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1  Using Arduino / Project Guidance / Re: real time implementation of home automation system on: March 18, 2014, 08:57:25 am
If you want DIY there is a compatible chip that includes a zigbee radio or just use the zigbee modules directly they have 8 GPIO's and 6 ADC inputs.

Frankly it's hard to beat Insteon/zwave on pricing (X10 as well but it's always a bit funky) and you can control an whole house of them from an arduino or just about anything else.

For just on, off, and dim the commercial product just works.  Adding in PIR room occupancy, temp, humidity, and water sensors (or whatever you can come up with), or interfacing with something in a more complex way (room AC and the like).

For distance zigbee, insteon and zwave all mesh things together so more devices more robust network in theory. 
2  Using Arduino / Project Guidance / Re: Hot Tub Temperature Control on: March 16, 2014, 05:30:53 pm
Hi, hot tubs all over the place, no wonder we have greenhouse gas problem.....LOL
Question, How long does it take to heat up, energy to keep hot, cost to maintain, cost of energy.
Ratio of use to non use?
Is it worth it?
If you need a hot tub to relieve stress, get another job...LOL
You might also add to your projects an energy monitor to see how much energy you are using.

Tom..... smiley

Replaced the controller on my hot tub years ago, with a custom PCB and arduino code.  Web interface and SNMP.  Still have to finish the 2.0 model with BT Audio and control. 

Hot tubs are wonderful for  many sorts of injuries.  The cheap ones are power hogs, making water hot with electricity is about your worst choice for cost, and insulation matters a lot.  Converting to much cheaper NG or wood heat primary/secondary heat can really reduce the expense.  That is also a whole different project.
3  Using Arduino / Microcontrollers / Re: Pin conflict on: December 09, 2012, 10:56:52 am
I am using the MP3 Player Shield from Sparkfun( and the MPU-6050( at the same time. But both of them uses the digital pin 2 and they can't work together. The MP3 shield uses it as "MP3-DREQ" as stated beside the pin and the MPU uses it as the interrupt pin. I tried all of the solution but none of them worked:

1. Remap the pin in the MP3 library. I changed a line that declares the pin for the DREQ and it still don't work without pin 2.

2. Bend the pin on the MP3 Shield so that it doesn't go into the Arduino. The MP3 won't work. It need the pin for sure.

3. Use the pinchangeint library to create more interrupt pins: I'm not sure whether it helps because it is very unstable.

4. Change the interrupt pin used my the MPU. I know there are 2 interrupt pins on the Arduino Uno but I failed to find where to make it uses the pin 3 instead of 2.

And now I'm running out of ideas and don't know what to do.. Has anyone used one of those and manage to remap either pin?

I think the line your looking for for the mpu is:

attachInterrupt(0, dmpDataReady, RISING);

Change that to 1 to use pin 3 on an uno.  Considering all the rest of the code it seems odd that they hard coded int 0.
4  Using Arduino / Microcontrollers / Re: Difference between EEPROM and flash memory on: November 11, 2012, 10:38:00 am
Volatility is not an issue - there is no problem with the RAM being erased when the power is lost in my application.

In which case, is there any advantage of FRAM over SRAM? Seems FRAM has very fast write speeds (or lack of!). I am also writing a lot to an SD card and thus will need to buffer lots of data in RAM until its written.

FRAM does not need power to retain the data.  As you say volatility is not an issue you probably do not need to use it.  Neither will really help you in regards to writing data to a SD card that needs to be internal SRAM and since it's block oriented it's uses a 512b buffer. 

Please note that your going to end up coping everything to and from internal sram constantly so your not necessarily during yourself a favor trying to use offboard sram. 
5  Using Arduino / Project Guidance / Re: Wire remote for GoPro Hero on: November 11, 2012, 09:19:34 am

I want to control the shutter of my GoPro HD Hero 2 via the iPhone/iPod-like connector on the back. Of course, I did extensive research and found this pinout list:

As you can see, there is no trigger in or trigger-button-in (I hope you understand what I mean. You can see a power-button-in). All the DIY projects I found use the power-button and set the camera to auto-capture mode, so the camera starts recording when it's turned on. But that wont be suitable for my project, I cant wait 5 seconds between every photo. But, GoPro itself sells a remote to plug into this connector , and a few on the internet managed to trigger it somehow. But I can't find anything about this "better" approach.

