555 timer project idea, need help

Discussion in 'The Projects Forum' started by adamclark, Oct 6, 2013.

  1. adamclark

    Thread Starter Member

    Oct 4, 2013
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    hello all,, So I have a project I want to build. I recently scavenged an RGB LED from a scanner. I tore the scanner apart because I found an instructable to build a cool desk lamp from the super bright white bulb in most scanners.. Well the one found and ripped apart had an RGB LED in it instead of a bulb. So I had a few issues making white light from it, but im getting that worked out with help in another area of the forums here. So I wanted to post this here to keep things separate.. Ok, with that said heres what I want to do.. I did a search of this site to figure out how to get the LED to light white and I read a few guys here talking about using 555 timers to control the colors with PWM. I have a dozen of the 555's and got to thinking about it.. So heres what I want to do... I want to build a desk lamp with the RGB and be able to control the colors with a single switch and some 555's. Now im kinda new to this and ive done a couple of 555 projects so Im not really familiar with the timer. right now im just interested in getting the light to work with a single switch to turn on red, blue, green, and white using 555 timers.. after that's figured out I might want to do some color fading and other cool things with it.. Thanks
     
  2. adamclark

    Thread Starter Member

    Oct 4, 2013
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    I have solved the issue with getting the color of my RGB LED right in another thread and asked for it to be closed. I am ready to move forward with the 555 PWM part of my project and would appreciate any ideas/help to be posted in this thread. Thank you
     
  3. bance

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    Aug 11, 2012
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  4. adamclark

    Thread Starter Member

    Oct 4, 2013
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    fig. 5.2 kinda makes sense, but I don't see how its adjustable... Would I have to use 3 555's to control the RGB to use all the colors? thanks for the help. getting started is the hardest part for me, Once I get going I will have some stuff built and be able to post schematics of what Ive got going on..
     
  5. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    Yes, you will need three.

    Do you know the current limit on each color for this LED?
     
  6. adamclark

    Thread Starter Member

    Oct 4, 2013
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    not sure on the current limit but I am using a 9v battery in my test circuit and I had a 1K resistor on the positive lead and it was working, but I accidently shorted out the resistor to straight 9 volts and it got really bright but did not burn out.. Just so you know what I got on the test board heres what I did.. the + 9v lead goes to the positive in on the LED through a 1K resistor. the other 3 leads are connected to the ground on my board through 0-6K pots. adjusting the pots allows me to tune to whatever color I want. off subject here but I was able to tune it to a yellow that was more yellow than any yellow LED ive ever seen.. but with some tuning I was able to get a nice white also.. Im assuming that the pots on the negative leads acted as current limiters when I shorted the 1K positive resistor to straight 9v which is why it didn't burn up. which leads to my next ?. Do I need the 1K resistor on the positive lead with the pots on the negative? This is going to be a desk lamp so it needs to be bright, but I don't want to burn it up.. but it was really bright in the scanner so that's why I thought of making it a lamp in the first place. theres a few numbers on the RGB LED, is there a way I could find a datasheet on it without knowing the manufacturer?
     
  7. bance

    Member

    Aug 11, 2012
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    It's probably a 350mA 1 watt per colour RGB LED... Google the part No. for a datasheet or the scanner (whatever it came out of) for a schematic. The advantage of having the 1K resistor is that when a pot is off (0 Ohms) there is still some current limiting in place. Have you considered using a microcontroller instead of three 555's?
     
  8. adamclark

    Thread Starter Member

    Oct 4, 2013
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    the thought has crossed my mind, ive even built the velleman kit pic programmer and have a couple pic 8p chips, However I am somewhat new to electronics and have no clue on programming microcontrollers. I have never written a single line of code. That is on the list of things to do and the ultimate goal for me is to learn arduino mc's.. my son and I are building a quadrotor drone and it will be mostly controlled by microcontrollers.. I have used the 555 a few times though so I try to keep my projects solid state for now until I get good grip on the basic components. then I plan on moving into microcontrollers
     
  9. adamclark

    Thread Starter Member

    Oct 4, 2013
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    If you would care to write the code and provide me a schematic I would be more than happy to try and build it..lol
     
  10. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    For fun, might try a 4022 or 4017 decoded counter with one 555 as variable clock, & 3 555's for LED drivers. Watch colors blend as speed is increased.
     
  11. bance

    Member

    Aug 11, 2012
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    I would quite happily write the code for you if I had the time, unfortunately I barely have the time for my own projects....;)

    However the code you would require to do this, is very basic indeed.

    An Arduino would be a good starting point, but you are mistaken in thinking an Arduino is a MCU (microcontroller,) it is in fact a development platform that uses atmel MCU's..

    The very first programme that is usually written is to turn an LED on, and the second is to make it blink (a form of PWM.)

    I hope I still have your attention!:D

    From there it is not a great leap to controlling three channels via a variable resistor and the ADC (Analogue to Digital Converter.)

