Most helpful positive review
40 of 42 people found the following review helpful
Looks very promising!!
on May 11, 2012
As an electronics hobbyist, I am planning to design my own Christmas light show this year and dreaded the idea of having to build boards with relays on them that could be controlled by my Arduino. This board has all the features I could possibly want, and it's designed better than what I would have done at a fraction of what it would have cost me to do.
NOTE: This uses a triac; so it's not going to work for switching on direct current loads. I verified that with a quick test. It works great for AC loads, but is not designed for DC loads. If you need to control DC loads, then you'll want to purchase the mechanical relay board also made by Sainsmart.
A schematic of how each relay is wired is given at the Sainsmart website. Based on that and some measurements I've made, here are some features that aren't obvious from the description.
1. Each relay is protected by a fuse. Granted, the fuse is hard-soldered to the board; so if you blow the fuse, you'll have to de-solder and re-solder a new fuse in place, but that's not a huge problem. Protects each circuit from drawing more than the 2 amps that the relay is rated for.
2. The signal from the Arduino doesn't cut on the relay directly. Instead, the signal from the Arduino turns on a transistor, which closes a circuit that turns on the relay. The relay itself is optocoupled; so there is plenty of electrical isolation between the Arduino board and the relay. No worries at all on my part about frying my Arduino board.
3. Each relay draws about 10 milliamps from the Arduino when switched on. If you're only turning on a few relays at the time, that is not a problem for the Arduino to handle. If you want to turn on LOTS of relays at the same time, the transistor design mentioned above allows you to provide an EXTERNAL dc voltage to turn on the relays and then the Arduino can be used to just switch on the transistors. It's a very elegant design that is ideal.
4. Each relay has an LED wired to the circuit so that when the LED lights up when the relay is switched on. This takes the guesswork out of wiring issues and wondering if you hooked things up properly.
I plan to eventually use 6 or more of these relay boards to be controlled by an Arduino Mega. Each relay will be used to provide power to an electrical outlet into which I can plug the Christmas lights. The time that I would have spent having to design a relay board just got eliminated so that I can spend more time on my light show design.
Overall, this is an excellent design. If I run into any problems, I'll post again, but it looks like it's going to do everything I could possibly want.
UPDATE: This board is fantastic! I've been using my Arduino to control AC loads with it. Works like a champ. Excellent buy for the money, since many board on the internet with this capability cost much more. If you want a solid, well built board that works, then this is the one for you.