A load is something that you want to control, or for this chapter, switch on and off. LEDs, transistors, optocouplers, relays, lights, electric motors, heaters, pumps, automatic garage doors, and TVs are all examples of a load. If you refer back to Figure 7.1, you will notice the word Load on the right-hand side of the diagram. This is where you connect the thing you want to switch on or off.
The transistors, optocouplers, and relays components appear in this aforementioned load list. Referring back to Figure 7.1, the relay appears as the load to the transistor sub-circuit while the transistor sub-circuit appears as the load to the optocoupler sub-circuit.
It's important to know two properties about the load you want to control:
- What voltage does the load require?
- What current does the load require?
Sometimes, these properties can be found on the device itself or in its manual or datasheet. At other times...
