The Binary-Coded-Display is an electronic component often used to represent numbers, like the ones in an alarm clock. Internally the BCD is a collection of LEDs joined together with at a common pin. To make the BCD light up two things must happen. The positive voltage ( battery + ) has to be applied via a 100 ohm resistor to a common pin. Then a Ground ( battery – ) wire must be connected to one or more other pins to switch LED segments on.
The real fun starts when you bridge multiple pins together with separate wires to create an unreadable display. Examples of such wiring patterns are shown on the left. Avoid connecting the two common pins labeled (c) to bridged pins and use a low voltage battery source of 3 to 9 Volts.
Some BCD displays are opposite in wiring, meaning that Ground (-) is applied to the common pins and positive (+) voltage is used to turn the individual LED segments on. Try it out!
Editor’s Note: Many have seen this little hack before, because it was featured in the Get Lo-Files news flier #1 inserted with every www.getlofi.com/shop order. Thank you.