To Mr. Bill Marsden

Discussion in 'General Electronics Chat' started by Jure George, Mar 17, 2012.

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  1. Jure George

    Thread Starter Active Member

    Dec 28, 2008
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    Hello Mr. Marsden



    My name is George. I am looking for a 555 I.C circuit alone to run 4 yellow LED`s in a chaser beacon setup. I run 1/16 R.C trucks and I would like to install a roof top safety warning beacon. The circuit has to be small so I thought, could the 555 alone handle 4 yellow LED`s on a 6v, 7.2v to a 12max. D.C battery source and the LED`s are about 20mA each. I would like to be able to have a variable resistor to adjust the rate at which the LED`s turn on and off.

    Can you help me with this? Could you show me a circuit with the parts` list to do this?

    Please let me know if you can help me with this.

    Thanks for your time and consideration.

    George
     
  2. Wendy

    Moderator

    Mar 24, 2008
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    I'm currently up between catnaps. I'll be back.

    Are you wanting the 4 LEDs to sequence, or alternate? If sequence there may be better chips to do this, and if size is a consideration SMT parts.

    It would also be a decent application for a µC, though I would be useless on this. The µC would use minimum parts count.
     
  3. Audioguru

    New Member

    Dec 20, 2007
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    The 555 is simply an oscillator. You also need a CD4017 (or CD4022) IC to sequence the LEDs. With a 6V to 9V supply the CD4017 (or CD4022) IC can drive the LEDs.

    A Cmos 555 and a 74HC4017 (or 74HC4022) work from a supply that is only 3V. The 74HC4017 (or 74HC4022) can drive red LEDs.
     
  4. Jure George

    Thread Starter Active Member

    Dec 28, 2008
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    Hello Mr. Marsden

    Thank You for your Fast reply. Yes I would like them in Sequence, #1 - #4 non stop untill the circuit is powered off. And to the other poster, I know about the other I.C used BUT since that one is LARGER compared to the 555 it is hard to hide it.

    Thanks Again Mr. Marsden.

    George
     
  5. DerStrom8

    Well-Known Member

    Feb 20, 2011
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    Hi George. Generally, we do not direct technical questions toward a specific member. We post them publicly so as to get a wider range of replies.

    Anyway, yes, the 4017 is larger, but it is still quite easy to hide. It takes up no more than 3 square centimeters, if that. If you want to sequence LEDs as you describe, you will not be able to do it with only a 555. All the 555 can do is turn the output on and off. I would strongly recommend the 4017, as it will make your life so much easier, and will not be difficult to hide. I suggest you take a look at this article that explains the operation of the 4017. In order to make it only sequence through 4 LEDs, you'll need to tie output 4 (since the count starts at 0) to reset, and connect your reset pin to a pull-down resistor rather than directly to ground. It will then only scroll through the first four outputs in this setup.

    Good luck!
    Regards,
    Der Strom
     
  6. Jure George

    Thread Starter Active Member

    Dec 28, 2008
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    Hi Der Strom,

    The Only reason I addressed this question to Mr. Marsden is because from everything I have seen, he is an expert in the 555. If he knows of a way to do it that`s fine by me.

    Also in your post you said for me to refer to the "article" what article, where?

    Thanks,

    George
     
  7. DerStrom8

    Well-Known Member

    Feb 20, 2011
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  8. Jure George

    Thread Starter Active Member

    Dec 28, 2008
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    Hi Again Der Strom

    Thanks for the link But I think there is some misunderstanding. I need to take 4 Yellow 3mm 20-25mA LED, physically, I will put them in a circle arrangement.

    I then need a SMALL Physical circuit that will be a LED chaser, if that`s the right term, turn on #1 LED On then Off then #2 LED to #4 LED continuously. Like a rotating beacon on a Warehouse forklift or heavy transport truck warning light. It will be covered by a plastic yellowish dome, size of Dome is not important. It will run on either 6v min. 7.2v mainly to 12v Max. battery in a remote control truck.

    I would like to vary the resistor timing with a variable resistor so I can set the speed of the rotation to my liking. All this MUST be SMALL and NOT be static sensitive or noise from servos or motors sensitive. When the prototype is done and tested, If I wanted to make an actual one for my truck, could I encase the Circuit in epoxy or similar to waterproof and shock proof it? OR would that affect it`s functionality and life span?

    I hope I`ve given you everything I am looking for. I need a Circuit and parts list PLEASE.

    Thanks Again

    George
     
  9. Wendy

    Moderator

    Mar 24, 2008
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    I would have said pretty much the same thing the other guys did, but I was pretty out of it.

    The way to normally do this is to start a post and explain what you want, then invite people like me via PM.

    Sorry to say, most of the replies you got were pretty accurate. Four lights (color matters for the analog part), four outputs. Then only advantage a 555 or 556 has over normal logic is the drive characteristics. It can actually reach 20ma for the LEDs, unlike most logic.

    What you need (if it is sequential) is something that does this on the outputs.

    0001
    0010
    0100
    1000

    And repeats. You don't have to use a 4017 or a 4022, but they will do this pattern almost without modifications. Unfortunately, their direct drive max is around 7ma, best case. So if you want 20ma you will have to use transistors, BJTs or MOSFETs.

    You might be able to make something with nothing but 555s, but it would be a much bigger pain overall. Timing with digital is pretty automatic, while a 555 is pretty much analog with digital outputs.

    I've covered most of the basics in my LEDs, 555s, Flashers, and Light Chasers article. Again, you might be able to do what you want to with a µC, I'm not sure.

    If you use discrete logic, you will need 2 chips (1 555, 1 other, and 4 transistors). From where I'm sitting you will need to make a PCB and used the smallest parts you can find.

    Four LEDs aren't much of a circle, but I suppose it would work if that is what you want....

    ...o
    o....o
    ...o
     
  10. Wendy

    Moderator

    Mar 24, 2008
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