What is an SPST relay?
SPST – Single Pole Single Throw. These have two terminals which can be connected or disconnected. Including two for the coil, such a relay has four terminals in total. It is ambiguous whether the pole is normally open or normally closed. The terminology “SPNO” and “SPNC” is sometimes used to resolve the ambiguity.
How do I test a SPST relay?
Listen for a click when the relay is energized. Check the energized condition of the relay contacts. Use a digital multimeter (DMM) to test the resistance between each pole of the relay and the corresponding NC and NO contacts for that pole. All NC contacts should read infinite resistance to the corresponding pole.
What is the difference between SPDT and SPST relay?
SPST simply mean single pole, single throw. The product controls one circuit with one On position. SPDT means that it is a single pole double throw which means it has two ON positions. This can be a variety of circuitry however.
How do you know if a relay is damaged?
The only tool required to check a relay is a multimeter. With the relay removed from the fuse box, the multimeter set to measure DC voltage and the switch in the cab activated, first check to see if there are 12 volts at the 85 position in the fuse box where the relay plugs in (or wherever the relay is located).
Why do relays have resistors?
In a relay, the resistor absorbs access voltage given off when the relay is activated. This will protect any other components in the circuit from voltage spikes. While the relay is ideal for full voltage applications, the built-in resistor will protect any sensitive equipment against voltage spikes.
How many terminal pins are in a SPST relay?
Such relay can categorized into normally open or normally closed type. ii) Single Pole Double Throw (SPST) – Such relay has 5 terminal pins which consists of a pair of coil pins, a common pin, a normally open (NO) pin and a normally closed (NC) pin.
Is there a single pole single throw relay?
SPST Relay. (Single Pole Single Throw Relay) an electromagnetic switch, consist of a coil (terminals 85 & 86), 1 common terminal (30), and one normally open terminal (87). It does not have a normally closed terminal like the SPDT relay, but may be used in place of SPDT relays in all diagrams shown on this site where terminal 87a is not used.
What kind of relay is a SPDT switch?
SPDT Relay (S ingle P ole D ouble T hrow Relay) an electromagnetic switch, consist of a coil (terminals 85 & 86), 1 common terminal (30), 1 normally closed terminal (87a), and one normally open terminal (87) (Figure 1).
How are dual make SPST relays used in cars?
Dual make SPST relays (Figure 4) are used to power two circuits at the same time that are normally isolated from each other, such as parking lamp circuits on German automobiles. The diagram below (Figure 5) shows a dual make SPST relay at rest, with the coil not energized.