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Group 18 Lucas Chokanis Daniel Ramirez Lloyd Harrison Philip Teten
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A Proposal from Researchers to Implement Their Algorithms Design an Experimental Thermostat to Control a Vehicle’s Heating, Ventilation, and Air Conditioning (HVAC) Systems Provide a Control System that is Feasible to adapt for Future Modifications
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Ability to Detect Input: ◦ Temperature of the Vehicles Interior ◦ Temperature of the Blower Motor ◦ Extra Temperature Sensor for Researchers Use Control Output: ◦ Speed of the Blower Motor (High, Med, & Low) ◦ Speed Command of the PMSM Motor ◦ Condenser Fan ◦ Clutch Control Implement a User Interface ◦ LCD Screen and LED’s for Feedback ◦ Push Buttons for User Control
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Electrically Noisy Environment: ◦ Use of Parts that Meet Automotive Requirements 15 ft Transmission Lines: ◦ PMSM Motor Control ◦ Two Remote Temperature Sensors Highly Intuitive Programming: ◦ Giving Researchers Ease of Understanding ◦ Communicating Multiple Temperature Readings Via SPI Bus
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Voltage Received: ◦ 12 to 15 VDC Output to Motors: ◦ 12 VDC Three Speed Blower Motor Control High, Medium, Low ◦ 12 VDC Condenser Fan ◦ 12 VDC Clutch Control ◦ Linear 0 to 2.63 VDC “Step” Speed Command Relays: ◦ Four 15 Amp Relays ◦ One 30 Amp Relay ◦ Coil Voltage of 12 VDC Microcontroller ◦ MSP430 or C2000
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ParametricsMSP430F2274-Q1TMS320F28030LM4F110B2QR Architecture16-bit32-bit Flash (KB)32 Frequency (MHZ)166080 RAM (KB)112 GPIO324443 I2C114 UART118 SPI/SSI124 ADC10-Bit/12 channels12-bit/16 channels12-bit/12 channels RatingAutomotiveStandard
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The chosen microcontroller is the MSP430F2274-Q1 for the following reasons: Ultra-Low power Code Composer Studio IDE Qualified for Automotive Applications Sponsor provided the MSP430 Target board and USB programmer
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Ambient temperature Sensor: ◦ Housed on main thermostat circuit board. ◦ Provides feedback to the user via LCD screen Blower Motor Temperature Sensor: ◦ Remote sensor location. ◦ 15ft away from main board as required by the customer. Its purpose is to keep track of the rate at which the blower motor is cooling. Auxiliary Temperature Sensor: ◦ Remote sensor location (<15ft away from main board).
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ModelManufacturerAccuracy Temp. Range Current Draw OutputPrice $ LM35A Texas Instruments ±0.25ºC -40ºC to 110ºC 60µA Linear Voltage 5.60 LM35CA Texas Instruments ±0.25ºC -40ºC to 110ºC 60µA Linear Voltage 14.61 ADT7420 Analog Devices ±0.25ºC -40ºC to 125ºC 265µA 16-Bit 4.87 ADT7320 Analog Devices ±0.25ºC -40ºC to 125ºC 265µA 16-Bit SPI 4.87 ADT7310Analog Devices ±0.50ºC-40ºC to 125ºC 265µA 16-Bit SPI 4.87 TMP100Texas Instruments ±3ºC-55ºC to 125ºC 45µA2.15
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The chosen temperature sensors were the ADT7320 for the following reasons: Very high accuracy rating on a wide temperature scale. We can expect reliable temperature readings in a cold environment such as the evaporator. User programmable with multiple features Temperature resolution up to 16-bits.
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Extending The SPI Bus for Long Distance Communication: ◦ For the remote sensors, it is possible that propagation delay could be significant enough to hinder data transmission. ◦ Once we attempt to conduct SPI communications at distances greater than 15 feet, we will know if propagation delay will require a hardware solution. ◦ If this turns out to be the case, dual differential transceivers will be used to refresh the clock signal protect the data transfer from noise. ◦ If the signal is fed back to the master from the slave, data transmissions between the master and slave will occur at the same delayed clock signal.
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Although the ADT7320 sensor performed above our expectations, we realized that an initialization subroutine was required for it to function reliably.