    One of the advantages of Arduino is that it is OSS (Open Source Software,) and as a consequence much of the code written by others is available free of charge to anyone who cares to use (modify or abuse,) it.

    In fact the Arduino IDE (Integrated Development Environment) programming software comes with code examples (in Arduino speak 'sketches') that will do at least the first two.

    A second advantage of the Arduino platform is that the hardware is also open source, this means that you can buy an appropriate atmel MCU with the Arduino bootloader pre-installed along with a crystal oscillator, a couple of capacitors and a USB-TTL interface, and make your own 'Arduino' on a breadboard or vero-board.

    All are available from Sparkfun or if you are really cheap Chinese suppliers on e-bay.

    How cool is that?:D
     
  12. adamclark

    Thread Starter Member

    Oct 4, 2013
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    im still following you,, I actually have an arduino uno board and a couple shields I was planning on plying with... From what ive read it was my understanding that it was indeed a microcontroller... but I also have a pic programmer and a few 8p chips to program with it.. Im confident I could learn to write the code, but it is a little further down the list in my plans of education.. but I might get it out and try to do a few small experiments with it.. just didn't want to hurt it by doing something that it cant do.. I already have a pile of 555's and a few other things that I have taken out of the game.. apparently a 555 cant drive a relay straight from its output..lol
     
  13. adamclark

    Thread Starter Member

    Oct 4, 2013
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    So would the pic I have be suitable for this? its a pic16f627-04/p microcontroller? What language is this code? I would be very willing to try to write the code and give building the circuit a shot as long as I have a place to ask questions.. im sure it would be a long road....
     
  14. adamclark

    Thread Starter Member

    Oct 4, 2013
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    oh,,, and ive recently read an article about this adc you speak of also,, so im kinda on your page
     
  15. adamclark

    Thread Starter Member

    Oct 4, 2013
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    im interested,, care to throw up a diagram I can chew on?? the color blend thing was on my list of cool things to do once I had the basics figured out..
     
  16. adamclark

    Thread Starter Member

    Oct 4, 2013
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    So whats the thoughts on the basics,, I want to get thing built so I can start to play around with it.. I looked for hours and cant find a single datasheet on the LED I have.. I know it will run on 9v straight but it gets warm quick and I don't want to hurt it.. also at 9v it makes a brilliant brite white without having to turn down the red.. So I am just going to assume that no more than 5v is the max for it to keep it alive awhile.. The basics I need to figure out first is I want to be able to toggle through all 4 colors with a single switch at the base, and I have a 5v 1000ma phone charger I want to use as a p/s... so once I figure this out I can build it and then start the cool things..
     
  17. adamclark

    Thread Starter Member

    Oct 4, 2013
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    after some thought, Is there a way I could vary the voltage to the led to control brightness?? or a way to increase the voltage slowly until I can get it to the brightest safest voltage possible? and how could I tell when that voltage is reached? Its gonna be a desk lamp so it has to be bright, and it could possibly be on for hours at a time.. its flat and about 3/4 inch square,, would putting a heat sink on it be of any advantage?
     
  18. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    For estimated 3W total, a heat sink would be advisable.
    A momentary pushbutton switch might be used to step a 4017 thru the three colors & 4th start a clock to give white.
    Forward Vs would be helpfull. With 5V supply could try 12 Ωs for blue, 18 Ωs for red, & 17 Ωs for green, should roughly give 150 mA to measure Vf.
    Wiil take a stab at a drawing.
     
  19. adamclark

    Thread Starter Member

    Oct 4, 2013
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    awesome,, cant wait for the schematic.. although im kinda lost at the low ohms, Ive got a 1k on it right now to limit current. Im assuming the 4017 takes care of the current limiter for the LED? Im going to have to find a datasheet on the 4017 also..
     
  20. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    A 555 can drive most relays directly.
    Here are some bits and pieces that might do what you want. Now I know what was left out--IC ID. Start with 555-OSC, A; 555-OS, one shot, B; 555-FF, flip-flop, C; 555-INV-R, D; up E; F; 4017- G; OR-H; INV-I.
    No telling at what state everything will be in at power-up, but cycling thru once should make avery thing normal?
    First SW push puts out a .1 to 1 s + pulse to cover up any SW bounce. resets C which is already reset,& advances 4017- G, one count. THe first stage of G, 0, pin-3 is high at reset so " 1' is used as first active step. When G-2, goes hi D-3 goes lo turning on R LED. Secsnd push turns on G LED, 3rd B LED. 4th push puts a hi on I input, output lo sets FF C. C-3 goes hi , enabling OSC, A. G continuously recycles, resetting every time G-1 goes hi. If SW is pushed again, FF, C is reset, stopping the clock - at a random output. May want to add an OR to G reset and diffrentiate C out for a secondary reset pulse. Wanted to keep first cut simple. Would prob. use a NOR IC for the OR & INV.
    A review might be helpfull??
     
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