Quick Makes

Egg Timer

Learn It

  • Boiling an egg requires perfect timing.
  • There are many ways to create a timing circuit, but one of the simplest ways is to use a 555 timer circuit.
  • The 555 timer circuit relies on a basic electronic timing circuit which uses resistors and capacitors to create differnt time lengths.
  • The capacitor take times to charge, we can use this to create a time delay.
  • We can calculate the time delay using a simple formula, t = R x C.

Try It


  • Try building the circuit above using circuit wizard.
  • Change the values of R2 and see how it affects the speed at which the LED flashes.

Build It

  • Below is the full circuit diagram. if you have time, you can try design one yourself.


  • Your circuit board will look like this.


  • You will need to add wires to the LED's, switch and Potentiometer (variable resistor).


  • You can now add these parts to your PCB, along with all the components.
  • Your final PCB should look like this.

CloseFinal.jpg Eggtimerfinal.jpg

Build It

  • The housing parts have been pre-cut for you, you will just need to mount your PCB in the box.


  • Make sure you test your egg timer before installing into the box.
  • First you will need to add the parts to the lid.
  • Starting with the LED's. These will need LED clips.

LEdclips1.jpg LEDclips2.jpg LEDclips3.jpg

  • You can then simply screw on the potentiometer and switch.
  • Before you add the potentiometer, you will need to break off the tag using a pair of long nose pliers.

POTtag1.jpg POTtag2.jpg

  • Your lid should now be ready to fit to the rest of the box.


  • First you will need to glue the bottom of the box together.
  • Make sure the parts are the correct way around.
  • Use masking tape to hold the parts together, wait till the glue is dry before fitting the top.


  • Once the glue is dry, you can fit the lid with the PCB and test it again.
  • The finished product should look like this.


Badge It


  • Paste a screenshot of your 555 timer circuit you designed and paste it into the word document (Or upload the picture directly).
  • Explain what happened when you changed the value of R2.


  • Upload photos of the front and back of your project.
  • Your solder joints are good, some dry joints or excess solder.
  • You component placement is good, a few of the components are off the board and not aligned correctly.


  • Upload pictures of your completed, working project in the housing. This has been put together to a high standard.