The Twitchbot is a fun little 30 minute project-y thing to do with all the lens modules you find taking apart CD-drives in search for motors and other fun stuff. Flicking it's antenna makes this bot twitch its eye and light up.

This bot is a variation on the blinky bug... I'm sure a lot of you people know it, and if you don't, the internet will help you find out.

The principle of a blinky bug is very simple: an LED is connected with a battery. Between those two there's a switch.
This switch is made from a long piece of wire (the antenna), almost touching a little loop made from another piece of wire (the LED lead)
As soon as the antenna gets touched, it starts vibrating and touching the inside of the loop, and so closing the switch, making the LED light up.

Using some scrap stuff from an old CD-player you can make loads of other Trash-bots as well...

Step 1: Salvaging Parts

First thing we'll have to do is search some stuff we could use... There's loads of awesome stuff inside a CD or DVD player!
What we'll need is an LED, the laser module of the CD/DVD player, some metal wire or even an old guitar string, some button cell batteries, some electrical wire and electrical tape...

You can use a lot of other parts in other projects or trash-bots! There are some motors in there we won't be using an a lot of other interesting stuff...

To put everything together we'll also need some hot glue and a little bit of solder...

MATERIALS
-laser module from CD/DVD player
-metal wire
-electrical wire
-2x 1.5V button cells
-googly eye
-LED
-electrical tape
-additional random decoration stuff

TOOLS
-hot glue gun
-soldering iron
-scissors
-small pliers
-wire snippers

Step 2: Searching What Makes This Bot Tick. or Twitch. or Whatever...

What you need to do now is find the 2 contact points on the laser module that makes the lens twitch.
I taped a wire to each side of a batter and started to search for the right contacts by holding the 2 wires against all the contacts I saw till the lens started moving...

Most of the time you'll fin the spot pretty soon and you'll see the lens twitch up and down, but in some cases the lens can also move sideways...

When you found the 2 contacts, make sure to note down which contact is which and which one needs to be connected to the positive or negative side of the battery.

Step 3: Attaching the LED

Next we'll start with adding the led to the bot...

Find a nice spot where you can put it and make sure it doesn't short any contacts the leads of the LED touches... If it does, you can always use a bit of electrical tape to shield the leads of the LED from the rest...

Both leads should be oriented to the back of the bot. Bend the shortest lead down against the bot and use some electrical tape to stop it from making contact with the back of the laser module. This lead will make contact with the negative side of the battery.

After you've bend the short lead of the LED down, add some hot glue and glue on a button cell with the negative side down.
Make sure to press it on good enough to ensure a good connection.

Step 4: Adding the Antenna

For the antenna we'll need a piece of metal wire, the stiffer, the better.
You can choose how long you want your antenna, as long as you can make the long part of it stay on the right position.
I found that 10-16 cm's is a perfect length for this bot.

Search a spot on the laser module where you can secure the antenna well.
Normally there'll be some holes on the laser module where the module gets guided through in the CD/DVD player. What I did was folding a little part of the wire double, to make it thicker, and put it through these holes.

I secured the whole end of the wire with hot glue... I used quite a lot of it so the antenna has a strong sturdy base.
The more secure you can attach the wire before glueing it down, the stronger it'll be when you secure it with hot glue.

We need to solder this end of the antenna down to the first contact of the laser module we found.
If you're lucky you can solder it down directly to the contact, like I did. If that seems impossible; no worries, you can use a small piece of electrical wire.

After you've done that you have to make sure you bend the antenna so it crosses the lead of the LED you bent up.

What you'll have to do now is bend this lead so it forms a little loop in which the antenna is trapped. You have to tweak both the antenna wire and the LED lead to make sure the antenna DOES NOT touch the little loop of the LED's lead. (Take a good look at the images for this!)

If you think the antenna wire will short something important by touching some contacts you can always isolate a part of the wire with shrinking tubes or electrical tape.

Step 5: Extra Power!

I noticed that one little button cell inst enough to make the bot twitch its ass off.
So I thought to just add a second. Maybe that's too much for the LED but on first sight it seems to work.

I glued the second button cell to the first with some hot glue, but i put a little piece of scrap wire in between to ensure the connection.

Don't forget the polarity of the batteries!

Step 6: Power It Up

The only thing that's left to make this bot work is connecting the second connection of the laser module to the positive side of the battery. If you think these 2 batteries will fry your LED, you can use a resistor instead.

Beware of shorting stuff here as well. If the cable shorts out stuff, use some shrinking tube or electrical tape...

Solder the jumper wire or resistor to the 2nd contact of the laser module you found in the beginning, and tape the other end to the positive side of the battery with electrical tape. If you want to turn the bot off you can just remove this piece of tape...

Step 7: Give It Some Personality!

Now there's only one thing we'll have to do: decorate your bot!

* add some decoration to give the laserbot some extra personality!
* dont forget to glue a googly eye on the lens of the lazer!!
* yay!

It's not that clear in the video, but this bot twitches his eye like his live depended on it...

If you want to know a bit more about how the lens module in a CD/DVD-player works; read on!
How CD's and stuff like that work in general, only Google can tell.

Focusing:
CD's don't always have the same thickness, so the lens in the laser module has to be able to move up and down to focus on the CD. The focusing mechanism functions a bit like a speaker does. It has a magnetized part surrounded by a coil of wire attached to the lens. An electrical current is passed through the coil which makes it move up or down, together with the lens.

Tracking:
The lens also has to be moved very precisely to read the data from the disc without a lot of mistakes The fine movement is handled by another coil which is fitted around the same magnet used for focusing. Instead of going up or down when current goes through this coil, it will make the lens twitch sideways.