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You can't even turn this unit off

Published on Wed, Sep 25th 2024 Science & Technology Rectangular HD

Aside from the very odd translation in the listing for this light, it appears that the extra cost-cut version has been stripped back to such a bare minimum that it has stability issues.

That's a big issue, since they have skimped to the point of removing the on/off switch, so the unit is active from the point it's assembled at the factory. When this one arrived its battery had been seriously over-discharged due to it turning on and off repeatedly while in its box.

Theoretically the box should block the PIR sensor from seeing movement completely, but I think it has created a situation where the sensor chips gain goes so high that it starts being affected by low level ambient electrical noise. It's not helped by the fact that there is no current limiting resistor for the LEDs, so the controller chip may be having thermal issues too, and the way its power is routed via the high current LED path also adds instability because the voltage will spike upwards when the LEDs turn off.

I tried the following things to try and solve the oversensitivity problem.

I added a 5.6 ohm resistor in series with the LEDs. Still false triggered.
I added a 22uF capacitor in parallel with the existing decoupling cap. Still false triggered.
I broke the positive track shared with the LED circuit and ran a direct link. Still false triggered.

The one thing that did seem to solve the problem was to put the unit on charge while in the box, suggesting that the battery voltage fluctuation and recovery when the LEDs turn off may have been an issue. That suggests that the cell impedance might be high because of the low capacity.
The charger was able to provide a more stable voltage under load.


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