I have been playing with the etherten and relay8 shield combo for a while, and noticed a very strange behavior when using a certain 12v relay module.
http://www.aliexpress.com/store/product ... 47083.html
This module, as you can see, has 8 inputs for 12v positive which I would connect to the Relay 8 + Out for all channels. Then the 2 blue terminals are marked COM, and are used for ground. There are only 2 terminals so a ground wire was connected from each Relay 8 channel to one of the 2 blue terminals, completing the circuits.
When a single channel is triggered via the web button, ALL channels are activated simultaneously! This was not happening prior to connecting the relay module shown above. When I was bench testing the etherten with the relay 8 shield, as I clicked the web buttons, only the selected channel would turn on, indicated by the LED on the relay8 shield.
But, as I said, once I connect the relay module, +POS to +POS, and -NEG to -COM... when a single channel is selected, they all turn on... All 8 relays and all 8 channels on the relay8 shield, as well all LEDS.
My theory is that the current that flows back to each channel on the shield through the blue -COM terminal, somehow triggers all the all other channels which of course then triggers all the 12v relays. Is this possible?? Seems odd to me, but I have since changed to completely independent +/- terminals with better results.
The EtherTen combines an Uno-equivalent Arduino-compatible board and Wiznet-based Ethernet support, along with a microSD card slot and Power-over-Ethernet support. [Product page]
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