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"bada bing" "bada boom"

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by timothyjackson, Oct 6, 2004.

  1. timothyjackson

    timothyjackson New Member

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    .....2nd set activated by pin 8 work. First set activated by pin 1 don't. they are permanently on and...dimmed...
     
  2. timothyjackson

    timothyjackson New Member

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    Hey audioguru,

    Solved it....took me at least 3 hours to find this tiny tiny tiny weeeeeeennnnyyyyyyyyyyy eeeeeeeeVILL little section of variboard bridging 2 tracks....this little devil was upside down hiding himself.

    I certainly learnt a lesson.

    take care

    timbo
     
  3. audioguru

    audioguru Well-Known Member Most Helpful Member

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    Hi Timbo,
    Are you talking about the Rabid circuit? It is exactly the same as Bill Bowden's 1st circuit, except if you look really closely, you'll see that the 2N3904 has its E and C connected backwards! The collector of a 2N3904 should always connect to a positive voltage (the opamp's pin 8), and the emitter should connect through the 100 ohm resistor R7 to the LED. The Rabid circuit also has a extra 100 ohm resistor added from the battery's positive to the rest of the circuit.
    Pin 8 is not an output, it is the positive power supply pin of the dual opamp.

    Rabid's "cheap-ass" red LED doesn't work because there is too much voltage for it to dim. If you add 2 LEDs in series like in Bill Bowden's circuit then they will dim much better.
    You can also add Bill Bowden's 2N3906 (and 2 LEDs and a resistor to positive) to pin 1 (output) of the Rabid circuit. Then it will be exactly like the circuit that you made with an LM324 quad opamp.
    The Rabid circuit has its cap charging backwards half the time. Two back-to-back caps as in Bill Bowden's circuit are better.

    Your other circuit probably got messed-up because you unbalanced the 47K resistors with a trimpot. The 47K resistors should be equal so that the LED sides dim equally (Rabid's R1 and R2).
     
  4. dave

    Dave New Member

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  5. timothyjackson

    timothyjackson New Member

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    Hey audioguru,

    Thanks for your reply. I admire you're timeless style. Very inspiring.

    More questions for you my friend.

    I loved the fading led circuit. I want to go a step further. I wish to use some lumileds. Mucho brighter, and massivo viewing angle. stock number 449-1630 at www.rswww.com. These have an I(f) max of 350mA, unsure of max V, think its around 5 to 9V. Given the higher power sourcing of this load, could bill bowdens circuit be modified to use these??...in guessing...I'd have to change the power source in light of the 350Ma, and, also change the discretes around/exiting the op amp, but not in to it? What do you reckon.

    Question 2 - What are you working on....what kind of things are grabbing you're attention????

    Take care

    Timbo
     
  6. audioguru

    audioguru Well-Known Member Most Helpful Member

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    Hi Timbo,
    To drive a Lumiled you would need a power darlington transistor with a heatsink. It would replace the 2N3904. The current-limiting resistor would also need to be changed. The dimming voltage would be wrong but it can be adjusted by changing the power supply voltage.

    I just finished my Stethoscope project. It had an original circuit that didn't work and had many complaints on 2 different web-forums. A doctor who built my version reported that it is "better than excellent".
    http://www.electronics-lab.com/projects/science/019/index.html
     
  7. timothyjackson

    timothyjackson New Member

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    Waow..thats amazing audioguru..I've got something to really aim for now. I love seeing stuff like that, really inspirational. Is there anythng different about the function of your stethoscope?

    Questions:

    1.) A power darlington transistor. Is their only one type? Would I use this for both 2N3904 "and" 2N3906? I assume it has the same pin configuration, i.e. C B E?

    2.) The darlington transister is used becuase the 2n3904/06 can't drive the lumiled load?

    3.) The "current limiting resistor" which you say needs changing, is this the one that would be connected to the LED (lumiled)?

    4.) "The dimming voltage would be wrong, but that can be changed by adjusting the power supply voltage" Would that be the power supply into pins 3, 6, 10 and 13? If yes, I assume the voltage would need to increase.

    5.) What about the capacitors. Wouldn't they need to be bigger??

    (sorry so many questions)

    6.) Heat shrink for a darlington transistor.... what is it,, a piece of metal???? can you recommend something via www.rswww.com......?

    Just thought - Why did you build a stethoscope?

