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| DC SSR Won't turn off |
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| rstofer:
--- Quote from: wraper on August 29, 2018, 10:22:32 pm ---They are also dangerous because of inferior insulation between control and power side. I would not use them even under tiny load if it's anything mains related. Actually I would not use them in any situation unless I'm on uninhabited island and have no other choice. --- End quote --- You would be better off to just twist the load wires together. Yank them apart if necessary. |
| Circlotron:
--- Quote from: Hero999 on August 29, 2018, 09:48:30 am ---There are two possibilities: 1) LEDs can light with a very small current and solid state relays leak a considerable current, even when off. 2) The SSR has failed short circuit, which is the most common failure mode. Test the solid state relay with an incandescent lamp. If it works, then it's #1 and the solution will be to connect a resistor across the LEDs. If it still doesn't work, then the solid state relay is bad and needs replacing. --- End quote --- Third possibility, the DC SSR is connected reverse polarity and it’s mosfet body diode is conducting. |
| Cerebus:
--- Quote from: Circlotron on August 30, 2018, 07:25:39 am --- --- Quote from: Hero999 on August 29, 2018, 09:48:30 am ---There are two possibilities: 1) LEDs can light with a very small current and solid state relays leak a considerable current, even when off. 2) The SSR has failed short circuit, which is the most common failure mode. Test the solid state relay with an incandescent lamp. If it works, then it's #1 and the solution will be to connect a resistor across the LEDs. If it still doesn't work, then the solid state relay is bad and needs replacing. --- End quote --- Third possibility, the DC SSR is connected reverse polarity and it’s mosfet body diode is conducting. --- End quote --- They are normally constructed with back to back MOSFETs with complementary gate bias precisely to make this a non-issue. I've never seen a polarised DC solid state relay, although I'm sure that there's someone out there who's cheap enough to have made one. |
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