Kids Basics: Flickering Flame Fireplace

Daniel Koch

Issue 53, December 2021

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A fireplace diorama ready to decorate a room or have a mini White Christmas at home.

Every December, our TV channels are usually filled with the Christmas classics from America or Europe depicting Christmas stockings hanging over a fireplace. This staple of family and kids’ film has become iconic around the world, even though less than half the world is cold enough to have a fire at Christmas time, and Christmas only features in some cultures.

However, a fireplace goes well beyond Christmas. Prior to electricity, fire was the main way to heat a space. While open fires and hearth fires later gave way to items like combustion heaters and oil-fuelled heaters (the famous Tiger Kerosene tank among many brands being a feature still found on some fibro-era homes), the fireplace remains an image of warmth and cosiness.

While few homes have one today, yours can! This one is made from cardboard or foam board, and is electrically powered from a plugpack. We tried batteries but they don’t last long enough. Its light comes from LEDs and the ‘flame’ is tissue or crepe paper ‘flickering’ in the draught of a fan. Electronically, it is very simple. Most of the complexity is in the craft itself. Having said that, you can really reduce the complexity if you build it as an open fire. But then, where would Santa get in if there is no chimney?


This project is built around a small case fan. These can be relatively expensive, but we decided to use one anyway because if you look after it, you can use these fans for years. You can build one into any project that generates heat and needs airflow, so it is definitely not a single-use purchase! You can get really cheap 80mm fans online for use in computer cases, but they’re too big for our needs.

The stone effect we used is printed on an office laser printer and glued on. We have provided the pattern for download, however, any printer should work. Unless it’s black and white, of course! Many home printers are inkjet, which are not as colourfast as laser printers. Colourfast means how well the colour bonds to the page, and inkjet inks can run or bleed when wet. So, be careful gluing them. It still works, just be sparing with the glue.

If you don’t have a printer or want a laser print, there are many places where you can take a PDF file and have it printed. Officeworks chain stores have this service, but many independent office suppliers, as well as your local library, offer pay-per-page printing services. Additionally, you could paint the stone or brick effect on. Stone is easier because it is irregular, but careful work can give a great looking painted-on brick as well.


There are several parts of a fireplace that are important to think about before you build. The grate is a metal structure which contains the fire. Some fireplaces have one, others just sit the fire on the ground. We are making one because it will help direct the air from the fan and hold the skewers which mount our ‘flames’. These are often black metal and you may want to pre-paint or colour some cardboard to reflect this. We used black foam core.

The fireplace is usually set into the wall, but also extends past it. This means that the fireplace looks deeper inside than outside. We get this effect by making a cardboard wall that sits over your built fireplace. The base of the fireplace is called the ‘hearth’, and is usually thick stone, brick, or concrete to shield the floor from heat. It extends out past the walls of the fireplace, in most cases.

The fireplace itself is lined with stone or brick to withstand and reflect the fire heat. The walls are quite thick and stick out a bit past the wall of the building. The chimney is set at the back of this space. In modern fireplaces, the chimney is a metal tube and entirely within the walls of the building. On historic fireplaces, the chimney was wider and partly extended out past the house wall. You can see this in some of our pictures.

Finally, on top of the fireplace is the ‘mantle’, which is another stone or brick part to keep the fire heat contained. This is often lined with wood on the outside on more modern fireplaces, and is the ‘shelf’ section you see Christmas stockings hung from in the movies. All of these things vary a bit with time and place. Fireplaces from a 1600s English mansion look quite different from the living room fireplace of a 1930s American house. Have a look around the internet, with the help of your adult, for pictures to help you decide.


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 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 avoid soldering to make the build more 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 drawing 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.

The Build:

Parts Required:IDJaycarAltronicsPakronics
1 x Solderless Breadboard-PB8820P1002DF-FIT0096
1 x Packet Breadboard Wire Links-PB8850P1014ASS110990044
2 x Plug-to-plug Jumper Leads*-WC6027P1017SS110990049
2 x 47Ω Resistors*R1, R2RR0540R7526DF-FIT0119
4 x Red High-Brightness LEDsLED2, LED4, LED7, LED9ZD0156Z0862C-
6 x Amber or Yellow High-Brightness LEDs #LED1, LED3, LED5, LED6, LED8, LED10ZD0166Z0866A-
1 x 50mm Case Fan-YX2504F1045DF-FIT0240
1 x 2.1mm DC Screw Terminal Line Socket-PA3713P0610AADA368
1 x 12V DC 250mA MINIMUM Plugpack-MP3147M9273BSS313080030

Parts Required:

* Quantity shown, may be sold in packs. You’ll also need a breadboard and prototyping hardware.

