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Circuit to Generate DC Power Circuit

  1. Jan 9, 2010 #1

    I'm very new to designing and building electronics involving anything outside of simple Transistors, resistors, capacitors, and diodes. I have a fair amount of experience with the parts previously listed and they may be the only parts I need for the task I am currently requested aid in building because I am incompetent when it comes to apply the simple knowledge I know in electronics. I am attempting to build a circuit which will drive about 80 5mm RGB LED lights in syncronized slow on/off oscillation. To specifiy the term slow on/off oscillation, I am hoping to use a circuit which will provide DC power to these lights which gradually increases magnitude and then decreases in magnitude so that the intensity of the lights will oscillate as they change color. These RGB LED's possess a common anode so I was also hoping to implement some IC which randomly distributes the electricity to each color cathode so that a syncronized yet new color is generated by the 80 LED's with every slow oscillation of color.

    Esentially I am asking what circuit would generate a Sine wave or sawtooth DC signal, and is there an IC which can randomly distribute this signal across different anodes? I know that this can probably be accomplished with a PIC or a microcontroller but i have no experience with either of these parts.


    P.S. I have googled this but I am overwhelmed with reasources describing AC power
  2. jcsd
  3. Jan 9, 2010 #2


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    I doubt if any ready made chip is going to suit what you want. There has to be some demand before producers will make something like that.

    That is why micros exist. They have a powerful set of tools in them and can do the job you want easily and cheaply.

    Eveyone should have a favourite micro. I can't understand the extreme reluctance people have to getting involved with them.

    Mine is the Picaxe.

    I use pieces of PC board and mount the components directly on one side without sockets.
    ICs are mounted with pins pointing up and earthed pins bent down and soldered to the the PC board. You will see why this is called "dead bug" construction.

    I get strips of computer header pins and break off short lengths of the pins, then cut the pins to make small tag strips. I solder the earth pins to the PC board and this supports the tag strip. Wires entering or leaving the board can be soldered to these tag strips or fitted to header sockets. These are cheap and pins and sockets come in strips for less than a dollar.

    The chips require 5 volts so I mount a 5 V regulator on the board, also on tag strips. This stops any risk of applying a higher voltage and wrecking the chip.

    Picaxe chips are programmed on the board they are going to be used in by arranging two resistors and a 3 wire cable to the computer.

    This looks like a great project for you to get some micro experience.
  4. Jan 9, 2010 #3
    Would you recommend any particular tutorials to learn this? Additionally what materials would you presume I would need to both learn and accomplish this project?
  5. Jan 9, 2010 #4


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    Get the free software from :

    Look for the software called BAS805.EXE from the above site.
    There are adequate examples and plenty of documentation in this file.
    All commands are explained with examples.
    Avoid the expensive development packs and programming boards.

    Do you want all LEDs to be the same colour at the same time, or do you want each to be controlled individually with random colours? The latter is more complex and will require more components, of course.

    I would devote some time to becoming familiar with the Micro controller you choose. This is fun stuff and will make a lot of your projects easier in the future.
  6. Jan 9, 2010 #5
    "Do you want all LEDs to be the same colour at the same time, or do you want each to be controlled individually with random colours?"

    Well I was hoping that all of the LEDs would project the same color at the same time, but I plan to have three or four seperate panels of LEDs displaced throughout the room so I hope that will not create any problems. Effectively I am attempting to make some cool mood lights.
  7. Jan 10, 2010 #6


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    RGB Leds.PNG


    You would probably need something like the above. It shows two RGB LEDs with the same colours being switched by a transistor and the brightness of each being controlled by a PWM output of a Micro.

    I have a small doubt here. It is possible that the PWM sources could beat with each other in the LED and produce a strobing effect which would not be very relaxing.
    If that happened, some filtering at the base of the transistors might be able to get rid of the effect.
    I don't have any RGB LEDs, so I can't try it. Maybe you could try it and find out before you commit to getting a lot of LEDs working.
  8. Jan 11, 2010 #7
    Wow thank you for the diagram and everything. I still have alot of reading and experimentation to do with the microcontroller before I get it working, but if I manage to get it up and running I will post a parts list, code, and a clip of it so anyone interested in the concept can have an easier time than me.

    Thanks alot V for the help
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