Exercise seven “Relay-Driven LEDs”. This experiment introduces the Relay component and is used to drive two LEDs. The heart of a relay is basically an iron core wrapped around wire. The electricity running through the coiled wire will produce a magnetic reaction, triggering an internal lever that closes two contacts. During this process the relay is said to be energized, allowing a low voltage signal or low current to travel through the circuit – lighting the LEDs.
The author is very specific about the type of relay required for the experiment. When shopping for your materials pay special attention to the model number in addition to coil voltage, set voltage, operating current, and switching capacity. All of which is explained nicely in the text.
Also be prepared to pull out the utility knife for the deconstruction of one of your relays. Although I am not a fan of ruining perfectly functioning components. I can appreciate the idea behind demystifying their inner workings for the sake of education.
The actual experiment itself, at least for me was sort of tedious when it came to construction. The major difficulty was attempting to fasten the hook up wire to the spikey legs of the relay. My advice: use a pair of needle nose pliers and bend the ends of the hook up wire into a small loop prior to placing it on the relay legs. Once the wires are in place, use the needle nose pliers to close the loop.
Lastly, this is the first experiment that required more than 6 volts; the requirement is 12 volts. However, the author has a great section on hacking an AC Adapter by cutting off the ends and using the wires to drive the circuit. For some, this may seem a little hairy. No worries though, the instructions are clear, concise, and there are listed precautions to ensure that using the AC Adapter is safe.
Overall, this was another fun experiment with excellent background information to drive the material home. I even enjoyed the tedious aspect of putting the circuit together. Sometimes it’s the little things [challenges].
AC Adapter, wire cutters and strippers
DPDT Relay (2)
680 ohm Resistor
Push button SPST
Hook up wire (22 gauge)