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Author Topic: How to power up to 30 ATmega328/168 on parallel  (Read 562 times)
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Hi,

I'm working on a"little" project on home automation, and I'm going to wire the whole house up, ataching about 30 boards running arduino. I need to power up all these, so I have two options:

-Use directly the power of the outlets (240V AC in Europe), with one transformer per board
-Use a pair of dedicated wires and just one big transformer. All the boards connected in parallel. I'm going to wire up the entire house anyway, so it wouldn't really matter, although I'd rather not use this.

The boards would be really simple: couple or relays, one or two sensors, and maybe one of them will have a fanvy LCD, but I can power up that one in another way, as long as it's just a couple of them.

I'd also accept any suggestion about the microcontrollers, maybe a cheaper or more power efficient one?

Thanks!

EDIT: it's a three story house, so considering that a main power transformer is located in the ground floor, and taking into account that I don't know how my house is wired, the farthest module from the big transformer might be about 50 meters away.

« Last Edit: November 01, 2011, 03:06:15 pm by manutenfruits » Logged

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I'd also accept any suggestion about the microcontrollers, maybe a cheaper or more power efficient one?
You might want to use a real Arduino for your development work but unless you are using the serial monitor capabilities you don't need to deploy boards with on-board usb/serial programming hardware all around your house.  Both Modern Device and Adafruit (and I'm sure some others) have boards without on-board programming capabilities that are roughly half the cost.

Don
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No I'm not using true, whole-board Arduinos, I'm just using the bootloader on standalone ATMegas, that communicate using an RS-485 transceiver. What I'm asking on that matter is any suggestion about using different ATMegas, with lower capabilities. They just need to decode a super simple protocol, act accordingly just powering on and off their pins and doing simple.

I'm not too experienced on microcontrollers, but I guess something like an ATMega88, or lower numbers indicate capabilities (EEPROM size, etc). I just need them to be compatible with the arduino bootloader
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Do the arduino's all talk to each other, or to a master?
Get copies of the last Sept/Oct Elektor magazine, great series on protocol for comm's between processors. Started in January, but last couple are where it really came together.

Also, local wallwart for each board unless you want to send out like 10V and use local switching supplies to power each board efficiently.
Such as http://search.digikey.com/us/en/products/OKI-78SR-5%2F1.5-W36-C/811-2196-5-ND/2259781
or an equivalent you can find in Spain.
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Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

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The smallest supported by the arduino platform is the ATmega8, where you can already do lots of things (at least in pure C). You don't give enough details about your system, like how much power each board is going to consume. If it consumes little power, you can run a 7-8V power bus and use just a 78L05 on each board. Otherwise the switching power converter as suggested by CrossRoads is the best option. But if you're going to spread the boards throughout the building it's better to power them locally, there are cheap 5V output switching power supplies (cellphone charger type).
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Get copies of the last Sept/Oct Elektor magazine, great series on protocol for comm's between processors. Started in January, but last couple are where it really came together.

Yeah, I've been reading them and they are covering exactly this, but I'm not done with them just yet. The second purpose of this post is once and for all learn how to properly power up devices, how to calculate the current needed, watts, how it behaves on long wires, how to convert it, etc. Like the basic guide. I've been running without learning to walk, and now I've reached the point where I have to really learn.

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Also, local wallwart for each board unless you want to send out like 10V and use local switching supplies to power each board efficiently.

Is wallwart an small AC/DC converter? The one you specify is DC/DC according to the datasheet (a simple regulator, but way more expensive than the one I had for my breadboard)

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You don't give enough details about your system, like how much power each board is going to consume.

That's what I mean when I say I don't really know how to calculate all those things. I've studied all this, but that was several years ago back in high school!

Thanks!



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The mega chip will consume some 16mA worst case. Then you need to add consumption for other parts, always worst case scenarios. For example, if you have 2 LEDs, that's more 20mA per LED, if you have some other actuator/sensor/expansion board, check their respective datasheets for consumption figures. Add them all up, multiply by 5 (assuming everything in your board runs at 5V) and you have your power consumption in mW (if all current values in mA).
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