I was asked to make some blinking eyes similar to those Rachel Lea Fox posted here: http://youtu.be/qnmWQMHBmqc. How could I resist a challenge? This post shows how I made some eyes – the blinking bit and sound will be covered in a separate post.
About an afternoon to make five pairs
Heat shrink sleeving (aka heat shrink tubing) and hot air gun (or insulating tape)
5 x Resistors ( 3 x 270 ohm for the green LEDs and 2 x 390 ohm for the yellow LEDs)
Scrap bits of sheet metal – lolly sticks would do
9V battery connector
Put the pingpong balls in an egg box
Spray them with black paint. Be careful – they may roll or blow out of the box. You want to keep one side white. *update – put a bit of blu-tack under each ball to stop them flying away – thanks for tip @crystalsinger. *
Let them dry.
The resistor value for each pair of LEDs was calculated … which is a whole post of its own. Coming later!
Each LED needs to be “dulled” by scratching the surface on sandpaper, and flattening the end. This gives more of a glow rather than a sharp point of light.
Trim the negative (flat side) leg of one of each pair of LEDs. (It does not actually matter which leg, but it helps to be consistent).
Trim one resistor leg, and solder it to the trimmed LED leg.
Trim the free leg of the resistor, and solder a short (about 10cm) piece of wire to it. Trim the other LED leg too.
Put two pieces of heat shrink sleeving on the wire (do this first!) Trim the other LED’s opposite leg – if the resister is on the negative (flat) side of one LED, trim the positive (rounded) side of second LED.
Split some speaker wire a small way, and put two more pieces of heat shrink sleeving on the ends. Trim the last LED leg and solder one wire from the speaker cable to each free leg of the LEDs.
To save faff later, connect the positive wire (with white line on it in this shot) to the free positive LED leg. Then heat all the heat shrink sleeving with a hot air gun. Insulating tape would also work to protect and insulate all the joints and bare metal, if you don’t have heat shrink sleeving.
With a hot soldering iron, poke a hole in the middle of the black side of each ping pong ball.
Do not inhale the fumes! (It smells like camphor).
The hole should be big enough for the end of an LED to fit in it, but the shoulder of the LED should butt up against the ball.
I used a scrap of sheet aluminium to make the eye connectors – but I’m sure lolly sticks would work.
Holes were drilled where the middle of the eyes were going, and in the centre. To give variety, I varied the inter-eye distance.
The holes are just big enough for the LED to fit all the way through.
The eye connectors were chamfered to get rid of nasty sharp edges, and then spray painted black to stop reflections.
Hot melt glue was added to the back of the eyes – careful not to get it in the hole.
The LED was pushed through the hole, and then through the hole in the back of the eye.
More glue was melted over the back of the eye, to stop the LED falling out and to stop the wires from wiggling too much.
I used hot melt glue to make the pupils. I also filled in any excess white with a black felt pen.
As I want to re-use these eyes, bootlace ferrules were crimped on to the free end of the speaker wire. For now, I attached the speaker wire to a 9V battery connector – the white striped wire connected to the positive side of the battery.