
	Thermostats Tutorial		3/25/91

1.This helpfile is displayed when you are in this .../tutorials/thermal
  Use the scrollbar on the right edge of this help to move up or down
  through this multi-page (15 step) tutorial.  Click in this scroll bar
  with the Left button to move down, right button to move up.

  With the cursor in this scrollbar you can also use the keyboard 
  uparrow and downarrow key to scroll up/down single lines.

  With the cursor inside of this window, (NOT within the scrollbar)
  you can quit this tutorial with the <F3> key, scrolldown with
  the <F1> key or scrollup with <F2>.

  IF YOU ACCIDENTLY "DONE" this help window and need to redisplay it
  type the following Allegro command:

        help tutorial

  If you quit Allegro or otherwise terminate this tutorial you will
  probably want to cleanup the ~/atutorial/ directory to conserve disk
  space, although users might want to preserve files for experiments
  beyond the tutorial instructions.

  You might also want to print out hardcopy of this file: 

    /usr/valid/tools/allegro/tutorials/thermal/tutorial.hlp    

  or view edit it in a separate window so you can record 
  numbers or make notes as a thorough tutorial student.

2.A.   As it starts, this tutorial automatically opens routed.brd 
       under the icons:       Design->Analyze->Thermal
       (thermal is displayed in the window upper left)

 Note: Thermal is designed to be easy to startup with no setup
       barriers to execution.  Of course proper setup is 
       required for accurate results.

  B.   To see the ease of defaulted execution simply pick (with the
       middle mouse button)  the  "EXECUTE"  menu option. 
       (Execute only takes about 15 seconds, even on slow systems) 

  Note: That several messages appear during execution ending with
        "Mean Time between Failure" prediction. Also displayed are
        the generated isotherm lines and hotspot rectangles. 
        This first display is mostly red because the color setup 
        for isobars and hotspots is tuned later in this tutorial.

  C.    Feel free to window in if you want to see the isotherm lines
        or hotspot boxes more clearly. (Thermal is fully integrated
        with normal Allegro interaction and you often want to iterate
        between component placement and thermal executions.)

3.In a separate Unix window in this same directory (Perform several
   left button clicks the arrow at the screen lower left to get to the
   Allegro top level "Shell" icon, and click Shell to bring up
   this Unix window.  If you are using a prior window be sure to
   cd ~/atutorial/thermal  )


          more th_report.txt

  Note that for each component the J_TEMPERATURE and C_TEMPERATURE
  (Junction and Case, temperatures in Centrigrade) are predicted.  
  Also note how the POWER_DISS  in watts is reported for each instance. 
  This is an input to the temperature calculation.

  For refdes R28 in th_report.txt what is the ?

      J_TEMPERATURE ________________________  
      C_TEMPERATURE ________________________  
      FAILURE_RATE  ________________________  
      POWER_DISS    ________________________  

4.Bring up ALLEGRO's  interactive "Define Reference 
  Designator Properties" with the softkey:

        Define->Property_REFDES

  HOld down the middle button with the cursor in the box to the left
  of J_TEMPERATURE and PULLDOWN to select "Show Current" before releasing.
   
  This produces a "Show J_TEMPERATURE" window" which you can scroll
  through picking(left button scrolldown,right button scroll up) the
  scroll bar on the right side of the window.

  Verify that the R28 J_TEMPERATURE is the same as  the report above.
  Show and verify the C_TEMPERATURE for R28 also.
  (Pick C_TEMPERATURE for show current pulldown, hint  R28 is near the
   bottom of the show message.)

  Scroll to find the MAX_POWER_DISS Refdes property line.
  Try and show current the MAX_POWER_DISS properties, note that none 
  exists.  (With no explicit power property on the instance a library 
  definition of power was used. )

  Use the middle button pulldown to "DONE" these SHOW windows.

5.Set the MAX_POWER_DISS property on R28 to .05
  To set this:
    Pick the MAX_POWER_DISS = ____  fillin.
          (the blank region should highlight)
    Type in .05  and then a CARRIAGE RETURN
    Middle hold down the MAX_POWER_DISS box to select ADD NAME= and
    respond  R28  then pick ENTER twice.

    Show current MAX_POWER_DISS to verify  R28 has this property set
    (When a value is filled into the set form it only shows the refdes
     name which match the value,  when the fillin is blank Refdes=value 
     is shown.)

6. Execute thermal again
  Note: Execution is complete when the "idle" message is displayed,
        while it is running "thermal execute" is displayed.

   Note the reduced temperatures for R28:(more th_report.txt, see #3)

        J_TEMPERATURE ________________________ 
        C_TEMPERATURE ________________________ 
        FAILURE_RATE  ________________________
        POWER_DISS    ________________________ 

    Note that Thermostats will always try to complete the process and report
    its results and assumptions.  Accuracy of course relies on user input.
    This type of control by specifying more precise power dissipations
    per component instances is important to the accuracy of Allegro
    thermal predictions.

