ENG3020 Advanced Electro Mechanical System Design . Explaining how a circuit works

.Explaining how a circuit works.A vibration plate or “power plate” is an exercise machine that sends high-speed vibrations through all of the muscles in your body. Using a vibration plate combined with a healthy diet and regular cardio will help you to achieve your fitness goals [1]. There are two movement patterns in vibration plates: linear vibration and pivotal oscillation. A linear vibration plate is a spring and eccentric wheels system. The rotation of eccentric wheel generates circular centrifugal force which drives the upper plate up and down in a regular oscillation. A pivotal oscillation plate is essentially a planar four-bar linkage system driven by a motor through a belt. The belt transfers the motor power to rotate the crank wheel. The crank wheel is linked to the upper plate (the rocker) by the coupler bar. As the crank wheel rotates, the coupler bar drags the link point up and down. The upper plate moves exactly like a seesaw swinging on a fixed pivotal axis. The movement is literally called pivotal oscillation [2]. This rotary to reciprocal motion conversion is used in oil pumpjacks [3,4].

A block diagram of the vibration plate control system based on Arduino Uno is shown in Figure 2.

Figure 2. Proposed Arduino Uno controller for a vibration plate

The system in Figure 2 should meet the following user requirements. The user interface consists of a TM1638 breakout board which has 8 pushbuttons, 8 LEDs and 8 Digit Seven Segment Displays. The system has a brushed dc motor, a motor driver circuit and an NTC temperature sensor connected to the case of the motor. When the motor overheats due to long term use or malfunctioning, the case temperature could reach temperatures greater than 70°C reducing its lifespan. The controller must stop the operation of the DC motor when the motor overheats (when the casing temperature exceeds 70°C). The motor driver has a safety protection that measure the current flowing through it. When this current is larger than 3A, the motor should stop and an error message should be displayed in the TM1638 breakout board.

Figure 3. Driver circuit for the DC motor

1. Design a signal conditioning circuit using an NTC thermistor that could measure temperature within 20?C to 100?C with ±3?C of tolerance. The output of this signal conditioning circuit should be interfaced to an Arduino Uno. The NTC thermistor used for this application is a NTC manufactured by Vishay and the ordering number is NTCALUG01A103F804A [5]. [10%]

2. Provide a detail explanation of the DC motor driver circuit in Figure 4. Indicate the purpose of the diode D4 and the DPDT relay component.

3. Design a suitable signal conditioning circuit for the Motor current considering that the reference voltage of the ADC is 5V. The motor control driver circuit is shown in Figure 4 and the current shunt resistor value is 500m?. The output voltage of this signal conditioning circuit should be higher than 4.5V when the current flowing through the motor is 3A and less than 0.5V when there is not current flowing through the motor (0A).

4. Draw a wiring diagram for linking the peripherals and the breakout board to the Arduino, describing the I/O used by Arduino.

5. Implement a TM1638 test program that allows manual control of the vibration plate. By default, the vibration plate is stopped. It starts running when pushbutton S2 is pressed. When running, LED8 is ON and the elapsed time in seconds is displayed in the upper four 7segment digits. The duty cycle as a percentage is shown in the lower four 7-segment digits which is 50% by default. It could be increased or decreased by 5% using pushbuttons S7 and S8 respectively.