In this video I explain how a relay works.
An electro-magnetic relay is constructed of a coil of wire that is wrapped around a soft iron core - known as a solenoid. It has a movable iron armature, a low reluctance iron yoke and a set of contacts. There can be multiple sets of contacts depending on the design and function of the relay. The yoke has a hinged armature attached which is linked to the movable contacts.
A spring holds the armature in position and when the relay is de-energised an air gap in the magnetic circuit is created. This condition delivers the the physical closing and opening of contacts. In an automotive relay with two contacts this would mean that one contact is opened while the other is closed. Different relays may have a greater/ fewer number of contacts depending on design. When an electric current is delivered to the solenoid a magnetic field is generated. This field triggers the armature and the resultant movement of the contacts either makes or breaks the circuit.
Although there are many different types of relay out there in the market the two most commonly used in the automotive industry are 'Make & Break Relays' and 'Changeover Relays'.
The terminals of a relay are numbered using an identification system known as DIN 72552. This system was developed in the German automotive industry and has since been adopted across the world as the standard method for labelling and identifying electrical terminals. DIN 72552 assigns a numeric code that clearly defines the function of each pin/ terminal in a relay. The table below shows the codes used in automotive relays.
85 Relay Coil Negative
86 Relay Coil Positive
87 Common Contact - Output
87a Normally Closed Contact (NC) - Output
87b Normally Open Contact (NO) - Output
88 Common Contact 2 - Output
88a Normally Closed Contact 2 - Output
88b Normally Open Contact 2 - Output
30 Feed/ Line In Positive
A micro relay is a smaller version of the more popular standard relay and are used when space is at a premium. Micro relays are more compact than the standard size and are an ideal choice when you need to save space - for example in an ATM fuse box set up with mini fuses. They have a smaller rectangular shape compared to the square cubed shape of the standard relay. Micro automotive relays use a different terminal number identification system compared to standard mini relays. See the list below for micro relay terminal numbering:
1: (4.8mm) Coil Positive
2: (4.8mm) Coil Negative
3: (6.3mm) Feed/ Line In Positive
4: (4.8mm) Normally Closed (NC)
5: (6.3mm) Normally Open (NO)
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30 сен 2024
