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1  Topics / Interactive Art / Re: Idea: Orrery on: September 18, 2013, 05:05:09 pm
Oops! Thank you. Original post corrected, so if someone else is reading this, don't worry about the apparent "non-error"... the original post WAS wrong, for a while. What would Orwell have thought?
2  Topics / Interactive Art / Idea: Orrery on: September 18, 2013, 06:07:41 am
So many ideas; so little time...

I hope someone will run with this... it could be a lot of fun.

1774 a man started building an orrery (model showing planets moving around the sun), with models of the planets hanging from the ceiling of his home, and moving around in step with the actual planets in space.

2013: A lot easier to make something like that, now that we have the Arduino. The mechanical elements remain a slight challenge, but the controls, the "clock" to drive the mechanical side a lot easier.

More on the above in the "Now THAT's COOL!" item at...

Did you know that in early April, the earth, the moon, and 5 out of the other 7 planets (pluto left out) were all in a line! See... if you'd had an orrery, you wouldn't have missed that!) (For those who haven't time to build a mechical one, there's a link to a nice online (or Windows or Mac screensaver) one at BlogRave.

If you know of an Arduino orrery driver, I hope you will post a link at the Playground (See link in menu bar at top of this page)
3  Using Arduino / Sensors / Re: phototransistor detecting led on: March 01, 2013, 11:31:55 am
Yes... but you have to write the software to make it happen.

Your "loop()" would have to "watch" the input from the photo-transistor, and turn the LED on (briefly, if you like) when a "positive edge" was seen.

Much easier just to have the LED on when the phototranistor is illuminated, off when it isn't.
4  Topics / Home Automation and Networked Objects / Re: Runing small program in main loop on: February 27, 2013, 04:03:37 am
Dear Mikee...

Were you saying you needed a way to tell if it is summer or winter? That you wanted your system to do AUTOMATICALLY, by itself, what it now does if you help it by pressing a button?

If so... well done for building your program using "black box" modules, where "somehow" inside the black box, and answer to "is it summer" is generated... but the main part of your program doesn't care about those details.

For the particular question you want the system to have an answer for... "Is it summer? Winter?" I would suggest a toggle switch! Twice a year, you flip it, and from then on, the system operates in the right mode, until the seasons change again, and you flip it back to the right season setting.

But, of course, that's no fun! So yes, a real time clock chip is the answer.

I would add a button to the system. Suppose it is May, and you have your system set to switch to "summer" operation on May 1st. But this year, summer is late, and on May 5th, you feel... Brrr... I want the heating system on "winter", even though it is supposed to be on "summer", by the calendar.

One press of the button would say "go to the other season for a day". Two presses: For two days. Etc.
5  Topics / Home Automation and Networked Objects / Re: arduino web thermostat controlled with android phone on: February 27, 2013, 03:54:39 am
An idea for anyone building such a system in a region where temperatures go low enough to freeze pipes:

Make it fail-safe. What if your Ardu-stat turns the heat completely off, by malfunction?

Easy to do:

Keep your old thermostat in the circuit. Set it to turn the heading on at, say, 40 deg F.

Wire your Arduino circuits in parallel across your existing thermostat (assuming that your system turns the heat ON when a switch in the thermostat CLOSES).

Now your Arduino can ADD heat to your house, but even if the Arduino is never calling for heat, the old thermostat can step in, save the day, should the temperature fall to 39.

More on Fail Safe Design at...
6  Using Arduino / Sensors / Re: Strange problem with batch of DS18B20's on: February 25, 2013, 09:39:13 am
Michinyon! That was naughty!

Dear Newbies: He was just kidding. There's only a "celcius" model of any of the 1820s. If you want to display the tture in F, there's nothing to stop you, but you convert the C reading to F in your software.
7  Using Arduino / Sensors / Re: phototransistor detecting led on: February 25, 2013, 04:49:46 am
Does that do more than create a not-inverted signal? (Does it do that?) Not that it isn't an improvement, if that's what the re-wiring is for... but I wondered if there were other advantages? (Assuming my guess is right as to one of them is!)

But!... to address the original question...

a) Have you somewhere in your code done something to re-program the analog pin for something else? (They can be treated as "ordinary" DIO pins... and set as outputs. In which case, you MAY have fried that "input" by now.)

b) Try this... test the input as follows... The first resistor is to "protect" things, in case your analog input has somehow become low impedence... as it would be it it is being turned into an output.

Connect a 10k (or so) resistor to the analog input. From the other end of that go to the wiper of a potentiometer... almost anything will do... about 10k by choice. Connect the top and bottom of the pot to 5v and 0 volts. Try the pot at different settings. What do you see with a voltmeter? What do you see if you "look" at the pin with software.

Should shed light on things...?

