P.H.A.N.S PWM HUB AIR-COOLED NOISE-REDUCTION SYSTEM GROUP MEMBERS: ADAM PALERMO, BRIAN HANSEN FACULTY ADVISOR: DR. ARASH TAKSHI INDUSTRY ADVISOR: DANA RODAKIS

Introduction  Adam Palermo, 25, Test Support Engineer I, Raytheon employee for over 5 years  Brian Hansen, 33, Field Engineer II, Raytheon employee for over 7 years

SCOPE Objective:  Establish the electrical specifications, software algorithm behaviors, and platform requirements of P.H.A.N.S. Non-Objective:  Specify mechanical performance and hardware dimensions of P.H.A.N.S.

Problem Statement Root-Cause Analysis  PC case cooling fans on a high performance system can be noisy. Why?  They are operating at ‘full throttle’ at all times. Why?  There is no system to control the speed of the fans based on the temperature of the PC. Why?  Most motherboards do not support temp/speed control of multiple (x10) PC fans. How do I fix this problem?  Buy a COTS system or design a stand-alone temperature-proportional fan speed control system.

Overview  Modular temperature-proportional fan speed controller  Offers acoustic noise reduction  Efficient PWM fan drive  Fault detection circuitry  Operational data via a LCD digital display to the user

Proposed Design  Independent control per zone (5 Zones)  Temperature and fault sensing at each zone  PWM fan speed control provided by microcontroller  Control unit with LCD Display module installed at an unused 5.25 inch expansion slot.  Menu selectable fan speed, temperature, duty cycle, and fault data.

Functional Block Diagram

User Interface

Hardware Interface and Control  Industry standard connections  4-Pin Molex peripheral connector  4-Pin Molex CPU fan header  USB type B  Temperature sensor header  LCD display module header

Microcontroller  Arduino MEGA 2560 R3  This project and prototype development module will provide the entire microcontroller platform. It is based on the Atmel ATmega2560 and provides 54 digital input/output pins (of which 15 can be used as PWM outputs), 16 analog inputs, 4 UARTS, a 16MHz crystal oscillator, a USB connection, a power jack, an ICSP header, and a reset button.

Electrical Specifications

Fan Speed Control Methods PWM Fan Speed Control (PWM)  Speed control by varying the duty cycle of a fixed frequency pulse train  Typical fixed frequency 30Hz  Duty cycle: 0% to 100%  Pulse train will drive the gate of an N-channel MOSFET

Fan Speed Control Methods Fan Start-up  Fan’s inertia must be overcome at start-up  Cannot apply PWM duty cycle from rest position  Instead, apply full rated voltage to fan for one second

Fan Speed Control Methods PWM Frequency & Duty Cycle Control  Frequency controlled by software and internal timers of uP  Duty cycle is proportional to the temperature  Temperature (V TEMP) read at GPIO of uP

Fan Speed Control Methods Minimum Speed  Sets a threshold for a minimum duty cycle  Fan will remain at minimum duty cycle even when the temperature continues to decrease  Some fans cannot operate below a certain duty cycle

Fan Speed Control Methods PWM OUT Output  Will drive the gate of a N-channel MOSFET  PWM output will be designed to quickly raise the gate voltage to final value  When microcontroller is in shutdown mode, the PWM output is held actively low  When the MOSFET is turned off quickly, the current in the fan will continue to flow in the same direction and will cause the voltage at the drain of the MOSFET to rise above the drain-to-source voltage rating of the MOSFET. For this reason, a clamp diode will be used

Temperature Sensor Design  V TEMP range of 0.56 to 4.44 volts  NTC thermistor (R T ) provides temperature variant voltage  Temperature dependent voltage divider circuit  As temperature increases, value of R T decreases and the voltage at the uP GPIO increases  R 1 helps to linearize the response of the sense network and aids in obtaining the proper voltages over the desired temperature range

Sensing Fan Operation  SENSE (GPIO) of uP is an analog input used to monitor fan operation  Senses fan current pulses, which represent fan rotation  Commutation of the fan current occurs as the fan pole passes the armatures of the motor  When a pulse is detected, the missing pulse detector timer is reset  If the missing pulse detector timer reaches 32 cycles, the loop for diagnosing a fan fault is engaged

Sensing Fan Operation  Fan current waveforms can be sensed using the scheme shown  The fan current flowing through R SENSE generates a voltage proportional to the current  The C SENSE capacitor removes any DC portion of the voltage across R SENSE and presents only the voltage pulse portion to the uP  The op-amp will amplify the waveform to a CMOS level.

Software Behavior Algorithms

LCD Display Module  RioRand LCD Module RRLCD204WB  20 Characters X 4 Rows  Arduino Support

Parts List

Dependencies and Assumptions  The user must provide a computer case that can accommodate up to 10 optional cooling fans  An unused 5.25 inch expansion slot must be available  The computer power supply harness must provide a spare 4-pin Molex peripheral connector  The computer power supply must support the added power requirements of the P.H.A.N.S unit as well as any added cooling fans  The user has general computer hardware knowledge or can hire the services of a professional computer technician to install the system

Test Plan  Identify subsystems & critical components to be tested or not tested  Evaluate risks of above  Develop data collection plan (sample 1 out of 100 widgets?)  Review measurement equipment and capabilities  Construct test procedure  Define pass/fail criteria  Provide troubleshooting guide

Website 

Hardware Demo  Removed due to upload size restrictions

Q&A