danjperron wrote:When you put a SSR you could forget about it. (unless the output short).
They don't make noise. (unless you are using AC and the valve start to vibrate)
I know, but that doesn't seem like an issue for this project. A click when you enter your code and another 2 minutes later doesn't seem like it would be a problem, although this is of course subjective.
Relay wear out faster since they are mechanical.
Again, doesn't seem like an issue on this project. One 2-minute cycle when you want to pour a beer? Doesn't sound like it's going to get a lot of use. Unless this bar gets a whole lot of traffic, or the life cycle is far lower than I suspect it is, the life expectancy of the relay is probably significantly longer than that of the kegerator. (My estimates: 10,000 cycles / 2 cycles/day (average) = 5000 days = 13.7 years. By this time his young children won't be young children anymore, the kegerator will have likely given out, the Raspberry Pi will be ancient, and statistically there's a good chance that he's sold his house and moved once or twice. I don't remember where I saw the 10,000 cycle number, but I found a PDF
that mentioned a 100,000 cycle life expectancy, which would multiply all those numbers by 10, giving the relay a longer life expectancy than not only the kegerator and the OP, but his young children and possibly his unborn grandchildren as well.) So... I'm going to go with... nonissue.
They have faster response. on industrial level they are able to operate in ms range.
Definitely not an issue here. It's responding to human input, not precision computer controls.
I did a PLC control on a paint chop, The omron relay didn't last more than 3 month. I change them for SSR. They were all operational after 10 years of usage.
Not sure what a paint chop is, but I suspect that it puts a relay through a whole lot more cycles than a kegerator could. The PDF I cited above with the 100,000 cycle life expectancy contains a theoretical case study of a commercial oven with a relay switching the burners on and off several times per minute, which adds up to over 600,000 cycles per year, translating to a 2 month life expectancy. This leads me to believe that your paint chop has a similar usage pattern, as it matches the theoretical life expectancy of the theoretical oven. If he's pouring that many beers in his home bar, I suggest he update his insurance and put the hospital on speed dial, because someone will have alcohol poisoning WAY before a relay would burn out. He would also be going through roughly one keg every hour, and this is even forgetting the fact that the relay remains open for two minutes, not just one pour.
I was asking about the benefits of a $30 SSR compared to a $5 relay board for this particular project, not in general. I know SSR has definite benefits for many applications, and is in fact the only realistic choice for many purposes. I just don't see the benefits for this particular project. Unless of course the OP is opposed to a confirmation click when the code is successfully entered and again when the childproof safety valve closes, which would be his prerogative.