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121  Using Arduino / Project Guidance / Re: arduino wifi shield on: January 31, 2013, 07:50:36 pm
This one is pretty nice and available. It shares a "feature" with several other WiFi shields - it's expensive ;-)
122  Using Arduino / Project Guidance / Re: Help! AMBX RGB LED light extension project! on: January 30, 2013, 07:14:26 am
This should actually be pretty simple.  You only need to sense voltage on the AMBX LED circuits and drive the appropriate "extension" LEDS.  In fact, it could be pretty easily done without any sort of microcontroller (arduino or otherwise), if you only want to match color for color.  Handle the power with a v-reg/voltage divider circuit (with current limiting resistors) and use some transistors to drive the new LEDs.  I'm no EE but I think that should work smiley.  Someone please correct me if I'm missing something. 

You want to power this whole thing from the AMBX board?  My main concern with that would be having enough available current.  If you are willing to use an external power supply things get much more simple since you can just buy one that gives you the output you want. 
Sensing the voltage drop across an LED serves relatively little purpose. LEDs are constant curt devices with a voltage drop ( called forward Voltage Vf) varying with changing junction temperature. You would need to measure the current through the LEDs. Or actually much better the duty cycle of the PWM signal controlling the brightness of the LEDs. Even that is not soo interesting. Finding out what the little chip does that sits on the PCB would be the real key to reverse engineer this circuit and will likely provide you with access what the software does that controls these lights.
123  Using Arduino / Project Guidance / Re: Advice on Arduino High Output LED Driver Shield on: January 29, 2013, 06:46:03 am
To address the thermal issues, looking at the data sheet it looks to me that the chip has a thermal pad underneath that will have to be reflow solders to the PCB to help dissipate heat. It is relatively common for high power LED drivers. The LT3496 we are using on our LED shield requires the same. In order to spread the heat over a bigger surface you need to likely place thermal vias in that area under the chip as well. If that still is not enough you may want to look at a PCP with 2oz copper thickness.
However, given the abilities of the chip you are using I'd assume you are looking more for a low cost solution, thus I'd suggest staying away from 2oz PCBs as these a rather expensive and not available from the usual low volume PCB houses e.g. batch PCP or OSH Park.

I am also wondering why you are looking at such high PWM frequencies. While the chip you are using has a low dimming ratio already ( 1% duty cycle resolution or 100:1), using such high PWM frequencies is not going to help that at all, unless the aim is to use as small as possible components, but in that case there is plenty of room on a Arduino shield ;-)
124  Using Arduino / Project Guidance / Re: RGB LED Matrix spread over 400 square feet (43 square meters) on: January 29, 2013, 06:18:51 am
What would be the viewing distance and viewing angle or in other words would the LED panel be installed vertically ?
What are the viewing environment be dark and indoors or outside in bright daylight ?

The above at a minimum will determine what output your light sources will need to generate.

Given the size of the project one could easily assume that you won't get away with small 20mA LEDs but need something that has more light output. Of course your project is technically feasible. That is really not the question!

The question really is what are your time and budget constraints ?
125  Using Arduino / LEDs and Multiplexing / Re: RGB SMT LED Cube, resistors, drivers, and shift registers. on: January 27, 2013, 08:34:49 am
For decoupling you usually need one larger cap, for example 47uH, and smaller caps for each chip involved with usual values ranging from 0.1uF to 0.01uF. The latter ones are for the high frequelncy noise and should be located as close as practically possible to the ICs.

Here's an excellent tutorial on it:

I order most of my components from places like Mouser, Digikey and Newark and they ship rapidly. Of course it depends on ones particular location but my things usually arrive within 3-4 days.
126  Using Arduino / Interfacing w/ Software on the Computer / Re: I2C and Flash AS3 -NEED HELP on: January 25, 2013, 10:54:12 pm
From what I understand AS3glue uses the Firmata protocol and Firmata can communicate with the I2C bus. Just google Firmata I2C example and see if your find some information that will help you complete your project. I've found several examples and also this thread that may help you.
127  Using Arduino / LEDs and Multiplexing / Re: Lost with 50w LEDs + PWM on: January 25, 2013, 07:45:36 pm
While you may be able to use the TLC... I'd suggest a much more versatile solution with 16 channels right out of the box
This uses the PCA9685 which is a 16 channel, 12 bit PWM chip. It's advertised as a servo motor driver, but what you use the PWM output for is up to you ;-)
We use it on our LED shield and it works by well
The nice thing with this chip is that it uses the I2C bus interface of the Arduino and does not use any of the PWM pins. Also this provides you with much more flexibility in terms of PWM frequency. Hard to beat deal at about $15.

I have not looked at both chips and compared if inputs/outputs are compatible but the PT4115 should be a good chip to pair with the PCA9685 as it has a 5000:1 dimming ratio ( alas only at 100hz PWM frequency, and decreasing with increasing PWM frequency )

128  Using Arduino / LEDs and Multiplexing / Re: Lost with 50w LEDs + PWM on: January 23, 2013, 07:33:52 pm
The current does not increase with the number of LEDs in series. That is why it is called a constant current power supply. What changes is the forward voltage so...

