Hello,
I am working on a device that measures AC current in a wire and then turns on a relay that turns on more devices.
I have been using this:
https://www.alibaba.com/product-det...pm=a27aq.27095423.1978240560.1.78372277WVXPSd

but a lot of them keep breaking down and the output starts flickering. Any suggestions? Maybe I am doing something wrong or if there is a better solution.

I tried to adjust the sensitivity but always the same problem.

 

What is the total device load, voltage (AC or DC) and current?

 

The voltage going through the sensor is 110V AC. The amperage is between 0.4 and 2amps. The current output from the sensor should be enough to turn on a relay. What I have been using is this:
https://www.digikey.com/en/products/detail/american-zettler/AZ2280-1A-120AEF/12171666

but I am not married to the relay

 

Have you looped the power wire through the current transformer a few times?
That will increase the signal so it will not be so sensitive.
And I think the sensor output is just a relay contact so the extra relay may not be needed if your load is not too big. It looks to have a contact rating of 300mA. If larger is needed, than use an external relay but make sure the curretn is enough.

 

maybe something like this...

 

maybe something like this...
View attachment 363936

Won't that turn the relay on and off 50 times a second?

 

A clue can be found in the description,

 

but a lot of them keep breaking down and the output starts flickering. Any suggestions?

Quick question (observation): Looking at Panic Mode's circuit (post #5) and considering your system keeps breaking down; do you have Diode D3 across the coil of the relay. as shown in panic mode's diagram?

 

So K1 & K2 constitute a normally open switch. When current is below a threshold the switch remains open. When current exceeds that threshold then the switch closes. What's the relay for? Are you controlling something that is higher power than the K1/K2 switch can handle? It appears the switch can handle 300mA (0.3A) AC or DC. So maybe you Do need a relay.


The following wire diagram suggests it can handle more than 300mA. But I don't know how much current a Contactor would draw. Small electric fan - that's less than 300mA. A relay coil might be below 300mA.

But if you're switching an inductive load then you need D3 across the relay coil pointed exactly the way shown. Cathode to the positive rail.

 

Won't that turn the relay on and off 50 times a second?

yes... some filtering would be needed. wife made me wrap it up so did not have time to finnish. so at least it is a conversation piece.

 

So K1 & K2 constitute a normally open switch. When current is below a threshold the switch remains open. When current exceeds that threshold then the switch closes. What's the relay for? Are you controlling something that is higher power than the K1/K2 switch can handle? It appears the switch can handle 300mA (0.3A) AC or DC. So maybe you Do need a relay.
View attachment 363962

The following wire diagram suggests it can handle more than 300mA. But I don't know how much current a Contactor would draw. Small electric fan - that's less than 300mA. A relay coil might be below 300mA.
View attachment 363963
But if you're switching an inductive load then you need D3 across the relay coil pointed exactly the way shown. Cathode to the positive rail.

I have probably around 1-1.5Amp load, that's why I am not using it directly.
So you are saying to add a diode between K1 and K2? (K1 and K2 are attached directly to the relay)
https://www.digikey.com/en/products/detail/american-zettler/AZ2280-1A-120AEF/12171666

If yes, what would be the suggestion for picking the part?

 

300mA rating for a relay output is quite low. even tiny signal relays with gold plated contacts are usually rated for 1-2A. they probably use some tiny SSR as relay. many of those are only good for 300mA.
if it is the output that fails, i would simply use an interposing relay. then the load current for current sensor output contacts will be low. interposing relay contacts can be 10-25A which is more than enough suitable to drive contactor, fan etc.

 

I have probably around 1-1.5Amp load, that's why I am not using it directly.
So you are saying to add a diode between K1 and K2? (K1 and K2 are attached directly to the relay)
https://www.digikey.com/en/products/detail/american-zettler/AZ2280-1A-120AEF/12171666

If yes, what would be the suggestion for picking the part?

if you are using current sensor to drive that relay, you need to match the circuit type. that relay has AC coil for 120V. since circuit is AC, do not use any diodes. in AC circuits suppression need to be not-polarized, such as MOV or RC. i would not worry about that since coil uses very little power (<3VA).

 

so maybe add another relay between the current sensor and the relay mentioned above (AZ2280-1A-120AEF)?

 

Looking at the above we see a rectangle with AC/DC as a power source. The switch merely turns on or off via SSR whatever is being controlled. If the load is greater than 300mA then an intermediate relay is needed. If it's running on DC then you need the diode shown in post #5, Diode D3.
Back in post 5 panic mode drew a DC circuit running on 12V. However, we don't yet have a clear picture of the latch that is being switched or what type and voltage the solenoid lock latch is.
Direct question: What is the voltage of the latch? Is it AC or DC or either? If you know the current draw of the latch, please share that with us as well.
So far we're guessing at whether it's 110VAC or 12VDC and a guess is as good as a stick of dynamite. It can blow things up.

 

I will double check all the numbers when I get to my shop. Thank you guys for your help so far

 

so maybe add another relay between the current sensor and the relay mentioned above (AZ2280-1A-120AEF)?

if the current sensor is driving relay mentioned above (AZ2280-1A-120AEF), no additional "in-between" relay is needed.

current sensor can drive load up to:
120VAC * 0.3A = 40VA
but coil of AZ2280-1A-120AEF only consumes less than 3VA

 

I don't know how this current sensor was designed. I built one using this type of SS relay.
I do not see it in the data sheet, but I believe if you over drive the LED, it emits less light until will becomes "flakey".

 

Have you tried looping a number of turns through the current transformer to increase the signal level as I mentioned earlier? Or do you just have the wire trough once?

 

There have been in the past year at least two threads with the same question, and a lot of good suggestions that work. So a bit of research should find those threads.