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newbie:Simple LED sequence?

Discussion in 'Beginner Electronics' started by Bart, Sep 17, 2005.

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  1. Bart

    Bart Guest

    Hi all,
    I want to make 4 LED's light up in the following sequence (looping):
    O O _ _
    _ O O _
    _ _ O O
    O _ _ O
    O O _ _
    _ O O _
    _ _ O O
    O _ _ O

    the above shows it has gone through two sequences, I'll want it to be
    continuous and with variable frequency (a potentiometer?)

    I've read up on 555 oscillators, logic gates (nand, nor, etc.), flip-flops,
    op-amps..........
    I don't know where to start. I DO have a nine volt battery and some
    LEDs.
    Any guidance is greatly appreciated,
    Bart
     
  2. JeffM

    JeffM Guest


  3. Looks good and a good explanation but... I'm missing a LED John. Or did you
    leave it an excercise for the OP? :)

    petrus bitbyter
     
  4. Hi,
    Ok I see your up on the 555 so I would say you should use a 555 to generate
    the clock (And yes, a pot would make it so you could alter the speed) and
    then for it to drive a decade counter.
    Put two diodes from each output so when number 0 was selected by the counter
    the two diodes would go to LED 1 and 2, number 1 would have two diodes
    running to 2 and 3, etc.
    I see you only want an 4 event counter so tie output 4 to the reset line.

    it would go something like this:

    LED1 LED2 LED3 LED4
    output 0 D D
    Output 1 D D
    Output 2 D D
    Output 3 D D
    Output 4 reset line.

    You could scrap the 555 for a variable resistor hooked to a capacitor and
    transistor, the resistor would mean the cap would charge slowly (And as such
    the voltage would climb slowly) until the voltage was such to activate the
    transistor which would ground the cap and restart the sequence.. a nice
    simple oscillator for you. :)

    Good luck
    Oliver Hannaford-Day
    Lichfield Electronics
     

  5. Once you have a 555 clock running you can hook up an old CD4013B like drawn
    below. This type of components runs on power supplies from 3 to 20V. Of
    course you have at least one problem left as these type of components can
    sink only a few mA of current. So your LEDs will be pretty dim or you have
    to use high efficiency LEDs. The series resistors can also be much lower
    then calculated as the outputs have an internal resistor inside. The best
    thing you can do is using an extra IC, a CD4050B. This one contains six
    buffers which are able to sink enough current to drive a LED.


    Vcc 3-20V +-----+-----+-----+-----
    | | | |
    .-. .-. .-. .-.
    | | | | | | | |
    | | | | | | | |
    '-' '-' '-' '-'
    | | | |
    | | | |
    V V V V
    - - - -
    | | | |
    | | | |
    | +--------+ |
    | | | |
    | | +--------------+
    .----. | | .---- | |
    +-----|D0 Q|---+--|-----|D1 Q|---+ |
    | | _| | | _| |
    | +--|> Q|o-----+ +--|> Q|o-----+
    | | '----' | '----' |
    | | CD4013B(a) | CD4013B(b) |
    Clock | | | |
    ----------+-----------------+ |
    | |
    +-----------------------------------+
    created by Andy´s ASCII-Circuit v1.24.140803 Beta www.tech-chat.de

    petrus bitbyter
     
  6. arem_29

    arem_29 Guest

  7. eric

    eric Guest

    Hi I would have used a 555 with a binary up down counter.
     
  8. Alexander

    Alexander Guest

    And You call yourself a Professional Circuit Designer???
    Ok, most of the time we have solutions that are not suitable for a beginner
    (PIC 10F series?).

    Alexander
    A.C.E. (Applied Communications Engineer)
     
  9. Alexander

    Alexander Guest

    I didn't mean it as patronizing just as fun.
    As more experienced designers we might more easily add a programmable
    device.
    Someone who just starts cannot do this because the programming is too
    difficult.
    I sometimes see a beginner add several chips with a cost of $15 or more
    which can easily be replaced by one FPGA or MicroController with a total
    cost of $5, and this makes the design also more flexible.
     
  10. So why shouldn't he call himself a Professional Circuit Designer? He often
    contributes circuits in the electronics newsgroups.