# Our LEDs came from, so voltage and current data may be different for LEDs from other suppliers.

This build does rely on a sharp craft or box cutting knife, and hot melt glue. This means having an adult help you is an absolute ‘must do’! You might have to plan some time with an adult to help you, whoever that adult ends up being. We think this might be a fun project with your grandparents, but an old enough sibling would be ok, too. As long as there is an adult available to help at the time and place you are going to build this, you should be ok.

The project is built into a small cardboard box. We used a standard mailing box, which many homes have a supply of these days, especially if you live in a state that went through lockdown. If not, you can use any similar sized cardboard box, or buy a mailing box from your local post office or office supplier. The rest of the build is made from foam core board. This versatile stuff is available at office and craft suppliers, but you can cut up a corrugated cardboard box instead. Foam core is just easier to cut, and is nice and flat and smooth to work on.

Step 1:

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 wire links to connect the two red (+) rails to each other, and the two blue (-) rails.

Step 2:

Install the first yellow LED in the middle of the board near the upper rails. Its legs need four empty rows between them. The long leg goes to the left and the short leg goes to the right. Do the same for a yellow LED against the lower rails, too.

Step 3:

Insert the four red LEDs. One goes on each side of the yellow LED already installed. Make sure the long leg goes to the left, and the short leg to the right. Also, make sure there are four empty rows under each LED, and that the leg from one is in the same row as the leg from the next LED.

Step 4:

Place four more yellow LEDs, outside the red ones. Again, there should be four holes underneath each, and the long legs go to the left, and the short legs to the right. Make sure there is one hole between the LED leg and the edge of the board at both ends, for the next step.

Step 5:

Install a 47Ω resistor (Yellow Violet Black Gold Space Brown) between the upper red (+) rail and the left-land-most yellow LED. Install another between the lower red (+) rail and the left-hand-most LED in the lower section. At the other end, place wire links between the final LED leg and the blue (-) rails.

Step 6:

Twist the wires from the fan loosely together to keep them neat, and push the bare ends into the power rails. The Red wire goes to the red (+) rail, and the blue or black wire goes to the blue (-) rail. Whether you use the upper or lower rails is up to you.

Step 7:

Insert two plug-to-plug jumper leads with a light-coloured one in the red (+) rail and a dark-coloured one in the blue (-) rail. Again, whether you use the upper or lower rails is up to you. Take a screw terminal DC socket, and install the light wire to the + terminal, and the dark wire to the - terminal. Make sure the pins are under the screws, not caught beside them.

Step 8:

Take the 12V plugpack and check the end. Most of the store-bought ones have heads that can change direction, unless yours is a left-over from old equipment. You need to have a centre-positive setup for this. There is a break-out elsewhere in the article that explains how this works on different plugpacks. When you’re sure all is well, plug it into the socket, and turn on the power at the wall outlet. You should hear the fan spin and see the LEDs light up. Turn it off if all is well. If not, see ‘Testing’.

Step 9:

Take a cardboard box to be the base of your fireplace, and open the lid out flat. With a sharp knife and a ruler, slice off the lid along the hinge. Using the ruler and a pencil or pen, mark lines from corner to corner, to find the centre. Be sure to do all of your cutting on a safe surface!

Step 10:

Cut a rectangular hole in the middle of the lid, using the downloadable template. Cut the lines ‘Cut This Line First’, then cut out the small hole in the middle. Line up the lines so they match the ones drawn on the box, then draw around the outside of the paper before cutting out. Use a sharp knife and a ruler for the cutting out.

Step 11:

Place the fan in the middle of the back panel of the box. Use a pencil slipped through the blades to draw a circle around the inside of the fan. It doesn’t need to be perfect. Also, draw around the outside of the fan. Remove the fan and cut this circle out, slightly wider than the drawn circle.

Step 12:

Turn on your hot melt glue gun. While it warms up, cut the pieces of cardboard or foam core board to make the grate. These are strips 1.5cm high. Two are 12cm long, and two are 5cm long. You can mark your cardboard or glue the template to the back, and use a sharp knife and a ruler to cut the strips.

Step 13:

Take the template that you cut the middle out of earlier. You will need to Cut out the area inside the ‘Cut This Line Second’ line. Use inside of this cutout template to line up the pieces of the grate, and glue them to the top of the lid.

Step 14:

Cut a hole to one side of the back of the box, to allow the DC socket through. Use hot melt glue to attach the socket to the bottom of the box, with the end out a bit so it will go through the hole when the box is assembled. Also glue the fan on. Make sure you find the arrow on the fan body which shows which way the air goes!

