Wiring Arduino, actuator, muscle sensor or potentiometer: In this next step we wire up all the components and get it ready to test out and install on the 3D printed brace. 

NOTE: These instructions are for the Arduino-based version which is not the latest version and does not include the machine learning and pattern recognition approach we are taking to pick up muscle signals. It is therefore not suitable for use cases where the muscle signal strength is really weak. If you are want to build the more advanced version, please help us complete the final challenges we are working on: Help Needed.

Wiring Arduino + Potentiometer
Using something like a potentiometer may be an easy way to get a usable device working really quickly. A Potentiometer is a Radio-dial-like knob that you can turn and which can simulate the type of signal we could get from a muscle. You turn it one way and the arm will pull up, you turn it the other way and the arm will go down again.  This 'knob' could be mounted on the arm brace, or if the user has movement in their fingers like my daughter has then you could potentially mount it on their hand. 

We tested out various different approaches using switches and other things but this circuit and approach worked the best. We found the following site that we used to help us: http://www.silvinopresa.com/how-to/arduino/control-a-servo-with-arduino-and-a-potentiometer/   

Wiring Arduino + Muscle Sensor
If you have a strong muscle signal to use then you could try the using a MyoWare muscle sensor to control the actuator. In our case, this only worked for me and not my daughter as her signals were just too weak.

However, if you want to test this out, here is a video we used to figure out how to do that:  https://youtu.be/-JYi08WKe6c

Wiring for mobility and ease of use
The above wiring is not suitable for real world use other than for testing. So the next step is to test out if the circuit works (After finishing step 6) and if it does, to come back here and make some final adjustments. 

  1. You may want to consider making a case for the Arduino and batteries. We looked here for inspiration: http://hackaday.com/2014/05/09/diy-arduino-cases-you-never-knew-existed/ 

  2. Next, you will want to make connecting and disconnecting the muscle sensor and batteries really easy. We did this by using the male and female PCB connectors we got with the Arduino starter kit.  Make sure the wire length is long enough so that the batterie and Arduino can be kept in the pocket. or on a belt.


Optional - Help build next version
The next version of the assistive arm that we are currently working on will not use the Arduino, potentiometer or the MyoWare muscle sensor but rather a series of electrodes that will provide a Raspberry Pi up to 8 separate raw signals from the limb. The onboard software will learn to recognize the unique signals being produced by the limb and use those to control the assistive device. 

With this approach, we were able to consistently pick up my daughter's muscle signals! If you want to help us with this challenge please go to this page: Help Needed.


Step 1 - Understanding the problem
  Step 3 - Measurements & 3D designing