Choosing transistor and diode for relay circuit


Just looking for some advice on choosing the transistor and diode for switching a relay with an arduino. I'll be switching the relay with the arduino 5V. The motors that will be powered are 24VAC two phase induction motors. The manual states a maximum of 1.35A @ 24VAC so I assume these: should do the trick but, please, correct me if I am wrong!

I am not sure how to choose the transistor and diode, however! Any help would be greatly appreciated :)

Looking at the datasheet, it states the relay has a 12 volt coil with a pick-up voltage of 9 volts - which means it will not operate directly from a 5 volt supply. So, apart from the supply powering the arduino, you will also need 12 volts DC to power the relay. Typically a 2n2222 will be capable of doing the relay drive and a 1n4002 will suffice as a back-emf suppression diode


There are diagrams of some existing relay circuitry here: Non-isolated and Here: OPto-isolated (These operate from just 5 volts).

Also, think about how you will start the system up without any relay activation until you want it.. Read the part about that issue here:

DISCLAIMER: Mentioned stuff from my own an example

Hey guys thanks for the info! Terry does your store have an Australian stockist? :P

I'm working on a relay circuit also and could use some assistance.

I'd like to use the Arduino 5V output to switch an Allen Bradley 700-HB33Z06-3-4 (15A, 277VAC) relay. The documentation says it is a 6VDC (80…110% of Nominal Voltage at DC) coil, Coil Consumption is ±10% for DC Coils: 1.3 W, Max. Allowable Leakage 25% of VA and 10% of W, and finally Max. Contact Resistance is 50 m?.