Wearable Device to Help With FoG Issues for Parkinson's

Recently my supervisor ask me to make a device to help with the Parkinson's patients who have freeze of gait (FoG) issues as a side project. As I like designing cool looking DIY electronics, so I decide to give a helping hand and design a wearable device for this project.

What is FoG?

FoG is a situation where a patient, usually with Parkinson's disease, having trouble walking on their own. When FoG occurs, they will have issues like trouble moving their feet forward for next step, reduce walking speed and reduced ability to balance. However, with the help of some external stimulant, like sound, vibration or light, they can restore their normal walking gait very soon by following the rhythm of the external stimulant. That is why we need to make a device that help them "walk normally" in some sense.

(Illustration extract from publication: Pozzi, Nicolò & Canessa, Andrea & Palmisano, Chiara & Brumberg, Joachim & Steigerwald, Frank & Reich, Martin & Minafra, Brigida & Pacchetti, Claudio & Pezzoli, Gianni & Volkmann, Jens & Isaias, Ioannis. (2019). Freezing of gait in Parkinson's disease reflects a sudden derangement of locomotor network dynamics. Brain. 142. 2037-2050. 10.1093/brain/awz141. )

And of course, this device is not limited to FoG patients. Pairing with a self written app, this device can be used for many purposes like app notification or even adding more sensors for other purposes. For this instructable, I mainly shares how the device can be make this small and portable while not scarifying battery lift and processing power.

For this project, you will need

• Battery (LiPo, 3.7V 600mA)
• A charger circuit and boost converter (I am using IP5306 because I have a few lying around, but you can use anything that works like TP4056)
• Switch
• Some wires
• N Channel MOSFET / Stepper Motor Driver
• LDO or buck converter (for stepping down the voltage to 3v for the vibration motor)
• Seeed Studio RP2040 (I pick this for its super small size, you can also use the XIAO BLE from Seeed Studio as well if you prefer a bluetooth BLE build in)
• HC-05 (for classic bluetooth device, as I already have a Android module working with this module)
• 3D Printer, hot glue and other tools

This project was attempted by one of the senior student in my research lab. At that time they created a giant 3D printed box and attach it to the patient wrist using Velcro. And as everyone expected, no one would like to wear this again as it is too bulky and ugly.

As this is my first time designing a wearable device and it is required to be as light and comfy to wear as possible, I decided to go with a 3D printed spring loaded design and separate the giant box design into two section. One containing the power electronics and the other one contain the control electronics. The spring in the middle of the two container can be replaced with another 3D printed one to fit different patient upper arm diameter. At two side of the device, there are two hook for binding in the Velcro so as to attach the device to the patient upper arm.

In order to make the device much thinner and lighter, I decided to split the electronics into two section

1. The powering section, which include the N Channel MOSFET (I am using IRF520 here, but you can use any alternative that fits your voltage level and power), the LiPo (3.7v, 600mAh) and a IP5306 based charging and boosting converter. The reason I pick this converter is that the motor require a bit high current to kick start and this module can output up to 5V 2A at peak (after stepping down by the buck converter, it is reaching 3A at 3V), which make the vibration motor highly responsive to control switching.
2. The control circuits, which include a Seeed Studio PR2040, a HC-05 classic bluetooth device, a buck converter for switching the 5V down to 3V (as I cannot found a 5V vibration motor that fit inside the case) and of course, a vibration motor

The wiring diagram is pretty straight forward. But it takes a lot of patient to work in such a small confined space so take your time and beware not to tear any tiny wires!

Assembling the power circuit is quite straight forward. You simply solder the battery to the charger circuit, wire the resistors to the MOSFET and solder all the connection point out of the circuit using a 2.54 x 4 cable. In here I am holding the completed circuit of the powering section.

Before we actually assemble the control circuit, we need to test the communication with our phone by testing the circuit on a breadboard and program it. As everyone knows how to program an Arduino nowadays, so I am gonna just leave my code here and skip this step :)

The next part is solder the control circuit section. First I solder the RP2040 to the HC05 module and tested all the connections one last time. Using the Android app "Bluetooth Terminal", I can control the PR2040 to turn a GPIO on and measure the voltage change using a voltmeter. Next, I hot glue every parts in place, and solder the wires coming out from the powering module to the control circuits.

As I am in a rush and I don't have time to order a PCB, this is already the best I can do. Otherwise, I will design a mounting PCB and solder everything in place nice and clean.

After the device is complete and everything is glued in place, I attach the Velcro to the device and give it a try. It fit perfectly and didn't fall down after some movements. (That is not my arm, I just take a picture of some other wearing it)

The next step is developing an app for this. For starter, MIT App Inventor 2 is a great place to started developing your app to control this device. However, due to time limit, I will leave this out for next post.

Have a nice day :)