I'm confused about the voltage and current rating of the relays on this shield. These are the specifications from this wiki (Relay Shield - Seeed Wiki):
Item Min Typical Max Unit
Voltage 7 9 12 VDC
Current 8 / 250 mA
Switching Voltage / / 35 VDC
Switching Current / / 2 A
Frequency Response -1 / 1 dB
Switching Power / / 70 W
Relay Life 100,000 / / Cycle
ESD contact discharge ±4 KV
ESD air discharge ±8 /
Dimension 80.0x58.0x21.2 mm
Net Weight 31±2 g
Is Switching Voltage the max voltage of the relay contacts or is that the max voltage of the coil that actuates the relay? I want to use it to control 120V AC, probably less than 1 amp.
The switching voltage is the maximum voltage it is rated to controll. This shield looks to be rated at 35VDC, so 120VAC would likely be a bad idea. You can find other relays that controll 120VAC, but I don't know of a shield that has them.
If you want somthing pre-built with a low risk of electricution you could look into this apparatus sold by sparkfun. It switches 120VAC with your standard 5VDC output. I can't say I've ever used one myself, but the reviews seem to say they work well.
If you look carefully at the picture of the relays, they seem to be rated at 3amps at either 120vac and 24vdc. But that seems to conflict with the information written in the description "The max switching power is 35VDC 70W for each channel."
I would suggest emailing the firm to ask them as 120vac contact ratings are not an unusual specification. E-bay seems to have over 500 listings on 'arduino relay' to choose from.
Thanks both of you! I have one of these (http://www.futurlec.com/Opto_Relay_4.shtml) but it is kind of a pain because i have to supply both 5 and 12 volts to operate it. The ebay options look like they will work great.
Thanks both of you! I have one of these (4 Channel Opto-Isolated Relay Board) but it is kind of a pain because i have to supply both 5 and 12 volts to operate it. The ebay options look like they will work great.
yea, reading through the e-bay list I just couldn't resist picking up a 2 channel unit even though I haven't an immediate need.