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pier

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Posts posted by pier

  4. white led

    in Electronic Projects Design/Ideas

    Posted

    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 = 350mA) through both is same. So, is the total current drawn from 78xx series(to220) is the same as the flowing current(i.e, 350mA) ?... ???



  5. white led

    in Electronic Projects Design/Ideas

    Posted

    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 volts I dont know what to do . My idea was to use a 7805 with good heatsink and a voltage divider for 3.5volts DC and put the 2nos of 1watt LED's in series . Is this correct ?

    Or I have found a link http://www.national.com/webench/ledrefdesigns.do

    Should i use something from this Ag . Please Suggest me .

    Thanks
    Pier .

  6. white led

    in Electronic Projects Design/Ideas

    Posted

    Hi AG
            I removed the led light from the roof top to put a better heat sink and when i touched the track side i got a good shock, The capacitors were still charged . Should i put and resistor across the capacitor bank so that they get discharged as soon as it is put off ? If so which would u suggest the value to be and its wattage ?

    thanks & regards.

  7. white led

    in Electronic Projects Design/Ideas

    Posted

    Hi AG
            Thanks for the circuit. Actually I am not building the circuit for 6 led's but i wanted to know the calculations for deciding the number of led's used for certain voltage available because i read somewhere in the web that u can use leds in series provided the voltage across the led string should not exceed 0.9 X Vcc volts.So As i asked in the topic before as per my assumation i took 3.5volts per led and voltage available is only 21 volts , 6 led's take the entire voltage(21 volts), so i was confused if it was right to do so ????The other circuit u gave me for 49 leds is still working excellent on my roof top :D :D . 

    Regards
    Pier.

  8. white led

    in Electronic Projects Design/Ideas

    Posted

    Hi AG
            Now suppose i have only 21 volts dc at the o/p of the power supply and i have to connect led's in series . Assuming the forward voltage is 3.5volts, can i connect 6 in series so that the total forward voltage reaches 21 volts dc ? I dont know the exactly how to calculate the number of led's to connect in the circuit . Can u please help me in this ?

    Regards
    Pier.

  9. white led

    in Electronic Projects Design/Ideas

    Posted

    Hi AG
            I made a board of 72 X 24 mm in size and the same size for the heatsink with a thickness of 3mm . Would this be a sufficient heatsink for a continious operation . I want to isolate the transistor from the heat sink and screw it up (Heat sink)on the roof of my room .

    Thanks
    Pier .

  10. white led

    in Electronic Projects Design/Ideas

    Posted

    Hi AG
            The circuit was on test for 3 days continiously and working fine . People are asking me how much power it consumes from the mains . Bulbs consume 60Watts as written on it when we purchase it here . Do we have to connect an Ampere meter in series with the live mains i.e.230/250 volts AC to measure its current and calculate its power ?

    Thanks
    Pier.

  11. white led

    in Electronic Projects Design/Ideas

    Posted

    Hi AG
            Its right as u said . The voltage across the 22ohms resistor is 0.6volts when the mains voltage reaches 345Vdc . The 13005 is getting very hot and i 've put a bigger heatsink now . I will put it under testing and let u know the result after 1 or 2 days . Thanks a lot for ur co-opeation in helping my project AG . :)

    Thanks
    Pier

  13. white led

    in Electronic Projects Design/Ideas

    Posted

    Hi AG
            I am such a fool, I forgot to connect the 3904 in reverse when i corrected the 13003 properly . Now its fine . The voltage across the 27ohms is 0.56 volts. I dont understand AG how are u able to find faults without seeing the circuit I connected . Thanks a lot AG . as i said is 0.56volts across 27e ok  ?

    Thanks
    Pier

  16. white led

    in Electronic Projects Design/Ideas

    Posted

    Hi AG
            I apologise for electrocuting myself :-X . I measured the voltages at different parts of the circuit :

    across 27 ohms resistor : 0 volts (no voltage)
    at the base of 13003 with respect to gnd : 14.25 volts
    across the 10k resistor : 0.59 volts
    at the collector of 13005 with respect to gnd : 152.22 volts

    All this voltages was measured when the input voltage was 300 volts DC.
    No components are heating up .

    Thanks
    pier

  19. white led

    in Electronic Projects Design/Ideas

    Posted

    Hi AG

    Thanks a million :D.The circuit works!!!!!!!. The 13005 is warm with a heatsink . I tried till only 280volts dc . I have to look for a high voltage transistor of to92  package (400volts as you said) for testing till the higher end of voltage . Mean while if you find some part numbers please let me know AG . I will look for it, if it is available here .

    Thanks :)
    Pier.   

  21. white led

    in Electronic Projects Design/Ideas

    Posted

    Hi AG
            Thanks a lot for the circuit . I will build the circuit today itself and test it, but one doubt (must be a dumb one, dont feel bad : i am weak in electronics) as u said before should i connect a high watt resistor as per previous calculations for the led's in series ?!!!

    Thanks
    Pier

  24. white led

    in Electronic Projects Design/Ideas

    Posted

    Hi AG

            I am sorry for asking that question . I looked into the datasheet only after posting my question, But I would still like to know the element Which is used as a reference . I am interested to build it and test it AG if you give me the values . I dont mind if it takes some time even .

    Thanks
    Pier .

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