7. "Done" the Properties Windows and Forms to clear your board display.
   Then hit PARAMS to view the default-or-user-setup thermal run.
   Routed.brd uses all default properties which would been seen for
   any new board execpt the  hotspot and isotherm color step thresholds 
   have already changed from the default:

   [CHECK]  HOTSPOTS  from 30 degC  to 70 degC  by Junction Temp        
   [CHECK]  ISOTHERMS from 30 degC  to 40 degC  incr .2 degC/line       

    to the current settings of:

   [CHECK]  HOTSPOTS  from 40 degC  to 55 degC  by Junction Temp    
   [CHECK]  ISOTHERMS from 45 degC  to 55 degC  incr .5 degC/line    


    Note that the previous EXECUTE used the parameter set(default) for
    
        Air Velocity :  0

    Set this to "Air Velocity" fillin parameter (bottom-most fillin)
    to 4 to represent a strong fan.

        Air Velocity :  4

   Set the Left and Bottom Conductances to .1 w/cm-degc to represent 
   conductive board mounting in the card cage.

    Execute again with these new settings

8. Now set  HOTSPOT to  50 to 70 
   and       ISOTHERMS    40 to 60   incr 2 degC

     Click the [CHECK]  off and then on again to the left of each of
     these settings to regenerate these graphics for the same underlying
     temperatures.
    
   Bring up the color for ANALYSIS and note the color
   transitions  Blue,Yellow,Orange,Rose,Red  intended to graphically
   express increasing temperatures.  Everything was red earlier because
   the temperatures predicted for the conditions (air velosity=0 ...) 
   were all off the top end.

9. Done the Thermal Analysis parameter form (Window out if needed), 
   to observe how the colors of hotspot squares & isotherm
   lines  now show an intuitive rainbow like transition with the lower 
   left board and components cooler.

10.Use color to turn off all the etch and type "unrats all"
   to better be able to see the  temperatures.

   Note that temperatures are defined only by component placements and
   their properties.  Thermal can be performed before or after etch 
   interconnect and the temperature predictions are completely independent   
   of the precise etch routing. (If you have time delete window all clines
   then rerun thermal to verify this.)

11.Zoom in to see the board temperature text of the form
   "T = xx.xx"    displayed in 25 positions in the 5 rows by 5 cols
   across the board specified in the thermal param form.

   Note how the board row/column to row/colum temperature variation is
   small compared to the large temperature increases predicted from the
   board to Case C_TEMPERATURE, temperature rises and case to Junction
   J_TEMPERATURE temperature rises.

12.Note that each run gave you a total "Mean Time between Failures"
   prediction for this board.  Note how the adjusted cooler board with
   air flow and non-zero edge conduction has a much longer mean time
   between failures. (Use the keypad uparrow key to scroll up to the
   previouse failure message, or more th_report.txt)

            Mean time between Failures = ________________________

      Change the PARAMETER Reliability ENv to "CANNON LAUNCH"
      Pulldown in the "Thermal Analysis Parameter Form"
      Also change the   HOTSPOTS to by "Failure Rate"

13.Re-execute and note the much smaller time between failures
   (Cannon launch is real tough on the smart bullet electronics.)

         Mean time between Failures = ________________________

    Also note how the hotspot rectangle now display their color grades
    according to .5 to 2 failures per million hour per their components.
    (The previous hotspot boxes were coded to temperature. Failure
    rates tend to be proportional to temperature but detailed 
    reliability properties and models also are taken into account.)


14.From a Unix shell window

     ls  /usr/valid/tools/pcb/text/th*

   (If you are in a nonstandard system the text directory 
    might be elsewhere type in the Allegro set command to see your 
    environment and the path to .../text)

       More the files   th_exec.txt, th_library-1.txt and th_library.txt

15.cp /usr/valid/tools/pcb/text/th_exec.txt .

   this gives you a local copy of th_exec.txt.

   vi it and enter before the "mode=preserve" line:

           mode=overwrite
           dev_name=RESISTOR-10K TH_CB_RES=50  TH_COMPLEXITY=100
           ref_des=R28 POWER_DISS=.03 HEAT_SINK_FACTOR=2

   re-execute thermal. See  how the R28 date in th_report.txt is revised.

   Note that the temperature goes down a few degrees because 
   of the lower power, lower thermal resistance to the board, 
   and heat sink air surface multiplication factor.   
   The failure rate goes way up (despite the 
   cooler, normally more reliable operation) because the higher 
   TH_COMPLEXITY defines a much higher MIL-HNDBK-217D baseline failure 
   rate for any temperature.
