Go Down

Topic: High Power RGB LED shield - 12bit/channel dimming - I2C (TWI) (Read 3141 times) previous topic - next topic


Apr 10, 2013, 03:58 am Last Edit: Dec 28, 2013, 02:45 am by Headroom Reason: 1
After slowly starting to redesign the shield in January I now have a functioning prototype and I am considering having a batch of these either manufactured or possibly manufacturing them myself.But lets take a little step back.

I used a number of five of a previous version of this shield in my own LED lighting project (trippylighting.com). The maker of the original shield sold these through his blog. The last entry on the blog is from Dec. 2012 announcing a christmas break and while there have been a few answers in response to inquiries on the blog he has not posted anything in over 9 months and appears to have lost interest in his creation.

Much to my dismay as I was hoping to use these in a few more projects. When it seemed a possibility that the blog would go offline another user of the shield created another blog and pulled all the information over so it would not be lost.
He invited me to co-host the blog and I accepted. We discussed having a batch of these manufactured in their original form, but as I started creating a costed BOM it became clear that the original Inductors would not be available anymore and we had to find alternatives.

Also there were a few things that I wanted to change and as one thing lead to another...
You can read more details here on our blog: http://ledshield.wordpress.com.

So let's quickly go through the Features the shield has to offer:

  • Three independent constant current channels. This shield will NOT operate common anode or common cathode LEDs!

  • Meant to drive high brightness LEDs with a constant current from 350 to 700mA.

  • 42V input. 36V output can drive up to 40W of LEDs.

  • On-board 5V switching power supply and I2C connectivity provide for standalone operation.

  • Shield stacks on top of an Arduino but can be operated independently as it only uses GND and I2C (SCA,SDL) from Arduino.
    Shield is stackable (also in multiples) onto Arduino Uno (Rev 2 and Rev 3) and Arduino Leonardo but can be
    connected and operated from any other Arduino Board or microcotroller platform that offers I2C.

  • 12bit PWM resolution per channel allowing for CIE lab brightness corrected dimming(library function).
    The 12bit PWM in conjunction with the LED driver chip provide a dimming ratio of 3000:1 and more.

  • Dynamically adjustable constant current (I2C) between 100mA to 700mA allowing for analog dimming.

  • Adjustable/programmable (I2C) PWM frequency 40Hz to 1.6kHz

  • On-board I2C pull-up resistors can be disabled by means of solder jumpers.

  • Shield is stackable onto Arduino Uno (Rev 2 and Rev 3) and Arduino Leonardo but can be connected and operated from any other Arduino Board through I2C.

  • Optional temp sensor to monitor led temp

  • An Arduino library that provides access to all functions is available on Github.

If all that sounds attractive, please come over to to our blog http://ledshield.wordpress.com and leave a comment if you're interested.
The original price of this shield was US$41.50 and we hope to keep it in that range, but that obviously depends somewhat on quantity.
The posted image is a prototype and a few minor refinements are needed, e.g. all the Arduino Pin labels are missing. The terminal block for power input (5mm pitch) is too tall to allow stacking multiple shields and will be exchanged for a smaller one (3.5mm pitch).




Are you using this driver in buck, boost, or buck/boost configuration?





Finally, after a little eternity I've put my LED shield up for sale at Tindie.com.

The difference to other offerings is that this shield is fully operated through the I2C bus (TWI) and requires only two pins (SDA, SCL) and GND. While the shield happily stacks in multiples on top of an Arduino Uno or Leonardo and most likely also a Yún and others it can be operated separately from the microprocessor.
So if your project requires:

  • independent control of more then 2 RGB LED's - it can do up to 64 -  and/or

  • a distributed system where each of the high power LEDs are many feet away from each other and/or

  • you need very smooth CIE lab brightness corrected dimming

Then this is what you are looking for.
Another "feature" is that these are assembled in the US, only use RoHS compliant, lead free solder solder and are fully function tested!

The best micro controller platform to use these with IMHO are the Teensy3.x http://www.pjrc.com/teensy/index.html as they have much more powerful I2C hardware than any Arduino I am aware of. They are fully Arduino compatible and Paul Stoffregen - the maker of these - is a very frequent contributor to the Arduino project.

I use a Teensy and these shields in my own lighting systems


Go Up