N00b question about relay shield


I'm just starting to learn about relays, high-voltage, transistors, and diodes (if anyone can point me to a good tutorial on these subjects I would greatly appreciate it).

One quick question: if I wanted to control something using 12V, and I had a relay shield (http://seeedstudio.com/wiki/Relay_Shield_V1.0) would I not need a diode as I've seen in other direct, connection examples? It didn't appear to me that this shield had a diode.



The schematic shows diodes across the coil relays as expected.

My book has excellent discussion of driving relays, high-voltage, transistors, and diodes.
High voltage in terms of 12V (higher than 5V that Arduino can interface with directly), not like 120AC.

(Amazon Best Sellers Rank: #277,918 in Books. Was 115,000 something yesterday, and 457,000 on Friday - almost fascinating watching the rating change by hundreds of thousands up & down daily!)

Thanks Robert! Bought your book last week! Finishing up Chapter 1.

Cool - now you just need your reading to catch up with your project :slight_smile:

What country are you in? Curious to see how global it's going.
So far I know of US, Mexico, South Africa, Australia, all from feedback here in the forum.

I'm in NYC. If you know of any tutors in the area please let me know!!!