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31  Using Arduino / LEDs and Multiplexing / Re: Need more control over PWM for led fade. on: November 03, 2013, 10:48:46 am
I re-read the OPs original post, and in that application when you fade in all color channels from zero that step is detectable, I agree. For the OPs intended purpose I'd agree that the little breakout from Adafruit seems ideal. Had not seen that one before, so thanks for posting it!

32  Using Arduino / LEDs and Multiplexing / Re: Need more control over PWM for led fade. on: November 02, 2013, 05:17:07 pm
Another thing that came to  ind is that if actually do want to use 16 bit, the Teensy3 has 10 pins that can do 16-bit PWM Not bad for $20!
33  Using Arduino / LEDs and Multiplexing / Re: Need more control over PWM for led fade. on: November 02, 2013, 05:04:16 pm
The steps come from a nonlinear response of the human eye to changes in brightness.
If an LEDs light output would be by some strange coincidence matched to that, 256 steps or 8-bit per color channel would provide you with smooth dimming.
The article here explains this fairly well. In order to linearize it is fairly common to use a lookup table that maps the 256 steps onto a 12-bit map.

I use that approach in my lighting systems ( see signature for links) and it provides very smooth fading using 265 steps per color channel. Only when fading very, very slowly at ranges vevery close to zero have I been able to detect steps. So in essence the speed which with you fade also has to do with the ability to detect steps. Having 12-bit dimming available I can still use a 10-bit lookup table to correct that behavior.

16 bits are nice if you want to use arbitrary scaling, say if you want to be able to only use only a quarter of the dimming range of your LED but still want to be able to smoothly fade, however is not really necessary at all in my experience. More is not necessarily better!
34  Using Arduino / LEDs and Multiplexing / Re: 10 Watt high power LEDs. on: October 31, 2013, 03:12:59 pm
I was merely pointing out that there was a technical inaccuracy in what you wrote and did want to point it out as it has been a misunderstand in more than one three/post on this forum. No reason to be defensive!

I am not sure I understand your problem not being able to draw enough current. You wrote in a post above that you are using current limiting resistors that will limit the current through the LEDs to 400mA. When you set the duty cycle of the PWM signal to 100% then the "switches" are on 100% of the time, thus you will draw these 400mA. If you want more current to flow you'd need to lower the value of the current  limiting resistors, or is there something I am missing ?
35  Using Arduino / LEDs and Multiplexing / Re: 10 Watt high power LEDs. on: October 30, 2013, 07:27:25 pm
If you are using current limiting resistors, then you will not damage the  LEDs. However the assessment that with PWM you can perhaps reduce average current but not peak current is still correct.
36  Using Arduino / LEDs and Multiplexing / Re: 10 Watt high power LEDs. on: October 27, 2013, 11:50:51 am
You CANNOT lower the current draw using PWM. You limit the overall energy going into the LED, however, if the current exceeds that of the LEDs spec you may have already shortened the lifetime of the LEDs.
37  Using Arduino / Interfacing w/ Software on the Computer / Re: Help RXTX on MAC OS X on: October 19, 2013, 06:58:27 am
Google translate:
"Hello, I have a problem I can not seem to use the RXTX library in Java, the installation does not work how. Can you show me how to install it please."

You may want to explain what exactly is not working. If you are comfortable reading English, then this link may help:
38  Using Arduino / Networking, Protocols, and Devices / Re: TouchOSC via Ardosc/Bonjour on: October 17, 2013, 08:27:10 pm
That's very good to hear. Congrats!
39  Using Arduino / LEDs and Multiplexing / Re: 10W RGB LED Project on: October 16, 2013, 05:25:57 am
As others have already noted, you are best off using a constant current power supply. There is a bare board for sale at that theoretically would fit your LED. The components you'd need are easy to find. The PT4115 can be found on eBay as well for $0.40 a piece! As a whole this would make for a really inexpensive LED driver that would allow 12 bit dimming.

