Circuit design consists of 5 stages
. Specification
The initial specification is basically a technically detailed description of what the customer wants the final product to offer. The product is aimed to measure the knee angle with high accuracy and warn the user if the knee angle is not in the range of defined angle while exercising. The stage requires preparing the components list. The component list has been prepared based on project goal and are listed below.
1. LEDs
Three LEDs have been used for serving different purposes. They give the user visualization feedback. Green LED will be turned on if the movement of the knee is in the defined range. Red LED is used for warning the user if exercise is not executed correctly and yellow LED counts correct movements.
2. Resistors
Four resistors have been used in the circuit. Yellow and Red LEDs have been connected to ninth and sixth pin of Arduino respectively with 220 Ω resistors. Green LED is connected to fifth pin of Arduino with 330 Ω resistor and flex sensor is connected to input pins of Arduino (VCC and PC3/ADC3) with 22 kΩ resistor.
3. Flex sensor
Flex sensor measures the knee angle with high accuracy. Due to the wide range of angle which can be measured with flex sensor, it is the best option for making smart knee cap.
4. Arduino Uno R3
Arduino Uno can be easily programmed and it is reasonably priced which makes the final product cheap and usable for everyone.
. Block diagram
The process normally begins with the conversion of the specification into a block diagram of the various functions that the circuit must perform.
. PCB design
This stage normally consists of designing the circuit in software. Many software can serve our purposes, however due to simplicity KICAD has been used for designing the circuit.
. Manufacturing printed circuit board
Final design will be transferred to the computer which is connected to 3D printer. 2-sided copper-clad PCB board is cut into desired size and then transferred to the machine.
Implementation
The last stage includes soldering the components on the prepared PCB.
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