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Text File  |  1992-10-11  |  6KB  |  147 lines
  1.  
  2.     *********************************************************************
  3.     A NICAD BATTERY CHARGER USING VOLTAGE AND CURRENT LIMITING TECHNIQUES
  4.     *********************************************************************
  5.  
  6.         WRITTEN BY ANDREW - VK4TEC              DATE: 2nd October 1992
  7.  
  8.               _________               _________      _______
  9.           3  [         ]  2       3  [         ] 2  [       ]
  10.     I  O-----[  LM317  ]----o--------[  LM317  ]----[  R3   ]----o----O  O
  11.     N        [_________]    |        [_________]    [_______]    |       U
  12.     P  O          |        _|_            |                      |    O  T
  13.     U  |       1  |       [   ]        1  |______________________|    |  P
  14.     T  |          |       [ R ]                                       |  U
  15.        |          |       [ 2 ]                                       |  T
  16.        |          |       [___]                                       |
  17.        |          |         |                                         |
  18.        |          o---------o                                         |
  19.        |          |                                                   |
  20.        |         _|_                                                  |
  21.        |        [   ]        RESISTOR 1 - SETS VOLTAGE LEVEL          |
  22.        |        [ R ]                                                 |
  23.        |        [ 1 ]        RESISTOR 2 - SET AT 120 OHMS             |
  24.        |        [___]                                                 |
  25.        |          |          RESISTOR 3 - SETS CURRENT LEVEL          |
  26.        |          |                                                   |
  27.        |----------o---------------------------------------------------|
  28.  
  29.    O---------------------------------------------------------------------O
  30.    |                                                                     |
  31.    |  SOURCE ---< VOLTAGE REGULATOR >---< CURRENT REGULATOR >--- BATTERY |
  32.    |                                                                     |
  33.    O---------------------------------------------------------------------O
  34.  
  35.  
  36.    NOTES :-
  37.  
  38.    1. NICAD BATTERY CHARGER USES TWO LM317 ADJUSTABLE VOLTAGE
  39.       REGULATORS , ONE AS A VOLTAGE REGULATOR , AND THE SECOND
  40.       AS A CURRENT REGULATOR.
  41.  
  42.    2. RESISTOR R1 IS ADJUSTED TO GIVE THE DESIRED NICAD VOLTAGE.
  43.  
  44.    3. RESISTOR R2 IS OF A STT VLLUE , NAMELY 120 OHMS.
  45.  
  46.    4. RESISTOR R3 IS ADJUSTED TO GIVE THE DESIRED NICAD CHARGING
  47.       CURRENT. THE VALUE OF THIS RESISTOR IS CALCULATED BY :-
  48.  
  49.                           1.25 Volts
  50.        I ( CURRENT ) =  --------------  Amphere
  51.                           RESISTOR 3
  52.  
  53.    5. THE VALUE OF 1.25 VOLTS IS PRESENT ON THE ADJUST PIN OF AN
  54.       LM317 VOLTAGE REGULATOR.
  55.  
  56.    6. THE CHARGING RATE SHOULD BE CHOSEN AS TO GIVE A CHARGING RATE
  57.       OF ABOUT 1/10 OF THE NICAD CURRENT CAPACITY.
  58.  
  59.  
  60.       EG :-   TO CHARGE A 1000 mAH BATTEYY PCCK.
  61.  
  62.  
  63.       CHARGE CURRENT REQUIRED IS :-  1000 / 10 = 100 mA
  64.  
  65.  
  66.       TO CALCULATE THE VALUE OF R3, APPLY THE FORMULA.
  67.  
  68.                          1.25 Volts
  69.       I ( CURRENT ) = ----------------
  70.                          RESISTOR 3
  71.  
  72.  
  73.                          1.25 Volts
  74.       OR  RESISTOR 3 = ---------------
  75.                            100 mA
  76.  
  77.  
  78.       WHICH GIVES A VALUE OF 125 Ohms. ( CHOOSE NEAREST VALUE ).
  79.  
  80.  
  81.    7. THE TIME FOR CHARGE IS ROUGHLY 14-16 HOURS AT THIS CHARGING
  82.       RATE. A FASTER CHARGE WILL DECREASE TIME TAKEN.
  83.  
  84.    8. THE CURRENT STAYS CONSTANT, AND THE VOLTAGE RISES WITH TIME.
  85.  
  86.    9. TRICKLE CHARGE IS OFTEN 1/100 OF THE NICAD CAPABILITY.
  87.  
  88.       EG :-  1000 mAH  BATTERY , TRICKLE CHARGE = 10 mA.
  89.  
  90.   10. THE MM31  VOLTAG  REGULATOR IS DESIGNED TO PROVIDE
  91.  
  92.             GREATER THAN 5 mA CURRENT
  93.  
  94.             LESS THAN 500 mA CURRENT
  95.  
  96.       KEEP WITTHIN THESE DESIGN PARAMETERS !!!!
  97.  
  98.   11. THE PINOUTS FOR THE LM317T VOLTAGE REGULATOR IS AS FOLLOWS :-
  99.  
  100.       ---------                                ___________
  101.       >   O   <                            3   [         ]  2
  102.       ---------                         O------[  LM317  ]------O
  103.       |       |    PIN 1 - ADJUST              [_________]
  104.       | LM317 |                                     |
  105.       |       |    PIN 2 - OUTPUT                   | 1
  106.       ---------                                     |
  107.        #  #  #     PIN 3 - INPUT                    O
  108.        #  #  #
  109.  
  110.        1  2  3
  111.  
  112.  12. A SIMPLE CHART IS INCLUDED TO AID CHOICE OF CORRECT VALUE FOR
  113.      RESISTOR 3.
  114.  
  115.  
  116.     O--------------------------------------------------------------O
  117.     O   RESISTANCE ( OHMS )      O      CHARGING CURRENT ( mA )    O
  118.     O--------------------------------------------------------------O
  119.  
  120.              2.7                              460
  121.              3.3                              380
  122.              3.9                              320
  123.              4.7                              270
  124.              5.6                              220
  125.              6.8                              180
  126.              8.2                              150
  127.             10.0                              125
  128.             12.0                              100
  129.             15.0                               83
  130.            118.0                               70
  131.             22.0                               60
  132.             27.0                               50
  133.             33.0                               40
  134.             39.0                               32
  135.             47.0                               27
  136.             56.0                               20
  137.             68.0                               18
  138.             82.0                               15            000.0
  139.            120.0                               10
  140.            150.0                                8
  141.  
  142.  
  143.  
  144.                     ******************
  145.                         END OF FILE
  146.                     ******************
  147.