As noted by others, connecting the LEBd to a " normal"  regulated power supply is not going to cut it. "Normal" regulated power supply keep the voltage constant. LEDs are constant current devices. LEDs, and particularly High Power LEDs such as yours get hot (you will definitely née a good heat sink!!!)  and when the temperature raise, the forward voltage will also raise. That is why a simple current limiting resistor is not a good solution.

The LED that you have linked to has very short leads on one side, so perhaps look for an equivalent LED with leads that are a little longer. While the LED in your image  is a common anode ( or cathode) LED, you can cut off the " bridge" to eliminate the problem and make it workable with the above linked board.

In general I personally would not trust these ultra cheap, un-binned Chinese mass produced eBay LEDs.
40  Using Arduino / LEDs and Multiplexing / Re: Driving 2 RGB LED strips on: October 09, 2013, 08:41:53 pm
That sounds like a good plan. If you want to prototype this before committing to a custom PCB try this motor shield from Adafruit.
the PCA9685 used on the board is really an LED driver chip.
41  Using Arduino / Networking, Protocols, and Devices / Re: TouchOSC via Ardosc/Bonjour on: September 21, 2013, 08:53:48 pm
You don't NEED Bonjour, but it is cool ;-)

I think I had the problem with the LED just blinking once too when I was figuring things out. IIRC the trick in TouchOSC is to use a toggle button (not a push button) and un-check the "local feedback" check box.
  • When you press the button once an OSC message is sent to the Arduino.
  • Then the LED is turned on.
  • then a message is sent back to the toggle button in TouchOSC to turn it on.
42  Using Arduino / Networking, Protocols, and Devices / Re: TouchOSC via Ardosc/Bonjour on: September 21, 2013, 05:34:28 pm
Replacing the Ethernet Shield with a WiFi shield will require some adaptions to the ArdOSC library. The ArdOSC library contains a few function calls to the lower level SPI functions of the Ethernet library.

I personally am not working with the ArdOSC library anymore as it is rather dated and not maintained anymore. I have rewritten my code to use the OSC library from CNMAT (Oscuino) It is writen and maintained by the inventors of the OSC protocol and actively maintained.
It uses the "regular" Arduino Ethernet and EthernetUDP libraries and is not directly hardware dependent. However, using hardware that can make direct use of the the Arduino Ethernet libraries is a not to be underestimated advantage to getting things to work very quickly.
For example I use a WIZ820io Ethernet module instead of the Ethernet Shield.

Any change in Ethernet related hardware will require you to change code in the used libraries unless the libraries that come with these shields e.g. the Seedstudio WiFi shield have compatible function calls.
43  Using Arduino / Networking, Protocols, and Devices / Re: How to control a bit in a register by i2c on: September 21, 2013, 07:03:46 am
44  Using Arduino / Networking, Protocols, and Devices / Re: List of Wifi Options with links on: September 21, 2013, 07:00:56 am
There are more options: Hydrogen WiFi shield and Platinum, which is a Arduino Mini with integrated WiFi.

Also, the Bridge solution is not limited To use only the slow Wiznet W5100 based Ethernet Shield.
You can use either one of the W5200 based Ethernet shields, or if you'd like something small you can go with an embedded Ethenet module like the WIZ820io ($20 here in the US) with is also based on the W5200 chip.
Then as another port suggested you can get a pocket router that runs DD-Wrt, which is an embedded router Linux. For example the TP link TL WR703n is a very good choice as it can be USB powered.

45  Using Arduino / LEDs and Multiplexing / Re: High Power Multiple-Channel LED Driver Questions on: September 05, 2013, 04:34:28 pm
For hight power LEDs with 700mA a linear regulator is really not a suitable solution. The shield you've linked to is actually a very inexpensive solution and is a switched DC/DC converter in Buck configuration. A much better higher efficiency solution requiring no heat sinking at the shield as opposed to a linear regulator.
You will need to use heatsinks for the LED's.

This shield is limited to 4 independent channels and you cannot stack another of the same shield on top of it to get to 8 channels as the shield directly uses the Arduino PWM pins and there is a limited number of those ;-)

Frankly, the LEDs you've linked to are also dirt cheap!
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