Electronic – arduino – can I drive 100 or so LRAs with WS2811 controlling DRV2603

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I would like to make a suit with 100 or more individually controllable Linear Resonant Actuators. Texas Instruments makes this http://www.ti.com/lit/ds/symlink/drv2603.pdf which take a PWM as an input to control the vibration intensity. I'm wondering if instead of lighting LEDs with http://www.adafruit.com/datasheets/WS2811.pdf could one of these be wired to 3 DRV2603s?

Looking at the data sheets, it seems the DRV2603 accepts a PWM between 10 and 250 khz. I'm not clear on what the WS2811 outputs. The datasheet reads 400 or 800 khz but that is operation freq. Here www.world-semi.com/en/Driver/Lighting_LED_driver_chip/WS2811/ I see 2.5khz scanning freq, so I'll assume that.

The other hurdle I see is digital input high current max of 3uA on the DRV2603 while the WS2811 has a constant current output of 18.5mA. I assume that would fry the DRV2603.

Are these totally incompatible? How would the DRV2603 treat a PWM of 2.5 khz? Would I get 25 levels of intensity instead of 255?

How does constant current work? Is there a way to make this chip output less current? Could I maybe drive an led and then throw a resistor in parallel with the LED to drive the LRA as a side-effect of lighting the LED? I've seen Running Man and I know that would look good at least.

I'm certainly open to more proper solutions but this seems appealing for the price of these components. I am planning on using an Arduino with adafruit's neopixel library if this approach proves feasible. The arduino will be used to communicate with a computer over USB serial, so if an alternate solution involves some kind of USB to lots of PWM outputs, that would be great too.

Thanks for any pointers.

Best Answer

Not sure if you have found answers to all your questions. You could connect the DRV2603 to a Lithium battery supply. You need to maintain the voltage rating of the datasheet (2.5-5V) rather than connecting to a current source.

When the LRAs are vibrating you will see the DRV2603 will consume around 30-90mA to vibrate the LRA.

For vibrating multiple LRAs, you can hookup say OUT+ of 10LRAs to 10 DRV2603s and connect the rest of OUT-'es to a switch. There is an example of this one in the EVM schematic. I would get a digital switch for that one so that you can communicate with a micro-controller.

You can also post your question on the E2E TI Haptics forum too for an in-depth Haptic questions.

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