Final Design

Our solution to this problem was broken down into two main sections: the circuit and the form factor. The conduction of a neuropathy test can be implemented with the circuit alone, albeit unconventionally, while the form factor dictates the interface between patient, operator, and the circuit.

The Circuit

As mentioned, the circuit contains all of the components crucial components for conducting the test. In our final design, the circuit included the following:

In a brief overview the circuit works in the following way. The same process is listed in the flowchart below to visualize the code run on the Arduino.

1. Operator switches on the power, and the Arduino immediately enacts a controller that sends a PWM signal via MOSFET through the 3.3 Ohm resistor. The fan disperses the warm air. The controller will continue to run and maintain the housing at 30 degrees C. Sensor data is taken from thermistors to calculate the error in the controller.

2. The operator will position the patient’s hand and the heating source as needed by the form factor, discussed later.

3. A start button is pushed: the ultrasonic sensor calibrates the distance to the patient, and the focal heat source begins heating the finger at 1 deg C/sec.

4. The patient will pull away when they feel pain. The IR sensor will trip. After confirming with the Ultrasonic that the patient has removed their finger, the focal heat source will turn off and the Arduino will send the time of the test and the temperature to the LCD screen. This temperature is recorded by another thermistor positioned over the second bulb, which runs in parallel to the bulb heating the finger.

5. The system resets, and maintains the housing at 30 degrees until power is removed. The LCD will indicate when it is ready for a new test to start.

The Form Factor

The form was very similar to the setup of the original rodent testing boxes. Its dimensions are 11’’  x 11’’ x 6’’ high. This is still rather large, but was designed at first so any hand, despite of its size, could rest comfortably on the glass on top. The components are as follows:

In terms of the box’s integration with the circuit, the components are housed a small container under the glass. The 2 halogen bulbs are placed symmetrically about the center of the glass so that the parallel bulb will have the same thermal boundary conditions as the one under the patient’s finger.

Performance (TBD)