Hey, I recently got an old train traffic light and decided to make some sort of party light (using MSGEQ7 + Arduino). I bought these: http://www.ebay.com/itm/111339754104?_trksid=p2059210.m2749.l2649&var=410324237499&ssPageName=STRK%3AMEBIDX%3AIT lights and planned to switch them using these: Output 24V-380V 25A SSR-25 DA Solid State Relay For PID Temperature Controller | eBay 24V-380V 25A SSRs. I chose SSRs hence I need to switch the light very often and for short intervals. I hooked everything up - 220V on the SSR and one of Arduino's digital pins straight to the SSR. Everything worked fine while testing. After period of time, the SSR stopped working - the light indicating active input worked, but the SSR didn't switch the AC. The interesting part comes here: I tried to raise voltage (since the SSR can be switched with 3 - 32VDC) and used a 9V battery. For some reason it worked again. I thought that it was a faulty piece and tested another SSR from the same batch (bought 2). The second one failed exactly the same way.
So my question is: what am I doing wrong? Too high current damaging internal components of SSR? Bad choice for fast switching of 220AC? If so, do I have any alternatives?
I don't know exactly which component has failed but those lights will have some sort of switching power supply and current driver inside them. They simply aren't meant to be switched rapidly like that (I assume you tried to PWM them).
An SSR is usually just two MOSFETs back to back (so current can flow both ways), you switch them both at the the same time.
No.
An SSR is normally made from a triac or two SCRs.
You very occasionly get a SSR with DC only capabilities and they have FETs in them, but never connect those to the mains.
It sounds like you are putting too much current in them, is their a seriese resistor?
Try out your SSR switching a standard 60W light bulb. I presume it will work just fine.
SSRs use Triacs which require a certain minimum holding current to work. A 7W bulb arguably draws about 10 mA, too little for the Triac to conduct, especially one rated at 25A.
Two things about those bulbs - the heatsink is generally properly insulated from the PCB and could easily become live, so ensure the whole "bulb" including that heatsink is fully insulated/ separated from any human (or animal) touch.
The other is that most of these cheap bulbs use all of the LEDs in a series chain fed by a bridge rectifier and with a capacitor in series before the bridge rectifier, limiting the current. The only interesting point here is that you should use zero voltage switching if you propose to switch them frequently.
Thanks everybody for helping me, I drew the sketch of my circuit. The datasheet says 7.5mA at 12V, so my Arduino's 40mA ruined it? I have one more ssr ordered, so I can test it when it comes with the resistor. Would 60 ohm resistor be enyough? (R = (5-2V)/(40-7.5mA))
Re: fungus
I don't know exactly which component has failed but those lights will have some sort of switching power supply and current driver inside them. They simply aren't meant to be switched rapidly like that (I assume you tried to PWM them).
I didn't PWM them, I just made a circuit that reads the music input's frequency, splits it into 7 channels (using MSGEQ7) and then based on the difference between each channel makes the light flash or stay on..
Re: Paul__B
Two things about those bulbs - the heatsink is generally properly insulated from the PCB and could easily become live, so ensure the whole "bulb" including that heatsink is fully insulated/ separated from any human (or animal) touch.
Thanks about that, I had to, however, find it the hard way when one of the internal wires came broken. Luckily it wasn't live..
The thing is that both SSR's are dead for switching at 5V, so they were damaged in some way - either too high current on the logic side (I can test that when the new SSR comes), or on the lightbulb side. If that fails I will have to use a LED and a driver and switch them using a transistor, right? I need a powerfull source of light due to the traffic light size - does anybody have a cheap (chinese) source of led lights (biger LED disc would be awesome)?
Yes, however I would probably need a heatsink for that too, which would raise the total price. Using 3 E27 LEDS with 3 relays just looked awesomely easy. I'm trying to get the lights incl. drivers under $30.
