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This project is a power unit for an Arduino Microcontroller. The unit is supplied power using a 9V wall adapter and a 9V battery. When AC power is available the unit draws power from the wall adapter, when there is a power cut the unit seamlessly switches to the battery as a power source and back when power is available. During a power cut an LE…
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README.md

README.md

Arduino Power Unit

Description

This project is a power unit for an Arduino Microcontroller. The unit is supplied power using a 9V wall adapter and a 9V battery. When AC power is available the unit draws power from the wall adapter, if there is a power cut the unit seamlessly switches to the battery as a power source and back when power is available. During a power cut an LED is lit to alert the user that mains power is not available. There is also an LED to warn the user when the batteries are low.

Schematics

This is a very basic schamatic of how the device switches between mains and battery power using diodes. It will always use the side with the highest voltage and since the wall adapter will always have a higher voltage (≈9.3V) it will draw from that and not the battery (≤9V) but when the power goes out the adapter voltage falls to 0V and it draws from battery. There should be little to no leakage from the battery using this method.

This is a breadboard schematic of the final circuit.

This a photo of the breadboard circuit.

This is a standard schamatic of the final circuit.

This is the Printed Circuit Board Layout of the circuit.

This is a photo of the PCB without components.

This is a photo of the finished PCB with components.

License (MIT)

Copyright (c) 2016 Conor Walsh

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

Thanks

Thank you for taking the time to look at this project I hope that it is of use to you,

Conor Walsh.

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