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Simple breadboard project with my 6 year old

Discussion in 'General Electronics Discussion' started by RobSmith, Jan 10, 2012.

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  1. RobSmith

    RobSmith

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    Dec 16, 2011
    Hi all,

    My 6 year old son and I saw this on youtube:

    I then pressed 'print screen' from the video to cobble together this:
    [​IMG]

    We made up the breadboard circuit and it works fine. I added some 820 ohm resistors on the LEDs as I was not sure about the current capabilities of the 4017 chip or if the LEDs were getting the full 9v and no current limitation. It works well and I made up another circuit giving Police, ambulance and fire engine noises along side the lights circuit on the breadboard.

    Then made the circuit diagram into this:

    [​IMG]

    It is mostly a copy of the youtube one so will also have copied the mistakes too. Does it look ok to the 'Flashing LED gurus' out there.

    Rob
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,497
    2,838
    Jan 21, 2010
    I can't be bothered looking up the 4017 or the 555's exact pinout to check, but if it's functional, I'd say you're OK.

    The lack of resistors on the 4017 driving LEDs is no big issue because the 4017 has outputs that are essentially current limited. That being said, I applaud your decision to insert resistors in there and it is a good thing.
     
  3. davelectronic

    davelectronic

    1,087
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    Dec 13, 2010
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,497
    2,838
    Jan 21, 2010
    Dave, the issue is that it is conventional to have a schematic that shows device functions rather than physical layout.

    I'm sure the physical layout is way more helpful than a conventional schematic for this person and their son.

    However it means that *I* can't check it without looking up the pins (OK, I know many of them on these chips).

    The main thing is, if the circuit is working, the wiring must be correct (or have non-fatal flaws). Even if there are differences they may be between the diagram and the wired up device. Same issue, if it works then they are probably not significant.

    The big question is the addition of resistors, which the OP has done correctly (or at least which are correct on the diagram).

    Sure, he can go look at the datasheets, but they probably won't help him answer the questions. But they might be interesting... And I'm happy if he does. And if they raise some questions, we'd all be pleased to assist him.

    edit: I agree though. The datasheets may also be of interest to others who come along later.
     
  5. davelectronic

    davelectronic

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    Dec 13, 2010
    Totally understand your theory and logic Steve. :)
     
  6. RobSmith

    RobSmith

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    0
    Dec 16, 2011
    I will add the pin functions to the diagram :)
    Rob
     
  7. Harald Kapp

    Harald Kapp Moderator Moderator

    11,522
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    Nov 17, 2011
    Hi Rob,
    if you're not afraid of buying in a German store, this could be a nice project for you and your kid:
    http://www.pollin.de/shop/dt/NDQ4OTgxOTk-/Bausaetze_Module/Bausaetze/TFK_LED_Wechselblinker.html
    It's a standard 2 transistor astable multivibrator with LED indicators. The beauty of this kit is that the breadbord is a 1-by-1 copy of the schematic. It uses a piece of drywall construction board and thumbtacks for setting up the breadboard. Everything is then connected by soldered pieces of wire.

    Regards,
    Harald
     
  8. Raven Luni

    Raven Luni

    798
    8
    Oct 15, 2011
    Greetings,

    The only thing I'd say is its probably not a good idea to leave pins 4 and 5 of the 555 floating. It might work fine with what you have but if you subsitute it for a different make of 555 you might get unwanted behaviour. I spent ages tracking down a problem with a 556 recently (same thing just 2 on the same chip). It worked fine until I substituted it for a different make then I realised I'd left the resets unconnected (pin 4 of the 555).

    You'll want to tie pin 4 to VCC and connect pin 5 to ground through a small capacitor (10nF or 100nF). The latter is less important but helps eliminate noise.
     
  9. RobSmith

    RobSmith

    56
    0
    Dec 16, 2011
    Thanks for that. I will modify my circuit to suit.
    Rob
     
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