Connect with us


Discussion in 'General Electronics Discussion' started by garage100, Nov 2, 2014.

Scroll to continue with content
  1. garage100


    Nov 2, 2014
    The above circuit was built on a matrix without transistors ( 2n3904 ) .
    The Circuit worked fine until the transition to the solder board which included all the parts. I checked the board three times .
    The Circuit is taken from
    I wanted to restrict the movement of four LEDs , so I shorted leg 10 to 15 in 4017 .
    In addition I wanted to control the timing and changed the capacitor connected to 555 to 100U and added variable resistors.
    The problems :
    1. After switching to a solder board the rotation stopped at the same group of LEDs repeatedly. the randomality has disappeared . Is there a mistake in a circuit attached ? Why doesn't it stops with a another group of leds in every rotation round?
    2 . The LEDs are piranha 5 mm 3v . When the group of blue LEDs turn on, the LED connected to the resistor(150) is flashing. Is the LED broken or is there a problem in 2n3904 ?

    I'm really desperate
    please help

    Attached Files:

  2. Colin Mitchell

    Colin Mitchell

    Aug 31, 2014
    You can't connected LEDs in series without a resistor
  3. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    Nov 28, 2011
    Your schematic is pretty short on information. What's the battery voltage? And every component should have a circuit reference so we can identify it when we're talking about it.

    Each of the four transistors drives a pair of LEDs in series, which have no current limiting resistor. As Colin says, you can't normally do that; the effect depends on the battery voltage and type, but is not likely to be good.

    This could be the reason why it always stops on the same group of LEDs.

    The red LED could be flashing because you accidentally used a flashing LED instead of a normal LED. Flashing LEDs are available; there is a little circuit inside them to make them flash.

    Your preset variable resistors are drawn wrong; if you only connect to the two ends, the resistance will be constant. You need to connect the wiper to one end.

    Edit: And welcome to Electronics Point!
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day