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16  Using Arduino / LEDs and Multiplexing / Re: Turning a simple 3w led w/arduino on: April 29, 2013, 06:43:35 am
There are lots of devices out there, particularly logic-level MOSFETS, that will directly take Arduino PWM outputs and drive high-power LEDs.

Although I haven't used this one, I may in the future...
http://www.onsemi.com/pub_link/Collateral/CAT4101-D.PDF

THis implies that you have soldering skills though. Otherwise there are many LED drivers out there. Just be certain to choose one with "logic-level" inputs, meaning that it will work directly with the TTL PWM signals from Arduino and not need level-shifting interface circuitry.
17  Using Arduino / LEDs and Multiplexing / Re: 0-10v PWM dimming problem on: April 26, 2013, 02:59:04 pm
> You need to use a PNP transistor, not an NPN.

Can you explain why just the NPN alone wouldn't work?

And the data sheet states "Please DO NOT connect "DIM-" to "-Vin".

Where else does it get connected?
18  Using Arduino / LEDs and Multiplexing / Re: Brightness control on: April 26, 2013, 01:11:27 am
Keep in mind that brightness levels of 0, 25, 50, 75 and 100% will look to the eye like brightness levels of about 0, 60, 80, 95 and 100%. This is due to the eye's nonlinear response to light. If you want visual levels of 0, 25, 50, 75 and 100% then you may want to start with 0, 3, 20, 50, and 100% and tweak from there. I recall seeing some algorithms that will calculate the relative "eye" brightness from LED % brightness. 
19  Using Arduino / General Electronics / Re: Clamp Comparator Output for Analog/Digital Input Pin on: April 24, 2013, 12:19:29 am
Where does the diode go?
20  Using Arduino / General Electronics / Re: Clamp Comparator Output for Analog/Digital Input Pin on: April 23, 2013, 06:43:36 am
By "in series" I assume you mean with the comparator output into the digital input.

I found (and have a few) comparators with TTL outputs which should work.
21  Using Arduino / General Electronics / Clamp Comparator Output for Analog/Digital Input Pin on: April 23, 2013, 12:21:54 am
I have an opamp as a comparator whose output I want to read with a digital or analog input pin and trigger an action when the comparator output goes high and a different action when low. Currently using +9v/-9v supplies for the opamp and want the comparator output to be compatible with the analog/digital pin (0 - 5v). A 5.1v zener from the comparator output to Gnd clamps the high output to around 5.1v but the low level is -0.7v. Is this -0.7v bad for an analog/digital input and how could I better the circuit to more accurately yield 0-5v comparator output for the analog/digital input?
22  Using Arduino / Project Guidance / Re: Can you run 2 different loops in 1 sketch?? on: April 19, 2013, 06:48:47 am
You can also set up an elapsed timer of sorts using millis() or micros() and save the time T0, then periodically check the time in a loop that goes off and does something else, and when the periodically checked time is greater than some chosen time span after time T0, trigger the other event. Kinda like watching your stopwatch until so many seconds have passed before doing something else. This allows you to "parallel process" in a sense based on elapsed time.
23  Using Arduino / LEDs and Multiplexing / Re: What's a "bright enough" LED for this project? on: April 15, 2013, 06:37:00 am
> 14 digital + 6 analog = 20

The 6 analog pins are input, not output. I did miss the RGB part though so, with the 14 pins can only light 4 RGB LEDs without adding multiplexers or drivers.
24  Using Arduino / LEDs and Multiplexing / Re: What's a "bright enough" LED for this project? on: April 13, 2013, 09:10:39 am
20 LEDs will somewhat of a challenge with only 14 outputs, won't it?
25  Using Arduino / Programming Questions / Re: DmxSimple Library Issues on MacBook on: March 26, 2013, 06:36:42 am
That worked! Also copied the library folders from the Arduino app to the "libraries" folder.
26  Using Arduino / Programming Questions / DmxSimple Library Issues on MacBook on: March 24, 2013, 08:21:46 pm
I download the DmxSimple library and copy it where expected:
/Documents/Arduino/libraries/DmxSimple

I load my sketch and by the colored highlighting of the DmxSimple commands, the editor seems to have recognized the library.
When I verify though, I get a long list of errors...


/Documents/Arduino/libraries/DmxSimple/DmxSimple.cpp:11:20: error: wiring.h: No such file or directory
/Documents/Arduino/libraries/DmxSimple/DmxSimple.cpp: In function 'void dmxBegin()':
/Documents/Arduino/libraries/DmxSimple/DmxSimple.cpp:57: error: 'digitalPinToPort' was not declared in this scope
/Documents/Arduino/libraries/DmxSimple/DmxSimple.cpp:57: error: 'portOutputRegister' was not declared in this scope
:

Although DmxSimple.cpp is in the library, it seems not to be able to find other components.
Have I installed the library in the wrong place?
27  Using Arduino / Interfacing w/ Software on the Computer / Arduino Coding on iPad on: March 24, 2013, 09:22:11 am
Is there an iOS app that allows Arduino programming and download to the Arduino from an iPad?  I'd like to be able to change project parameters in the field using something smaller than a MacBook. May not exist since I can only find WiFi control apps.

Perhaps a small 10" Windows netbook would be the right solution?
28  Using Arduino / LEDs and Multiplexing / Re: Random RGB Values Give Pastel Colors on: March 24, 2013, 09:01:02 am
Great idea... and I like the idea of randomly altering random numbers!
29  Using Arduino / LEDs and Multiplexing / Random RGB Values Give Pastel Colors on: March 24, 2013, 08:30:12 am
Have some RGB LEDS in a strip and looking to create some random colors for a background effect. When I calculate three random numbers say from 1 to 50 (so they're not too bright) then set the R, G, and B LEDS to those values I get different colors but they're always pastel and never vivid.

Is there a way to process the random numbers somehow to weight them toward more vivid colors, maybe pick numbers from 1 to 255 then scale them down to reduce brightness?

Would I have better luck to create an array of RGB numbers for colors that I want and just randomly step around the array?
30  Using Arduino / Project Guidance / Can Uno be Programmed with Both USB and Vin Present? on: March 23, 2013, 01:50:33 pm
My project runs from a regulated +9v going to Uno Vin and I'd like to debug the code while its powered from the 9V. If I plug in a USB cable to reprogram it with my MacBook, is there an issue because it's still powered by 9v? I read that the Uno uses the higher of its input voltages but still not sure if its okay for the onboard regulator and my Macbook USB port.
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