Toy Blinking Halloween House

This article is will show you how to make a LED light dimming spooky house. The house LED lights turns ON and OFF (blink) when you rotate the variable resistor.

This is a great toy that you can put outside your door or near your letterbox during Halloween.

The first video shows the blinking Halloween house working (11 seconds). The second video shows all the steps in making this toy (1 minute and 36 seconds).

Materials: Red 10 mm Bright LEDs - 3 (I used two but you might need spare), Small Matrix Board, Lead Free Solder, 27 ohm resistor, 16 mm 100 kohm Variable Resistor (I used 24 mm 100 kohm variable resistor), Knob For Variable Resistor, 15 cm Length Wire, Two AA Switched Battery Holder, AA Batteries - 2, A3 (Australian Standard) Black 600 gsm Cardboard or Equivalent (297 x 420 mm or 11.7 x 16.5 inches), Lead Free Solder, Masking Tape.

Tools: Scissors, Craft Knife (photo shown), Pencil, 40 cm Ruler, Eraser, 60 W Soldering Iron, Soldering Iron Holder, Circuit Holder, Wire Stripper, A3 Size Metal Sheet.

The voltage across LED1 is equal to the voltage across LED2:

Vled = Vled1 = Vled2

The maximum current entering each LED should be 20 mA. At the circuit nodes where the LEDs are joined the current is the sum of the currents of the two LEDs - 40 mA. The voltage across the each LED is about 2 V. The sum of voltages across each component is equal the supply voltage (3 V):

Vs = Vled + Vr1 + Vr2

The current is maximum when Vr1 is zero. This happens when the variable resistor resistance is set to zero ohms (short circuit). Therefore:

Vs = Vled + Vr2

Vs = Vled + Ileds*R2

R2 = (Vs - Vled) / Ileds

= (3 V - 2 V) / 40 mA

= 1 V / 40 mA

= 25 ohms

With E12 resistor series there is no 25 ohm resistor so I chosen the next number is series which is 27 ohms.

I chosen length of 7 cm because this would be enough to fit the switched AA battery holder. I chose the height of the roof as 3.5 cm which is half of 7 cm. I used Pythagoras theorem to calculate the length of the roof:

Roof Length = SquareRoot(((House Length/2)^2)+((House Length/2)^2))

= SquareRoot(((7/2)^2) + ((7/2)^2))

= SquareRoot((3.5^2) + (3.5^2))

= 4.9497 cm

= 4.95 cm

Draw the house template with a pencil and ruler on the A3 cardboard sheet.

Cut out the house template with scissors. Do not use a craft knife. The 600 gsm cardboard is thick. Sometimes the knife cannot cut the cardboard properly because of its thickness.

Draw the door and windows with a pencil.

Place the cardboard cut out on the metal sheet and cut out the door and windows with a craft knife.

Fold the template into a house.

Seal with masking tape.

Each LED has two pins. One is shorter than the other. The longer pin is anode that should be connected to the positive node of the circuit. The shorter pin is the cathode that should be connected to the negative node of the circuit. The positive circuit node of the circuit is the second R1 pin (the first R1 pin is connected to the positive end of the battery). The negative circuit node first R2 pin (the second R2 pin is connected to the negative end of the battery).

Use the scissors carefully to make a hole in the roof of the house for the variable resistor. Use masking tape to attach the LEDs to the ceiling of the house as shown in the photo. If you put the LEDs on the floor the light from the LEDs will not shine on the surface on which the house is standing.

Test the circuit and attach the knob.