    Thanks audioguru

    Timbo
     
  8. audioguru

    audioguru Well-Known Member Most Helpful Member

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    Hi Timbo,
    The original Stethoscope project had many errors that I corrected. The moderator over there argued that my theory was wrong. He argued also about my Plants project correction. He is eating his foot now, actually both feet!
    The Stethoscope project has U1b, a precision low-pass-filter (that was wrong) which reduces background sounds like people talking, unlike other Stethoscope circuits that have just a simple tone control.

    Answers:
    1) There are many power darlington transistors, NPN and PNP like the 2N39xx's. They also have C B E pins. You must select them for voltage, current and power ratings.
    2) A darlington transistor has 2 transistors inside that have a high current gain to amplify the few mA from the opamp to the hundreds of mA for the Lumileds. A power type can handle the high current and power (heat) that would destroy a 2N39xx.
    3) To increase the Lumiled current to hundreds of mA, the current-limiting resistors that connect to them would need their value reduced a lot, and their size increased to 1W or 2W because they will get hot.
    4) The power supply voltage to the whole circuit will need to be adjusted to match the voltage of the Lumiled. Don't use the Rabid circuit's R6.
    The voltage at pins 3, 6, 10 and 13 will automatically be at half-supply voltage, because the 47K resistors are equal and divide the supply voltage exactly by 2. Therefore both LED sides will be balanced.
    5) The capacitors are on the low-current opamp part of the circuit and are not affected by the high output current.
    6) A black, finned, aluminum heatsink is needed for the darlingtons, and maybe another for the Lumileds. For the darlingtons it should be about 6cm long by 2.5cm wide and have fins protruding about 2.5cm. A thermally conductive but electrically insulating kit mounts the darlingtons with bolts or a clip, with thermal grease used for good heat transfer.
     
  9. timothyjackson

    timothyjackson New Member

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    audioguru...the oak of advice. I'll tell my grandchildren about the great audioguru hehe... better have my own children first.

    I like the analogy of one eating ones foot... espcially if they are in the medical profession. funny.

    OK... will digest all the info...I love the capacitor answer....(did not know that)...

    1 question before I order the parts....

    Am i using a darlington transistor for the 2n3904 and 2n3906, so the new circuit would have 2 darlingotn transistors. Or, is it just one darlington to replace the both (im guessing its just the one)

    Thanks audioguru. You're a rock.
     
  10. audioguru

    audioguru Well-Known Member Most Helpful Member

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    Hi Timbo,
    If you are building Bill Bowden's "snake-eyes" 2nd circuit with 2 sets of LEDs (except you are going to use a Lumiled for each set), then one Lumiled will be brightening while the other is dimming. You can't do that with only one transistor. The darlington transistors replace the 2N39xx transistors, an NPN darlington replaces the 2N3904, and a PNP darlington repaces the 2N3906. See, NPN for NPN, and PNP for PNP.

    If your RSWWW link worked, I would have helped you select them.

    Those Lumileds are really bright, don't look directly at them (sunglasses?).
     
  11. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    There's no 'www' it's just http://rswww.com.
     
  12. timothyjackson

    timothyjackson New Member

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    Thanks audioguru

    Thanks Nigel
     
  13. audioguru

    audioguru Well-Known Member Most Helpful Member

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    Hi Timbo,
    Get a TIP110 or TIP120 power darlington NPN transistor and a TIP125 power darlington PNP transistor.
    Sorry I couldn't find a heatsink, RS's pictures don't work.
     
  14. timothyjackson

    timothyjackson New Member

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    Hi Audioguru

    Many Thanks.

    Heatsink? Is this like a metal profile which takes heat away from a componnent? Generally speaking, do heatsinks take any other form??

    In bill bowdens circuit, why doesn't he use two NPN transistors? I don't understand.

    Timbo
     
  15. audioguru

    audioguru Well-Known Member Most Helpful Member

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    Hi Timbo,
    I described the heatsink before. Since the darlingtons will be dissipating only a few Watts, a heatsink for them won't be required if you keep their current below about 200mA. For up to 350mA, the heatsink requirement is small, so even bolting the darlingtons to a metal box (with proper insulation) will be OK.

    Bill Bowden's "Snake-eyes" #2 circuit shows a 2N3906 which is, and is shown as (see the arrow at its emitter?), a PNP.
     
  16. timothyjackson

    timothyjackson New Member

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    thanks audioguru

    Will get cracking on this one

    timbo
     

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