Here are the simple techniques which will help you know the technology behind relays & it has different types and packages.
THE TECHNOLOGY BEHIND RELAYS: Relay are essentially switches that you can turn ON/OFF by applying electricity to a coil inside the relay and when you energized the coil you create a magnetic field to trap at a little contact and it will magnetically close the switches and when you take away the magnetic field which is the electricity, the circuit will open up again. Note: relay comes in different sizes, colors and Packaging.
POINT TO BE NOTED ON TECHNOLOGY BEHIND RELAYS
They are two major to be noted when working on any relay, there are
- The voltage required to energized the coil, (note: you need to applied the required voltage for a particular relay and they are of two types AC and DC with the ranges 5A-40A and 30v-240v.
- The switches are of three different types such as SPDT, DPDT and SPST.
SPDT: SINGLE POLE DOUBLE THROW
(Note: At the bottom it has five terminals, the two terminal by the side are used to energized the relay and the first one in the middle terminals is the com and the one in the middle is the Normally Close (NC) and the last one is the Normally Open (NO).
Comments: Once you energized the coil.
If their is no electricity on the coil, it will be as it is on the diagram above, Note: that’s why d and e are Closed together (NC) and d & c are Open, in these conditions it’s called NO. Which is Normally Open and when you energized the coil, the NO. will automatically Closed and it will be NC. which is Normally Close. And that is why it’s called single pole double throw because their is a single pole that is used to control the two terminals which are NO and NC. And it’s called double throw, because it has two terminals such as NO&NC.
NOTE: For SPDT relay, the voltage and current ranges are as follows 12v, 20A, 30A and 40A. Depending on the type of work it will do or fits eg:(12V 20/30A, 12V 30/40A), here the first ampere is for Normally Open and Normally Close respectively.
SPST: (SINGLE POLE SINGLE THROW) THE TECHNOLOGY BEHIND RELAYS
SINGLE POLE SINGLE THROW is Normally 5v.
Comment: in SPST their normally have four legs, two for coil and two for switches, when you energized the coil, the switches closes and the contact will be between the c and d in the figure above.
DPDT:DOUBLE POLE DOUBLE THROW
DOUBLE POLE DOUBLE THROW can come in 120VAC.
Comment : when you energized the coil with 120VAC, the two contact which are the COM 1 and COM 2 will switch at the same time and (from NC to NO) and that is why it’s called Double Pole, because of the two switches (COM1 AND COM2) and Double Throw because of the two NC&NO and the Two COM 1&2.And it is not connected together, it only work when the coil is energized
Relay in general can be use as a switch majorly in industries and also in some home appliances such as stabilizer etc. with this method above you can easily know the behavior of relay.