Connecting 3V3 from USB to 3V3 of power supply?
Posted:
Sun Jun 21, 2015 7:30 pmby kolban
I'm far from an electronic engineer. I was looking at this image found on the Github site:
https://github.com/esp8266/Arduino
And it shows not only a common ground between the power supply and the USB<->Serial but it also seems to show a shared power supply. Can anyone confirm this is correct? I would have assumed that they would have shared a common ground only?
Re: Connecting 3V3 from USB to 3V3 of power supply?
Posted:
Sun Jun 21, 2015 8:46 pmby lethe
You should never directly connect voltage sources. So you answer actually depends on the USB serial adapter. You should only connect the VCC pins to each other, when the serial adapter is not powered by the USB port (most adapters are bus powered, however there might be exceptions).
Re: Connecting 3V3 from USB to 3V3 of power supply?
Posted:
Mon Jun 22, 2015 1:14 pmby kolban
Thanks Lethe,
From your response, I get the impression that for most USB serial adapters, one should not connect the voltage sources together. What I read from the schematic is that the illustration does seem to show them being connected. I'm wondering if we need to ask for a change to the schematic or a warning/description of what is meant/implied by connecting the two together? If, as I believe, a hobbyist like myself stumbled over this diagram, they would be inclined to wire the supplies together as described.
Re: Connecting 3V3 from USB to 3V3 of power supply?
Posted:
Mon Jun 22, 2015 2:21 pmby ArnieO
I agree. The Vccs should not be connected together like that, if the USB/TTL adapter has voltage output.