Subscribe to Make Magazine Today!

Make: Projects

I, Screechy

A light-sensitive oscillator toy.

I, Screechy

This project is an attempt at designing a simple toy based on the principle of a light sensitive oscillator. It produces sound and light that vary in frequency with the intensity of light falling on it.


Step #1:

I, ScreechyI, ScreechyI, ScreechyI, Screechy
  • Download schematic and PCB files in EAGLE format from here.
  • The circuit works using a combination of an oscillator and a frequency divider. You can read an explanation here.

Step #2:

I, ScreechyI, ScreechyI, ScreechyI, Screechy
  • You can use a general-purpose PCB for this project. But it's much cleaner to use a custom PCB.
  • You can easily make a PCB at home using the toner transfer technique described in this link.
  • Using the above link as guide, print out the PCB design on photo paper on a laser printer, iron it on to the copper laminate, and once the toner sticks, etch it out with ferric chloride. You can then drill holes in the PCB using a 0.8 mm bit on a Dremel tool.

Step #3:

I, ScreechyI, ScreechyI, Screechy
  • A pencil drawing on the non-copper side of the PCB will help you place the components easily. There are 2 connections that need to routed over the board manually using wires. Connect a wire between the two points labeled "A", and another wire between the two points labeled "B".
  • Solder the components on to the PCB.

Step #4:

I, ScreechyI, ScreechyI, ScreechyI, Screechy
  • Use a dremel or any other tool of choice to cut holes for the LEDs, LDR, and switch.
  • Solder wires to LEDs, LDR and switch, and fix them on to the enclosure before soldering the other end of the wires to the PCB. I did it in the opposite order first and had to cut the wires to fix it!
  • Drill some holes in the cap to let the sound out.
  • Insert the PCB and 9V battery into the bottle. Place a small sheet of plastic in between to protect the PCB's solder joints from shorting on the battery.
  • Enjoy your screechy robot!


Read more details about the project here: