one LED. Plan out on a sketch of your artwork where the LEDs will need to go. Think about where the cardboard dividers for the ‘moving’ zones will be, and what will block the light from one LED to an area. We added the cardboard divider in black marker to help us.
We need a string of LEDs that light up together. Cut pieces of twin-core speaker wire that are long enough to go between the LEDs in your artwork. Cut one longer bit to go to the breadboard. Strip the ends, and twist them into pairs with the stripe on one side meeting up all the way.
Take the number of white LEDs you need and twist them into the exposed so that their longer legs go to the unstriped wire, and the short legs get wrapped up in the striped wire. You’ll need to tape the joins afterward, but we left some open so you can see.
Cut five plug-to-plug jumper wires in half, and bare the ends. Put four of them aside, and twist the halves of the last one onto the longer wire from step 12. Tape the joins. Make sure you can see which wire is the striped wire, and which is the unstriped wire. This string of LEDs lights the unmoving section of the artwork.
To light our basketball, we only need one LED per zone. If your zones are bigger, follow along from the step above to increase the number of LEDs. Because we have four ‘moving’ zones, we need four LEDs (or groups of LEDs) to light them. Cut four lengths of speaker wire that will reach from your breadboard to the zones, and bare both ends. Twist a half jumper wire to each side of one end, and tape the joins.
Twist an LED to the remaining end of each of the four speaker wires, so that its long leg goes to the unstriped wire and its short leg to the striped wire. Tape the joins. If your ‘moving’ frames or zones need more LEDs, twist more shorter bits of wire and more LEDs like in steps 11 and 12.
Connect the longer string of LEDs for the unmoving section of the artwork so that the striped wire, through its jumper wire, ends up in the lower blue (-) rail and the unstriped wire connects to the 150Ω (brown-green-black-black- -brown) resistor in the last row.
Connect each of the four LEDs or strings of LEDs so that the unstriped wires connect to the 150Ω (brown-green-black-black- -brown) resistors, and the striped wires connect to the left-hand legs (collectors) of the BC337 transistors. Work one at a time and left to right, so that all the components and connections for each ‘zone’ or frame line up, up and down the board.
Connect the wires from a 4AA battery pack with the red wire to the upper red (+) row and the black wire to the lower blue (-) row, and install the batteries. You should see the frames or zones light up one at a time, then there will be a pause before they light up one after another again. The string connected at the far end of the board, with no transistor, should be on all the time. If anything is not as expected, disconnect power and check all connections.
Using your planning paper from above, copy your artwork onto another sheet of black card, trimmed to fit inside the box. Use a pencil or knitting needle (if you have one) to make holes where the LEDs will go. Then run hot melt glue over the edge of the dividers, on the artwork that you installed in step 5 of the craft, and glue the new piece of card on.
Insert the LEDs through the holes, and use masking tape to hold them in. Make sure you’re placing the right ones in the right spot. The zones light one after another, so think about which one you want to light when to give the ‘movement’ you want.
Connect the batteries and give everything one final test. Check any connections have not come loose from the breadboard, particularly the wires to the LED strings.
If all is well, gently place the breadboard and batteries into the box and lower the excess cable in as you close the lid. You’ll have to open it to turn the circuit on and off, by taking out a battery or ONE of the battery pack wires.
How It Works:
There are two parts to this circuit. One part is centred on the NE555, and we’ll look at that first. The NE555 contains a device inside it called a flip-flop. This controls the output, and its triggers, most of the time, are to turn off at two thirds the supply voltage, and on again at one third. This is sensed by pins 2, the trigger pin, and pin 6, the threshold pin. Because the voltage at pin 2 is zero at the start, the flip-flop flips, and the output at pin 3 turns on. This does give an output to the load, but it also supplies current to the 47kΩ resistor, which charges the 2.2μF capacitor. It charges past the ⅓ point, and on until the voltage across it reaches ⅔ the supply voltage.
Pin 6 now comes into play. It is watching for the supply voltage to reach that ⅔ point, and when it does the internal flip-flop flops, and turns the output off. The output pin, pin 3, is able to both source (supply) and sink (drain to ground) current. With the output off, the capacitor discharges through the same 47kΩ resistor to ground through pin 3. When the voltage across the capacitor reaches ⅓ supply, pin 2 senses it and triggers the flip-flip to change the output to high, or on, again. The cycle continues.