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4 Digits 1 Decimal Accuracy
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Driver Uses Less Pin Outs Good for Intuitive Programming B3B2B1B0LCD Display 00000 00011 00102 00113 01004 01015 01106 01117 10008 10019 1010- 1011E 1100H 1101L 1110P 1111(blank) D1D2D3D4Function 0000No Change 0001Store Data in Latch 4 to be Displayed in Digit 4 0010Store Data in Latch 3 to be Displayed in Digit 3 0100Store Data in Latch 2 to be Displayed in Digit 2 1000Store Data in Latch 1 to be Displayed in Digit 1 1111Store Data in All Data Latches, Display All
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View Changing: Scroll Through
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Temperature Set for Nominal Setting
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Setting the Blower Motor State
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Solid-State Relays (SSRs) Vs. Electromechanical Relays: Relay TypeProsCons Solid-state Faster switching times Increased lifetime (no moving parts) Bounceless switching No sparking or arcing Silent operation Higher ON resistance (more power dissipated) Small OFF resistance (small reverse leakage current) Fails “short” Electromechanical Lower ON resistance (ohmic contacts) Higher OFF resistance (no current flow) Fails “open” Noisy Shorter lifetime (10^5 to 10^7 switching cycles) Switch bouncing Arcing across contacts
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Motor Control: Choosing Relay Current Rating DC Supply Voltage (V) LO-speed Current (A) MED-speed Current (A) HI-speed Current (A) 12.05.78.615.0 12.55.98.915.6 13.06.29.016.1 13.56.49.316.9 14.06.69.517.4 14.56.89.818.0 15.07.19.918.7 Blower motor current draw (low, medium, and high speeds) Note: Highlighted values are interpolated values due to limitations in test equipment.
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Motor Control: Choosing Relay Current Rating Condenser Fan Motor Current Draw DC Supply Voltage (V) Motor Current (A) 12.07.0 12.57.5 13.07.9 13.58.2 14.08.7 14.59.1 15.09.4 Note: Highlighted values are interpolated values due to limitations in test equipment.
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P/S section:3.3V5V Items Drawing Current 6.5 mA – MCU50 uA – LCD driver 795 uA – Temperature sensors (3 x 265uA) Total per section:7.3 mA50 uA Design current limit: 10 mA1 mA P/S efficiency:91 %84 % Current Draw
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3.3V P/S EFFICIENCY 5V P/S EFFICIENCY
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Load Supply Voltage (V) Supply Current (mA) 3.3V Output Current (mA) 5V Output Current (mA)Efficiency (%) Minimum121311.39.7755.2 151211.39.8348.0 Medium121112.26.3954.7 151012.26.3948.1 Maximum12 12.86.8153.0 151112.86.8146.2 Regulator Efficiency
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Item PriceQuantitiyPaidTotal Microcontroller - MSP430F2274-Q1 Free Sample1Yes- Temperature Sensors - ADT7320 $ 4.873Yes $ 14.61 PCB by PCBFabrication.com $ 76.006Yes $ 457.00 LCD Display - Lumex LCD Free Sample1Yes- LED for User Interface Owned8Yes- Push Buttons for User Interface $ 0.195Yes $ 0.95 Dual Differential Driver - DS90LV027AQMA Free Sample2Yes- Dual Differential Receiver - DS90LV028AQMA Free Sample2Yes- Shielded Twisted Pair - C1352-100-ND $ 66.961Yes $ 66.96 NPN transistor 200mA ICmax, 40V Vce(breakdown), through hole $0.1710 Yes $ 1.74 Switching Regulator - TI LM26003 Free Sample3 Yes - Relay automotive SPST 12V, 15A$1.796Yes $ 10.74 Relay automotive SPST 12V, 30A$5.022Yes $ 10.04 Capacitors $2.5065 Yes $ 17.47 Diode, Schottky 40V 30mA, through hole $0.665 Yes $ 3.30 Inductor 1mH, 10% through hole $2.793 Yes $ 8.37 Resistors $0.7277 Yes $ 6.79 TSSOP-20 to DIP-20 SMT Adapter (for TI LM26003 chip) $4.492 Yes $ 8.98 TOTAL $ 606.86
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