I inadvertently (i.e. wasn’t paying due attention) reversed the 5v and GND connections to my emonth yesterday. I realised when I heard a pffffft noise and got a slight burning smell. I’m pretty sure the device is toast now - my own fault.
Is there anything at all that I can do to salvage it (or bits of it), or do I just chalk it up to experience and add “double check the wiring” to my mental list after “check the wiring” for the next one?
The data sheet says the maximum input voltage is -0.3 — +7 V. I think you might have exceeded that.
I’d be very surprised if anything has survived, but you might have been lucky, and the damage is confined to the XC6206 regulator, which provides the 3.3 V for everything else. Whether you are able to desolder that and replace it could be a problem.
The best I can suggest is desolder that (it’s under the battery box - circuit diagram and PCB drawings are in the Wiki) and try it with ordinary zinc carbon (ideally, they are low power) batteries. If it works, then continue using it on batteries or replace the regulator if you’re able and need the 5 V supply.
Or you could ask The Shop: [email protected]
You could add “Use a current-limited power supply” as well to your list - with the current turned well down, you would probably have avoided damaging it, as there’s a reverse-polarity diode shown on the schematic of the XC6206, and it’s that which (hopefully) has melted and gone short-circuit, protecting everything else.
Thanks for the suggestions Robert. It hadn’t occurred to me to check powering it by battery.
I put a couple of batteries in the holder, the green light came up and the device started showing in emonCMS so I’m back in action again. My soldering is ropey enough, let alone desoldering so I think I will stick with the battery supply for the moment.
I wouldn’t celebrate too soon - you might find that the damaged regulator is still draining the battery, in which case it will need removing somehow or other. As it’s no good anyway, I’d be inclined to put a hot iron on top of it and hope enough heat gets to the solder and melts it, then it will just slide off the pads without damaging the board itself.