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first post here so be kind :) disclaimer : I am not a professional and nor I have any engineering background, all this is part of a hobby.

After fiddling for months with SonOff / Tasmota / MQTT / Home Assistant I decided to move on to something more reliable for my garden light automation system. I got too many issues with the devices disconnecting from WiFi because my garden is to large for this technology and I can't add more access points. So I figured out some electrical contraption without any connection to anything "intelligent".

What I want :

  • Turn on my garden lights when the sun sets.
  • Turn of them at midnight.
  • Being able to manually turn on lights after midnight if needed.

My hardware :

My design : design schematics

My question : Do I have (and if yes how to) to protect the light control switch load output, because while in "manual" mode, it will be directly connected to line and may be fried.

Thanks for reading me !

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    \$\begingroup\$ What powers the timer relay while the light is in manual-on mode? \$\endgroup\$
    – mike65535
    Apr 27, 2021 at 16:35

2 Answers 2

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You can make it even simpler than that.

enter image description here

Figure 1. The manual switch can just bypass the timer and light sensor.

The triac or relay in the light control switch will not suffer from "backfeed" on the output (but note that there is no datasheet available for it so this is only an educated assessment).

That switch is a 2-way switch - up or down. Most confusingly they are sold in North America as "3-way" because they have three terminals or three wires.

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  • \$\begingroup\$ Thanks for your answer. That was the design I had in mind in the first place, but I was concerned about the light control switch being connected to the line on both input and output and indeed the NK-301F is a cheap Chinese component you can't find the datasheet of. \$\endgroup\$
    – catmembert
    Apr 27, 2021 at 12:29
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If you're concerned about connecting something to the output of the control just rearrange the switch wiring:

enter image description here

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  • \$\begingroup\$ Thanks, this one is clever ! By reversing the manual switch wiring, the light switch componnent is always protected from backfeed. \$\endgroup\$
    – catmembert
    Apr 28, 2021 at 6:48

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