LED Faces Project

The first thing you need to do is draw on card and then colour in the face of the character you want to use for this project. You could use card, although it will need to be quite thick, or you could use wood as long as it's not too thick, since the LEDs and variable resistor will need to go through it. It would be a good idea to paint the face, especially if you do use wood, but what you use of course is up to you. As an alternative, you could print out the face of the character and then stick on to card or wood but the eyes will need to be big enough for the LEDs.

When you have the face drawn and coloured, or a print out fixed to card or wood, it will need to be cut round so that you get the outline of the face. It is a good idea, if possible, to use a face you front-on; that is, you can see all of the front of the face.

The next step is to make a hole in each eye for the LEDs to go through; I used 5mm but what size you use is your decision although too small or too big may look odd depending on the character. You will also need to make a hole for the variable resistor which will alter the brightness of the LEDs as well as turn the power on or off. As I used a Super Mario face I placed the variable resistor where Mario's nose is but you could choose a different place. If the variable resistor doesn't have a built-in switch then you will need to use a separate switch incorporated into the face; in that case the push button type would be best.

As can be seen below the circuit is very simple, however, there are a few things to consider. Firstly, what is the forward voltage drop of a single LED, and what amount of current will it need? This will determine the value of R1 so that when VR1 is at its lowest value, the LEDs will still be operated below their maximum ratings.

You will see that I've used a 9V (PP3) battery as they require no battery holder; you can just use a battery snap. Also, as I used blue, high brightness, LEDs which have a higher forward voltage drop than other colour LEDs of the same size, I was able to put both LEDs in series, keeping the total current down.

Depending on what LEDs you use, you may need to use a different value for R1 and possibly VR1 as well.

After placing the LEDs into the holes for the eyes and you have fixed the variable resistor in place, you should be able to solder without the need for a circuit board. Don't forget to use a heatsink on the LEDs when soldering them to protect them from too much heat from the soldering iron. Make sure you get the connections to the variable resistor the correct way round otherwise the LED brightness will increase before the switch turns the power off (if using a variable resistor with an integrated switch); it would be best to test before soldering.

All content of this and related pages is copyright (c) James S. 2011