{"id":19408,"date":"2025-11-24T23:52:41","date_gmt":"2025-11-24T23:52:41","guid":{"rendered":"https:\/\/staging.rayzeek.com\/?p=19408"},"modified":"2025-11-24T23:52:42","modified_gmt":"2025-11-24T23:52:42","slug":"led-motion-switch-welded-relay","status":"publish","type":"post","link":"https:\/\/staging.rayzeek.com\/cs\/blog\/led-motion-switch-welded-relay\/","title":{"rendered":"The Pantry Poltergeist: Why Your LED Motion Switch Is Stuck “ON”"},"content":{"rendered":"

You walk into the pantry, and the lights snap on. Perfect. You grab the cereal, close the door, and walk away. Ten minutes later, however, you notice a glow under the door crack. The light is still on.<\/p>\n\n\n\n

You wave your hand in front of the sensor. Nothing. You adjust the time dial. Still nothing. You kill the breaker, wait, and flip it back on. The light immediately illuminates, bypassing the sensor entirely.<\/p>\n\n\n\n

Your pantry isn’t haunted. You\u2019ve just experienced the most common failure in modern DIY lighting: a welded relay.<\/p>\n\n\n\n

The motion sensor you installed\u2014likely a standard residential-grade unit intended for a few incandescent bulbs\u2014has physically fused its internal metal contacts. Inside that plastic housing, a tiny copper arm slammed against a contact point with enough heat to liquefy the metal. It is now a permanent wire. No amount of waving your hands or tweaking sensitivity dials will separate those contacts. The only fix is the trash can.<\/p>\n\n\n

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The intense electrical arc from inrush current can be hot enough to physically weld a relay’s contacts, causing the switch to fail permanently on.<\/figcaption><\/figure>\n<\/div>\n\n\n

This doesn’t mean you bought a “bad” switch. It means you plugged a capacitive load into a device built for resistive ones. The LED strip itself isn’t the problem; the black brick powering it is.<\/p>\n\n\n

The Wattage Rating Trap<\/h2>\n\n\n

If you look at the back of your LED driver (the power supply), it might read “Output: 12V DC, 60 Watts.” You do the math. Your switch is rated for 600 Watts. You are using 10% of its capacity. You should be safe, right?<\/p>\n\n\n\n

This is where the physics of LED drivers betrays the average installer. That 60-Watt rating is the running<\/em> load\u2014what the driver consumes once it\u2019s cruising along. It tells you nothing about the first millisecond of operation.<\/p>\n\n\n\n

LED drivers are essentially massive capacitors disguised as power bricks. When they sit idle (like in a pantry), those capacitors empty out. When the motion sensor clicks “ON,” those empty capacitors act like a black hole for electricity. For a tiny fraction of a second\u2014often less than 2 milliseconds\u2014they pull as much current as the copper wire can physically deliver to fill themselves up.<\/p>\n\n\n\n

This is called Inrush Current.<\/p>\n

Mohlo by v\u00e1s tak\u00e9 zaj\u00edmat<\/h3>
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