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Topic: Arduino Mega (Arduino NooB) (Read 5980 times) previous topic - next topic


I'm new to Arduino and I have question...


Hi all!
I'm Interested in purchasing an Arduino Card because I want to build an Home Automation system. I'm supposed to build a new house in the next couple of years and I want to start designing it (even though I know I might not eventually install it in the house it's a nice thing to design and play with).
I think I'd better get the Arduino Mega coz it has more I/O connections and it seems easier than expanding a smaller Arduino with some other methods (I saw all kinds - I2C, Shift Registers and more...).

I was trying to figure out what are the differences between these Mega cards...
Can you please help understanding the differences (if there are such).

Link 1 - http://arduino.cc/en/Main/ArduinoBoardMega
I know its a 1280 but ebay is full of these... you can barely find the 2560 at ebay.
What are the differences from the 2560 version?

Link 2 - http://arduino.cc/en/Main/ArduinoBoardMega2560

Link 3 - http://cgi.ebay.com/Arduino-MEGA2560-ATMEGA2560-ATMEGA8U2-USB-Cable-/260725146026?pt=LH_DefaultDomain_0&hash=item3cb46e01aa
the bottom two links show Arduino Mega 2560 but it looks a little different. Are there any differences?
which one should I pick?
Where can I find the cheapest 2560?

Second question -
Are all the shield fits Arduino Mega or will I be limited in shield options because I choose the Mega (instead of the Uno for example)?

Thank You all in advance!


Jan 21, 2011, 04:04 pm Last Edit: Jan 21, 2011, 04:04 pm by newman Reason: 1
The Mega 2560 is an update to the Arduino Mega, which it replaces.

this was present in the second link you gave :) ! it is the latest one along with the uno


that one has a crystal unlike the one on the arduino page

Are all the shield fits Arduino Mega or will I be limited in shield options because I choose the Mega (instead of the Uno for example)

no all the sheilds are designed to go with both the uno and 2560


better get the Arduino Mega coz it has more I/O connections

One thing to remember though is that your sensors and actuators will be placed over a very large area, IMO it's not practical with many such devices to have long cable runs back to a central uC. Too much noise, voltage drop, ESD potential etc.

For this reason I would suggest distributing your processing, and that means a network of some kind. It can be something simple based on RS-485 or similar.

As for the various Mega options, I'll let someone with more Arduino knowledge answer that.


Rob Gray aka the GRAYnomad www.robgray.com


You may find your home automation system will actually use many arduino boards for different purposes.

What I would do if I were you in at this point in get any arduino with a USB connection and start playing with the various modules you will want in your home automation system.  For example, you may want to open / close blinds and/or interface with lighting systems, etc.  I would work each of these individually.  Once you are up to speed and have a couple of "modules" created it will be much more clear how your final system will look and work.  

Some notes from someone who has created quite a few home automation systems.  
- Some items may be better served using off the shelf products while other parts of your system will be DIY friendly.  Arduino is great, but don't get caught by the hammer/nail syndrome (once you have a hammer, everything looks like a nail).  
- You may also consider thin clients in your scheme.  They are quiet, low power and can do lots of the heavy lifting without a need for a full fledge / loud / high support computer.
- You may find that creating "web enabled" components using an ethernet shield allows for easy integration and provides the distance needed for full house communication.  

Sounds like you have the right plan to start now for a house you plan to build in a couple of years.  This gives you plenty of time to work out the details, so you know what to wire up when the time comes.  


thanks for your help.

newbie, about the ebay link, you said that that one has a crystal which the one on the Arduino site doesn't have.
what is it uses for? timing?
is that essential?

is that board on that ebay link a genuine Arduino?
if so, how come it's not on the Arduino hardware page?

is it preferable to order that one (the one on ebay) instead of the one you see on the Arduino hardware page? (it's also the cheapest price I saw till now...)

Graynomad, you mean that because the cables are spread all over the house over too long distances, I will have problems with the operation?
how can I solve it using an RS-485?



you mean that because the cables are spread all over the house over too long distances, I will have problems with the operation?

Yes, for example a temp sensor may only produce 1v if it's cold, you don't need much noise to stuff that up and also if there is a voltage drop in the line you could read a much different value.

RS-485 doesn't fix the problem as such, what I (and I think marklar) am suggesting is that you have several processors (or "nodes", could be Arduinos or any other processor/board type) distributed around the house, each taking local readings and feeding the information back to a central controller.

RS-485 is probably the best medium to feed this data between nodes and the controller.


Rob Gray aka the GRAYnomad www.robgray.com


I see... that is a good idea considering you can get the cheap Arduino's for about 25-30$.

sorry, but English is not my mother tongue so there are some phrases I'm not familiar with, like what you mean when you say it's better I'll use "thin clients"? you mean low-level computers or something else?

beside that, by "off the shelf products" you mean like X10 products?


I just took a look, it has been a few years since I worked with the thin clients and I just don't see any good options in that area right now (prices too high).  The idea is a small computer with a flash based hard-drive.  They are low power and no noise.  If you see such an option, take a close look.  

As for "off the shelf" - x10 is an example.  Any automation products you an find that allow for microprocessor control and/or has a web interface will be a good candidate for easy integration.

Details on my home grown thin client / off the shelf solution:
- HP Zone control using (off the shelf) XP Embedded based thin clients
- IR control using (off the shelf) - http://www.usbuirt.com/
- Music control via media player control running in XP thin client app
- X10 control using RS232 controller (off the shelf)
- Example:  http://store.homeseer.com/store/TI103---X10-Computer-RS232-Interface-ACT-HomePro-P20C45.aspx

I was working with x10, but not the wireless transmitters.  Instead I would use the computer based x10 control via a serial port.  This was then run on a thin client with a web interface to create a quiet/low power zone controller.  The zone controller also provided IR input and output as well as picture frame and music for the zone - all custom apps using raw RS232 comm control.  The thin clients even supported ELO touch screens, so the picture frame could also double as a "house and zone" menu system.  Even with no touch screen the IR would allow a standard IR remote to control the on screen menus (i.e. via the TVs VGA port for living room).

It is easy to send web commands to other zone machines from any other machine.  Why a web interface, if possible, is almost a no brainer.  

If I were to expand this system now, I would create my own web enabled shade / curtain controllers and a web enabled sensor panel via arduino.  

Most of the thin client work was created using VB6 and running on embedded XP.  Apps could be run from a flash drive directly or via the LAN.  

This was long ago, much cooler stuff is bound to be out now - just giving some perspective on using some off the shelf products.


I have a bit of a problem with X10 products - most of them are working on 110v and I'm using 220v (I'm from Israel).
there are 220v products but they are 3-5 times more expensive than the 110v ones...
I found a way to modify them in order to make'em suitable for 220v but I think it will take a lot of time an effort...
isn't there a simpler way of controlling and dimming light (beside X10) or is it the cheapest and easiest one?

the link you gave with the X10 rs232 device, is it something similar to this one?

because if so, there's already a library for that using this psc05/tw523 device...

something else - most of the shields, when you install them on the Arduino card, also give you access to the I/O or analog connections.
my question is, are those connections still can be used or they are just there for being like Test Points (for taking voltage readings and stuff) ?
because I think the shield is supposed to use these connections for whatever his role is, right?


are those connections still can be used

All signals not used by the installed shield(s) can be used for other purposes.


Rob Gray aka the GRAYnomad www.robgray.com

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