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Topic: Powering the Pro Mini (Read 954 times) previous topic - next topic


Hello everyone. I'm building a device where I'm going to hook to attach a Pro Mini onto another board using an IC socket. (BTW, I've made an Eagle library for that which I could share if there's enough interest)
My question is about powering the device. Can I power it by connecting Vcc to +5V? The device is the 5V version, but the reason I'm asking is because of the regulator. Some regulators will work like a diode when applying a voltage from the wrong side, without any input voltage, and conduct and simply fry.


I want someone to correct me if I'm wrong, but this was how the voltage regulator worked on a different system:

If you put a nice clean already-regulated +5V onto the "5VDC" pin, and no other power source, then this supplies the board with 5V and you're all set.  Just leave the "VIN" pin unconnected and don't expect it to supply any current.

If you put something on "VIN" pin instead, you must give at least 7V or so, because the regulator needs to be able to chop down at least a volt or two to arrive at the desired 5V.  Then the regulator will provide +5V to the "5VDC" and the rest of the board.

For boards with power jacks, the "VIN" and the + pole of the jack are directly connected, and are the same thing.


Jan 14, 2009, 05:58 am Last Edit: Jan 14, 2009, 05:58 am by mem Reason: 1
Just to add to  halley's post, for boards with power jacks, the jack is connected to Vin through a diode. This prevents damage if a power source is plugged in with reverse polarity.

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