(You can get around the need for a pot with a pair of resistors in series across 5v to 0v... again, about 10k, and for a "wiper", just use a flying lead and touch top (5v), bottom (0v) and "the middle"... where the resistors connect to each other.)
8  Using Arduino / Sensors / Re: Temperature Sensor drops over time on: February 25, 2013, 04:46:25 am
How long are the wires between sensor and Arduino? A few degrees drift is a VERY small difference in voltage. Maybe (exceeding my knowledge of physics here) some induced voltage is building up/ draining off?

Part of the reason I prefer to deal with the "little problems" that the 1-Wire sensors throw up... at least the signal, when you finally master getting it, is immune to such issues. Please, maybe, revise the subject of this thread to include "TMP36" in it?
9  Using Arduino / Sensors / Re: Strange problem with batch of DS18B20's on: February 25, 2013, 04:40:59 am
There are various VERSIONS of the "1820"... that letter in the middle is important... 18B20, 18S20, etc. There are datasheets for each, and if you look closely, you'll see how they differ. (Some have wider ranges, at the cost of less precision, some are cheaper, etc, etc.)

The basic priciples they all run on are consistent... but the control of features, and the reporting of temperature sensed varies in details.
10  Using Arduino / Sensors / array of photodetectors on: February 25, 2013, 04:37:57 am
In the Wimote, there is a neat little chip...

You put it behind a lens, a bit like film in a camera, or a sensor in a digital camera, but instead of capturing an image, it starts sending out a stream with the X/Y cooridinates of the 5 brightest points of (IR) light it currently "sees".

I'm looking for something similar. Any ideas? The brightest single point of any color of light would be fine. 256x256 more than enough resolution. Thanks for ideas... or even the right terms to put into Google!
11  Using Arduino / Interfacing w/ Software on the Computer / Re: Suggestions on how to move a file from SD card to the PC on: February 24, 2013, 02:04:38 pm
Silly question, I suppose... but couldn't you put the sensor(s) on longer wires... have the Arduino in an upstairs room, to make SD card available for "sneakernetting" data to PC?

Having it (Arduino) outdoors, even in enclosure, is asking for trouble, anyway!
12  Using Arduino / General Electronics / Re: Transistor or optoisolator to simulate pressing button on key fob? on: February 24, 2013, 01:24:51 pm
When you were trying the opto-isolators, did you try measuring the voltage across the pins connected to your wires connected to the fob? If it was was being told to "connect" the wires, you should have seen the voltage between those two points go to zero.

I like opto-isolators because they are "simple".... and should work. Should. That word again.

Good luck!

More on them at...
13  Community / Bar Sport / Re: Flattr- the next Facebook? on: January 22, 2013, 05:17:48 pm
PayPal IS great... for many things. And thank you for asking what Flattr does better.... I've added a section to my page, as no doubt others have, or will, wonder(ed).

But PayPal takes 30 cents from any gift, plus a percent. (Except if the sender is sending from a bank account... and how many do?)

More importantly, if you invite people to $upport you, $how appreciation, via PayPal, you are also inviting them to go to the trouble of logging into their PayPal account, etc, etc.

To give money to a Flattr account holder, you just click the Flattr button (assuming you have set up a Flattr account... easy, and a "one off" chore.) It is a little bit like giving a site a Facebook "Like". And you can give really small amounts.... say 25 cents! Not a lot, and certainly too little to warrant signing into your PayPal account to do... but a little thank you for a helpful blog post, etc, is something that maybe people would ACTUALLY DO, as opposed to "planning to get around to someday". And if enough people contribited even 25 cents each, the reward to the poster might add up?

Yes, Flattr takes some money too... but not a flat rate + percent on each transaction. They fund their operations by taking 10% of anything you transfer to your Flattr account from the outside world. Seem like a lot? Well, maybe it is... and maybe it will come down, if they can get some scale, and reap the economies? And even if it doesn't, isn't it worth it for the simple and useful service provided?

Neither Flattr nor PayPal... nor a credit card is the way to make large donations to worthy causes. But for little "atta boys", I think Flattr is worth giving some support, to see where it can go.
14  Using Arduino / General Electronics / Re: Assistance with electricity. Safety first. on: January 22, 2013, 05:34:30 am
Those stickers are there for a reason. No devices are 100% reliable, but at least
some have been tested.

... not only that, but Mr Murphy is incredibly clever. He can make the least obvious "little flaw" turn into a problem.

ANYWAY... for more on ways to work with household voltages safely, at not exhorbitant expense....
15  Using Arduino / General Electronics / Re: Digital Switch? on: January 22, 2013, 05:30:40 am
Another answer, dull and old fashioned, but very accessible, is the relay.

Help on these at....

.. which tells you about a "gotcha" you need to avoid being got by.

The Arduino output would go to the "Out" at the left of the diagram. It isn't as hard as it may seem from the limited info at the site above.

If you can stand having to watch a video clip...

If you can READ (!)... you can go to....

(GASP! It might have been easier just to write my own than to locate that! Google! There MUST be decent guides out there to this basic topic!)

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