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Topic: Choosing an SSR (Read 991 times) previous topic - next topic

justjed

Hi Folks.

The next stage of my little project is to turn on the AC when the fish tank gets too warm. I'm not going to try to use the Arduino as a continuously controlling thermostat, just using it to kick it on. Easiest thing is to just put a switch in between the AC unit and wall power. It's an old Fedders through-wall unit. Landlord is a EE, and he says there's no problem switching just one leg of the 220VAC supply. (I had initially thought of using a DPST NO relay.)

So, off I went, looking at SSRs. I'm wondering whether there's any reason to be skeptical about the $10 unit at MPJA, given that anything else I can find is $30 or more (Mouser, Panasonic). The one at MPJA kinda looks like it has a Kodak logo on it, which makes me nostalgic for Kodachrome, but informs me not one whit about whether it's a good part.

BTW, yes, I will be appropriately careful about using mains voltage. I'll be building something resembling this powerswitch tail.
... it is poor civic hygiene to install technologies that could someday
facilitate a police state. -- Bruce Schneier

RuggedCircuits

Nope, no qualms about MPJA. They're a surplus distributor so sometimes parts are in stock, sometimes they're not, sometimes they just entirely disappear once stock runs out. In exchange for this uncertainty you get a good deal.

--
The Rugged Circuits Yellowjacket: 802.11 WiFi module with ATmega328P microcontroller, only 1.6" x 1.2", bootloader

JimG

The only minor criticism I have is that it doesn't seem to include a "safe" touch cover.  Many SSR's, even the inexpensive ones, have a clear plastic shield that makes it more of a challenge (not an impossibility) to touch the live terminals.  I'm being picky, but if you can find one similarly priced with a cover, that 's a better solution.

Jim
TC4 Open Source Digital Thermometer and Temperature Controller
http://code.google.com/p/tc4-shield

justjed

... it is poor civic hygiene to install technologies that could someday
facilitate a police state. -- Bruce Schneier

justjed

Just a followup. This SSR showed up. It's a Kodak, PN 611490. I have duly searched for a datasheet and come up empty. The input resistance is about 891 ohms, so that's good news. But what I hadn't thought about was whether I need a big heat sink for the load. From the faceplate of my A/C unit, the load will be ~ 8A @230VAC. The MPJA page for it says,
Quote
Opto-Isolated, "0" voltage turn-on, internal snubber
which tells me not much.

So, anyone have some experience or memory to draw on here?

@JimG. It's going to be inside an enclosure, but your point is well taken.
... it is poor civic hygiene to install technologies that could someday
facilitate a police state. -- Bruce Schneier

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