This string of on-off pulses is fed to pin 14 of the CD4017. This is a decade counter, which means it has ten outputs. Every time the clock pin, pin 14, receives a high signal, at ‘advances’ the count. This means that the current output turns off and the next turns on. After the final output has turned on, the cycle starts again. The CD4017 has a reset pin, which can be fed a high signal to reset the count to zero at any time. If you want to make, say, a wheel with your artwork and do not want the pause between movements, take the next output along from whichever is the last one you use, and connect it to the reset pin.
The outputs of the CD4017 can at most deliver 10mA. That’s not enough for our LEDs which draw between 15mA and 30mA each. The BC337 transistors are placed so their bases connect to the outputs of the counter. The current supplied from these outputs is limited to safe levels by the 1kΩ resistors, which gives a small current to the base of the transistor.
Transistors are current amplifiers, which means that they allow a current from collector to emitter, and this current is proportional to the current at the base. After a certain minimum value, a very small current at the base causes changes in the chemical make-up of the transistor.
As the base current increases, so does the amount of current that can pass between the collector and the emitter. Once the base current reaches a certain upper value, the transistor is said to be 'saturated', and is passing is maximum current from emitter to collector.
Feeding too much current to the base once the saturation current has been reached can cause damage to the transistor, hence the resistors to protect the base. We've used an NPN transistor here, so the base current flows from the base, to the emitter, which is connected to ground.
In a PNP transistor, the other main type, current flows from the emitter to the base, and out through the control circuit to ground. This is why NPN transistors are usually used with their emitters to ground and the collector to the load, while PNP transistors are usually used with their emitters to the voltage supply, their collectors to the load, and the base to the control circuit.
The arrow is always on the emitter in the symbol, and tells you where the current flows, which tells you what type of transistor it is. The BC337 can handle 500mA continuously, so that’s enough for sixteen of our thirstiest LEDs.
There are a few other components on the board. The 150Ω resistors limit the LED current to safe levels. LEDs have a very low internal resistance, so low that they will not current-limit themselves. Without a resistor, more current will; flow than is safe, slowly destroying the LED. It won;t happen immediately, and it may even tale 100 hours, but it will happen. Even if you match the voltage exactly, don;t be tempted to go without a resistor on any LED.
The 100nF capacitor at pin 5 of the NE555 keeps electronic noise from causing issues when that pin, the control voltage pin which can alter the point that the flip flop switches at, is unused. The 100μF capacitor across the supply rails helps cope with small surges in current demand and keeps the power smooth.
WHERE TO NEXT?
You could alter the circuit to not have the pause after movement, as this suits some artworks and not others. This is especially useful if you want to have something like a car or bike wheel continuously appearing to rotate.
In this case, you might only want three outputs, or maybe more. Doing so involves connecting the next output after the last one you used for lights, back to the reset pin 15. In our case, if we took output 4 (remember, they start at 0, so we used 0, 1 , 2 , and 3) and connected it to Reset, our ball would start flying through the air again the second it hit the hoop.
You could also add more zones by using more of the outputs of the CD4017, but you’ll need a bigger breadboard and some careful wiring planning. Sadly the outputs of the CD4017 are not in the same order as its pins. See the diagram within the schematic for that. This is because of the internal structure of the IC.
You may also want to diffuse the LED light more before it gets to the coloured paper. This can be done with baking paper over the LEDs but this needs to be done before assembly, as hot melt glue does not come off easily.
You can also alter the timing of the counter by changing either the 2.2μF capacitor or the 47kΩ resistor, or both. Increasing either will slow the count rate, and decreasing either will speed it up.
Unfortunately there is no way for this circuit to keep the outputs on like a bar graph, so you can’t light the letters of, say, your name, one at a time with the previous ones staying on until the whole word is lit. A different circuit or a set of ‘latches’ for this one would be needed. You could fiddle with Silicon Controlled Rectifiers (SCRs) like we did in the Book Safe alarm back in issue 24, but it’s unlikely to be worth the effort. If you can figure that one out on your own, you’re probably ready to just research a more suitable circuit!