147 lines
5.9 KiB
Plaintext
147 lines
5.9 KiB
Plaintext
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*********************************************************************
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A NICAD BATTERY CHARGER USING VOLTAGE AND CURRENT LIMITING TECHNIQUES
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*********************************************************************
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WRITTEN BY ANDREW - VK4TEC DATE: 2nd October 1992
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_________ _________ _______
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3 [ ] 2 3 [ ] 2 [ ]
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I O-----[ LM317 ]----o--------[ LM317 ]----[ R3 ]----o----O O
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N [_________] | [_________] [_______] | U
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P O | _|_ | | O T
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U | 1 | [ ] 1 |______________________| | P
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T | | [ R ] | U
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| | [ 2 ] | T
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| o---------o |
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| _|_ |
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| [ ] RESISTOR 1 - SETS VOLTAGE LEVEL |
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| [ R ] |
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| [ 1 ] RESISTOR 2 - SET AT 120 OHMS |
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| [___] |
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| | RESISTOR 3 - SETS CURRENT LEVEL |
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|----------o---------------------------------------------------|
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O---------------------------------------------------------------------O
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| SOURCE ---< VOLTAGE REGULATOR >---< CURRENT REGULATOR >--- BATTERY |
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O---------------------------------------------------------------------O
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NOTES :-
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1. NICAD BATTERY CHARGER USES TWO LM317 ADJUSTABLE VOLTAGE
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REGULATORS , ONE AS A VOLTAGE REGULATOR , AND THE SECOND
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AS A CURRENT REGULATOR.
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2. RESISTOR R1 IS ADJUSTED TO GIVE THE DESIRED NICAD VOLTAGE.
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3. RESISTOR R2 IS OF A STT VLLUE , NAMELY 120 OHMS.
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4. RESISTOR R3 IS ADJUSTED TO GIVE THE DESIRED NICAD CHARGING
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CURRENT. THE VALUE OF THIS RESISTOR IS CALCULATED BY :-
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1.25 Volts
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I ( CURRENT ) = -------------- Amphere
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RESISTOR 3
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5. THE VALUE OF 1.25 VOLTS IS PRESENT ON THE ADJUST PIN OF AN
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LM317 VOLTAGE REGULATOR.
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6. THE CHARGING RATE SHOULD BE CHOSEN AS TO GIVE A CHARGING RATE
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OF ABOUT 1/10 OF THE NICAD CURRENT CAPACITY.
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EG :- TO CHARGE A 1000 mAH BATTEYY PCCK.
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CHARGE CURRENT REQUIRED IS :- 1000 / 10 = 100 mA
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TO CALCULATE THE VALUE OF R3, APPLY THE FORMULA.
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1.25 Volts
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I ( CURRENT ) = ----------------
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RESISTOR 3
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1.25 Volts
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OR RESISTOR 3 = ---------------
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100 mA
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WHICH GIVES A VALUE OF 125 Ohms. ( CHOOSE NEAREST VALUE ).
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7. THE TIME FOR CHARGE IS ROUGHLY 14-16 HOURS AT THIS CHARGING
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RATE. A FASTER CHARGE WILL DECREASE TIME TAKEN.
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8. THE CURRENT STAYS CONSTANT, AND THE VOLTAGE RISES WITH TIME.
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9. TRICKLE CHARGE IS OFTEN 1/100 OF THE NICAD CAPABILITY.
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EG :- 1000 mAH BATTERY , TRICKLE CHARGE = 10 mA.
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10. THE MM31 VOLTAG REGULATOR IS DESIGNED TO PROVIDE
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GREATER THAN 5 mA CURRENT
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LESS THAN 500 mA CURRENT
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KEEP WITTHIN THESE DESIGN PARAMETERS !!!!
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11. THE PINOUTS FOR THE LM317T VOLTAGE REGULATOR IS AS FOLLOWS :-
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--------- ___________
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> O < 3 [ ] 2
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--------- O------[ LM317 ]------O
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| | PIN 1 - ADJUST [_________]
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| LM317 | |
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| | PIN 2 - OUTPUT | 1
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--------- |
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# # # PIN 3 - INPUT O
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# # #
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1 2 3
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12. A SIMPLE CHART IS INCLUDED TO AID CHOICE OF CORRECT VALUE FOR
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RESISTOR 3.
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O--------------------------------------------------------------O
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O RESISTANCE ( OHMS ) O CHARGING CURRENT ( mA ) O
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O--------------------------------------------------------------O
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2.7 460
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3.3 380
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3.9 320
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4.7 270
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5.6 220
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6.8 180
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8.2 150
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10.0 125
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12.0 100
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15.0 83
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118.0 70
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22.0 60
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27.0 50
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33.0 40
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39.0 32
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47.0 27
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56.0 20
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68.0 18
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82.0 15 000.0
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120.0 10
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150.0 8
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******************
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END OF FILE
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******************
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