What does this thing I found on Ebay do?

Projects General Guidance
1

I saw this while browsing on Ebay but I don't know what it is.

Can someone explain to me what it does and what are some applications it can be used for?

http://www.ebay.com/itm/Arduino-plug-and-play-5V-Relay-Module-V3-Sensor-Shield-buckled-cable-/190615922009?pt=LH_DefaultDomain_0&hash=item2c61982559#ht_2143wt_1163

I see the description that it's a relay, but why does one use a relay for? Would this allow an Arduino to control a normal house lamp connected to an 110V outlet?

Thanks for explaining to a noob!

2

The 240V 10A contacts of the relay would be good for turning on large AC loads like small appliances and lamps.

Looks like to use it you would either have to find a source for the cable or you would need to buy their "Sensor Shield" and cables.

3

I see the description that it's a relay, but why does one use a relay for? Would this allow an Arduino to control a normal house lamp connected to an 110V outlet?

Yes, that is a good example of a usage of a relay. An Arduino output pin has limited voltage and current output capacity, where as a relay has isolated contact outputs that can switch any voltage or current within the contact ratings for the specific relay used. The relay choosen has to have a coil voltage and coil current rating suitable for either direct connection to a arduino output pin or using a intermediate switching transistor between the arduino output pin and the relay coil. That relay module you linked to has the switching transistor built into the module. The price is nice also.

Lefty

4

Thanks for the explanation guys.

Lefty, How did you know that the relay had a switching transistor built into the module? I didn't see that anywhere in the Ebay ad.

5

noobtoarduino:
Thanks for the explanation guys.

Lefty, How did you know that the relay had a switching transistor built into the module? I didn't see that anywhere in the Ebay ad.

It's that little three-pin surface mount thing you can see in the picture.

6

noobtoarduino:
Thanks for the explanation guys.

Lefty, How did you know that the relay had a switching transistor built into the module? I didn't see that anywhere in the Ebay ad.

From the picture of the module lower in the ad. There is a small three terminal surface mount component labled Q1.
Q is a somewhat standard label symbol for a transistor and transistors normally have three terminals, and knowing that such a large relay would require a switching transistor, I just made a wild ass guess. :wink:

7

Ah I see now. Thank you for the edification!