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Thread: I need help placing a switch on some LEDs

  1. #1 I need help placing a switch on some LEDs 
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    Hello,

    Okay so I am modding my computer case to have a switch to turn off all the lights that are attach to the fans.

    I have 8 fans and in each fan there is 4 LEDs (32 LEDs). The problem is that I am scare of burn up the LEDs and because I have no general idea what voltage they are I am in a debate about doing it.

    Also I needed advice in how should I set it up. I was thinking about having a serial circuit on each fan and then have a parallel circuit on to attach each fan. The problem is that I am not very keen about the difference between Serial and Parallel.


    Also just the fans are made by ASPIRE.


    If there was no religion in which Gods would be the main issue, war would now be a fight agaist the best scientific theory.
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  3. #2  
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    Led's each require a curent limiting resistor, usually if multiple led's all operate together they are wired in series with a single resistor.

    Now series and parallel,

    Tak a batterey and place a bulb directly across it's terminals, next wire another bulb directly to the battery contacts, and a third etc these are wired in parallel, remove one bulb and the others remain lit.

    Now imagine a a single wire placed in a circle so that it's two ends are connected. - Cut the wire and place each end onto the two contactcts of the bulb, cut the wire in another place and attach the two ends to another bulb, then a third etc - this is wired in series (cut the wire in another place and join a battery into the circuit). disconnect one lamp and all the lamps will go out.

    For your problem, how many wires are there going to each fan? if it is two then unless you take it to pieces you will only be able to turn the fan and leds off together. IF there are three or more wires then you need to disconnect them one at a time to see which one(s) are for the LEDs.


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  4. #3  
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    Okay... So this is how it looks...

    Each Fan has a LED and I can remove the two wires (Possitive and Negative of course).

    My plan was to skip the resistor by dividing the voltage using Serial or was it Parallel between four LEDS in each fan.

    I think I might just make a sketch of what it should look.
    If there was no religion in which Gods would be the main issue, war would now be a fight agaist the best scientific theory.
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  5. #4  
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    What about this... the power source is 12v DC
    If there was no religion in which Gods would be the main issue, war would now be a fight agaist the best scientific theory.
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  6. #5  
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    You'll find none of them will light in that congufration, All diodes only conduct in one direction - Leds (depending on color) will need from 1.8 to 4.0 volts each, so I reckon it would be best to keep them in pairs. As you have drawn the diodes the Positive (from the battery or supply MUST be connected to the left hand side of the diode, (or each pair) The right hands side of Each pair MUST go through a resistor to the negative side of the battery. - Leaving out the resistor will destroy the LED - No question of it. Generally Red/Green/Yellow Leds require about 2 volts each whereas White/blue diodes require about 3-4volts.
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  7. #6  
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    Well I think it is white... or better UV...

    anyways... is there any way you can draw me a basic sketch of how it should be?
    If there was no religion in which Gods would be the main issue, war would now be a fight agaist the best scientific theory.
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  8. #7  
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    as you have shown the four pairs of diodes, just connect all the left hand sides together and then to the battery positive, with each right hand side going through a resistor, the other sides of the four resistors then going to the negative side of the battery, use 470ohm resistors.

    THen you redraw it and I'll comment again..
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  9. #8  
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    Okay... So I kind-off got you instruction... well not really

    so this new Circuit is labeled. Also I could add another 12volt supply if needed... like if one 12vold can't turn all 32 LEDs.
    Direct Link to picture (in which it look better)
    http://img.photobucket.com/albums/v371/itstemo1/led.png
    If there was no religion in which Gods would be the main issue, war would now be a fight agaist the best scientific theory.
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  10. #9  
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    Firstly you have shown the supply wire going from left to right, down and then back, which is shorting out the battery, so you need to 'snip it' at the right hand side. Secondly when you do this the top diodes will work but the bottom ones are all the wrong way round. - the switch should be connected to one side of the battery with the other to each string of LED's.
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  11. #10  
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    Oh okay... I think I got it... I will make another one in about 20 more minutes... Got to do some HW
    If there was no religion in which Gods would be the main issue, war would now be a fight agaist the best scientific theory.
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    HouseWork eh? - good lad!
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  13. #12  
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    No actually Homework that was due at 4 (5GTM)

    So what do you think about this?

    http://img.photobucket.com/albums/v3...mo1/Lednew.png
    If there was no religion in which Gods would be the main issue, war would now be a fight agaist the best scientific theory.
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  14. #13  
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    That will work just fine, you may have to adjust the the resistor value, without the spec for the LED's (ie voltage and current) I cannot say, the value I have given you is on the conservative side, all the leds should light, with reasonable intensity.
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  15. #14  
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    Oh yeah... forgot to tell you I got this thing to control the intensity.