Step 15:

Place the breadboard on the middle of the box, and glue the back of the box together. Without the lid attached, the back of the box will no longer stay together on its own. Place the lid on top temporarily, and use the hole to line up the breadboard so the LEDs can shine through. Take it off again and use Blu Tack to hold the breadboard in place.

Step 16:

Cut two slots in each of the short ends of the grate, so that the end pieces are divided into roughly equal sections. The slots need to go most of the way down the grate. They hold bamboo barbeque skewers later on, so make the slots slightly narrower than the skewers.

Step 17:

Cut pieces of white crepe paper to look like flames. You can go for basic triangles, or shape the edges to look more uneven. We used a mixture of both. Lay out enough to make two rows 9cm long with a few small gaps.

Step 18:

Run a bead of hot melt glue along a skewer, then lay it down over the ends of the crepe paper flames. Repeat for the second set of flames. Trim the bottom with scissors so that there are no loose bits of paper to flap around below the skewer. Only trim to the glue, don’t worry about trying to trim the glue flush to the skewer.

Step 19:

Lay the skewers into the slots in the grate. Place them so that the paper flames are arranged straight up, although hopefully, they will fall over easily, which is important later. Once you are happy that the flames sit over the hole in the box, cut the ends of the skewers flush with the sides of the grate.

Step 20:

Place the box lid onto the box, and seal the gaps with masking tape if needed. It is a good idea now to test it, so plug in the power at the back. The fan should start and the LEDs light up. If not, check connections. If so, watch the paper and make sure it moves in the air current from the fan. You can experiment with different shapes and sizes of paper pieces. Just make up more skewers, and change them out to see the effects.

Step 21:

There is no longer a cutting guide for these steps as they will be different depending on the box you used. Cut pieces of foam core board 10 to 12cm high. Hold a ruler up to see which height looks good before you mark and cut. The pieces need to go along the back and sides of the box. But remember, the sides need to be at least 4cm shorter, to leave a hearth.

Step 22:

Glue the back and sides on, along with more pieces to form thick walls. These will be two pieces for the front, and two for the inner sides. This gives the thick walls that most fireplaces have. You should now have a fire in a grate, inside a thick-walled fireplace, with a hearth in front.

Step 23:

Make the mantle by stacking three or four pieces of cardboard or foam-core the same size and glueing them together. You can cut each layer to form the stepped mantle seen on some fireplaces, but we went for the classic, old-fashioned ‘slab of stone’ style with square edges. Make sure the mantle overhangs the walls by at least 1cm for the proper effect.

Step 24:

Before gluing the mantle down, cover both it and the walls of the fireplace with either stone or brick print-out. You could also paint them plain colours, or paint on brick or stone. Note that the inside of a fireplace would never be painted, so use colours like smooth stone or concrete. Also, some mantles are edged with timber. Glue down the mantle.

Step 25:

Most fireplaces are set into a wall, so we need to make one for the top of our fireplace. Cut a piece of cardboard or foam core board The same width as the mantle, and either paint it or glue coloured paper to it. You can also add a chimney. Metal tube chimneys are hidden inside the wall, but older stone or brick chimneys come through.

Step 26:

Glue the wall to the top of the fireplace, about half-way back from the front of the mantle. Use a cut-down skewer as a brace to help keep it upright. You could also cut braces from cardboard.


If at any point you power up your circuit and there is neither light nor sound, unpower it immediately and firstly check the polarity and voltage of your plug pack. If both are correct, work forwards. Check connections from the back of the 2.1mm DC socket, where the wires may be beside rather than under the screws, or the screws may be in contact with plastic insulation and not metal wire. After this, follow to the board. Make sure all the polarities (- and +) are correct.

If you got fan movement and not light or light and not fan movement, check individual connections. Check for physical jamming of the fan, and each LED leg. It is easy to have one in the wrong row, or an LED the wrong way around. Also, check the power supply connections at each end, so the resistor is in the + rail and the wire link in the - rail.

If you can’t find a problem and it still doesn’t work, take a break, do something fun. Move around or eat something bad for you like ice cream, and come back to it later with a fresh mind and rested eyes.


On the face of it, this is a really simple circuit. However, there is still plenty to learn. However, it won’t take nearly as much explaining as some Kids’ Basics, and some makers will already know this stuff. We use LEDs a lot in Kids’ Basics, but rarely like this. Often, we use one resistor per LED. This time, we have five LEDs per resistor, and two groups. What’s going on?

All electrical circuits can be broken into two basic categories: Series, and Parallel. Sometimes, you can have a mix of both, which is what we have here. To read on, we have to assume you already know a bit about voltage and current. If you don’t, we’ll have to explain it another time because it would take quite a few pages to do properly! That’s the reason we need to assume it instead of just explaining it anyway.

