Design advice - telemetry and accelerometry

Sensors IMU & Motion
1

Hello.

I am seeking some broad advice on the design (i.e. selection of components) of a piece of wearable technology that I would like to make.

Aim - I want to measure the acceleration of the wrist when throwing a ball.

Constraints

  • The measurement device needs to be small and battery powered

  • I want to wirelessly transmit the measurements

  • I need to capture peak acceleration (which is well above 20 g)

Capacity

  • I can solder and assemble hardware

  • I have Arduino experience

  • I can 3D print an enclosure

  • I can learn new skills

  • If I can get the data to a PC via Bluetooth, I’ll be able to handle the subsequent processing

Questions

  1. The only 3-axis accelerometer I can find here that goes above 16 g is the ADXL377. Is this suitable, are there better choices?

  2. To capture the signals from the accelerometer breakout board and transmit them via WIFI/BLE, I was looking for a small form factor option like the “ESP32 Thing” (although it appears that it doesn’t handle analog inputs when using Arduino). Is there a better choice?

  3. Will I be able to transmit 3 channels of data at 100 Hz?

Thanks in advance, Dan

2

Hi Dan,

That is a neat project and I think we have a couple of options that will work for your microcontroller/transmitter. I will answer your questions below:

  • - That is pretty much correct. We do have this [[LIS331 Breakout](https://www.sparkfun.com/products/10345) that can be configured to +/-24g but that may not be a large enough range for your project.
  • - The ESP32 Thing could work for this project. The [[ESP32 Arduino Core](https://github.com/espressif/arduino-esp32) does have some analog functionality and you can do analogRead(), just not analogWrite(). That GitHub repository linked above will have more information regarding reading analog inputs. This [[project example](https://docs.espressif.com/projects/esp-idf/en/latest/api-reference/peripherals/adc.html) using the Espressif IDF might be helpful for getting started with that code. Another option would be to use the [[SparkFun Pro nRF52840 Mini Dev Board](https://www.sparkfun.com/products/15025). To learn more about this board, I would recommend reading our [[Hookup Guide](https://learn.sparkfun.com/tutorials/sparkfun-pro-nrf52840-mini-hookup-guide) and the two programming guides linked in that tutorial.
  • - A short answer is yes, you can. There are some mitigating factors regarding your Bluetooth transmission speed but both Bluetooth 4.2 (on the ESP32) and Bluetooth 5 (on the Pro nRF52840) should be able of handling sending data from the ADXL337 at that rate.
    • ](https://learn.sparkfun.com/tutorials/sparkfun-pro-nrf52840-mini-hookup-guide)

    I hope this helps you get the right parts for your project.](https://www.sparkfun.com/products/15025)](Page Not Found - ESP32 - — ESP-IDF Programming Guide latest documentation)](GitHub - espressif/arduino-esp32: Arduino core for the ESP32)](https://www.sparkfun.com/products/10345)

    3

    Thankyou TS-Mark!

    I did read your reply the day after you posted it but haven’t thanked you until now. I am moving ahead with your suggestions.

    Regards, Dan