PCB Step 2: Timer LED Power


Get power to one of the timer circuits and light its LED


  • .22uF ceramic capacitor * 1
  • 7805 voltage regulator * 1
  • Tactile switch * 1
  • 1/4" screw * 1
  • Nut * 1
  • 220 resistor * 1
  • Natural key LED * 1



Double check to make sure you've got the correct LED color before soldering!

  1. Solder the .22uF ceramic capacitor to C61.
  2. Solder the 7805 voltage regulator to U21.
    1. It will lay flat against its outline on the back of the PCB, with its text facing outwards, its tab pressed firmly against the exposed copper rectangle on ther PCB, and its legs bent into their holes. To help hold it there while soldering, attach its tab to the PCB with the screw and nut. It's important that there's no visible gap between 7805's tab and the copper plate on the PCB.
    2. Solder its legs on the front of the PCB.
    3. Solder its tab to the copper plate on the back of the PCB by applying solder to the sides of the tab where it meets the copper plate. You may need to use a higher temperature on your soldering iron and/or apply additional flux if using a non-flux solder.
    4. Remove the screw and nut for later use.
  3. Solder a tactile switch into S1, making sure it's perfectly flat against the PCB.
    • A trick I like to do is to solder just one of its legs to hold it in place, then remelt the solder while pushing it in from the other side.
  4. Solder a 220 resistor to R1.
  5. Solder the LED to D1, making sure to match its outline.

It should look something like this when done#

It should look something like this when done


The components' brands and colors for PCB, LEDs, and wires may look different from yours, and that's okay! What's important is that the part types and values are in the right spots.

Test it#

With the battery attached and power switch on, press S1. You should see the LED at D1 turn on!