Photo 2. The LED is polarized and will only work right if installed the right way. The longer
lead is the anode and the shorter lead is the cathode.
Find the five (5) LEDs and take a closer look at them. See Photo 2. Each one has two long leads but one is a little longer than the other. This is important! The longer lead of each LED,
called the “anode”, goes in the hole in the PCB with the square shape. The shorter lead, called the “cathode”, goes in the hole with the round shape. Now find the line of holes along the edge
of the PCB where the LEDs are supposed to be installed. Notice that half of the holes have around shape and the other half have a square shape. Like the IC, they only work right when they
are installed the correct way. If you put them in backwards, they won’t work right at all; not even a little bit.
To build the classic tinyCylon, put the long lead in the hole with the square shape and the short lead in the hole with the round shape and push the LED all the way down until it is sitting right
on top of the PCB, with most of its leads sticking out the backside. Flip the PCB over and solder just one of the leads to the PCB. This will hold the LED in the PCB and let you flip the PCB
back over and check that the LED is still lined up right. If not, you can move the LED around until it is all lined up. Then go back and solder the other lead. Doing it this way is a lot easier
than trying to solder both of the leads at once and then trying to go back and unsolder both leads so that you can adjust the position of the LED.
Once the solder connections have cooled, clip off the extra leads sticking out the back. Do not cut into the actual solder connection.
Install one LED at a time. This is a lot easier than trying to install all five (5) LEDs at once
OK, that’s how you make the classic tinyCylon, but that’s not the only way that you can put it together.
As long as you make sure to match up the long lead with the hole that has the square shape and the short lead with the hole that has the round shape, nobody says that you have to
mount the LEDs flush with the PCB. You can leave them sticking out so that you can bend and twist the LEDs into different shapes; just don’t let the leads touch each other or it won’t work
You can also mount the LEDs from either side of the PCB as long as the long-leg-square-hole rule is followed. The only component that can’t be mounted on either side of the PCB is the
computer chip. The chip must be installed on the side of the PCB with the drawing of the chip on it.
The push button, the resistor and the battery holder leads can be installed correctly from either side. This flexibility lets you have all the LEDs on one side and all the other components
on the other side