01-04-2017, 08:54
I have quite a lot of experience constructing circuit boards which contain sensitive (usually ic) devices that require careful handling and use. Having been involved with the WeatherDuino project since 2014, I have read carefully the notes, guidance and instructions that Werk_AG has posted as I've been building the several boards that I have so far.
Even so, I've recently made a very stupid, basic mistake that we have been warned about, and which has destroyed my PLUS rx board.
The warning, which has been very clear for a long time is basically that you must NEVER risk having power applied to the PLUS rx board via the USB connector only.
I chose to try achieving that by remembering to connect my board to the computer only after switching on the external 9v supply and also disconnecting from the computer before switching off the 9v supply. Although I tried, unfortunately I didn't succeed and the result was strange intermittent behaviour and the eventual complete failure of the board. As I had been using this board for testing, it was not running continually so was regularly powered on and off as well as connected and disconnected from the computer. Although I tried my best to remember the sequence, I've obviously got it wrong at least once - which maybe all it takes to cause damage.
The thought has occurred to me that there are also other ways in which this situation might arise. The most obvious is a scenario where the PLUS rx is properly connected to external 9v power via the mains supply while the attached computer has battery power available or is fed by an Uninterruptable Power Supply of some kind. In the event of a mains power failure - or failure of the 9v supply, the USB connector will be supplying power to the board while there is NO external power available - the board-killer situation!!
The only solution which is guaranteed to prevent the risk of damage, either accidentally as above or through a moment's carelessness as in my case, is to REMOVE THE DIODE on the Meduino as strongly recommended by Werk_AG in post 3 here:
http://www.meteocercal.info/forum/Thread...uick-Guide
I'm off to do that myself right now while I wait for a replacement board to arrive...
Apologies for "shouting" in places but I'm so annoyed with myself!! I'm sure you will be equally annoyed if you too make such a silly mistake so please, do that modification now!!
Allan.
Even so, I've recently made a very stupid, basic mistake that we have been warned about, and which has destroyed my PLUS rx board.
The warning, which has been very clear for a long time is basically that you must NEVER risk having power applied to the PLUS rx board via the USB connector only.
I chose to try achieving that by remembering to connect my board to the computer only after switching on the external 9v supply and also disconnecting from the computer before switching off the 9v supply. Although I tried, unfortunately I didn't succeed and the result was strange intermittent behaviour and the eventual complete failure of the board. As I had been using this board for testing, it was not running continually so was regularly powered on and off as well as connected and disconnected from the computer. Although I tried my best to remember the sequence, I've obviously got it wrong at least once - which maybe all it takes to cause damage.
The thought has occurred to me that there are also other ways in which this situation might arise. The most obvious is a scenario where the PLUS rx is properly connected to external 9v power via the mains supply while the attached computer has battery power available or is fed by an Uninterruptable Power Supply of some kind. In the event of a mains power failure - or failure of the 9v supply, the USB connector will be supplying power to the board while there is NO external power available - the board-killer situation!!
The only solution which is guaranteed to prevent the risk of damage, either accidentally as above or through a moment's carelessness as in my case, is to REMOVE THE DIODE on the Meduino as strongly recommended by Werk_AG in post 3 here:
http://www.meteocercal.info/forum/Thread...uick-Guide
I'm off to do that myself right now while I wait for a replacement board to arrive...
Apologies for "shouting" in places but I'm so annoyed with myself!! I'm sure you will be equally annoyed if you too make such a silly mistake so please, do that modification now!!
Allan.