Arduino Projects for Amateur Radio

CHAPTER 11

Universal Relay Shield

One of Dennis’s many interests in ham radio involves “boatanchor” radios … you know, the ones that cause the house lights to dim when you turn them on and then glow in the dark if you turn the lights out. Every now and then he runs across an application for an Arduino that would be ideal for controlling one of these old sets, but the digital IO pins just can’t handle the higher voltages used in these old radios. The solution is to use a relay.

There are many relays that can be controlled by a 5 VDC signal and with sufficiently low current as to not stress the IO pins on the Arduino. These relays can switch several hundred volts and a respectable amount of current and come in a very compact size. Figure 11-1 ...