Ssr insufficient current from arduino?

Hello everyone
I have an R3 board I am wiring to a Fotek SSR to control a 240 Vac load (light bulb). I know the circuit works because the load turns on when the input to the Ssr is connected to a 9V battery. However when I connect the SSR to the arduino (say for instance to the 5V and gnd pins), the SSR turns on (Led on the Ssr flicks on) but the load doesn't. The Ssr input side reads 5v on the multimeter as well. I'm wondering if it's a current issue since the input voltage is within the correct range for the SSR (3-32V).

Any thoughts?

Where did you buy the SSR ? can you give a link to that ? Did you buy it at Ebay or amazon ? Perhaps it is fake.

Most SSR need 3V or more and a few milli-amps. That's perfect for a 5V Arduino board. It is not a current issue. Perhaps something is wrong with your SSR.

Can you test with somethine else ? For example a 5V power supply ?

Any thoughts?

Its a common problem Fotek purchased from eBay and elsewhere. They seem to work fine under any rated load providing you control them with 12-32VDC, not 3-32VDC.

Hmm yeah I'm starting to think it's the SSR. I think the voltage is dropping internally and thus unable to switch the load side
Bought it off ebay
I don't have another 5v source unfortunately
Might try with a few AA batteries with 4.5v and post back

Just added some links my previous post ... a solution is provided (providing you have a 12V-32V supply).

Post a link for the ebay site for the SSR.

I am using several Fotek SSRs everyday for over a year, controlled by directly from mega, no issue at this point. The SSRs control a 25w fan(inductive load), and several other loads ranging up to 200+w. Maybe it's a QC issue? Especially at that price.

I am using several Fotek SSRs everyday for over a year, controlled by directly from mega, no issue at this point. The SSRs control a 25w fan(inductive load), and several other loads ranging up to 200+w. Maybe it's a QC issue? Especially at that price.

Yes. You shouldn't have any problem controlling an SSR with an arduino if the arduino gnd is connected to the "-" screw terminal of the DC input.

My guess would be that Danyboyee's FOTEK SSR is counterfeit.

The inner workings of Counterfeit FOTEK SSRs

. The Ssr input side reads 5v on the multimeter as well. I'm wondering if it's a current issue since the input voltage is within the correct range for the SSR (3-32V).

...I don't have another 5v source unfortunately
Might try with a few AA batteries with 4.5v and post back

If you're getting 5V across the relay it's NOT a current issue and a different 5V source won't help.

Current is a function of voltage and resistance/impedance ([u]Ohm's Law[/u]). If the resistance/impedance is too low and the load tries to "pull" more current than the Arduino can supply, the voltage will drop (and therefore the current will drop).

We don't know the "resistance" of the SSR, and since it has an LED inside the resistance isn't constant, but we know the 5V is holding-up so we know it's not a current problem.

.

The SSR is this one http://vod.ebay.com.au/vod/FetchOrderDetails?qu=1&itemid=191732705117&transid=1282805889009

I know you can’t measure the resistance across the input side of the SSR, I was thinking that perhaps the voltage Drop across the external LED and possibly across the other internal circuitry would lead to the voltage across the LED coupled to the photo sensitive diode to be below the threshold for activation.
So likely to be a dud SSR which actually requires a higher input voltage to function (hence it working with a 9v battery)

Your Ebay item without having to log in : 24V-380V 40A 250V SSR-40 DA Solid State Relay Module 3-32V DC To AC | eBay

At least you bought the cheapest SSR-40 DA.
How to get a good SSR-40 DA from Ebay ? I don't know. They all seem to be 'FOTEK'.
Around 7 AUD are brandless SSR-40 DA, and above 10 AUD are other brands.
They are cheaper at AliExpress.

I might buy a PQLYT SSR instead from aliexpress. They are 8 USD on aliexpress and seem to suffer less from counterfeit issues than the foteks
Thanks for your help everyone

Don't buy Fotek. They were caught by UL for using a counterfeit UL mark on their product. Whether Fotek is making bad products OR someone else is selling fake products with a Fotek name, is unclear. Bottom line, it might be a major risk to install a mains switching product that comes from an unknown supplier. Be aware.
UL report:
UL Website warning about Fotek

I have personally seen posts here on the forum of bogus FOTEK SSRs. One poster took one apart and found a junk circuit inside.

Hi,

I would buy another brand.

Tom... :slight_smile:

At the very end he says: “I consider using them”.

Just an update
Received a PQLYT SSR this week, purchased from AliExpress
Works to spec! Same setup that I had for my "Fotek", but now functions as it should.
Lesson learned, avoid "Fotek"-like SSRs from online retailers!