ZeroCrossing AC Dimming

Hello,

First time I post here, so bear with me. :smiley:

I am bulding a circuit to dim an AC light. Already built the zero cross detector with H11AA1, this one works.
But the SSR will switch just from 12v. Tried with a BT137, can't get it working.

My question is, How can I trigger 12v from the Arduino ?

Any suggestions are welcome .

apparentvj:
Hello,
First time I post here, so bear with me. :smiley:

I am bulding a circuit to dim an AC light. Already built the zero cross detector with H11AA1, this one works.
But the SSR will switch just from 12v. Tried with a BT137, can't get it working.

My question is, How can I trigger 12v from the Arduino ?
Any suggestions are welcome .

Do you have the details of the SSR? Are you sure that it requires 12V? (DC, I assume.) It's fairly common for them to have a wide input voltage range, often 3VDC to 32VDC.

If it does, all you need is an NPN small-signal transistor connected in common-emitter configuration, with about a 10K resistor from the Arduino pin to the transistor base, and the SSR DC input connected between the transistor's collector and the 12V rail.

Some SSRs can be used for dimming, but not all.
Some only turn on at (near) zero-crossing and others are suitable for random fire.

Hi, thanks for help guys.

I know, it says 3v to 32v, LED get lit at 3v but no switching, same at 5v.

I'll try with a npn transistor. Tried with some transistors I had at hand, but without luck. I think some of them were pnp or probably faulty. (scavenged parts)

I already checked the internet for info, but not finding anything useful.
That's why I came here for help.

@OldSteve
Does it look right ?

btw, mine looks exactly like this. cheap chinese. the reseller couldn't tell if it's random or not.

@Runaway Pancake

read about it, i hope mine is not random switching.

Thanks again dudes !

You show that backward the NPN switches to ground

Untitled_Diagram.png

@be80be

Thanks a lot ! :slight_smile:

be80be is correct. You need to connect the SSR +ve to +12V, the SSR -ve to the transistor's collector. The transistor's emitter connects to ground. The base connection is fine.

But before you do anything else - There are a great many sellers peddling counterfeit Fotek SSR-40 and SSR-25 solid state relays, and these SSRs are known to burst into flames.

The fact that your's has ratings for 3-32VDC, yet won't even switch with 5V applied indicates that it could possibly be one of the counterfeit items.

I'll see if I can find the article I read a short time ago, that has pictures showing a real Fotek SSR and a counterfeit one. From memory, it wasn't too hard to tell the difference.

Edit: Just looking at the pictures, on close examination your's looks very much like a genuine Fotek SSR, except that at the bottom right corner of the indentation that holds the label, a real one doesn't have a sharp 90 degree corner in either the plastic or the label, it's 45 degrees on both.
On the pic you showed, the label has the 45 degree corner, but the plastic casing doesn't.
Otherwise, your's definitely looks more like a real one than a fake.

It might just be a good fake, though, so I'll leave it up to you to decide. Apart from that small detail, it looks OK, but if I were you I'd watch it very carefully at first.
Here's the link to the UL warning:- UL warns of solid state relay with counterfeit UL Recognition Mark

burst into flames

:o

I just found this, which increases my suspicion that your SSR might be a fake, when also taking into consideration the minor fault that I noticed earlier.. It looks just like the pic you showed:- The inner workings of Counterfeit FOTEK SSRs

Be very careful.

Edit: And here's a mention of a fake, (with the more easily detected label), which wouldn't switch until 5V to 5.3V was applied, instead of the rated >= 3VDC. It's an SSR-60, not an SSR-40, but still....:-
How to destroy a fake FOTEK SSR

Be even more careful. :wink:

I think the op problem is the led doesn't light with the power backward. But from your link steve it looked like most problems there was in over rating, etc trying to use a 12 amp at 25 or a 20 at 40 as long as the op is using less amps then half the rating he should be good there.

I guess you should always add a fuse to the circuit and have a smoke detector near by. :sunglasses:

Or

Just buy from a reputable supplier.

.

be80be:
I think the op problem is the led doesn’t light with the power backward. But from your link steve it looked like most problems there was in over rating, etc trying to use a 12 amp at 25 or a 20 at 40 as long as the op is using less amps then half the rating he should be good there.

Very true, there probably won’t be a problem at that current, but I had to mention it.
Also handy for others that read this thread in the future, that plan to use one for currents closer to the rating. :wink:

From reply #2:-

… and others are suitable for random fire.

He wasn’t kidding. :smiley:

Yeah, its a counterfeit SSR. I've used one before and that relay required 12VDC on the input to reliably switch the load. It's been crippled in most every aspect. The new specs for your relay would be something like:

[color=teal][b]Label      True spec[/b][/color]
3-32VDC    12-24VDC?
40A        20A?
24-380VAC  48-240VAC?

apparentvj:
@Runaway Pancake
read about it, i hope mine is not random switching.

That's random firing.
It's a technical term.
If your intention is to do dimming (phase control) then it needs to be random - unless you're figuring on using (triggering) every other alternation or something.

Is definitely a fake, but I’ll not be using it over 10A.
The first thing to check is the weight, mine feels very hollow.

I compared once with a genuine one, and is at least half the weight. As the genuine ones are filled with resin, but the cheap ones are just coated a tiny bit.

You could really tell without comparing, it just feels light and hollow.

“random fire” . haha ha :))