    http://www.jameco.com/webapp/wcs/sto...oductId=255661
    http://www.jameco.com/Jameco/Products/ProdDS/255661.pdf

    So yeah... I don't know how to place it... It got three legs and I just don't understand what is the third one for?
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  16. #15  
    Cooking Something Good MacGyver1968's Avatar
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    A potentiometer is just a variable resistor. The outside pins, (1&3) connect to the ends of the resistor. Pin 2 connects to the variable "slide" that moves up and down the resistor. So you would need to use 1&2, or 2&3. It's also a good idea to throw a small fixed resistor in series with it, so if you crank it all the way down to no resistance, you don't burn up the leds.
    Fixin' shit that ain't broke.
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  17. #16  
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    Okay I think I got this one. I hope this is the last sketch I need to make. Anyways. I added the pot but wasn't sure if it is place right. I use this website to guide me.

    http://www.walter-fendt.de/ph14e/potentiometer_e.htm

    Anyways... this is my new sketch
    http://img.photobucket.com/albums/v3...emo1/led-1.png
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  18. #17  
    Cooking Something Good MacGyver1968's Avatar
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    I'm sure MB will correct me if I'm wrong...

    You shouldn't need R10 as you already have limiting resistors for the banks of leds. ( I know I said add one, but I didn't look at your schematic properly)

    I think you have R9 set up as a "voltage divider".

    You might try this:



    It's been awhile since I've done schematic work...I'm I missing anything MB?
    Fixin' shit that ain't broke.
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  19. #18  
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    Quote Originally Posted by itstemo1
    Oh yeah... forgot to tell you I got this thing to control the intensity.

    http://www.jameco.com/webapp/wcs/sto...oductId=255661
    http://www.jameco.com/Jameco/Products/ProdDS/255661.pdf

    So yeah... I don't know how to place it... It got three legs and I just don't understand what is the third one for?
    The minimum number of legs needed t support an inanimate object is 3 - see tripod. - they are NOT legs they are connections!

    PLace it in your dustbin. I approved an earlier cicuit of yours to get you going, I can't spend time forever correcting you if you want to go and add frilly bits. - Varying the leds is way out of your league I'm afraid, you'd need to vary the volts of a 2.0 volt LED from about 1.83 to 2.02 volts but each LED will be different. You might PWM them but I suspect that too would be too complex for you. - Sorry mate, times up! - NEXT!

    Mac, nice try but all that pot is gonna do is feel like another switch, nothing till you get right to the end! - it may even burn out.
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  20. #19  
    Cooking Something Good MacGyver1968's Avatar
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    Quote Originally Posted by Megabrain

    Mac, nice try but all that pot is gonna do is feel like another switch, nothing till you get right to the end! - it may even burn out.
    That was what I was worried about. 10k would be a little much.

    It would kinda like having a volume knob on a stereo that was numbered 1-10, and you wouldn't get any sound until you cranked it to 9 1/2.

    Thanks MB
    Fixin' shit that ain't broke.
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  21. #20  
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    If it was a log pot though it could be 9.999999999999999999999999999999999999999999999999 999 BANG!
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  22. #21  
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    Megabrain Thanks for all the advice. I will keep the final one that you advice me in.
    If there was no religion in which Gods would be the main issue, war would now be a fight agaist the best scientific theory.
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  23. #22  
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    Well after testing the circuit with 6 sets of 4leds it seems to work. How long does it take for a LED to burn out?
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  24. #23  
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    If you run it within it's specified rating I believe they have lifetimes up to 100,000 hours, typically 10-20,000 hours at max rating (from memory) - if you exceed these ratings lifespan will begin to drop dramatically, if run many times their rated value it could all be over in less than the blink of an eye.

    And thanks for coming back with the results.
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  25. #24  
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    Okay this some how ended up sucking all my power from my PSU in my computer.

    I am only did one serial of 4 LED's and placed the switch. For some odd reason one of my HDD (main HDD) kept turn on and off.

    It might have been the part where I am at my limit of my PSU but... 4 LED's ... c'mon!
    If there was no religion in which Gods would be the main issue, war would now be a fight agaist the best scientific theory.
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  26. #25  
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    Gosh after two years of working (and slacking off) I finally finish the project and did some extra modifications. This includes using a NPN transistor and plug it a Audio splitter. This is what I get.

    http://youtube.com/watch?v=jwmOhPFUqbA
    If there was no religion in which Gods would be the main issue, war would now be a fight agaist the best scientific theory.
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