I'm a noob, i was still in the planning process; i want to be able to control 2 lamps from an arduino board. Hope you guys can help me
The question is, what is the safest multi SSR setup
what kind of SSR that suitable
and why are they so expensive.
And how many SSR an arduino can support
Thanks, I'm really interested with arduino. I'm starting this project soon. I don't have alot of money to put in so I'm in need with help as to reduce my cost as much as possible.
As a general rule it is not a good idea to play with mains voltages for your first project. If you are having to ask these sorts of basic questions you are not ready to play with mains yet.
To answer your questions:-
what is the safest multi SSR setup
One where you don't kill yourself.
what kind of SSR that suitable
Ones that are rated for twice the current you want to switch.
and why are they so expensive
They are not but that's life.
And how many SSR an arduino can support
As an SSR takes little more than an LED you can have as many SSRs as you have outputs. However switching that much mains can bring it's own interference problems.
The relay will have a rating such as "20A @ 230V". Using a higher rated relay is particularly important for motors where the starting current is much higher than the running current. BTW, I have found this place to be a good source for SSR's: http://www.mpja.com/products.asp?dept=133
I know this is off-topic... but reading through these forums I kinda get scared...
We can't stop praising the power arduino brought to the people, and although true, there's also some responsability and knowledge to have before doing some things...
There hasn't been any Arduino related injuries that I know of, except maybe fried boards or computers... but allowing people to think that is ok to start making machines without some sense of safety or basic knowledge about electricity can come at a high price.
Let's hope not.
I'll say that an SSR is, like pointed out before, cheap. I design one myself for an application and in the end it would have been a better solution to buy ready made SSRs than incorporating them in the circuit board... but you only learn with mistakes.
That being said... if you want to dig about this at your own risk, search for MOC3031... it is a very handy chip for these applications. But remember that it is still best to use a ready made solution... specially when you don't know much about electricity!!!
Yeah, what they said. Don't kill someone else, yourself, or burn down your house. All these are easy when playing with household power.
Back to the arduino side of the discussion, note that not all SSRs can be driven directly with an Arduino digital output. IIRC, the powerswitch tail comes with a resistor and a transistor if you buy it from Lady Ada.
I bought some SSRs on ebay. They were actually 2 SSRs in one package. A single arduino pin could drive one of the SSRs, but not both at the same time. When I tried it, the 220V motor made a horrendous noise for a few seconds until I got it unplugged. Went back, read the datasheet, realized I forgot to multiply current requirement x2, added a 2n2222 and all was well.
