Prosthetic Arm and EMG

I have always wondered, how something so difficult, like prothesis is made. Well, now as I know a little bit of electrical engineering, I got this the answer. The secret lies in EMG sensor - it detetcts electrical impulses in the muscles, then amplifies and filtrates them and this signals go to the microcontroller. There these signals are evaluate and move servos. Pretty simple, right? But it's true only for cheap prothesis. Advanced one is far more difficult...

I wanted to make something interesting, so I added TFT screen, which can show different information like time, date, tempreture, humidity, gesture controll and battery life (Didn't finish last two thigs, though. I was in hurry as it was for my engineering conference).

Here we don't need a large list of components:

Resistors - 3x10k, 2x1M, 220, 2x100k

2xLM324 (Amplifier)

One can of soda (or other aluminium thing)

ESP32

4xServo

2xButtons

TFT Screen

Time and date module

Temperature and humidity module

Strings

I used very simple ciruit of EMG sensor without filtering. This won't really make our sensor worse, but before using it, you'll need to use some water on your hand so it would be more sensetive. As you can see on the second picture, I used aluminum cuts for electrodes. Mainly, you need water because of such electrodes, but you can buy better ones online, which I recommend. But if you don't really want to spend more money, you can just cut soda can (or other aluminium object) to get those.

I've soldered everything straight away. But you shouldn't do that! LM324 will be damaged due to extreme tempreture of soldering iron. Use IC holders.

Now we can move to the "brain" of our prothesis - ESP32. It would control our display and servos and it would get signals from EMG and modules (I didn't include tempreture and time modules on the circuit, but they are easily connecte, so I hope, you won't have problems with that). We'll need to upload a code for this thing to work. That will be a few steps futher.

Here are 3D models of every part of prothesis (I found them on the internet. You can use different model if you want). After you connect them together, you need to put strings into fingers and wipe them with servos, so they can pull fingers down. You can attach servos to the prothesis using different methods. I used scotch tape.

Here's the code for ESP32

You can solder these components straight away

For me, it was pretty hard project, but it was very interesting! Hope, you'll get such kind of joy from creating as well.