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6406  Using Arduino / Project Guidance / Re: ArdweeNET - simple and robust networking for monitoring and control on: July 05, 2011, 07:36:23 pm
Thanks CB. It boosts my confidence level knowing someone else has scanned the design and not found any fundamental errors.

I seldom prototypes things, preferring to go straight from paper to PCB, but when you design by yourself with no-one to look over your shoulder  it's easy to get so close you don't see the problems.

6407  Using Arduino / Project Guidance / Re: ArdweeNET - simple and robust networking for monitoring and control on: July 05, 2011, 09:52:57 am
I guess the design is bang on then so I've started PCB layouts.

Here's a quad +-20A sensor node.

Approx lifesize (on my screen anyway), should be 40mm wide.

This one is larger than standard because of the relatively huge connectors needed for 20 amps.

Bear in mind that this is effectively a tiny Duemilanove that is dedicated to reading current and telling the world the results via RS-485.

6408  Community / Products and Services / Re: New product: Digit Shield on: July 05, 2011, 09:00:55 am
Hi Michael,

Love your boards.

I'm working on a 4-digit board myself at present (not a shield so no competition), there's something very satisfying about getting LEDs to work, much more so than LCDs smiley

6409  Using Arduino / Networking, Protocols, and Devices / Re: serial com port communication with Mega on: July 05, 2011, 05:53:22 am
The netbook is using simple serial communication.
Does this means it's NOT using USB?

But when I connect it to the netbook and change the com port to 4
It won't necessarily be on the same port with a different computer.

6410  Using Arduino / General Electronics / Re: RS232 shield on: July 05, 2011, 05:49:39 am
have a look at

6411  Using Arduino / General Electronics / Re: beginner question about connecting two components.. on: July 04, 2011, 09:39:58 pm
The 3.3v TX output from the IMU will "probably" work if fed directly to the AVR RX input. (anything over 2.5-3v should be seen as a logic high)

The IMU may have "5v tolerant" inputs, if so you can feed the AVR TX directly to the IMU RX. (check the data sheet)

If not you can use two resistors as a voltage divider to reduce the AVR 5v to 3.3.

6412  Topics / Home Automation and Networked Objects / Re: Starting an Home Automation project on: July 04, 2011, 09:29:08 pm
a relay is used to turn on / off lights, isn't it?
Often a relay is a good choice yes.

And if I'm not wrong I can also check if the relay is turned on or off.
Use a double-pole relay and use the spare pole to read the relay status, or keep a variable in RAM that tells you what the current state is.

Where can I found an example code about it?
DigitalWrite (relayPin, HIGH); should about do it.

how can I control the power of the light to make them more ligher or less?
I assume we're talking AC mains. Normally a Triac can be used to adjust the brightness. It can also be used to turn on/off the light so in this case it's a better choice than a relay.

However, a normal triac is not isolated from the mains (that's bad) but you can get opto-isolated versions that are or just use an opto-coupler.

I can use relay but I don't understand if it's a standard eletronic component or if I need to build one like this:
You need to do as the PDF says or something equivalent. But that's not "building a relay", it's just controlling one.

How can I develop and manage them? What do I need to do that (the elettronic parts). Are there some "already made" (something that is developed for arduino) parts to use?
You need to develop a "network" of some kind. Given the number of times we get asked this I'm surprised nobody is ever interested in posts about new networks smiley, maybe there's already too many around.



6413  Using Arduino / Programming Questions / Re: Need to understand Serial-RS485 master/slave addressing on: July 04, 2011, 08:55:32 pm
Here's a hint

D  = CR
A  = LF
6D = m
65 = e
73 = s
73 = s
61 = a
67 = g
65 = e
20 = SPACE
73 = s
65 = e
6E = n
74 = t

I don't know what send/receiveMSG() does (can't find the source at that link) but I doubt you can use it on the same port at the same time as Serial.print/receive().
6414  Using Arduino / Installation & Troubleshooting / Re: Arduino versus LabJack on: July 04, 2011, 10:26:47 am
is it possible to trigger (external 20 Hz signal) the arduino?
Is it possible to send instructions to the arduino?
Is the arduino able to execute the instructions during the 20 Hz stream?

Yes to all the above.

6415  Using Arduino / LEDs and Multiplexing / Re: Multiplexing 90 analog inputs on: July 04, 2011, 06:42:41 am
How will you measure resistance? You will need another 90 resistors to form 90 voltage dividers I would think.

will the arduino have a delay of more than 2 sec to complete all recording and comparing of arrays?
It should be much faster than that. The actual readings might take about 25uS max I think, add some for the program and you're well under 2secs.

You will need analogue muxes, 6 4067s or 12 4051s.

