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  1. pier1

    0-30volts Lab power supply

    I have made the 0-30 volts lab power supply which is there on this site . I want to know if it was possible to add a FINE TUNE provision for accurate selection of the O/P voltage . Please help me .
  2. pier1

    white led

    Hi AG         I connected a 11 Ohms resistor as the load . I noticed that the o/p voltage of the lm317 regulator was 3.6volts dc when the input voltage to the regulator was varied from 7.82volts dc to  17volts dc . The lm317 is cooler then before now . Is this enough AG  ??? as the forward...
  3. pier1

    white led

    Hi AG Then I will have to use a 9 volts 500mA step down transformer. Will that give enough voltage for lm317 ?
  4. pier1

    white led

    Hello AG             The LED forward voltage i measured is 3.48volts . So it wont be sufficient na ?
  5. pier1

    white led

    Hi AG         So I would have to use a 6 volts stepdown 500mA transformer,bridge and a filter which would give an o/p voltage of 8.64 volts dc across the filter capacitor to reduce the voltage to lm317 ?
  6. pier1

    white led

    Hi AG         What should be the resistor value instead of 3.9 Ohms if i put only one LED ?
  7. pier1

    white led

    Hello AG             Could these heat sink be sufficient for the regulator ? I first used PI49 and found the regulator over heating .
  8. pier1

    white led

    Hi AG   Since i am weak in electronics i am getting confused . In the ckt the 3.9 Ohms is connected from o/p to adjust terminal so when the LED's are drawing 350mA current, then is the current flowing through the 3.9 Ohms resistor ? Or from where is it drawing current ?
  9. pier1

    white led

    Hello AG             One more doubt before connecting the load, should the 3.9 Ohms resistor also be 2 watt ?
  10. pier1

    white led

    Hello AG,               Can I put a 25 ohms resistor in instead of the led's  to see the voltage across it ? If so should it be a 2watt ?
  11. pier1

    white led

    Hello AG             The o/p of the lm317 is 15.45 volts(open voltage). Will it harm the led's .
  12. pier1

    white led

    Hi AG         Which is the ideal resistor to be used in series with the LED to find out its exact forward voltage ? I have a 6volts battery as a source .
  13. pier1

    white led

    Hi AG         Thanks a lot for that . What will happen if the input voltage rise beyond 230 volts, as i measure 17.3 volts at 1000uF capacitor . And what is the calculation for finding out the o/p voltage of the lm317 AG ?
  14. pier1

    white led

    Hi AG,         So the value of the resistor is 1.2ohms ?
  15. pier1

    white led

    Hi AG, Should i take tho o/p at pin 2.
  16. pier1

    white led

    Hi AG         My multimeter measures 17.3 volts across the 100/25 capacitor. What will be the o/p of the LM317 ? Hows the circuit now ?
  17. pier1

    white led

    Hi AG         I could find an lm117 as a current regulator circuit in the datasheet (application notes) 317 is used as a voltage regulator and a reference with voltage regulator . Is this the same way i should do to the lm317 (picture) ?
  18. pier1

    white led

    Hi AG         How about this circuit, and the current regulator you suggested me . If correct what could be the value of r3 ?
  19. pier1

    white led

    Hi AG,         Sorry for the 7805, it was supposed to be 7808 . On the projects Q/A forum, the lm317 thread you have put up a circuit using 78xx series for current regulation . Shall i follow that ? One doubt : Assume when two leds(3.5v each) are connected in series the current(each led =...
  20. pier1

    white led

    Hello AG             I bought 2 new 1watt white led (lumileds), Its specifications are 3.5volts DC 350 mA             Since it is a costly one , As you suggested before i would like to use a isolation transformer(9 volts, 500mA), Bridge rectifier(w10m) a good filter(1000uF/16v) . For the 3.5...
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