<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Ken Brown:
It's been way too long since I studied electronics. Would I need a RC protection on a solid state relay? I thought RC worked only for DC output. I'm way out of the loop. I'd like to continue this, my jerky was great, but I don't want to screw up my Stoker. </div></BLOCKQUOTE>
Mechanical relays are subject to some problems on the output contacts, particularly when run at very small fractions of the design current. Above a threshold (say a few percent of design capacity, for your relay this rating is 100ma or about 1.2 watts) the contacts are cleaned by the arc that occurs naturally when a make or break occurs. Thus, the output contacts don't usually require protection to avoid premature failure. Of course, they fail much quicker if run at much more than the design current.
On the input side, you can reduce the kick back into the driving circuit using a snubbing diode (one that absorbs the reverse voltage when the relay de-energized.) Almost any diode with a reverse voltage rating of at least 10 times the operating voltage (say 5*10=50 volts in this case) will help. There are 'better' diodes than the old 1N4002, but they are hard to find off the shelf. A snubbing diode is placed across the low voltage input coil terminals (not the AC output). Diodes normally have a bar printed near one terminal. For this application, you place the bar near the +5V side (away from the ground). Use a volt meter to determine which is which, if you do not already know.
As I indicated in my first post, since the Stoker output fan cable is intended to control an inductive device (a fan motor) it is probably sufficiently protected as shipped. If I knew what device was used, I could look at the specs and tell you, but I have not yet purchased a Stoker, so I can not tell what device is used and if it is adequately protected for driving a relay.
A solid state relay has neither the input issues nor the output issues I have described. Those issues are the ones that solid state relays were designed to fix, and they do a pretty good job. Used as designed, they are an order of magnitude more reliable then their mechanical counterparts.
The take-away is that you are probably fine (you could ask John about the issue or at least what device is used to control the output to the fan).
If you build another of these interfaces or this one fails for some reason or your Stoker starts resetting itself during operation, replacing the relay with a solid state version is probably in order.
One further suggestion: since this is likely to be used outside or around moisture, a GFCI outlet would enhance safety and reduce the likelihood of fatal shocks from the equipment you are powering.