SSR troubles - won't drive a load

[voodoobrew]

Hi everyone. I've been having some troubles with my SSRs for a new build.

The story is that I cannot get either of them to switch a dummy load (eg 40W lightbulb, kitchen kettle, etc). My low voltage signals happily switch the SSR causing the built in indicator LED to illuminate. But this has no effect on the 240V device attached.

Running a multimeter across the output sockets shows both 240V when the SSR is inactive and active. I understand that there will be a leak current, but thought it worth mentioning for the sake of completeness.

The SSRs themselves are common Fotek 25DA that I'm sure plenty of people have experience with.

Here is an annotated photograph of my wiring, and some explanatory notes...

The AC comes in on the male IEC connector at the top and exits through the two female connectors on the right. I have the active switched by the SSRs before nipping out to the female connectors. The thin blue and black leads are my low voltage signal wires (3.3V).

Is this behaviour familiar to anyone? And does anyone have any thoughts why this isn't working?

 

[Whiteferret]

Maybe swap the active supply and the switched active on the SSR it might make a difference. I know on the Omron SSRs I have they sometimes stay on even with no signal supllied to them if the 240v side are wired wrong.

 

[Pokey]

Does the switch wire voltage stay above 3 volts? I'd try it with a higher voltage since your almost off the bottom of the input range.
Are you getting 240 volt between active and neutral on your outlet or back in the circuit? Worth checking to make sure all the neutral connections are ok.

 

[voodoobrew]

Okay - further developments to this...

I replaced my signal wires with a 9v battery to test it independently - all works fine. Nothing wrong with any of the wiring.

So it would seem that the problem is that although my Raspberry Pi is providing enough signal to make the indicator LED illuminate it isn't switching the SSR. Which is odd because the SSRs clearly have 3V written on them and my RPi should be spitting out 3.3

So perhaps driving a pair of transistors and switching it with the 5V supply might be the way to go.

 

[MastersBrewery]

from what I've seen of other R PI setups they've used the 5v to drive relays, so that should fix it, also just ensure you sheild the R PI from any 240v as emi can screw with it's signaling

 

[QldKev]

Maybe 3vdc is enough, but the Pi is not producing enough current. What is the output of the Pi rated to? From memory SSRs need 7.5mA each.

QldKev

 

[MaltyHops]

I thought this too but if you zoom in on the attached pix, the Pi output seems to be rated at up to 2A (5V+) - might be worth test driving each SSR separately with the Pi.

Ed. So that thing at the top of the pix is not the R.Pi ?

 

[voodoobrew]

Yeah, having read up on the Pi the 3v3 system is only rated to a total of 50ma. So it's probably struggling with all the outputs I'm driving.

My plan now is to run them through a darlington array powered off the 5V power supply.

 

[QldKev]

Yeah, having read up on the Pi the 3v3 system is only rated to a total of 50ma. So it's probably struggling with all the outputs I'm driving.

My plan now is to run them through a darlington array powered off the 5V power supply.

I had the same issue with my Auber pid. I'm running a 20mA led plus 3 x SSRs. So I also needed to up the amps to them.

I thought this too but if you zoom in on the attached pix, the Pi output seems to be rated at up to 2A (5V+) - might be worth test driving each SSR separately with the Pi.

Ed. So that thing at the top of the pix is not the R.Pi ?

Nope that's just the power supply