I have some solid state relays that switch 120v with a 5v input - I think they actually can go up to 12v.
They seem to work for some things such as a standard wall transformer powered device.
My problem is with a couple 120v powered fans - when the arduino puts the pin high to the relay, the fan does not switch on. However, with the pin still high, if I unplug the fan and then plug it back in, it works!
If I then tell the arduino to put the pin low, it shuts down the outlet, the fan shuts down. It will not restart by putting the pin high (digitalWrite).
I am pretty sure there is no issue with the arduino and the 5v side of the relay, I suspect there is some electrical concept here that is the problem. I used a 120v plug outlet checker and it says my outlets are wired properly - I have a ground, nothing is reversed or disconnected on the 120v.
One possible hint - when I first plug in the A/C 120v feed line to the relays, I notice power is fed to the outlets for an instant, even though the arduino has all the relays low. That may have nothing to do with it though. Maybe they are junk relays?
No, I am writing the pins high right in the main loop of the arduino. I do not switch from high to low at all, I just write them high. I have tried writing them high right at the beginning and also writing them high over and over within the loop, no difference.
I'm not sure but I think the problem may be that the fan doesn't draw enough current thriugh the SSR, try connecting a light in parallel and see if it works.
So I tried having a few different things plugged in parallel and no luck.
Another interesting thing - I have these pigtail plugs - aka transformer eliminators - and they have an orange light inside. When I plug that in, it lights up, normal brightness. When I plug the fan in, the light goes out - or at least is very dim.
Im working with relays as well and found a schematic helpful here at the arduino site. Ive found that putting a diode between the poles of the 5v side of the relay to work well in assuring the relay de-energizes after powered down. Funny thing with those relays...they store energy in the coils for some time otherwise.
Heres the link to the schematic. http://www.arduino.cc/playground/uploads/Learning/relays.pdf Also, Id try this schematic if you have the electo parts handy. Also a 2n4401 will work. Requires very little power from your arduino to power the relay. Does any of this help?
Thanks, I think I fixed the issue, I purchased some small mechanical relays. The relays I had were solid state, really old and I am not sure what brand, etc. I believe they were obtained at a surplus sale of some kind > 15 years ago - was hoping I could use them instead of $. The new relays work great.
i should note too...perhaps it is the relays. i`d check the ratings on them again and also take a gander at the power requirements of the fans. watts and such. amps times volts. hopefully none of that is foreign to you, but better hinted at than left alone.
good luck. sure you will succeed.
The original problem with your solid state relay not being able to turn on the AC fan but able to work with other kinds of 120vac loads is most likely that the fan motor is a very inductive load and many SSRs don't work well with inductive loads like motors depending on the size of the motor. If you search the web about using SSR with inductive loads I'm sure you will find better explanations and possibly a solution or two. In the mean time a standard electrical relay can work fine if you spec the contact ratings correctly and use a switching transistor to drive the relay coil.