Does the galvanic isolation exist between the relay's coil and its contacts when the relay is actuated?
Thanks in Advance!
Yes.
However, there is more than one way for any spark or voltage or current peak to reach the Arduino.
It all depends on how the circuit is wired. Some automotive relays ground a contact when energized and one side of the coil is also grounded. In that case the answer is no.
What causes you to ask the question?
Paul
SLA--T90-.pdf (3.6 MB)
Hi, I'm using SLA-5VDC-SL-A relay and we'll be controlling the 230VAC max:30A load using esp32. In order to isolate the mains voltage from esp32, I have three options right now
- Using solid state relay (though it's rated for the 25A max, I don't think it could barely handle at least 20A)
- If the relay has the galvanic isolation between its contacts and the coil when it's actuated then directly use the relay with the common power source. (I've attached its datasheet for reference )
- If no galvanic isolation between its contacts and the coil then opt for the dedicated isolated power supply for the relay.
What option would you suggest?
IMO, "galvanic issolation" is just a spark away to being non-issolated.
You do realize that the aluminum plate on the bottom of the SSR is there so you can attach it to some type of heat sink, don't you?
You use the term galvanic isolation like it is some magic specification. At some voltage, there is NO galvanic isolation in anything. You must specify the voltage at which the isolation breaks down and it always does.
I sincerely hope your 230 volts is AC and not DC because the SSR will not function with DC.
Paul
Then I suggest reading the datasheet for it:
https://www.radiolocman.com/datasheet/pdf.html?di=135565
And you'll see the insulation ratings for this relay in detail. Bottom line is the insulation between coil and contacts is rated 1000VAC for 1 minute.
Its very typical for relays to be isolated between coil and contacts, but the actual precise answer is always in the datasheet for the device in question.
230V is AC
It's 1000VAC for 1 minute between its open contacts, when the relay is not actuated.
And 2000/4000VAC between contacts and coil for 1 minute, when the coil is energized or not?
Also, I think there is no need to worry about the isolation, I don't think the AC transient voltage spike would last for more than a minute (eventually MOV would burn before it causes any damage to esp32 and the rest of the circuitry) and also for the voltage less than or equal to the 500Vac there is very high resistance of 100M ohm between its contacts and coil (indirectly a galvanic isolation for less than 500V)
Funniest thing I have read all day.
I guess he has never had his equipment destroyed after the MOV burns up!
Paul
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