I am having problems with my 4 channel relay module, all relays just work fine and without any problems when switching 12V DC current (1A) - they turn on and off with the familiar loud and clear click sound.
The problems start when I try to switch 230V AC (0.1A) ~20W. The relays work fine for a few seconds but if I try to switch them off it makes a far more silent click sound and it remains turned on (turning them on again makes also a far more silent click sound). The only way of changing the relay to "normal" is to unplug the load, wait a few minutes and trying again. Then they work without any problems again.
This behavior holds true for all my four relays and is pretty consistent.
Does anyone of you has an idea what could possibly be wrong with my relays - they do not seem welded internal because they work just fine without any load or the specified DC load.
I am using the following relay module and I have connected an external 12v power supply and removed the jumper.
Maybe a "dumb question" but are you using the normally-open or the normally-closed connection? (i.e. The NC connection will be "on" when there is no power to the relay coil.)
Relay contacts can stick to each other, depending on your load, current and voltage. This will or has already damaged the contacts. Get relays with contact material better suited for your load and use a snubber (MOV, filter...) to relieve the contacts.
I also suspect that the load is causing the contacts to stick. They're not sticking together permanently (yet!), but getting slightly welded together until removing the load breaks the circuit.
Throw those relays out and get more. They're already damaged and will probably get worse over time.
This. Not the same ones though - those relay modules are extremely inexpensive, so I would not have any expectation of the relays being particularly reliable. You might consider SSRs if you want to switch AC in any project you want to last.
What kind of load are you switching? Is it inductive (motor)?
There are more complaints on cheap relais, but it is rated for 10 A 250VAC, so 0.1A should be no problem...
... and if it really is, then I think these relais should not be for sale with this rating...
... are these for sale in Europe or USA (not via bangood or Alibaba, but via local suppliers)?
The ratings are for the diameter of the contact and nothing more. The actual contacts are hemispherical to allow for misalignment. When there is contact between the two, it ONLY a point on one hemisphere to a point on the other. I dissected several failed relays a few years ago and discovered how they were REALLY made.
You are probably right.
As an engineer I think you should tackle the cause and not the consequence.
And then have a secondary protection to cover unforeseen problems...
But maybe people at songle are better engineers. Or have different optimizations (price, price, price), because we always buy the cheapest and not something that will last...
Relays have been used for switching AC for many decades without issues so it should not be a problem. Its normal to hear a click on the contacts closing, but not on opening unless its a change-over relay.
I see nothing in the circuit that should cause these issues.
Can you show the rest of the circuit - the load that is connected to the relays and its supplies?
Circuit diagram requested at least 3 times now, I'm guessing it must be a state secret as nothing yet forthcoming.
I suspect something other than welded contacts............
Answer will most certainly be in what info is not provided.
