The ShiftBar is a 3-channel constant current LED driver module by macetech based on the Allegro A6281. This is a carrier board that is similar to the ShiftBrite, but designed for controlling external RGB LED modules, such as the ultra-bright Satellite Module 001. Using just three digital output pins and a simple protocol, your microcontroller can control a long chain of ShiftBars. Each ShiftBar in the chain can be independently changed to any of the 1,073,741,824 possible colors to create dynamic displays and decorations.
- Supplies 10 mA to 150 mA per LED channel.
- On-board potentiometer for current control.
- Input voltage range from 5 V to 17 V, with no separate logic supply required.
- Overtemperature shutdown protects the LED driver from overheating.
- Adjustable current for each color channel lets you correct for slight differences in brightness.
The ShiftBar can also be used with the lower-power 003 and 004 satellite modules, though if you want to control more than one, Pololu recommend you use the OctoBrite, which can control up to eight of these satellite modules.
Example ShiftBar applications
An example setup using a Micro Maestro to control a ShiftBar (or chain of ShiftBars) is shown below. Digital outputs 0, 1 and 2 are used to send the control signals to the clock, latch, and data lines, the enable line is connected directly to GND, and 12V power to the Maestro is delivered from the ShiftBar chain. Maestro source code to control a ShiftBar is available in the Example scripts section of the Maestro User’s guide.
|Connecting the Micro Maestro to a chain of ShiftBars. A single 12V supply powers all of the devices.|
In the Halloween display below, each pumpkin contains a Satellite Module, and the entire display is driven by a single ShiftBar chain, controlled by a microcontroller. Details of the project are available here.
Using the ShiftBar
The pinout of the ShiftBar module is shown below. As with the ShiftBrite, signals are sent in to the CI, EI, LI, and DI pins, and these signals are sent out to the CO, EO, LO, and DO pins. Terminal blocks are provided for the power connections and the connections to the external LEDs, which should be configured in a common anode (low-side switch) arrangement. Pololu's custom six-conductor cables, available in lengths of 6" and 12" and 24", can be used to easily chain together multiple modules. You can make your own shorter cables with Pololu's 3" wires with pre-crimped terminals and Pololu's 0.1" 6×1 crimp connector housings.
A potentiometer on the ShiftBar controls the current limit on each LED channel, from 10 to 150 mA. Turning the potentiometer in the direction shown below increases the current limit.
The ShiftBar is pin-compatible with the ShiftBrite, so for further details and example code, please see the instructions on the ShiftBrite page. Pololu also recommend careful reading of the Allegro A6281 datasheet (315k pdf) as well as the macetech documentation page.
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