Progress Towards Penta Buzzer Project

[LittleBigPopit]

Hi all,

Just wanted to let you all know that I've also been working on my own DIY Tass-like buzzer project. I'm currently working on a second iteration of my Penta Buzzer and this second iteration is mainly inspired by the FreedomWavePD gloves CBailey11 showed. I want to iterate on the idea and bring some software features that I'm hoping will benefit those who'd like to use the buzzer gloves.

I've been working on writing a C++ library for the DRV2605 chip so that others can better use its functionality. The main results of my work are that the Linear Resonant Actuator (LRA) buzzer I'm using is able to buzz at frequencies other than it's resonant frequency of 235Hz. I currently have a pretty basic setup that is sending frequencies from about 20Hz to about a maximum of 950Hz before becoming unstable at either end. There is a noticeable droppoff in effectiveness below 100Hz or above 400Hz. I'm not sure how to describe how 'effective' the buzzing is, other than it felt less impactful. I also made some modifications to the default configuration so that it would overdrive the 1.8v LRA to 5v, and in turn, the LRA gets warm after short use.

I'm currently using a setup with a NFP-ELV0832B LRA, a DRV2605L breakout board, and that's connected to a Seeed Studio XIAO ESP32C3 microcontroller via I2C.

The reason I'm currently pursuing this avenue is due to the ability of the DRV2605L chip to change frequencies with imperceptible speed, its accuracy in hitting those frequencies (I had it playing a short tune by buzzing the notes), and the ability to change the intensity of the vibrations without needing to reduce the frequency like with the ERMs from my previous design.

Let me know your thoughts. I'd like to try and work out any issues as early as possible.

[Neurosmith]

Wondering if you've had a chance to try the DRV2605 to drive audio exciters rather than LRAs?

[LittleBigPopit in reply to Neurosmith]

I have not. But it is on my list. I've got a couple audio exciters sitting here that I want to test.

[Neurosmith in reply to LittleBigPopit]

Looking forward to your results. I've found audio exciters that match the 8 ohm spec for the DRV2605 but their frequency is typically in the 600 hz range or more. Getting the DRV2605 to modulate off the market audio exciters to run around the 250 hz of Tass' protocol would be great.

[LittleBigPopit]

# Update:

Tested this setup with the Dayton DAEX-9-4SM audio exciters with positive results. They have a rated resonant frequency of 200Hz and the DRV2605 can drive them quite well. The calibration sequence doesn't like them very well, but with defaults or manual calibration it is able to run.

## Pros:

Maximum intensity seems greater.

The DAEX-9-4SM seems much more directed. If I place my finger on the correct side, I feel the buzzing like normal, but if I place my finger on the back side of the device while its buzzing, I can barely pick it up. There still is buzzing making its way down the wire just as much as with the LRA.

## Cons:

Gets warmer faster than the LRA I was using. As you'll see below, this is most likely due to the higher current consumption.

Becomes unstable at around 800Hz on the high end. That's most likely because I'm pretty inefficient in my control loop at around 2.4kHz control frequency.

## Other notes:

I also did some measuring of current consumption out of curiosity. This was done between source (5.1v) and the DRV2605 with maximum intensity.

| Frequency (Hz) | Audio exciter Current (Amps) | LRA Current (Amps) |

| -------------- | ---------------------------- | ------------------ |

| 110 | 0.45 | 0.11 |

| 247 | 0.45 | 0.11 |

| 311 | 0.45 | 0.11 |

| 494 | 0.40 | 0.09 |

| 783 | 0.32 | 0.07 |

Neurosmith