Formula about led flasher & Timer Chip..!!

Discussion in 'General Electronics Chat' started by redlight000, Apr 9, 2010.

  1. redlight000

    Thread Starter Member

    Feb 26, 2010
    66
    2
    Hi all,

    this is a formular from a good electronic book, & I Just cant grasp on how to enter this on my scientific calculator... it's a Timer rigged in astable mode..

    R1=4.7k
    R2=10k
    C=10uf electroltic cap... the resistor is 1.5k on the output for the Led..
    and the above circuit flashes the Led at about 5.8zh.. thats that bit..

    Now the author, broke down the equation on how it arrived at 5.8hz..
    1/0.7 x 10 x 10 to the negitive power of six x (4700 + 20,000)

    now I'VE DONE ALL THE EQUATIONS on the calc, and done them all correctly.. but I cant seem to get this spot on .. 5.8hz can anyone help on that please..??
    ========================================================

    These are the maths done on the calculator.. and turned out spot on..

    example 1)

    Amplifier gain..
    Calculate the value of Av
    Voltage gain AV=20 Log Vo/Vi
    =20 log 3/1x10 to the negitive power of 3=
    69.54242509dB

    How to enter that into the calc =
    press 3/[EXP]3[+/-] = 1.-03 ON DISPLAY
    =[log] [X] 3.477121225 on display
    20 = 69.54242509
    = the answer!!!!!!!!!!
    now I entered all that & yet I cant do the above one ie the 5.hz one its doing my head...

    thanks if anyone can help on the top above bit Post..
    ??
    regards redlight000< binary lol
    :D
    :)
     
  2. Wendy

    Moderator

    Mar 24, 2008
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    This should be in the chat forum.

    Schematics are needed.
     
  3. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    If the chip is 555, I come up with 10.3 or 8.1 Hz, +- 20%.depending on R1,R2 placement.
     
    Last edited: Apr 10, 2010
  4. redlight000

    Thread Starter Member

    Feb 26, 2010
    66
    2
    Hi Bernard,

    what you mean you replaced your R1+R2?
    because mine IS R1=4k7 4.7k
    R2 = 10k 10000 ohms
    C1=10uf electrolytic cap
    in pins 1+2 of the 555 chip!!
    R3 = 1.5k <<< thats coming from pin 3 to the led to limit the current to the led ..
    and as I said the author states in the BOOK "after all the math that turns out 5.8hz.. or 6hz per second..
    ok
    cheers
    from
    red angry light
    :D
     
  5. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    Placement, not replacement; need schematic for further help.
     
  6. Wendy

    Moderator

    Mar 24, 2008
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    Which is what I asked for. You no give information, you no get information.
     
  7. Jazz Bass Special

    New Member

    Apr 9, 2010
    24
    5
    redlight000 likes this.
  8. redlight000

    Thread Starter Member

    Feb 26, 2010
    66
    2
    Hi Bill,
    well thats a bit of a problem.. its a bit small in the book you would hardly see it..
    Im not that fussed.. on it.. its the calculator thats getting me not the arriaval of 5.8hz thats a diddle
    .. lol
    cheers m8
    :D
    Ok I see yur point... I may try...at some later stage..

    :_)

     
  9. Pencil

    Active Member

    Dec 8, 2009
    271
    38
    Try this:

    1/((.7x(4700+10000)x(10x10^-6))+(.7x10000x(10x10^-6)))=

    I haven't had a calculator with an [EXP] button for exponents
    in several years so I don't remember the exact key stroke sequence
    for that part. (10^-6 means 10 to the negative sixth)

    Note: Parentheses are required.
     
    redlight000 likes this.
  10. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    If you want to keep it simple, then just shift the decimal place in the resistance instead of using 10x10e-6.
    For example:
    T1 = 0.7x(0.0047+0.01)x10
    T1 = 0.1029
    T2 = 0.7x0.01x10
    T2 = 0.07
    F = 1/(T1+T2)
    F = 1/(0.1029+0.07)
    F = 1/0.1729
    F = 5.7836899942163100057836899942163
     
    redlight000 likes this.
  11. Wendy

    Moderator

    Mar 24, 2008
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    Windows calculator has a scientific mode, but I keep a calculator next to my keyboard just for these kind of calculations.
     
  12. retched

    AAC Fanatic!

    Dec 5, 2009
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    Pbbbbtt.. I use my fingers. And I lost two of them in a lawnmower accident.

    kidding.. If you want a good replacement for windows calculator with a bunch of good scientific options, try calc98. calculator.org

    From roman numerals to the periodic table of elements.. just everything you need. and its free.. Also It runs on linux under Wine.
     
    redlight000 likes this.
  13. Wendy

    Moderator

    Mar 24, 2008
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    redlight000 likes this.
  14. redlight000

    Thread Starter Member

    Feb 26, 2010
    66
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    Hi Pencil.
    Nope I tried entering it.. then I get stuck on what to press.. div head me) EYES rolling,
    thanks though
    :D
     
  15. redlight000

    Thread Starter Member

    Feb 26, 2010
    66
    2
    Hi Sgtwookie,
    you are a maths Wizz I done it!!!! yepeeeeeeeeeeee
    thanks very much for inputing all that.. for me I do really think alot of that.. although I dont normally show it... thanks again..you genius...
    :D
    regards
    redlight000
     
  16. redlight000

    Thread Starter Member

    Feb 26, 2010
    66
    2
    Hi Bill,
    thanks for that.. see as stupid as I feel, I still cant grasp some of the maths, you kindly put up.... If Im honest.. with the math side I can do it.. as you can see from the posts on here... wait..) but not all see what I go by is "Starting Electronics by Keith Brindly) Fab book & learnt so much from that.. I normally start R1 as 4.7k & R2 as 10k.. and then choose C/ for the freq) which I've got Mimms small hand book,

    So that give me a rough Idea on how to get say a 1000hz or 7hz.<< not exact though...
    thats how I go about it."YES" I do the maths,, you have to if I design my own sound generators & flashers etc... blast that VERY bright red Led ... in a different post.. that made me ill...
    thanks again...
    regards
    redlight
    :D
     
  17. Pencil

    Active Member

    Dec 8, 2009
    271
    38
    Sorry about that.

    It works on my calculator exactly as shown.

    I have [^] for exponents and formula appears on
    display as I type so I can "proof read" or edit before
    hitting =.

    Math not strong suit?

    It is better to learn basic concepts and build on that, but
    some times a well organized notebook with formulas, examples,
    and good notes can get you through.
     
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