EEVblog Electronics Community Forum
Electronics => Beginners => Topic started by: ve7xen on April 01, 2021, 08:38:23 pm
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I have one of the counterfeit Fotek relays (it is labelled as a SSR40-DA 40A job) that are all over AliExpress, and figured it would be usable for a relatively low current (ca. 3A) mains switching job in a project. On wiring it up, I've noticed that it generates a (quiet but noticeable) 60Hz hum whenever mains is applied, regardless of whether the control lines are connected.
I haven't actually used SSRs before, but this doesn't seem normal to me as what should be a solid-state part that shouldn't be passing any current or burning any power while off. Should I be concerned? It otherwise seems to be working as expected.
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The noise is likely from the snubber in parallel with the switching element.
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but this doesn't seem normal to me as what should be a solid-state part that shouldn't be passing any current or burning any power while off.
Just a technicality but this is not correct: when off most SSR's pass a milliamp or two.
At least enough to brightly light a 230VAC LED, ask me how I know ;)
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The noise is likely from the snubber in parallel with the switching element.
Yes, especially if it's a ceramic capacitor, which is piezoelectric and will also be responsible for the significant leakage current.