Thursday, December 1, 2016

Check Check and Doublecheck !!!

One of my projects was nicely coming along. In reality it was just a stupid project being a portable thermometer using an ESP8266 that displays the temperature on a web-page. So nothing special. The breadboard version worked like a charm to I transferred it to some stripboard. And then disaster struck.

It just did not work. The dreaded blue smoke materialised and my ESP was fried !!! Damn what happened ???

So I checked my stripboard soldering over and over and I just couldn't find a fault. There was only one thing left to do: check the power supply.

My intention was getting power from a USB power source be it from a computer or a power bank.
For that reason I use cheap USB power cables from the dollar store. I cut the cable and strip the wires.

The wires are colored just like they need to be: Black for ground, Red for VCC Green and White for the USB data channels.

I hooked up a mulimeter and it looked allright. 4.9 volts is great. But hey look at that closely. It does not say 4.9 volt !!! It says - 4.9 volt.

So I took out my trusted polarity checker (find the sory on that by CLICKING HERE) and hooked it up. Black to Black and Red to Red. And then it was obvious. The red light was on. Polarity was reversed !!!!

And then I switched the power leads: Red on Black and Black on Red and there it was: the blue led went on: everyting. ok.

So there you have it: the color of the power leads from the USB cable were reversed. The GND was on the RED cable and the VCC on the black cable !!!! Some idiot in the factory switched the colors of the cable. Everything on the connector side was ok, just the colors of the cable had been switched.

So before you hook anything up:, NEVER TAKE ANYTHING FOR GRANTED and CHECK !!!! Check !!!! CHECK and DOUBLECHECK !!!

This is the first time I say in my web-log: this was no fun at all.

Till next time.

Luc Volders

P.S. Check and Doublecheck !!!