Step 5The power indicator LED.

The power indicator LED will only light if it is installed the correct way round, so note that the PCB position has a "+" symbol to indicate the long lead (the anode). LEDs generally have a longer positive lead and a small flat surface on the negative side of the resin package. If you look through the LED you will see that one of the electrodes is anvil shaped inside and holds the chip, while the other electrode is quite thin and just goes up the side of the anvil. Generally speaking the anvil is on the negative lead (but not always).

The power indicator LED is a simple but very useful addition to any control module. It makes troubleshooting so much easier if you can see that your unit is powered up and the 5V supply is healthy.

Step 6Adding the voltage regulator

The voltage regulator is an incredibly neat little component that takes any voltage between about 8 and 32V in at one side and regulates it down to 5V at the other side. It must be installed the correct way round, and as such the PCB graphic shows the outline of the plastic case.