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1  Forum 2005-2010 (read only) / Bugs & Suggestions / Re: DS1820 giving me wrong temperature on: January 31, 2009, 11:12:46 am
What's the comma in your [glow]2,37[/glow] ?

Unanswered question.

In (mainland) Europe (ie not here in the UK), the decimal point is routinely marked with a comma.
If you check the code above, you'll see that the comma is entered as a literal. It isn't a mistake - just the way things are done in some places!
2  Forum 2005-2010 (read only) / Interfacing / Re: Make Arduino execute commands on computer? on: January 12, 2009, 10:11:56 am
Agree that if you can do it in a Linux/UNIX shell (or PHP/Python/Ruby/whatever) then you should have something that would run with minimal modification on Mac.

There were two points about AppleScript
1/ its relatively easy
2/ its capable of finer interaction than most of the application command line options I've come across. Its even two-way. Mac apps can reply to (hence control) your script, perhaps even passing calculated parameters back to the Arduino.
And with (commercial) additions, AppleScript has simplified access to all elements of most apps' GUI - from a script! (Apple does provide a similar free, but for once less easy, access.) See
This would allow the Arduino to, for example, 'click' any specified button in any dialog box within the application.

Regarding another recent thread, sadly OpenOffice doesn't (not yet anyway) talk AppleScript.
3  Forum 2005-2010 (read only) / Interfacing / Re: Make Arduino execute commands on computer? on: January 11, 2009, 02:58:24 pm
I was wondering if there is some way that I can have my Arduino Duemilanove execute commands on my computer (which is running Ubuntu 8.04.1 amd64).
Can't help much on the Linux specifics, but one preliminary is to sort out exactly what commands you want to issue. That is independent of getting that command triggered somehow.
If you can't do what you want from the Ubuntu command line, then I can't see how you can get it done from an external trigger.

Then you need a program running on your Ubuntu machine that can
a - get stuff from the serial port (ie the Arduino)
b - if needed, interpret that stuff
and c - issue the appropriate command
This means a bit of programming in a some sort of 'proper' language.
For all I know, you might even be able to achieve what you want entirely with a shell script...
But it seems PERL might be a better choice than PHP -

The Mac has AppleScript, which allows messages to be passed to running programs -- as well as starting or quitting programs.
Massimo Banzi himself has released a miniature Mac app that takes individual characters from a serial port (ie an Arduino) and uses them to trigger whichever of the AppleScripts written by the user

More generally for Mac, SerialPort X makes serial ports (like the one hooked up to the Arduino) fully available to AppleScript.
And I'm sure there are lots of other tools available!

Does Ubuntu have an analogue of AppleScript? Sorry, I don't know of one.

Naturally, you also need to have an Arduino setup to send the expected data or commands up the wire to the computer. (Beware the unexpected!)
Like I said, sorry I can't help with the Linux detail, but hopefully I've outlined the sort of thing you need to be aiming for!
4  Forum 2005-2010 (read only) / Interfacing / Re: iTunes Visual? on: January 14, 2009, 04:02:46 pm
And if you are using a Mac you can do that sort of thing fairly easily from AppleScript.

SerialPort X makes the Aduino available to AppleScript.
5  Forum 2005-2010 (read only) / Development / Re: Mega 1280 Daughterboard? on: April 29, 2009, 05:17:31 am
The pins aren't expensive.
A 28-pin turned pin socket (maybe wirewrap version) does that job. My first search turned up 14-pin 0.3" wirewrap examples - two of those at about a dollar each in domestic quantity...
Through-hole and flow solder. Quick and easy assembly.

I don't have any idea about the cost/difficulty of the surface mounting of the 1280 and its tiny pins. I've been way away from assembly for plural dozens of years!

I also don't know the 'issues' involved with these chips - hence my question being asked.
If there's a handful of binary choices, it'd be cheap to design the board with bowties and solder-pads so that anyone that knew they wanted it different, could change it straightforwardly.

I'm presuming that there wouldn't need to be any support ICs on the daughterboard - is that wrong?

I'd have expected that such a daughterboard, even at current 1280 chip prices, could be sold profitably well below $30 - half the price of a mega.

Slightly surprised so many folk would read the topic and not comment. Whether "daft idea" or "I'd have one" - so thanks Westfw!
6  Forum 2005-2010 (read only) / Development / Mega 1280 Daughterboard? on: April 28, 2009, 07:15:16 am
Maybe silly or impossible.

I don't know, so I'm asking -
- could it work?
- would it be useful?
- would it be popular?

The idea:
Put a 5v 'mega' 1280 onto a 'breakout board' equipped with pins to fit, and operate in, a 'classic Arduino' uP socket.
Clearly, you wouldn't get all the extra I/O.
So why might it be interesting?

- the extra code space
- should be fairly cheap, the chip seems to be $10 or less
- so, a simple, cheap upgrade for existing boards
- and the ability to more cheaply change the large-code-space chip rather than scrapping an entire £50 Mega after a hardware screwup
- and there's the possibility of offering some additional I/O (some extra analog, PWM and serial?) in a non-standard fashion for those that want or need it round the edge of the daughterboard (a bit like the Mini).  

I've encountered such cpu upgrade daughterboards on other systems - would it work for Arduino and these chips? Is this a practical possibility? That's the first hurdle.
7  Forum 2005-2010 (read only) / Development / Re: Battery Charging? on: January 14, 2009, 12:59:22 pm
I have an Arduino developed AVR circuit inside a project box that is going to be battery powered (DSLR intervalometer) and i want to put 4 x AA rechargeable batteries (2700mAh or something like that) inside the box to power the AVR and the LCD.

