I've been playing with these LEDs and they have become my go-to LED for many microcontroller projects. They are a little tricky to get used to but once you understand them, they are huge win.
Pros:
This is probably the biggest drawback of these LEDs. Basically a 1-wire serial timing based protocol that requires a microcontroller is used. See the diagram
:
There is no HW in typical microcontrollers that can drive this protocol so a software implementation (aka bit banging) is used. Worse, this requires disabling interrupts during the transfer. But, that is mitigated by several facts:
Here's the schematic
As you can see, a single pin is used to control 8 LEDs. SW, BOM and the Eagle PCB files are available on github
I have also uploaded the file to OSHPark and people can order the PCBs from them. The cost is about $9 for 3 boards.
Here's short video of the board in action. The LEDs are so bright that they overwhelm my camera. The colors are much better in person.
A note on the software. It uses Atmel Studio 7.0 which is a free download and must be programmed via the ISP connector. Any programmer that supports an ATTiny85 and ISP should work fine. The ATTiny85 supposedly comes default to 8 MHz but I've gotten several that default to 1 Mhz. It's a simple matter of setting the fuses to get it running at 8 MHz. I'm hoping to put together an Arduino version of the SW as the ATTiny is supported by the Arduino IDE.
Pros:
- RGB with a single pin
- very bright
- inexpensive off ebay/aliexpress (about $0.10 each for individual LEDs)
- available in a number of assembly formats (individual, strings, arrays)
- control multiple LEDs with a single pin. Practical limit is in the 1000s.
- 16M values of color/brightness available
- each color controllable in 256 brightness steps
- hand solderable (see cons)
- works with even low end microcontrollers (8 MHz ATTiny 85, for example)
- lots of libraries and sample code available
- arduino compatible
- code requirements are small.
- SMD (though hand solderable and this is the 21st century)
- a little big for some indicator LED needs
- requires microcontroller/cpu
- protocol requires bit banging
This is probably the biggest drawback of these LEDs. Basically a 1-wire serial timing based protocol that requires a microcontroller is used. See the diagram
:
There is no HW in typical microcontrollers that can drive this protocol so a software implementation (aka bit banging) is used. Worse, this requires disabling interrupts during the transfer. But, that is mitigated by several facts:
- transfer time is fast - approximately 30 uS per LED.
- no ongoing maintenance - once set, the LED will remain at that setting until changed.
Here's the schematic
As you can see, a single pin is used to control 8 LEDs. SW, BOM and the Eagle PCB files are available on github
I have also uploaded the file to OSHPark and people can order the PCBs from them. The cost is about $9 for 3 boards.
Here's short video of the board in action. The LEDs are so bright that they overwhelm my camera. The colors are much better in person.
A note on the software. It uses Atmel Studio 7.0 which is a free download and must be programmed via the ISP connector. Any programmer that supports an ATTiny85 and ISP should work fine. The ATTiny85 supposedly comes default to 8 MHz but I've gotten several that default to 1 Mhz. It's a simple matter of setting the fuses to get it running at 8 MHz. I'm hoping to put together an Arduino version of the SW as the ATTiny is supported by the Arduino IDE.
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