PCB making it's a really exciting thing, but when you need to etch, it will be boring if you use ferric chloride (in average it takes 20-30 minutes to be ready). During this time you need to agitate it to speed up the process a bit, but you also need to take care that the ferric chloride didn't spill out.

In this instructable I will present how to build an automatic agitator from an old CD ROM drive quite simply and low cost.

Step 1: The Old CD ROM Disassembly

First, you need an old CD ROM drive which you need to disassemble carefully, not to break anything.

Step 2: Assembling the Controller Board

You need some basic electronic components and an IC:

7x 4.7 kiloohm resistor
4x BC337 transistor or other similar
2x 100 nanofarad capacitor
1x 2 way pin header and socket
1x 3 way pin header and socket
1x 2 pin terminal block (PCB mountable)
1x small size (6x5cm) prototyping board
1x 4017 decade counter IC
1x socket for the IC
Some wires

Note: put the IC in the IC socket to avoid damaging by thermal shocks.

Operation

When the device is turned on, the IC Q0 output will be active, and the motor starts to spin to a direction. If the limit switch is pressed by the tray, the IC receives a pulse on its CLK pin and the Q1 output will be activated. The motor changes its direction and it keep this direction until the tray reaches the other limit switch. This switch sends a reset pulse to the IC and the Q0 output will be activated again and the motor changes its turning direction again. This cycle is repeated until the agitator is turned on.

Step 3: First Power Up

To power up the device you need a power supply. I used a wall adapter for this purpose. This has two advantages: it’s really cheap and you can change the voltage easily.
With the voltage changer switch you can control the agitation speed.
Before connecting the power supply to your controller board check the polarity twice.
Set the voltage to 3V and plug in the wall adapter. If your agitator seems to be stuck, reverse the motor polarity and move the tray a bit by hand.
If the problem persists, you should check the connections between the components again.

The test video: