I want to interface 12v relay to arduino board. I found this relay infographic and it is very useful to me. Can any one suggest power supply for arduino relay.
If you use a 5v relay, you won't need an external power supply. The relay can be driven directly from the Arduino providing the current draw is low, 15-20mA.
Ken
If you want to go with 12V relay then you need a transistor being powered through a resistor at its base from Arduino, emitter to GND, collector to relay and the other end of the relay to 12V. Don't forget the protection diode parallel to the relay with cathode connected to 12V.
My description is based on a NPN type.
Pls use the search either in this forum or in the I-Net. There you will find thousands of answers and schematics for this question.
Most relay modules have on-board optocouplers and relay drivers on the inputs (IN1, IN2, etc.), and accept standard TTL levels for activation. So you don't need anything between you arduino and the relay board (unless you are obsessive about current spike protection, like I am).
However, a 12V relay module needs a 12V power source to drive the relays (VCC).
Your link shows mostly SONGLE type relays. The 12V standard version uses 37.5mA for the coil and would also need current for its driver and led. I think a good estimate would be 50mA per relay. I would just double this figure, so for an 8-relay Module, I would use a 12V DC supply rated for at least 800mA.
RuneJ:
Most relay modules have on-board optocouplers and relay drivers on the inputs (IN1, IN2, etc.), and accept standard TTL levels for activation. So you don't need anything between you arduino and the relay board (unless you are obsessive about current spike protection, like I am).However, a 12V relay module needs a 12V power source to drive the relays (VCC).
Current spikes from relays causing havoc show up regularly on these forums - you are right to
be obsessive - I'd agree that you should use opto-isolation whenever its available. This means
you use a separate power supply for the relays anyway, so whether its 5 or 12V doesn't matter,
and it doesn't matter if the relay board is powered up or down at different times to the Arduino.
More robust.
To connect the 4 Relay board to an Arduino is very easy and allows you to turn on and off an wide range of devices, both AC and DC. The first to connections are the ground and power pins, You need to connect the Arduino +5v to the 4 Relay board VCC pin and the Arduino ground to the 4 Relay board GND pin.
... or you could omit the GND to Arduino and get added opto-isolation with this: