Hardware Reference
In-Depth Information
Normally Open
pin
Normally Closed
pin
Coil
Common
pin
Figure 10-11.
A single pole-relay diagram
In Figure
10-11
you can see the pin connections for the relay. You want to use the normally open side of the
relay. When you apply a current to the coil, the circuit on the other side of the relay between the common pin and the
normally open pin will become closed. This is simulating pressing the button on the remote control. You don't want
to connect anything to the normal closed side of the relay. If you are really unlucky and your relay has no part number
and no circuit diagram, you're just going to need to figure it out manually. This is not difficult:
1.
The easiest connection to identify is the normally open and common pins, as they will
have no connection without power applied to the relay coil.
2.
The second easiest connection to identify is the normally closed side. When measured
with your multimeter it should read very close to zero resistance.
3.
The last pins should obviously be the relay coil but it's wise to check them, especially
if your relay has more than one pole inside the relay. The resistance between the coil
terminals can vary between makers of relays but it should not be an open circuit or a
closed one, so the multimeter should read some resistance.
Once you understand how the relays work, you can begin to connect them:
1.
Place two relays into the center of your breadboard so that the relay has one side of its
legs on one side of the breadboard and the other legs on the other side. Take a look at
Figure
10-12
to see how I have placed my relays.
