The “Lowly” Diode

I am sure that all of my “technically-oriented” readers are familiar with the diode, but I wonder how many know of the unusual (and simple) applications of this device other than as a rectifier. This month, we will look at a few that can come in handy when building or modifying equipment.

Application 1. Controlling Two Devices Over One Wire (With a Return)

Often it is desirable to control different devices with just one wire and the circuit of is a way to do uses only two wires (counting the return), when you expand it as also shown, four devices can be controlled with just three wires (2 + the return), and so forth. From the schematic you will see that a low voltage AC source is “steered” by the diodes so that the positive half-cycle drives channel 1, the negative half-cycle drives channel 2, and so forth. Both channels are independent of each other and can be controlled separately or simultaneously, as desired. The resistive loads show can be relay coils, incandescent lamps, or anything similar. Since the output voltage to the individual loads is half-wave rectified AC (or DC with a lot of ripple), a capacitor may be needed to smooth out the DC at the controlled point.