    PIC10F2xx will be suitable for fixed frequency. I'd go for a 12F675 because
    there's no need for extra components but one potentiometer for the variable
    frequency that was asked for.

    The point is however that the OP seems to have hardly any skills in
    electronics so I doubt whether he can reed the schematics we provided.
    That's not to blame the OP. After all this is a "basics" group so he put a
    good question on the right place. But that's also why I try to keep it as
    simple as possible and leave it to the OP to ask further if he needs to.

    petrus bitbyter
     
  11. So why shouldn't he call himself a Professional Circuit Designer? He often
    contributes circuits in the electronics newsgroups.

    PIC10F2xx will be suitable for fixed frequency. I'd go for a 12F675 because
    there's no need for extra components but one potentiometer for the variable
    frequency that was asked for.

    The point is however that the OP seems to have hardly any skills in
    electronics so I doubt whether he can reed the schematics we provided.
    That's not to blame the OP. After all this is a "basics" group so he put a
    good question on the right place. But that's also why I try to keep it as
    simple as possible and leave it to the OP to ask further if he needs to.

    petrus bitbyter
     
  12. So why shouldn't he call himself a Professional Circuit Designer? He often
    contributes circuits in the electronics newsgroups.

    PIC10F2xx will be suitable for fixed frequency. I'd go for a 12F675 because
    there's no need for extra components but one potentiometer for the variable
    frequency that was asked for.

    The point is however that the OP seems to have hardly any skills in
    electronics so I doubt whether he can reed the schematics we provided.
    That's not to blame the OP. After all this is a "basics" group so he put a
    good question on the right place. But that's also why I try to keep it as
    simple as possible and leave it to the OP to ask further if he needs to.

    petrus bitbyter
     
  13. ehsjr

    ehsjr Guest

    It was another damn "use a PIC" post. Some of these posters drive
    me crazy. Never a "Wow John, you sure put a lot of work into that,
    nice job!" Never a complete project, with a schematic and source
    code. Just "you could use a PIC". Hell, if you did what those
    pic-ophiles do, your posts would say "use a soldering iron."
    One thing's for sure - we can't criticize the PIC designs posted as
    solutions to requests from posters. I'll tell you this, I'll put
    any one of the solutions you've offered in the newsgroup against
    all of the posted "PIC solutions", combined. Your solutions are
    always great. Theirs are non-existant.

    Ed
     
  14. Agreed. I could probably have made a movie of it in the time it would
    take a PIC-er to just get started! Here it is:
    http://www.terrypin.dial.pipex.com/Images/LED-Sequencer4MB.wmv
     
  15. Alexander

    Alexander Guest

    Exactly some people take to soon a PIC, GAL, FPGA or any other device. Most
    of the times this are more experienced people who need a flexible design or
    know that in the future the design could get more functions.
    I had a simple design, when it was finished and in production for half a
    year, the customer wanted a redesign with a lot more functions. All it took
    was 2 days of programming and debugging. The PCB didn't change although the
    customer thought it did ;).

    Alexander
     
  16. Alexander

    Alexander Guest

    So was my remark several post ago.

    The fact was that I anticipated the client's inablity to know what he
    wanted.
    So I build it the way I could easily adapt it for his future needs.

    As A mattor of Facts I suggested the sings he later wanted in the first
    place, but NO way listen!

    And Yes there was a nice fat check!!!

    Alexander
     
  17. default

    default Guest

    Have you actually done that? Seems more likely the transistor would
    gradually rise into conduction as the base voltage climbed to .6 volts
    or so. At that point it would limit the voltage from rising further,
    but not discharge the cap . . .

    What you propose (a relaxation oscillator) would probably take more
    than one transistor, or an Thryistor or Unijunction transistor.
     
  18. default

    default Guest

    Four 555's or two dual 555's or a quad monostable timer would work.

    The falling output of one 555 is ac coupled into the next (the
    datasheet shows how with a cap and two pull up resistors)

    The outputs from the 555's are steered to two LED's via some diodes.
     
  19. Jasen Betts

    Jasen Betts Guest

    use common collector configuration, (aka emitter follower)
    I think the plan was a delay after the button is released.
     
  20. Jasen Betts

    Jasen Betts Guest

    maybe something could be done using a transformer :)
    yeah... you're right. I thought we were talking dice...

    Bye.
    Jasen
     
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