Experimental Engineering Thermal Control System

(EETCS)Group 18

Lucas ChokanisDaniel RamirezLloyd Harrison

Philip Teten

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

Motivation

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

Objectives

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

Challenges

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

Specifications and Requirements

The Proposed System

Microcontroller

Parametrics MSP430F2274-Q1

TMS320F28030

LM4F110B2QR

Architecture 16-bit 32-bit 32-bitFlash (KB) 32 32 32Frequency

(MHZ)16 60 80

RAM (KB) 1 12 12GPIO 32 44 43I2C 1 1 4

UART 1 1 8SPI/SSI 1 2 4

ADC 10-Bit/12 channels 12-bit/16 channels 12-bit/12 channelsRating Automotive Standard Standard

Microcontroller

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

Microcontroller

Temperature Sensors

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).

Temperature Sensors

Model Manufacturer

Accuracy

Temp. Range

Current Draw

Output Price $

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-BitSPI

4.87

ADT7310

Analog Devices

±0.50ºC -40ºC to 125ºC

265µA 16-BitSPI

4.87

TMP100 Texas Instruments

±3ºC -55ºC to 125ºC

45µA 2.15

Temperature Sensors

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.

Temperature Sensors

Temperature Sensors

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.

Temperature Sensors Communication

Temperature Sensors Communication

Although the ADT7320 sensor performed above our expectations, we realized that an initialization subroutine was required for it to function reliably.

Sensor Initialization

User Interface

User Interface

User Interface 4 Digits 1 Decimal Accuracy

LCD Display and Driver Driver Uses Less Pin Outs Good for Intuitive Programming

B3 B2 B1 B0 LCD Display

0 0 0 0 00 0 0 1 10 0 1 0 20 0 1 1 30 1 0 0 40 1 0 1 50 1 1 0 60 1 1 1 71 0 0 0 81 0 0 1 91 0 1 0 -1 0 1 1 E1 1 0 0 H1 1 0 1 L1 1 1 0 P1 1 1 1 (blank)

D1 D2 D3

D4 Function

0 0 0 0 No Change0 0 0 1 Store Data in Latch 4 to be Displayed in

Digit 40 0 1 0 Store Data in Latch 3 to be Displayed in

Digit 30 1 0 0 Store Data in Latch 2 to be Displayed in

Digit 21 0 0 0 Store Data in Latch 1 to be Displayed in

Digit 11 1 1 1 Store Data in All Data Latches, Display All

LCD Display and Driver

User Interface View Changing: Scroll Through

User Interface Temperature Set for Nominal Setting

User Interface Setting the Blower Motor State

User Interface

PMSM Communication

PMSM Communication

Power and Motor Control

Solid-State Relays (SSRs) Vs. Electromechanical Relays:

Motor Control

Relay Type Pros ConsSolid-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

Motor Control: Choosing Relay Current Rating

Motor Control

DC SupplyVoltage

(V)

LO-speedCurrent

(A)

MED-speedCurrent (A)

HI-speedCurrent

(A)12.0 5.7 8.6 15.012.5 5.9 8.9 15.613.0 6.2 9.0 16.113.5 6.4 9.3 16.914.0 6.6 9.5 17.414.5 6.8 9.8 18.015.0 7.1 9.9 18.7

Blower motor current draw (low, medium, and high speeds)

Note: Highlighted values are interpolated values due to limitations in test equipment.

Motor Control: Choosing Relay Current Rating

Motor Control

Condenser Fan Motor Current Draw

DC SupplyVoltage

(V)

Motor Current

(A)

12.0 7.012.5 7.513.0 7.913.5 8.214.0 8.714.5 9.115.0 9.4

Note: Highlighted values are interpolated values due to limitations in test equipment.

Motor Control

P/S section: 3.3V 5V Items Drawing Current

6.5 mA – MCU 50 uA – LCD driver795 uA – Temperature sensors (3 x 265uA)

 

Total per section: 7.3 mA 50 uADesign current limit:

10 mA 1 mA

P/S efficiency: 91 % 84 %

Power

Current Draw

Power

3.3V P/S EFFICIENCY 5V P/S EFFICIENCY

Power

Load

SupplyVoltage

(V)

SupplyCurrent

(mA)3.3V OutputCurrent (mA)

5V OutputCurrent (mA)

Efficiency (%)

Minimum 12 13 11.3 9.77 55.2

15 12 11.3 9.83 48.0

Medium 12 11 12.2 6.39 54.7

15 10 12.2 6.39 48.1

Maximum 12 12 12.8 6.81 53.0

15 11 12.8 6.81 46.2

Regulator Efficiency

Power

Power

Power

The Proposed System

Board Layouts (Board 1)

Board Layouts (Board 2)

Administrative ContentItem Price

Quantitiy

Paid Total

Microcontroller - MSP430F2274-Q1 Free Sample 1 Yes -

Temperature Sensors - ADT7320 $ 4.87 3 Yes $ 14.61

PCB by PCBFabrication.com $ 76.00 6 Yes $ 457.00

LCD Display - Lumex LCD Free Sample 1 Yes -

LED for User Interface Owned 8 Yes -

Push Buttons for User Interface $ 0.19 5 Yes $ 0.95

Dual Differential Driver - DS90LV027AQMA Free Sample 2 Yes -

Dual Differential Receiver - DS90LV028AQMA Free Sample 2 Yes -

Shielded Twisted Pair - C1352-100-ND $ 66.96 1 Yes $ 66.96 NPN transistor 200mA ICmax, 40V Vce(breakdown), through hole

$0.17 10Yes $ 1.74

Switching Regulator - TI LM26003 Free Sample 3 Yes -

Relay automotive SPST 12V, 15A $1.79 6 Yes $ 10.74

Relay automotive SPST 12V, 30A $5.02 2 Yes $ 10.04

Capacitors $2.50 65 Yes $ 17.47

Diode, Schottky 40V 30mA, through hole $0.66 5 Yes $ 3.30

Inductor 1mH, 10% through hole $2.79 3 Yes $ 8.37

Resistors $0.72 77 Yes $ 6.79

TSSOP-20 to DIP-20 SMT Adapter (for TI LM26003 chip) $4.49 2 Yes $ 8.98

TOTAL $ 606.86

Research

Design

Fabrication

Coding

Testing

Parts Ordered

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Progress

Questions?