connecting this relay to a pin

This relay is rated at 5v, 30 mA on the coil, so can it be connected directly to an i/o pin on my board? http://www.sparkfun.com/products/524

In theory, you could, since the pins are rated to source 40 mA - but I wouldn't (unless you're only using one or two, and have a good reason to avoid using a buffer circuit). If you do, remember you still need a snubber diode across the coil...

Yes, but you should wire a diode across the coil terminals in reverse bias to suppress transients when de-energizing.

Lefty

Ah yes, seems like that's a fly by or flyback diode... something like a 1N4448, or does it need to handle more power like a 1n4006? thanks

SouthernAtHeart: Ah yes, seems like that's a fly by or flyback diode... something like a 1N4448, or does it need to handle more power like a 1n4006? thanks

Not sure, but I like 1 amp diodes for things like that, so my vote would be any of the 1N400x series.

Lefty

hi there i have a question how do you people know about that diode and ic names (numbers?)

because we have been using them for years. They seep inside your skin. My telephone extension at work is 741 - now how many of you know what one of those are - been using them for 40 years.

hehe! okey well i thought that we should somehow learn that somewhere ! ;)

Grumpy_Mike: because we have been using them for years. They seep inside your skin. My telephone extension at work is 741 - now how many of you know what one of those are - been using them for 40 years.

hee hee love the number op amp as I recall?!?

Fyi - this place sells a board with 4 relays that you can connect directly to an Arduino output pins. It is not a "shield" that mounts on the arduino but comes with wires for each relay that are easy to connect to whatever arduino board you have. Also you have to provide a separate 12V supply to the relay board to activate the relays. Here is the link: http://www.pimpmyprop.com/RB4RelayBoardDetails.htm.