Faulty Relay?

I bought this relay and tried splicing it into an extension cord. I'm in Australia so mains power is 240 so the 340 rated relay should be more than sufficient. Using this and also this also this page I know that in Australia the brown wire would be the live one. I confirmed this with a continuity test between the pin marked "L" and the brown wire.

When I plug everything (running the brown wire through the relay) in and use a lamp to test, the light bulb is flickering when the relay should be closed. You can see in the youtube video below that the light flickers despite the input there not even being anything connect to the bottom pins. If I run 5v across the bottom connectors on the relay the light turns on as it should.

What is going on here? Is this a case of a faulty relay or is there something I'm missing here?

http://youtu.be/qda_aAuOVrQ

PS: Reason this is on the arduino forum is I want to control this with an arduino, but I ran into problems before I even got that far! Any help would be greatly appreciated :)

... despite the input there not even being anything connect to the bottom pins.

In other words, the input is not defined. Thus the output isn't either. If you provide zero volts (rather than not connecting) it should be open.

Also I'm wondering if that relay is suitable for a fluorescent globe. Try an incandescent one.

More reading I found:

http://electronics.stackexchange.com/questions/40044/can-i-use-a-ssr-for-switching-a-fluorescent-light

http://www.phidgets.com/docs/Solid_State_Relay_Primer

http://www.practicalmachinist.com/vb/general/fluorescent-lights-not-working-solid-state-relay-controls-266438/

Thanks Nick,

Fluroescent vs Incandescent is a good point. I couldn't find an incandescent in the house but going to shops later. Will update soon.

It doesn't actually say on the website but I believe the relay is normally closed. I get that flickering behaviour whether the relay is connected with 0v or not at all. When I put 5v across the input terminals the fluro global comes on and stays on exactly as it should. Unlike the people on those pages it seems I'm having trouble with the closed state of the relay. From what I could tell they were all getting quick flickering in the open state.

How would a solid state relay be normally opened or closed? I have never heard of that.

Can you explain how you connected "0v"?

crimsonbinome22: Thanks Nick,

Fluroescent vs Incandescent is a good point. I couldn't find an incandescent in the house but going to shops later. Will update soon.

It doesn't actually say on the website but I believe the relay is normally closed. I get that flickering behaviour whether the relay is connected with 0v or not at all. When I put 5v across the input terminals the fluro global comes on and stays on exactly as it should. Unlike the people on those pages it seems I'm having trouble with the closed state of the relay. From what I could tell they were all getting quick flickering in the open state.

It's most likely that your SSR is misbehaving because the fluorescent lamp contains a ballast which is an inductive load that can cause problems like this if you don't have a properly calculated and installed 'snubber' which is a RC in series across the SSR output terminals. First test with a standard Incandescent lamp and see if your SSR does not then work correctly.

Lefty

I went back to look at my notes from when I started work on my reflow oven controller. I used a similar SSR, but I bought directly from Crydom. I did the same as you. I tried to test the relay with my lamp which had 3 CFLs in it. While I was able to turn it on fine, it acted funny when the relay was turned off.

A solid state relay is basically an opto-controlled triac. So it will let some leakage current to pass even when it is in the off state. This may be charging up the CFL enough for the momentary flash.

CFLs are built notoriously cheap and probably lack proper filtering. As retro suggests, some external filtering might be needed with it.

Hi, the reason that the SSR has problems with fluorescent lights is that the internal triac turns off at zero current. this is okay with resistive loads because the voltage at this time is also zero.

The power factor associated with flouro lights means that at zero current there is still voltage present because of the lag or lead in current that occurs with respect to the voltage. This causes erratic switching of the triac.

Tom.. :)

I have a couple of these ssrs .. resistive loads are ok, but not inductive, i stick to regular relays for what you're doing...

But it's about time i had a play with an ssr it's been gathering dust.

Thanks for all your help, I'm learning a lot here. So I tested the relay with an incandescent globe and it works fine. Problematic for me though since I need to use it with a CFL (putting it above my basil plants).

So if I want to drive a CFL with a relay my options are: 1. Use a mechanical relay: In this case can anyone suggest a decent relay of a similar design to the one I have? I liked that one I had because it let me tuck the live wire safely away. I've had a look on Australian supplier websites but couldn't find much other than standard pin/breadboard type relays which make me a bit uncomfortable at these voltages.

  1. Buy an RC snubber and install it in series on the live wire. In that event, how do I choose a snubber? While I've been testing it's been driving a 20W lamp, but it'll be driving a 130W one at 240VAC soon.

crimsonbinome22: Thanks for all your help, I'm learning a lot here. So I tested the relay with an incandescent globe and it works fine. Problematic for me though since I need to use it with a CFL (putting it above my basil plants).

So if I want to drive a CFL with a relay my options are: 1. Use a mechanical relay: In this case can anyone suggest a decent relay of a similar design to the one I have? I liked that one I had because it let me tuck the live wire safely away. I've had a look on Australian supplier websites but couldn't find much other than standard pin/breadboard type relays which make me a bit uncomfortable at these voltages.

  1. Buy an RC snubber and install it in series on the live wire. In that event, how do I choose a snubber? While I've been testing it's been driving a 20W lamp, but it'll be driving a 130W one at 240VAC soon.

An R/C snubber would not be wired in series with the 'live' AC wire, but rather just across the two output terminals of the SSR. Proper sizing of the snubber involves knowing the inductive value of the load which you probably don't know. Perhaps just searching of snubber circuits would give you examples of starting values to try. Keep in mind that the capacitor must be a non-polarized type and of suitable voltage rating for mains power use. If your not experiance with AC power wiring and cautions then you are probably better off using a electro-mechanical relay, they are still useful devices after all these decades. Lefty

Would a metal oxide varistor do the job ?

While all of this discussion on inductive versus resistive is important, let’s remember that the issue is when the relay is “off” is when the light flickers. Not when the relay is “on”. After all, the CFL should have a PFC circuit to help reduce the inductive effects.

The flickering is most likely due to the leakage current of the relay when it is “off”. It’s not a perfect open. Crydom’s relays are specified with 3mA of leakage current. I’d imagine this cheap knock-off is about the same.

So the small amount of current leaking through when the SSR is “off” charges up the rectifier and capacitor input filter in the CFL. Leakage current causes a gradual increase in the capacitor voltage. When the voltage is high enough the bulb conducts causing a light flash and discharge of the capacitor. Then the cycle starts over.

You almost need a bleed resistor connected to the output to neutral, to help bleed off that leakage current. Or as other have suggested, change to a mechanical relay. Or try different makes of CFLs to see if one has a less susceptible design.