Output pin loading - driving relay coil

I want to drive a relay that is rated at 28ma coil current. Do I need anything more than a direct hookup to drive forever for years and years?

Here is the relay: http://www.digikey.com/product-detail/en/IM03NS/PB1204-ND/1927544

Thanks.

you want a diode placed backwards across the + and - side of the relay to prevent back emf from hosing your microcontroller. Like a basic 4000 series black rectifier diode with its - (cathode / stripped side) on the + wire, and its + (anode) on the negative wire.

when you disengage a coil it will kick back a very large voltage as the magnetic field collapses, the diode shunts it to ground, and not your digital output

I would add a reversed biased diode across the coil terminals to help suppress transients.

Lefty

Thanks for the advice.

The relay will be driving an irrigation solenoid with the following specs: solenoid: 24VAC, 370mA inrush current, 190mA holding current, 60 cycles

http://www.sprinklerwarehouse.com/Hunter-Sprinkler-Irrigation-Valve-p/srv-100g.htm

The relay is double pole and will switch both sides of 24VAC at the zero crossing point of the AC waveform. Is anything needed to handle the collapse of the solenoid coil field? Is there anything in the solenoid coil at the zero crossing point?

Thanks in advance.

growerdick:
Is anything needed to handle the collapse of the solenoid coil field?

Yes, the diode that was mentioned above....

fungus:

growerdick:
Is anything needed to handle the collapse of the solenoid coil field?

Yes, the diode that was mentioned above....

... was ment across the 5V relais coil. The valve solenoid is a different thing

The relay is double pole and will switch both sides of 24VAC at the zero crossing point of the AC waveform. Is anything needed to handle the collapse of the solenoid coil field? Is there anything in the solenoid coil at the zero crossing point?

The relay or the valve solenoid won't do that by themselves, I fear.

I don't see where you (and your Arduino) get the 24VAC zero crossing information from.