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automated light control power source

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heya guys, this is my first post :D i apologize in advance if this question has been asked already, i searched the forums and couldn't find what i'm looking for. If it has been asked, please accept my sincere apologies, and point me in the right direction.
now i know that plenty of people have designed and built electronic light dimmers/switches using microcontrollers. i'm working on a project that uses a microcontroller to automatically switch lights on and off as a person enters and exits a room respectively. however i have reached a practical roadblock. in all the circuits i have seen, no mention has been made as to how the microcontroller recieves it's power supply (gennerally 5V). now i have considered using a basic power supply to transforn the AC mains power to the DC microcontroller power, however i am concerned about the size of the transformer and whether it will fit in the wall mounted switch housing. does anyone know how the microcontroller recieves it power in an autommatic light switching circuit?
btw, im using the microcontroller to allow for remote access, so i cant leave it out and hardwire a solution using discrete components.
thanks guys and gals, i look foward to the ideas you have:)
 
If just want to power the microcontroller, there are some very small mains transformers. https://www.farnell.com/datasheets/65263.pdf
The smallest of that range are 15 mm tall.
However, I would suggest that you do your prototyping with mains power further away.
For very small currents, if you don't need isolation, there are transformerless designs. You will find some on this forum. However, they are more dangerous to work on, and they can blow lots of components if you get things wrong. Some of the things that you can get wrong are not at all obvious.
Those little transformers are just about indestructible as long as you get the mains on the correct pins.
 
thanks so much for the information Diver, thats a big help. though i was wondering, do you happen to know how proffesional light controllers (those you buy in a store) are powered? i was also tinkering around with the idea of using a small battery and low power design methods (putting the microcontroller in sleep mode, interupts rather than polling, etc). i think it's feasible, since the lights will be off for most of the day, so the battery should last quite a while. the batteries could be mounted in the unit (kind of like the compartment in a tv remote) an the side of the light controller, and have an led to indicate when it needs to be changed.
thanks again
 
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