Paul turned up and said that his dashcam had suddenly stopped working. It's a Nextbase 512GW. The light on the Nextbase plug-in PSU was on, but the device itself was dead. I have a spare so I connected it to the PSU and that one didn't work either. I tried a different PSU and both devices worked fine. I checked the output of the first PSU and it was
11.3V. I think I was lucky that I didn't end up with two broken dashcams. I had a look inside the faulty PSU. Nothing to see at all, but a nasty burning smell filled the room.
So one assumes then these are usb powered devices? ie 5v? Unfortunately its not the first time I've heard of a psu managing to go over volts. One might have expected some kind of simple protection, like a 6v zenner and a fuse!
I had problems with a couple of security cameras that get their power from
5V wall warts, although with cylindrical connectors rather than a standard Mini-USB, Micro-USB or USB-C connector.
One device was constantly rebooting - I noticed that it didn't show up when I did an IP address scan of my network, and then when I went past it, it was constantly panning its camera side-side and up-down, which it does during the power-on-self-test.
I know from bitter experience that PSUs fail a lot more often than devices, so I swapped it onto the other camera's PSU. No joy. Then I noticed that the originally-good camera was failing to boot at all on its PSU. So that was one dead camera (didn't work on either PSU) and one dead PSU (camera worked on one PSU but not the other).
The PSUs are giving varying readings of between 4.8 and 5.1 V DC (varying as my high resistance multimeter takes successive readings). And there's about
0.2 V AC (*) present on what should be stabilised DC. Not good. Sadly I can't measure the voltage with the camera load attached - unless I cut into the cable to expose its sheath and core wires.
Cheap Chinese Foscam cameras. Probably due for upgrade anyway, as they are only 640x480 and the picture is fuzzy even by 640x480 standards. But a lot of modern cameras seem to communicate using proprietary apps on phones, and don't seem to have a simple web interface for configuring and for viewing the camera, which can be used on any browser on any device (Android phone, iPad, Windows/Linux PC). Or else they use rechargeable batteries which must be removed, recharged and replaced every few days.
One thing I discovered as I was testing: I have kept a variety of 5 V and 12 V wall warts as spares. And one of them, a PSU for an old Nokia phone that used cylindrical rather than Micro-USB, is putting out about 10 V DC instead of 5 V. Thank goodness the plug was the wrong size to fit the camera because I may well have tried it without measuring the voltage.
I wonder whether the recent spate of 10-second power blips that we've been having may have killed one of the PSUs and the other camera. Sod's Law: after a bad spate of power blips last year, followed by almost blemish-free power since then, the electricity company had a planned power cut last month while they cut back overhanging branches as a precaution - and the recent spate of power blips (I've counted 5 in two weeks) dates from when that work was done. What's the betting they unwittingly moved a branch that was OK, so it's now closer to the 33 kV lines. Northern Powergrid are sending the team out again to check for anything dodgy. I wouldn't mind but it's a major exercise every time there's a power blip to get all the wireless repeaters in my mesh network to boot up in the correct sequence so they don't sit there indefinitely retrying to connect. The perils of living in an old house with thick walls that need a mesh of repeaters because a single centrally-placed router/wifi isn't good enough.
(*) as measured on the RMS AC setting, though I doubt whether the waveform is a simple sine wave ;-)
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