Does anyone here have information about how to accomplish this?


Seems somebody already did this on a pic looks like some fiddling with the ID pins gets it working.  Emulating the IR remote should also work.
6  Using Arduino / Project Guidance / Re: Multiple power supply question on: November 10, 2012, 01:58:16 pm
I'm using a Mega R3 with seven, backlit, lcds.  Each LCD has three LEDs drawing 20mA. 
Since this would exceed the limits of the arduino, I am planning on using a separate power supply for the LEDs and the contrast pins (Vo on the lcds.)

The problem I'm concerned about is that each display has a common ground for all of its circuitry, so the display will need to be grounded to arduino and to the other power supply through only one pin.

Is this actually a problem?  Is solving it as simple as tying the grounds together?

If the whole thing is running at 5v just power the Mega from the single larger supply. 
7  Using Arduino / Project Guidance / Re: I2C for longer distance LED light bar system on: November 10, 2012, 01:53:13 pm
I am a veteran programmer and somewhat familiar with electronics. I have an Arduino Mega 2560 microprocessor. I am wanting to build an industrial application which will consist of 5 foot long “bars” each having 4 LEDs. I need the ability to daisy-chain these bars out from the microprocessor and control any combination of turning on/off the LEDs on each bar. I am considering using I2C with extender boards but need some serious help in understanding if this is a practical design. The LED “bars” will be about 8 feet apart and on my application there will be a total of 24 bars each having 4 LEDS. I am considering using CAT5 wiring and connectors to daisy-chain and hopefully carry enough voltage to drive the system. Thanks for any advise on how to build such a system.

That is a pretty standard NXP chip that cost nowhere near the 20 bucks they are looking for it.  You might want to look at DMX it's pretty much 485 serial and much better suited for going the distance since it's primarily used for theater work.  Cost should be similar if not cheaper than the i2c option your looking at.  Check out for the standard pin outs you can put power over pins 4 and 5.
8  Products / Arduino Due / Re: Arduino Mega or DUE? on: October 29, 2012, 08:35:50 pm
Honestly right now the Due hardware is showing piles of weaknesses much like the hardware that came before, give it time for better designed kit to come out from other vendors.  The software side is mostly there.

What are the piles of weaknesses? and what other vendors can do that we can't do?


The most glaring not connecting up the built in Ethernet and wiring multiple pins together effectively limiting external ram use come to mind.  I have not yet received the one I ordered but made some in the shop, I think you really limited yourself in trying to keep the the mega form factor which in itself was trying to keep comparability with the previous generations.  I'm already thinking of a lot of kit that does not have the correct values for current limiting resisters where a 3ma is not going to be enough. Now granted I think the breadboard compatible form factors make more sense for a hobby/learning device. I love the ecosystem you guys have created but I've never been thrilled by the hardware. That is the strength of open source hardware I can just pop up eagle make what I want by building on the great works you guys have already done.
9  Products / Arduino Due / Re: Arduino Mega or DUE? on: October 29, 2012, 10:45:46 am
i have to buy an arduino board with more i/o pins and a better clock cycle,so was looking at mega, but the recent launch of due, has confused me,should i go for due?..wont there be some bugs present in it?

