The P1 JeeNode which was recently hooked up to my smart meter stopped working – or maybe I switched USB adapter and never checked?
First thought was to check it out, and although that provided some useful insight, it didn’t solve the problem: node blinking furiously and – more importantly – no data packets!
Well, it turns out that this thing was the problem:
That’s not a Texas Instruments unit, or rather: it’s probably from a rejected batch which found its way to the “surplus” market again (got it from Pollin in Germany, long ago).
Hooking it up to the scope tells the whole story at a glance – first the unloaded output:
Not stellar, but not shocking either. Let’s zoom in on the start of the voltage bumps:
Mweh… nasty. But here’s the same output with a JeeLink plugged in:
Whoa, right… totally useless as a “5V supply”. Ready for the garbage bin… plunk!