1. Thermal and Power Management of Industrial LCD Panels

2. Team Members Dustin Collins – Group Leader Enclosure and Hardware
Brian Post
Software
Patrick Hensley
Hardware/Ladder Logic
Zack Linkous
Hardware/Firmware

3. Background
All electrical devices emit some level of heat as loss during operation
Generally undersired
Generally the problem is resolved by using fans and heatsinks so push heat out of the enclouse through vents

4. Background Not all enclosures can have vents though.
The enclouse, especially metal ones can disipate heat on their own, however it may not be enough.

5. Background
In an industrial setting where the ambient temperature is already elevated the additional heat generated by any enclosed electrical system can push the components to their thermal limits
In addition having sealed enclousres can be considered a crucial factor for the environment

6. Background
The buildup of heat can lead to reduced lifespans of components
Electrolytic capacitor lifespans are heavily dependent on temperature
It can also lead to premature failure of parts in the most severe cases

7. Background
In order to remove the heat from the enclosure we chose to add a thermoelectric based cooling system.
Solid State
Light Weight
Relativley low cost

8. Background
In an LCD the backlight and the inverter generate the bulk of the heat loss of the components
In addition, industrially rated LCDs are sealed off from the enviroment making them much harder to keep at desired operating temperatures.

9. Background
The addition of a solid state cooling system allows for LCD to be kept within a desired operating temperature while keeping the system completely enclosed

10. Defining Terms Used
Peltier Cooler – A solid state device that generates a thermal gradiant in response to a current applied to it.
Enclosure – A sealed metal box that is unable to have convection cooling (vents in the box itself)

11. Discussion
In order to operate the solid state cooling system several components are needed
Temperature sensors
Fans and heatinks for the Peltier Coolers
Peltier Coolers
Controller

12. Discussion – Temperature Sensors
Off the shelf analog output sensors were used
Transfer Function of the Sensors is given as
Vout = ( *Temp(in Celcius))V
For our expected operating range (10-55 Celcius) sensors will produce V
Sensors are capable of operation up to 100C
At which point they output 3.05V

13. Discussion – Peltier Coolers
Develop a temperature gradiant in response to a current passing through it.
Electrically they can be modeled as a resistor
Resistance is provided in datasheet for device
The amount of heat that is transfered with a Peltier Cooler in given by W = P*I*t
W is watts, P is the Peltier Coeffecient, I is current, and t is time.

14. Discussion – Peltier Coolers
Our Peltier Coolers are rated at 8.5A continuous at 15.4V
130W input power.
Have a Peltier Coeffecient of .64
With 130W input can get 36W of net cooling (Takes into account the losses with the Peltier Cooler)
Ineffecient, but solves the problem
Device resistance of 1.5 Ohms

15. Discussion – Fans/Heatsinks
For proper Peltier Cooler operation the heat from the hot side needs to be removed outside and the cold side needs to be warmed up on the inside.
Need 130W of cooling on the outside of the panel to remove heat from the hot side
Need 36W of “warming” on the inside to add heat to the cold side
Since it is assumed the enclosure is metallic it can act as part of a heat sinking system.

16. Discusstion – Fans/Heatsinks
The enclosure can act as a large heatsink itself
Strategic fan placement on the inside of the enclosure can circulate the air on the inside and allow for the enclosure to act as a heatsink and remove hot spots on the inside

17. Discussion - Implimentation
Fan Driver Circuit

18. Discussion – Fan Control Circuit
Each fan bank has a MOSFET driver circuit assosciated with it
The digital inputs to the fans are optically isolated via opto-isolators
The driver circuits are designed as active low
Applying a voltage greater than 3.0V will pull down the voltage applied to the gate of the MOSFET turning it off.
Applying a voltage less than 1.0V will pull up the voltage
Input voltages between 1.0V and 3.0V are considered invalid
LED’s added to show that the corresponding fan is on

19. Discussion – Implimentation
Peltier Driver Circuit

20. Discussion – Pelteir Driver Circuit
Fundamentally the same circuit as the fan driver
Designed with larger MOSFETs to accomidate the higher power requirements of the Peltier Coolers

21. Discusstion – Controller Implientations
PLC Based
Microcontroller Based

22. Discusstion – Controller Implientations
PLC Implimentation
Intended as a solution for large industrial settings
The many built in function blocks allow for simplification of programming
Easily field modifiable by technicians with appropriate software
Easily networked
Many industrial approvals can be attractive to customers

23. Discussion – Controller Implimentation
Microcontroller
Much lower hardware cost compared to a PLC
Higher development cost
Intented to serve as a low cost option for installations that may be remote/isolated or ones that are meant to be sent fully assembled.

24. Discusstion – Controller Logic
Up to 45 Celsius no fans or Peltier Coolers are turned on
At the 45 Celsius fans turn on to circulate air inside the enclosure to help cool it off
At 50 Celsius one Peltier Cooler and it’s cooling fan turn on to help cool down the system
At 55 Celcius a second Peltier Cooler turns on to further the amount of cooling provided
At 60 Celsius an audio and visual warning is given
At 65 Celsius an automatic shutdown is preformed to prevent damage

25. Discussion – Controller Logic
All components shut off with a 5 degree hysteresis

26. GUI Integration
The controller and computer program communicate through a port.
Controller and program both send and receive information.
The GUI receives updates as to what is happening in the LCD panel.
This includes temperatures, fan states (on/off), thermopile states, etc.
It also sends commands from the program user. (manual control)
This includes turning fans or thermopiles on or off, and shutting the LCD down in case of overheating.
The GUI mostly receives data from the controller and as to how it is interpreted will be detailed in the design slide.

27. GUI Design
Main function- Initializes and constructs the user interface.
Opens a specified port and listens on it until it receives data from the controller.
Data is interpreted, checked against preset temperature ranges, then displayed as appropriate (detailed in flowchart).
Displayed temperature values can be converted between C and F.
At specific intervals a time stamp and information will be written to a log file.
Interrupts can occur at anytime. This mostly happens when the user is operating the control panel.

28. GUI Flowchart

29. GUI Display

30. Data Logging Format

31. Conclusions
Individual components have been tested and found to be functioning
Give statisfactory performance as individual units
Time will be invested in improving the prototype box and doing performance analysis on the box
Emphisis on testing the unit as a whole once comlpete

32. Questions