# SPDT Relay with 8Pin

I needed a SPDT relay with 240Vac so I bought this relay from Maplin http://www.maplin.co.uk/p/15a240vac-spdt-miniature-relay-n07aw

But I am heaving problem to wire this relay because it has 8 pins not like other SPDT relays 5, I couldn't find any documentation about this relay. The only thing that I have is this diagram which is printed in relay . Would also be helpful if someone can confirm that I need to power this relay with 12V, I will use also Arduino to control this relay

As it says on the top:

COIL: 240VAC 50/60 Hz


The relay uses 240 volts AC to turn on. Sorry, out of luck with the 12V, but you can try it and it may work.

• Firstly sorry about my question but I am new in electronics. How exactly can I apply 240volts AC, because this relay it will be used to run also a 240V AC motor Jul 22, 2014 at 16:47
• It will work with the motor, but it won't work with your Arduino. Jul 22, 2014 at 16:49
• how do you mean it won't work with Arduino. Is there any possibility to make this work with Arduino? Jul 22, 2014 at 16:58
• You need a relay with a 12 volt DC coil to work with the Arduino - this relay has a 240 volt AC coil so can't be controlled by the Arduino. Jul 22, 2014 at 17:07

1-2, 3-4 and 5-6 are connected to each other (in pairs) internally, as the diagram shows. There are thus only those three pairs and the coil, so 5 connections as you'd expect. Beta is an older Taiwan-based firm and you may be able to find more data online.

The coil, as fuzzy says, is 240VAC. If you want to try it on DC, measure the resistance and calculate the appropriate nominal voltage as $V_{DC}$ = $\sqrt{0.9R}$ (since this type of relay uses a 900mW coil for DC).

For example, this datasheet for a similar type of relay shows a resistance of 19K ohms for a 1.2VA coil, which indicates it would work well with about 130VDC. Not very useful.

• I will use this relay for switching 240V AC motor, can I use this formula also in this case? Jul 22, 2014 at 16:50
• Yes, what you are switching does not affect the coil- they're only connected mechanically- but I'm not saying that DC voltage you calculate will be a number you want to see. Jul 22, 2014 at 16:57

When choosing a relay you have to consider at least two facts:

1. What to control it with (Coil)
2. What you want to control (Switch)

What to control it with (Coil)

A standard Arduino is a 5 Volt device and each port can deliver 40 mA http://arduino.cc/en/Main/arduinoBoardUno.

So if you want to control a relay coil without a driver then 5 V/40 mA is maximum values for the relay coil.

With a driver, a simple transistor, protection diode and a current limiting transistor you can buy a relay (Maplin code: N06AW) with a 12V coil and that will do the work.

Example :

I couldn't find any 5Volt relays at Maplin.