This diagram shows three light bulbs. They each have a voltage drop of 12V across them, which means it takes 12V to make them light properly. There is 12V between V+ and GND, so that’s perfect. Each bulb also draws 100mA. Because the voltage from the supply is connected to one side of each light bulb, and the ground to the other, current flows from the supply, through each light bulb, to ground. 100mA flows through each bulb. This is a parallel circuit. In parallel circuits, voltage drop stays the same for each branch, and current adds up. That means this circuit draws 300mA at 12V, because there are three 100mA light bulbs in parallel. If we added a fourth bulb, it would draw 100mA too, and the total would be 400mA.


Most plugpacks that you can buy as generic items not designed for a specific piece of equipment have a system where the tip can be changed, both for size and polarity. Polarity means whether the inside is positive and the outside negative, or the other way around. 95% of equipment uses a centre-positive arrangement, which means the inside of the plug is positive and the outside negative.

Many plugpacks, if they have a fixed plug, have the polarity marked on the body. So does most equipment that needs a plugpack. It will have the voltage, whether it is DC or AC, and the current required (on equipment) or the current available (on a plugpack).

To cope with different plug sizes, there is usually a two-pin arrangement on generic plugpacks and a selection of plugs. Instructions are provided on how to tell which way is which. Sometimes they are a label on the cord, while sometimes it’s a piece of paper that you either don’t see and throw away with the packaging, or lose before you need it. The two common systems. One has the word ‘TIP” marked on the cord end of the two-pin socket, and a + and - sign marked on the plug heads: Line up the + with TIP for centre positive, and - for centre negative. The other pain system is to have + and _ on both the heads and the cord socket body. Line up + with + and - with - for centre positive, or + with - and - with + for centre negative.

What if we connected three of them one after another? 100mA would flow through the first one, then through the second, then through the third. Only 100mA would be drawn! However, the voltage drop is fixed. Each bulb draws 12V, and it does not come out the other side because the energy is used in the light bulb. It has no more potential. The current moves (which is why we have to have a circuit even though the energy is already used) but it can do no more work. The bulbs would not light.

Instead, voltage drops in a circuit add up. We would actually need to provide this circuit with 36V! 12V would drop across the first light, 12V across the second, and 12V across the third. This is a series circuit. In series circuits, voltage drops add up and the current stays the same.

It gets more challenging when we talk about different voltage drops and currents. In the parallel circuit, the voltage drop across each branch will always equal the supply voltage. That’s fine if you just have a resistor, because the voltage drop can be anything, the current changes to suit. More on that in a moment with Ohm’s Law. However, if it’s not a resistor, we have trouble. What if one light bulb was 12V while the others were 6V, and the supply was still 12V? The two 6V ones would still drop 12V across them, and probably fail.

In a series circuit, what if the light bulbs are all 12V but one is rated for 500mA while the other two are rated for 100mA? Depending on how the bulbs are made, either the 100mA bulbs would limit the current and the 500mA bulb would be dull, or the 500mA bulb would present as a partial short circuit, drawing too much current through the 100mA bulbs and destroying them.

Before going further, we need to talk about Ohm’s Law. It applies for now to pure resistors, which means components which only have resistance. That is, they do not have capacitance, inductance, or reactance, and are not semiconductors. Basically, plain wire, and dedicated resistors. Ohm’s Law states that the voltage dropped across a component is equal to the resistance of the component in Ohms, multiplied by the current flowing through it in Amps.

Some things have a fixed resistance. For example, resistors and wire. It is actually not fixed, it is affected by temperature and other factors, but for our purposes, we can think of it as fixed. Wire has very little resistance but the resistor as a component is designed to have more. They are always measured in Ohms, or multiples like kilohms (one thousand ohms) and megohms (one million ohms). That means that we look back at the triangle. If we leave in resistance because it is fixed and known, we get voltage drop divided by resistance equals current.