6416  Using Arduino / General Electronics / Re: beginner question about connecting two components.. on: July 04, 2011, 06:36:13 am
the Uno just has inputs labelled Tx and Rx also
It does but they are also connected to the USB chip and this usually causes problems.

to connect it to the mega
The Mega has inputs labeled TX1,2,3 and RX1,2,3, just pick a matching pair (say 1) and

Serial1.available() etc etc

to connect it to the mega to use those values on the fly
Don't know what this means. What is "it".

on both chips?
What's the second chip? If you mean the IMU then yes, just connect IMU Tx to the Mega RXn and IMU Rx to Mega Txn.


6417  Using Arduino / Project Guidance / ArdweeNET - simple and robust networking for monitoring and control on: July 04, 2011, 12:05:49 am
For the last couple of weeks I've been working on the design of a simple (from the application programmer's point of view) async network for monitoring and control applications.

Yes, another one smiley However I'm pretty sure that this is different in many ways. Basically it's a poor-man's low-speed cross between Ethernet and CAN.

It uses an ATtiny84 as the network interface, this handles most of the bush clash and synchronizing issues. There's code also running on the application processor but this doesn't have a lot to do so in general the application is free to read sensors or do whatever it does.

Basic features are

  • Open design, no royalties, licensing fees or costs for intellectual property. Creative Commons and/or GNU licenses will apply.
  • Only implements a low-level transport layer similar to the OSI layers 1 and 2.
  • Implements a "publishing and subscribing" model, nodes publish at will and subscribers act on the published data.
  • Multi-master with non-destructive collision detection.
  • Wide supply voltage, VBAT can range between 7 and 30 volts.
  • Very fault-tolerant physical level (uses RS-485 transceivers).
  • High level of error detection (relative to the intended applications) for reliability, including packet-level CRC and watchdog ICs.
  • Rogue applications on nodes cannot kill the bus.
  • Six-wire flat telephone cable and RJ12 6/6 modular jacks. Wiring includes power and data signals.
  • Four-wire (RJ11) and 8-wire (RJ45) cables/jacks can also be used.
  • Plug in backwards immune. Power and data auto adjust.
  • Flexible wiring topology, “anything goes”.
  • Uses off-the-shelf standard electronic components.
  • Bit rates from 2400 to 115200 with auto-bit rate detection.
  • Standard node size is 40x40mm, however a node can be implemented with as little as 6 components and fit on a PCB approx. 12mm square or even smaller.
  • Nodes can be neatly daisy-chained.
  • Use the processor of your choice; AVR, PIC, Picaxe, ARM, 8051 etc

Here is a 3D graphic of a typical node.

Note that these are essentially cut-down Duemilanoves with built-in RS-485 so they can be used with your own networking code if that's preferable.

There is a small range of these being designed right now, things like RTC, accelerometer, current and voltage measuring inputs, relay outputs, temperature inputs, LCD and LED displays, USB interface etc.

And the network interface looks like this

If you've got this far then I guess you are at least mildly interested so have a look at my site for some more information

And if you're really interested there's a design document (still a work in progress)

RFC (Request for Comment)
I'm about to start PCB designs so this is a good time to ask the knowledgeable folk here for comments. Of particular interest to me are major stuff ups, is there anything here that just won't work? But of course all ideas are welcome.

So if you have any thoughts either post here or email me.

Thanks for your time guys.


6418  Topics / Home Automation and Networked Objects / Re: Using Arduino with C Bus on: July 03, 2011, 10:59:58 pm
C-bus is designed and pushed by Clipsal

However for the life of me I can't find their download page so I've copied some files to my site. Applications.pdf Interface Requirements.pdf Quick Start Guide.pdf Serial Interface User Guide.pdf

There's a lot of info there so knock yourself out.

I don't know much about this particular protocol, I just collect this kind of data because I'm interested in monitoring and control networks.

EDIT: Just found a Clipsal site that might have more info

6419  Using Arduino / Project Guidance / Re: Would love feedback on first solo code for project on: July 03, 2011, 08:37:02 pm
pinMode(vccPin, OUTPUT); digitalWrite(vccPin, HIGH);
  pinMode(gndPin, OUTPUT); digitalWrite(gndPin, LOW);

Are you powering the MAX chip from IO pins?

If so it's a novel approach and should work as the chip only draws about 1mA but it's a little strange.

6420  Topics / Home Automation and Networked Objects / Re: Using Arduino with C Bus on: July 03, 2011, 08:20:31 pm
AFAIK c-bus works with "normal" serial data at 300-9600 bps with 9600 being the recommended speed.

It's a full ISO 7 layer protocol which seems something of an overkill.

Despite me having what appears to be a comprehensive set of documentation PDFs I'm buggered if I can see what the PHY layer is.

C-Bus supports a number of interfaces such as RS232 and TCP/IP
These of course are two totally different and non-comparable things so that's not much help.

cable lengths up to 1000 meter using Cat-5 cable
This implies RS-485, no way RS-232 will do this.

Anyway if you can figure out how to connect to the PHY layer it should be easy to sniff the data with a serial port, the protocol is well documented.

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