I am looking for a schematic for a simple battery charger circuit that I can use to plug into my project box, via a jack plug, to charge the batteries inside.

Simple question, before worrying about recharging those batteries - have you successfully run the project assembly from 4x rechargeable AAs ?
Generally 4x NiMH AAs are likely to deliver less than 5v ...

Recently, I was reading ladyada's description of getting a regulated 5v supply out of 2x AAs. For more battery duration, I suppose you could do that stuff with 2x2 AAs (two parallel stacks of two batteries in series). I like the way she brings her unit to a usb socket, making it easy to power (or recharge) anything that expects to plug into usb. Hmmm.
She describes the whys and wherefores here

As an alternative to AAs, though Mike justifiably says Lithiums have been difficult, I believe there are now fairly economical ICs that will look after their charging process. (And Lithium cells do provide more stored energy in less weight.
Lithium charger chip example
And breakout board

And there is even a compact Arduino-compatible board that has the facility already on-board. Just directly plug in the (lithium) battery. Recharge via usb or a charger that looks like usb... And using such a board could make economic sense rather than adding a separate charger.
8  Forum 2005-2010 (read only) / Interfacing / Re: Accurate analogue input reference on: July 13, 2009, 05:35:29 am
The internal 1.1V won't drop, but it's not a particularly accurate reference to begin with (something like +/-9%).

The AVR's are not designed for "accurate" A/D readings. ...

Then again, you haven't really specified how "accurate" you need your results to be! ...
I didn't realise the reference spec was as 'loose' as that! 9% or1 in 11 ...

Giving an A/D with 10-bit precision (and likely sensitivity) but less than four bits of accuracy... ouch!

I would hope that the internal reference would be stable on any given chip (not much ripple or variation with the chip's temperature for example). So that one could rely upon it for measuring small changes - although for accuracy of absolute measurement, one ought to be properly calibrating each individual AVR/sensor combination. Hmmm.

9  Forum 2005-2010 (read only) / Interfacing / Re: Opto Isolation of analog inputs on: June 26, 2009, 09:55:22 am
What are you trying to measure?

The best way of doing difficult stuff, is to find a different, easier, way!
10  Forum 2005-2010 (read only) / Interfacing / Re: SSR vs. EMR on: June 25, 2009, 01:55:50 pm
An SSR (appropriately conservatively rated) should be fine to switch the compressor on and off. Yes, after its switched off, you should give it a few minutes (maybe 3?) to settle before switching it on again.
While PWM will vary the output from a resistive heater, you won't find an SSR (and certainly no mechanical relay) that will switch as fast as the standard Arduino PWM outputs.

I believe it is possible to adjust the 'hardware' PWM output frequency, but hopefully someone else can explain how that is done to both of us!

Regarding the control algorithm, did you see this thread?
11  Forum 2005-2010 (read only) / Interfacing / Re: controlling flourescent light fixtures on: June 16, 2009, 08:43:20 am
Thanks for that!  smiley
12  Forum 2005-2010 (read only) / Interfacing / Re: controlling flourescent light fixtures on: June 16, 2009, 07:26:20 am
While I think SSRs are a brilliant encapsulated and isolated solution for switching mains from an Arduino, could I ask a question or two, specifically about fluorescent lighting?

SSR's are said to be a bit vulnerable to current surges.
Does switching a fluorescent tube produce any troublesome transients on the mains supply?
If so, would specifically choosing a zero-crossing-switching SSR be helpful?
13  Forum 2005-2010 (read only) / Interfacing / Re: Where would you get a button for this? on: February 14, 2009, 10:15:37 am
Since it is stated that it must be "durable" - why not use a capacitive touch sensor?
Nothing to wear out. (No moving parts.)
And artistic freedom to design your own 'button'.

Incidentally, I didn't realise that the Sirius Cybernetics Corporation had already opened an office in London! ¬
14  Forum 2005-2010 (read only) / Interfacing / Re: Solid State Relay Problem? on: January 12, 2009, 10:34:41 am
Your SSR should be able to operate (switch/trigger/be-controlled-by) a 9v battery connected across its "control" terminals.

One important part of debugging (software or hardware) is to 'prove' operation of sections (functions/subroutines/hardware modules) in isolation, before sticking them together.
Here, you could test your relay by using a (proven good) battery to trigger the ssr connected to a (proven good) lamp. Then prove the pump by connecting it to mains power. Then prove that the ssr can switch the pump by connecting the pump in place of the lamp, and operating the ssr from the battery, before replacing the battery with a simple on/off signal from the Arduino, before finally putting your chosen logic behind switching that Arduino output.
One step at a time is plenty!

Now, help me here people, please -- am I right in thinking:
1 -  that one shouldn't "play" with rapid on/off switching of an AC motor to try to control its speed ??
- and because I note that the pin shown in the diagram (10) is a PWM pin -
2 - that anyway you cannot simply feed a normal mains electricity SSR with a very fast PWM signal, like the PWM that the Arduino produces with analogWrite ??
15  Forum 2005-2010 (read only) / Interfacing / Re: Controlling a heavy Motor Load on: January 14, 2009, 01:29:10 pm
-The relay must be NC, such that if the logic fails, the motor stays connected to mains voltage

Not sure about the reason for that requirement, or the multiplicity of ways the "logic" might fail, but -

Is there such a thing as a normally-closed SSR ?
I've not noticed one.

Added - but the design of an SSR provides (optical) isolation between signal and power sides. Spec sheets should give details.
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