For a circuit of ideal resistors in parallel, the voltage drop across each will be the supply voltage. Therefore, the current through each is found by Ohm’s Law. In this circuit, we have a supply voltage of 5V, and resistors of 100Ω, 1000Ω (1kΩ), and 10,000Ω (10kΩ). The whole voltage drops over each one, so we used Ohm’s Law to find the currents. The total current drawn by the circuit is 50mA + 5mA + 0.5mA = 55.5mA

What happens if we connect the same resistors in series? The voltage drop is now spread across all three, but not equally. It is spread equally per ohm so the 100Ω resistor drops less than the 1kΩ resistor, which itself drops far less than the 10kΩ resistor. The current, however, is based on the total resistance. So, the voltage drop is across all three and the current is based on the total resistance. That leaves us with the equation with the diagram:

In any given series or parallel circuit, the whole supply voltage will be dropped across any connection from positive (V+) to ground. With resistors, the voltage drop can change, as long as the total power turned to heat by doing so does not exceed what the resistor is rated for. However, many components are not like this. Many components, including most semiconductors, have a fixed voltage drop, and a current rating. The voltage drop is the value that it takes to make electrons move through the material. Exceeding it can cause damage. These components also usually have a current rating. Exceeding that can damage things, too.

So, you might have spotted the problem. We want to light up a bunch of LEDs. LEDs have a ‘Forward Voltage’ rating, which is the voltage at which they emit the best light. It is usually close to the maximum voltage they cope with. So close that we can consider the Forward voltage (VF to be the maximum voltage. This is a voltage drop, as work is done and energy lost in doing so. They have a maximum current, too. The catch is that LEDs do not have enough internal resistance to limit the current passing through them. If you connect an LED with a VF of 3V to a 3V supply, more than the rated current will pass through. It won’t fail straight away, but it will fail early. Even if it lasts 100 hours, that’s nothing for a device rated for 100,000 hours.

Here is our circuit schematic. Each LED will only drop its VF across it. We know from above that we can add the VF values together and pass one current through the lot. However, the total supply voltage must be dropped across the branch in a series circuit. Happily, this works in our favour. We need to limit the current through the LEDs! Different colours of LED have different forward voltages. Red LEDs typically have a VF of 1.6V to 1.8V, amber and yellow 2V to 2.5V, and green, blue, and white LEDs from 3V to 3.5V. Check your LED’s datasheets from the seller if available. Our red LEDs have a VF of 1.8V while our amber LEDs had a VF of 2.3V. Current was 30mA for both types.

We knew we would be working with 12V, so we chose to try three amber LEDs and two red. That’s (2 x 1.8V) + (3 x 2.3V) = 3.6V + 6.9V = 10.5V. Note the bracket we added so you don’t forget order of operations. At a total 10.5V of drop across the LEDs, we needed to drop another 1.5V to make it to 12V, and we want it to happen at 30mA. Enter Ohm’s Law!

1.5V ÷ 0.03A = 50Ω. Note that we converted 30mA to 0.03A by dividing 30 by 1000, because we need all calculations to be in base units and there 1000mA in an Amp. Also, 50Ω resistors are hard to get, so we went with 47Ω. It’s close enough in this case.

However, that still wasn’t enough light. That’s why we have two identical series strings connected in parallel. We can add as many of these strings of five LEDs and one resistor as we want. Each one drops 12V and draws 30mA. We just add 30mA to our total current draw for each branch we add. Our LEDs, then, draw a total of 60mA for this circuit.

We chose to run the circuit off a plug pack because the fan draws 190mA. Added to the LEDs, to give 250mA, that would drain batteries too quickly. If the fan was just a DC motor, it would need a separate supply or lots of filtering, flyback diodes, and other fun to avoid damage to more fragile components like LEDs. However, the brushless motors in these fans are made by creating a rotating magnetic field with a bank of coils, driven by an electronic circuit which already has all manner of filters and protection on it.

In summary: For series circuits, voltage drops add up, one current through all parts of the circuit (for that arm, between V+ and GND). For parallel circuits, voltage drop in each branch is the same and must be equal to V+, and current for each branch adds up to a circuit total.

Also remember that in a series circuit, the current may not be limited by the lowest-current component. You can overload a component if something else in the series branch is able to draw more current and there are no limiting factors.


Now all that remains is to plug in power, and your new fireplace is ready! Almost. It still needs to be decorated. You can make Christmas stockings or decorations if you are going for a theme. If it’s not a Christmas theme, you can decorate as you wish. One of our examples is shown with a bunch of tiny jars and bottles from the craft section of a dollar shop, all with coloured water or glue or random objects in them.

You could also make a mantle clock, books, or anything else you can think of. Look around the internet, with your adult’s help, to find examples. Almost no two fireplaces are the same. Some have no overhang on the mantle or extension on the hearth. Some are entirely within the wall, especially in some older homes where a central wall was often big enough for a person to squeeze into, to carry pipes and such.

Besides that, you can experiment with the flames: The shape and size of the paper, and the number of rows. You can add in logs to the fire, or add another row of LEDs.

You could get very adventurous, and make a full diorama with a floor and walls. We added more card to one of ours to give a floor complete with floorboards, and house walls. This was more effort but we feel this one looks the best.