ARDUINO BASED VIRTUALBENCH USING PC OR TOUCH PAD

ARDUINO BASED VIRTUALBENCH USING PC OR TOUCH PAD AS DISPLAY Project ID: FYP_HD_01 Supervisor: Dr. Roland Siu-kwong IP Member: Chan Tze Kin, Jacky Li Lok Si, Shalott Lam Yuen Ching, Suki (14073736 D) (14074109 D) (14075205 D)

Background ▪To reduce cost ▪To reduce size ▪To allow students to conduct experiment everywhere ▪Arduino MEGA 2560– low cost and small microcontroller

Objectives Functions : ▪ Multimeter Voltage: 0 -5 V Current: 0. 01 -0. 5 A Resistance: 0 -100 kΩ ▪ Programmable DC power supply Output voltage: 0 -5 V ▪ Virtual oscilloscope Sinusoidal, square and triangular waveforms Frequency: 0 -500 Hz, voltage ranging from -5 V to +5 V

Objectives (Cont’d) ▪Virtual function generator Sinusoidal, square and triangular waveforms Frequency: 0 -10 k. Hz, voltage ranging from -5 V to +5 V User interfaces : ▪Visual Studio Graphical User Interface (GUI) ▪Portable TFT touch shield

System Diagram

Multimeter Voltage measurement ▪ Internal analog-to-digital converter circuit of Arduino ▪ Digital numbers from 0 to 1023 ▪ limit of measurement value = 5 V ▪ one unit read by Arduino : 5÷ 1023 ≈ 4. 8876 m. V E. g. 1023÷ 5 ≈ 204 is equivalent to 1 V Voltage measurement for AC ▪ Compare voltage values and find the amplitude ▪ Root-mean-square value = amplitude / root 2

Multimeter (Cont’d) Current measurement ▪ ohm’s law: I = V÷R ▪ 1Ω test resistor ∵ little voltage drop and power loss ▪ I=V Current measurement for AC ▪Compare voltage values and find the amplitude ▪Root-mean-square value = amplitude / root 2

Multimeter (Cont’d) Resistance measurement ▪ voltage divider calculation: ▪ Auto ranging circuit ▪ If the Rx ≈ input resistance Vout will be (supply voltage – 0. 7)÷ 2 ( 0. 7 is the general voltage drop of a diode) ▪ Arduino switches the input resistance to estimate the nearest value

DC power supply ▪ Arduino internal function: Pulse Width Modulation (PWM) 0 -5 V, square wave DC supply ▪ PWM to voltage converter circuit ▪ The gain is (1+R 2/R 1) ▪ Gain of 2 to obtain 0 -10 V supply ▪ R 2=R 1=10 kΩ

Virtual function generator ▪ Arduino Mega 2560 send HIGH signal to Arduino Uno ▪ Signal pass through resistors to generate waveform ▪ Low pass filter (R+C) for pure waveform ▪ Frequency tuning ▪ 500Ω variable resistor ▪ Amplitude tuning ▪ 50 kΩ variable resistor

Virtual oscilloscope ▪ Similar to voltage measurement ▪ Involve curve plotting on GUI and touch shield ▪ Voltage read by Arduino ▪ Send to GUI and touch shield for curve plotting ▪ Touch shield display: ▪ C programming language ▪ GUI display: ▪. Net framework settings

Difficulties encountered Current measurement ▪ Original method: The AD 623 AN Instrumentation Amplifier was used to boost the voltage ▪ Advantages: Increase the resolution Extend the range of value measurement ▪ Problem: Uncontrollable gain ▪ Solution: Use simple circuit with only a test resistor

Experiment (Multimeter, Virtual oscilloscope) Step 1 DC supply, Experimental board, Function generator Step 2 Measure by the project and display on GUI and touch shield Step 3 Control experiment by real digital multimeter and oscilloscope Step 4 Compare readings of project and existing laboratory apparatus

Experiment (DC power supply, Virtual function generator) Step 1 Command through GUI and touch shield Step 2 Measure the output using existing laboratory apparatus Step 3 Compare commands to the project and readings of the measurement

Results ▪ Ranges of measurement by Multimeter ▪ Voltmeter: 0 -5 V ▪ Ammeter: 0. 01 A to 0. 5 A ▪ Ohmmeter: 0 -50 kΩ ▪ Output range of DC power supply: 0 -10 V

Results ▪ Virtual oscilloscope Sinusoidal wave Square wave Triangular wave Frequency 0 -300 Hz Vpp 0 -10 V ▪ Virtual function generator Sinusoidal wave Square wave Triangular wave Frequency 50 -3 k. Hz 200 -3 k. Hz Vpp 0. 8 -2. 7 V

Discussion Problems: ▪ Low accuracy and limited range of current measured by ammeter ∵ Small test resistance results in low voltage for the Arduino's Analog Input pin ▪ Limited range of frequency measured by virtual oscilloscope ∵ Low speed of communication port reading

Discussion (Cont’d) Problems: ▪Remarkable noise in virtual oscilloscope ▪Limited range of frequency of waveforms generated by virtual function generator ∵ Restricted Switching frequency of PWM in Arduino board Limitation of 500Ω variable resistor

Discussion (Cont’d) Improvements: ▪ Ammeter ▪ Investigate methods for controlling the gain of AD 623 AN Instrumentation Amplifier ▪ Virtual oscilloscope ▪ Find the source of noise and reduce it ▪ User interfaces ▪ More detailed and flexible characteristic can be modified by users

THE END THANK YOU