If you've got 10 LEDs in series with a 300mA current rating and 2.5 Vf/ LED then you still need to supply 300mA to the LEDs but 10 x 2.5 + X Volt for it to work.
129  Using Arduino / Interfacing w/ Software on the Computer / Re: I2C and Flash AS3 on: January 20, 2013, 10:37:38 am
You forgot a lot of other things as well ;-)

For example what is the overall goal of the project ? What do you want it to do ?

For example how is the Arduino connected to the PC ?
 A schematic would be helpful!
130  Using Arduino / Microcontrollers / Re: Creating your own application to program MCU on: January 20, 2013, 10:19:33 am
I am not sure the responses so far address what the OP really wants to achieve.
 Perhaps the OP may want to better explain what he actually wants to achieve.

In order to connect a toy ( what size are we talking about ? ) to a WiFi network you wound not need to "program" the SSID and WPA key into the Arduino. What you have to do is to configure the Arduino side of the WiFi connection with these parameters. That does not really per se require you to connect the device to a computer Via USB, and compile/ upload the hex co to the Arduino, even though that could probably be one way, alas thats rather complicated!

A more common way would assume that the toy comes with a builtin WiFi "device" that, similar to many pocket WiFi routers, comes configured as its own Access Point (AP). You'd power the toy up and then connect to the Toy-WiFi device via Internet browser. The Toy-WiFi device then would serve a web page to allow configuring the WiFi connection to connect to the Users Home network and ultimately to the Users computer.

The next question is, once you have established a WiFi connection, what do you want to do with it ?
That may determine what protocol is best for what you want to do, TCP, UDP ?
Do you also want to access it from mobile devices ?
131  Using Arduino / Microcontrollers / Re: Standalone Arduino <-> computer communication on: January 20, 2013, 09:54:09 am
If you don't already have the Atmega I would suggest the Arduino compatible Teensy or Teensy++ boards. These also use Atmel micro controllers but have a much improved USB inteface compared to the "standard" Atmega boards.
Te Teensyduino software plugin for the Arduino IDE will provide you with many more examples, including some for a USB Joystick. The Teensys also have much smaller footprint comparable to a Arduino Nano for the Teensy++. For a joystick application the even smaller Teensy should be fine and only costs $16.
132  Using Arduino / LEDs and Multiplexing / Re: Lost with 50w LEDs + PWM on: January 19, 2013, 04:54:56 pm
In general the inability to find  a data sheet would personally concern me, but I suppose that is normal for a lot of eBay stuff from ominous sources. Based on a recent post using that same sort of LED for Aquarium lighting, you should be able to find at least a data sheet for the single LED elements that they have assembled in this package.

Also make sure you have sufficient heat sinking, possibly using a fan if you intend to run these close to their max current. The 50000 h lifespan is likely not applicable if you run them at max current and will be definitely many magnitudes smaller if you don't heat sink properly.

A second suggestion is to use a switched constant-current power supply. Most high brightness LED drivers are switched constant-current power supplies for reasons of energy efficiency. Otherwise they would dissipate too much heat and also would need a lot of heat sinking. Energy efficiency is also the reason of a relatively low PWM frequency.

Perhaps if you post a little more about your project you'd also be rewarded with more pointed advice.
133  Using Arduino / Networking, Protocols, and Devices / Re: Ethernet Shield Hangs When Combining Sketches on: January 16, 2013, 06:38:18 am
The circuit diagram shows two processors because the Atmega processor used on the Leonardo is available in different packages TQFP, VQFN etc. There is only one processor on the Leonardo board.
134  Using Arduino / Microcontrollers / Re: amazon nano clone (china) fails on: January 15, 2013, 06:41:16 am you've discovered yourself, you get what you pay for.
If you need a well made small Ardino compatible board I'd strongly suggest you check out the Teensy boards. All US made. Excellent support.
Even then smallest one is better than a Nano and at $16 priced very competitively. Not to speak about the newest Arm based Teensy 3, which is also Ardino compatible and vastly more performance than a nano.
135  Using Arduino / Networking, Protocols, and Devices / Re: BlueTooth vs. Wifi on: January 14, 2013, 05:29:50 pm
Unfortunately that solution will not work for me, as the device is not designed to be used near a router.  I am just trying to find a way, other than BlueTooth (if possible) to create a connection between two devices, one being the Arduino.  I don't need internet access.  I guess WiFi is probably overkill for what I am trying to achieve.  Maybe I should just face the fact that I will need to stick with BlueTooth.
No, WiFi is not overkill. It may have much more data transfer rate than you need, however it is ubiquitous and nearly all mobile phones, tablets, laptops etc. can easily connect to it.
Bluetooth on the other hand is much less power hungry than WiFi.
If power in not a problem than you still should be able to connect the Ethernet card to a little Pocket router such as the TP- Link WR703n or WR702n. These accept 5V USB power and you can run them off of the Arduino. Not only is that likely less expensive than a WiFi shield but also probably works better. The TP link can work as its own AP, so you can connect directly to it without the use of another router.

I've done it in two projects and it works flawlessly.
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