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Led Strobe circuit help???

Discussion in 'LEDs and Optoelectronics' started by AGLite, Mar 2, 2012.

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  1. AGLite

    AGLite

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    Feb 19, 2012
    Hi guys,

    I have a problem with a circuit i am modifying... Its a circuit from radioshack's electronics lab booklets. It uses the 4049 IC and the 4066 IC. It has adjustable speed using a pot., I didn't want that so I put in a 4.7k resistor to get the flash speed I wanted. It operates off of 6 volts and runs two leds alternating just fine. But I need it to run on 9 volts and run 4 panels of 18 5mm leds. All of it should be on a 9 volt battery for bicycle lighting or maybe two 9 volts. I put this circuit on a perfboard but it does not work correctly. It flashes out of sync and much faster. It also stores power in the ground terminals on the labs breadboard now when I tried to re do it on the breadboard to see whats wrong with the actual board on the perfboard. All wiring is checked countless times. Ohh and pin 9 of the 4049 is what is holding power to the ground.

    Pictures are attached along with a schematic.
     

    Attached Files:

  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,489
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    Jan 21, 2010
    Your first problem is the 4066. It has a fairly high ON resistance, so if you have multiple LEDs, you'll have issues with this.

    Your second problem is that the 4049 has a limited output current. More than 1 LED in parallel is going to cause problems.

    The best option would be to use the signal passing through the 4066 to switch a transistor which can then switch a higher current load (your panel of LEDs)
     
  3. AGLite

    AGLite

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    Feb 19, 2012
    Ok gotcha, do you think you could walk me through the process?
     
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    look at the "transistor driver circuit" on this page.

    It should not matter which circuit you use because it appears your duty cycle(s) are 50%
     
  5. AGLite

    AGLite

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    Feb 19, 2012
    how do i find the signal passing through the 4066?
     
  6. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    Pins 2 and 4 of the 4066 are the pins which need to be connected to the base of transistors via a suitable resistor (as shown in my earlier link)
     
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