Questions about Police light circuit

Discussion in 'The Projects Forum' started by Oxygen454, Nov 11, 2015.

  1. Oxygen454

    Thread Starter New Member

    Nov 11, 2015
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    I have been searching YouTube and websites for a few days now and I have some questions.

    Project: Power Wheels Farm Tractor

    Circuit to make: flashing yellow LED's (similar to police lights) 6 LED's on one light cluster, 6 on another

    I found this post but I'm not sure what VR1 and Q1 are. No parts list but I'm guessing variable resistor and transistor?) What part name would these be?
    [​IMG]

    http://forum.allaboutcircuits.com/threads/led-flasher-help-needed.17499/page-2

    I'm running 12 volts.

    An example would be the red and blue flashing lights on the bumper.
     
  2. Wendy

    Moderator

    Mar 24, 2008
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    I drew that schematic quite a view years ago. The symbol is a zener diode, the voltage of which is 12VDC.

    The symbol for R1 is indeed a variable resistor, the value of which is 100K.

    Q1 and Q2 are not critical. I usually use a 2n2222a or a PN2222a.

    Those are simple wig-wag lights with low power LEDs, I have drawn higher power models that use 1W or 3W LEDs.
     
  3. Oxygen454

    Thread Starter New Member

    Nov 11, 2015
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    Thanks for your reply! Your circuit is exactally what I was looking for. I will have to find out the wattage of the LEDs I will use. I guess brighter the better as I may use it on our shop truck for onsite installs as well (with yellow).

    I haven't played with electronics since highschool.

    Great work.
    I really appreciate your help!

    (Just in case I would need a higher wattage model, where could I find your drawings?)
     
  4. Oxygen454

    Thread Starter New Member

    Nov 11, 2015
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    Before I go shopping, is my list correct to the schematic?

    R1 - 100k variable resistor
    R2 - 390 ohm resistor
    R3 - R7 - 39 ohm resistors
    R8 - 390 ohm resistor
    LED - 8 Yellow (I'm using yellow)
    U1- 555 ic chip
    U2- 4017 ic chip
    Q1 - 2n2222a
    Q2 - 2n2222a
    C1- 100uf
    VR1 - 12 volt zener diode
    VR2 - 12 volt zener diode
    CR 1- 4 - 1N4454 diode

    [​IMG]

    I will post pics as I mod the John Deere tractor. :)
     
    Last edited: Nov 20, 2015
  5. Wendy

    Moderator

    Mar 24, 2008
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    The rules have changed since I did this. My higher wattage model has a PCB design, but was posted elsewhere on the web.

    The circuit shown is for 20ma LEDs, it was meant for a low power application. Give me time and I will post the other circuit elsewhere, it was designed to use 1W or 3W LEDs.
     
  6. Oxygen454

    Thread Starter New Member

    Nov 11, 2015
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    Thanks! Higher wattage probably would show up a lot better.
     
  7. Oxygen454

    Thread Starter New Member

    Nov 11, 2015
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    Did you have any luck on finding your other circuit?
     
  8. Wendy

    Moderator

    Mar 24, 2008
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    K, I've started to watch this thread, which means there will be notifications when it is responded to.

    You might find these files interesting. Have you ever used PCB Express?
     
  9. Oxygen454

    Thread Starter New Member

    Nov 11, 2015
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    No I haven't. I have read about PCB express but am yet to work with it.

    Sounds like you design the board and they make it for you?
     
  10. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    @Oxygen454
    Be very careful with 1 and 3 watt LEDs. They can cause temporary blindness with short flashes but bigger damage to eyes with longer looks - especially at short range and with kids. Those kids will be at eye level and get much more photon flux than you as an adult as you stand higher.
     
    JohnInTX and Wendy like this.
  11. Wendy

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    Mar 24, 2008
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    Gopher makes a good point about high power LED brightness.

    I make my own boards, but I use PCB Express. You can have them make it for you, but I prefer roll my own.

    How I make PCBs

    Wendy's Index
     
  12. Oxygen454

    Thread Starter New Member

    Nov 11, 2015
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    Thanks for the tips! Maybe I will go with a regular style LED. I was thinking of using 4 on each side of the front.

    The rear will be flashing at a slower rate back and forth.

    I will check out your links Wendy.

    (I still plan on using at least 1 watt for our shop truck at work. That will will be a near future project. )
     
  13. Wendy

    Moderator

    Mar 24, 2008
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    For automotive brightness is OK. Distance will reduce apparent brightness, and using several 1 or 3W LEDs is appropriate for a vehicle rack.
     
  14. Oxygen454

    Thread Starter New Member

    Nov 11, 2015
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    PCB express looks cool although my work may not be impressed with me using there brand new laser printer.

    I am thinking of using 1\2 watt LED's at minimum with Wendy's schematic. Probably no more than 4 LED's per side in the front.

    I have two LED flashlights to power the headlights.

    I'm plan on using some orange LED's in the tail lights which will flash once back and forth.
     
  15. Oxygen454

    Thread Starter New Member

    Nov 11, 2015
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    The front LED's will go on either side of the Deere symbol. My son is almost 4 and is 3.5 feet tall. The LED's should not bother him being so low. He knows about flashlight safety as mine are very bright.

    [​IMG]

    Rear flashers...
    [​IMG]
     
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