When HN users recommended it
1 HN user recommended this in 2017, in one comment.
20072026
Each tall tick is one HN user's first recommendation. A short tick is the same user again. Click a tick to jump to the comment.
1 HN user recommended this in 2017, in one comment.
Each tall tick is one HN user's first recommendation. A short tick is the same user again. Click a tick to jump to the comment.
Amazon should have a UL certification required policy on anything that runs off line voltage. Even then, there's stuff on Amazon with fake UL certifications. Like this solid-state relay.[1] There's been a UL warning notice out on this item for over a year.[2] Yet it's still on Amazon. The fakes are rated for far more current than they can handle.
Switching power supplies are easy to do badly and hard to do right. I had to design one recently. A switching power supply is a short circuit waiting to happen. A switcher puts DC, as rectified line voltage, through the tiny transformer. Then it cuts the power just before the transformer saturates, becomes a small DC resistance, and starts to burn up. This happens a few hundred thousand times a second. If the switching MOSFET remains on too long, the device will burn up. A switcher is thus always on the edge of burnout.
MOSFETs tend to fail in the ON state. A static charge from a finger touch on the gate input can very easily blow out a MOSFET. The gate of a MOSFET has only a few atoms of thickness between it and the body of the semiconductor, and is very vulnerable until wired into a circuit with anti-static protection. Even in good plants, some will be damaged in assembly, especially in very dry weather.
Thus, switchers need protection circuitry. This adds considerably to the cost and complexity. Ones that don't have it will mostly work, but when they fail, you have a really bad day.
[1] https://www.amazon.com/MYSWEETY-SSR-40DA-Single-Semi-Conduct...
[2] https://www.ul.com/newsroom/publicnotices/ul-warns-of-solid-...