What are you looking to do?  Honestly right now the Due hardware is showing piles of weaknesses much like the hardware that came before, give it time for better designed kit to come out from other vendors.  The software side is mostly there.
10  Using Arduino / General Electronics / Re: DG408 wiring on: October 10, 2012, 10:07:51 am
Hello, I have DG408 (

and it says in the following scheme that there is V+, V- and gnd, what does V- stands for?

thanks in advance,

Just what it says negative supply voltage.  That chip normally runs with 15v +- but supports a lot of different configurations. If you want to use it with positive voltage only connect v- to gnd as the datasheet says on page 6.
11  Using Arduino / General Electronics / Re: Is my relays wiring schema correct? on: October 09, 2012, 05:18:47 pm
Hello smiley

Just a little question: is this schema correct? (I want the relays Normally Open)


Looks about right, without the spec sheet for that relay board it's hard to tell.  I've gotten some that inverted the input so you had to be HIGH to have the relay be off easy way to check is to connect just power and see if the relays click if they do it's inverted.
12  Using Arduino / Project Guidance / Re: "External" memory for program memory? on: October 09, 2012, 05:13:58 pm
I know, from what I have read, that the stock Arduino device comes with a fixed amount of memory that can be used for running sketches, ranging from about 4k, to 256k or so, depending on the Atmel chip used.

I also know that by using a SD shield, or an Ethernet shield that has a built-in SD card reader, I can use the SD chip for data-logging and such.

Question #1:
Has anyone tried to use the SD card's memory for extended data storage, used programmatically?  For example:  I want to use an Arduino with an Ethernet shield, (containing an SD card reader), as a web server and I want to put multiple web-pages on the, (much larger!), SD card rather than main memory?

Question #2:
Is it possible to use the external memory on the SD card as additional storage for larger sketches than main memory will hold?  Can I execute out of the external memory, or is there a paging scheme that would work?

If this hasn't been done, than this is an area ripe for research, but if it HAS been done - at least in part - I'd really rather not re-invent the wheel again if I don't have to.


1 yes it's pretty trivial to do.  It does use a pile of sram as the sd card is fat formatted thus block oriented so your reading 512b at a clip. Please be specific I'm assuming your talking about flash as main memory though that's what most would call sram.  If not take a look at progmem before thinking you need to deal with sdcards.

2 Yes but it's a great big PITA far easier to get a chip with more flash like the 1284 than to fiddle around with this.  This method is also very SLOW and wastes sram to do so.  If you think you need more flash than a 1284 provides consider if an 8 bit micro is the right processor type for your application.   
13  Using Arduino / Project Guidance / Re: Ah, the Leonardo! on: October 09, 2012, 01:25:58 pm
no, the question is, can i, how do i? is it possible to be able to read keyboard input from other USB keyboards on the computer a leonardo is plugged into?

Now you can use one of many usb host chips and plug an arduino inline to sniff or add whatever keystrokes you want.
14  Using Arduino / Project Guidance / Re: Anybody?! Started with Contiki or other 6lowpan on: October 07, 2012, 05:43:57 pm
Has anyone of you tried and accessed internet utilising Arduino and Contiki OS? and offcourse made something communicate?

Yes and it works fine.  Forget which lib I used but the hardware was an enc since the 5100 does not support ipv6.  I would suggest not using a standard arduino if you want ethernet with either chip something like the 1284 has enough sram is needed to do it well.
15  Using Arduino / Project Guidance / Re: Need help to set a register on: October 05, 2012, 03:04:37 pm

I am sitting this evning and came upon some small stuff for my model railroad, and I have 2 switchs when then first one is pressed and then released again I need an output to go HIGH until the second switch is activated.
Could anyone help me with that, I believe that I need to setup a register, and the when the first swicth is HIGH it will set the register a "1" and when the register is "1" the output is going to be HIGH until register is set to "0".

Hope that some one can help me.
And yes I am new to this and it is about 15 + years last time I made a program.

Regards RedOrder

This is pretty straight forward logic.  Simple example:

if (digitalRead(buttonPinA) = 1) { digitalWrite(SomePin, 1); }
if (digitalRead(buttonPinB) = 1 && digitalRead(SomePin) = 1) { digitalWrite(SomePin, 0); }

Probably want to use a library or some external components to debounce or otherwise cleanup the button presses.  
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