How can I protect the coil from melting/welding inside?
On this thread I started, I've come to the solution that my relay coil was fried/melted/welded inside so it just does not trigger. My current relay's in1 does not affet the relay coil but in2 works perfectly and I believe it's due to cutting the 220v power abruptly.
The coil only works at 5 volts dC, not from the primary power you are switching. The contacts inside are probably eroded away due to arcing. Pretty common for such cheap relays.
Typically relay boards are supposed to have diode built in, either inside the relay or added on PCB near the coils. Cheap ones might not have it though.
As other said, cheap relay were probably burned out from arcing on contact. I'd look at places like Digikey or Mouser and look for relay with 5v coil (or 3.3v if you're using 3.3v Arduino) and the contacts are rated at more than what you need. (250v AC or more, about double the amp you are planning to draw)
Can you post a link showing how the motor control circuit is supposed to be wired? That picture only shows the wires, not how to connect them to a controller. Are the direction wires supposed to connect to the 230V line or neutral? Are the direction wires only connected momentarily while the motor starts or constantly? I don't believe those puny relays are capable of handling 3 Amps inductive for very long.
If I understand you post correctly it seems there is some confusion on the load vs the coil. In a mechanical relay the coil (in your case 5V energized) is not electrically connected to the contacts (which I assume are powering some 220V load).
Therefore abruptly disconnecting the 220V power (mains?) would not adversely effect the relay coil.
If the relay contacts were welded closed, it would make contact even with all inputs disconnected on the control side, is this the case?
The motor connections are correct. I can confirm that as I've tested all the inputs with all possible combinations (of course short circuit connections excluded) via direct connection to 220v power source. I got this information from the owner of the motor. He states that he uses this motor on thousands of products and has vast knowledge of it. Also, when I've replaced my relay, it just works perfectly for a time. So, no connection problem on the motor end
JohnRob:
If I understand you post correctly it seems there is some confusion on the load vs the coil. In a mechanical relay the coil (in your case 5V energized) is not electrically connected to the contacts (which I assume are powering some 220V load).
Therefore abruptly disconnecting the 220V power (mains?) would not adversely effect the relay coil.
If the relay contacts were welded closed, it would make contact even with all inputs disconnected on the control side, is this the case?
Yes I believe that seems like the issue. How can I protect the relays from this? Can you provide any guidance please?
In my mind (and apparently others) you still need to address the initial power-up period of the circuit. The way it is wired (according to your Fritz diagram), on power-up both relays will be not energized so the direction 1 and direction 2 will be energized at the same time. Its difficult for me to focus on protecting contacts from a issue I don't believe exists. In my experience, a 640 ma motor should not be able to damage a 10A relay contact. Of course there is the possibility you just had a bad relay.
Have you considered rewiring the relays so the direction lines are connected to the NO connections of the relay?
Just because the relay is rated for 220VAC, it doesn't mean the circuit was designed to handle it. All traces from the contacts would need to have 1/8" clearance from adjacent traces. Additionally the traces would need to 0.283 inches (ie., greater than 1/4" inch) wide to handle the 10 amps.
The board I have does not meet this requirement, thus making shorting, arcing, and fire a possibility. If those connectors are on a 0.2" spacing, there is no way the 1/8" gap and 1/4" trace width could fit.
