Automotive Relays - What Are They And Why Do You Need Them?

A Relay is an electromechanical or electronic device through which a heavy load can be switched ON & OFF with a nominal input of current & voltage. This article focuses on electro-mechanical relays used in automotive applications.

Another important function of the PCB Relay is quick switching off(0.05Sec Max.). The more time the contacts of a switch take to break at full load, the more sparks will be generated due to electromagnetic effect on contacts in a switched on state. Prolonged sparking will mean more wear of the contact points and the danger of contacts melting and generating a fire. International standards have very stringent relay specifications. The endurance of a relay is generally specified in millions of switching operations.

How to Understand the Electrical Specifications of a Relay

Basic 5pins Car Relays feature electrical ratings for both the coil and the internal switching contacts. The coil voltage rating is the voltage required for the coil to operate correctly. The switching circuit of the relay also features a voltage and ampere rating. This is the maximum rating of the switch contacts and should NOT be exceeded. Double throw relays often have 2 x switch electrical specifications. One for the normally open terminal, the other for the normally closed terminal. ie. N/O: 35A at 14vdc, N/C: 20A at 14V

Let’s use the car horn as an example. When you press the steering-wheel boss to activate the horn, a small current – less than 0.5 amps – is sent from the horn switch to the Auto Relay. The relay’s electromagnet then activates an internal switch, which bridges the main 12-volt supply to the horn’s terminal. Most horns require at least 10 amps to work. If it is a twin-horn set-up, you are looking at 20 amps at least. A relay’s switch typically handles 30 to 40 amps.

A Push Button Switch is a type of switch which consists of a simple electric mechanism or air switch mechanism to turn something on or off. Depending on model they could operate with momentary or latching action function. The button itself is usually constructed of a strong durable material such as metal or plastic. Push Button Switches come in a range of shapes and sizes. We have a selection of push button switches here at Herga.

Push button switches are used throughout industrial and medical applications and are also recognisable in everyday life. For uses within the Industrial sector, push buttons are often part of a bigger system and are connected through a mechanical linkage. This means that when a button is pressed it can cause another button to release.