
Solenoids, Relays, and Other
Analog Outputs 6
Solenoids
A solenoid is an electromagnet that activates a mechanical function, such as a
plunger. Solenoids are used to latch safety covers closed so they can’t be opened
while a machine is in operation, or to unlock the doors in your car when you push
the keyless entry button on the remote. Solenoids can open and close valves in
industrial processes or push the record head against the tape in a tape player.
Solenoids come in many shapes and sizes, and are capable of exerting a force
from less than an ounce to several pounds. There are two basic varieties: contin-
uous duty and pulse duty. Continuous-duty ...