Question About Leds

[cukaracha]

hey there

just wanna ask. i have this project going on that requires LEDs to be installed really close to the electronics (ie. pickups, selector and pots). will this in any way interfere with the sound quality of the pickups??

thanks

[Tim37]

shouldn't usualy dc doesnt cause noise

[Donovan]

If they are to be blinking, then you will possibly have some clicking on the on/off.

[Prostheta]

If that were the case, I presume that the clicking could be reduced by smoothing the transition slew between off and on using an RC circuit in there somewhere...? Or would the Vdrop of the LED cause a click when the ~0.7v transition is achieved? Never tried it myself, and never experienced noise from LEDs in audio circuits, so I presume the timer would be the culprit if clicks were introduced.

Anyway, that's a whole different can of worms. Tim37 hit the target first time.

[Donovan]

If that were the case, I presume that the clicking could be reduced by smoothing the transition slew between off and on using an RC circuit in there somewhere...? Or would the Vdrop of the LED cause a click when the ~0.7v transition is achieved? Never tried it myself, and never experienced noise from LEDs in audio circuits, so I presume the timer would be the culprit if clicks were introduced.

Anyway, that's a whole different can of worms. Tim37 hit the target first time.

Could be like you said, smoothable, but maybe not. Testing is on order. It mat be that the clicking is due to inrush current. If it is found to be so, I'd try minimizing the current as much as possible. Check out this thread from a few weeks ago. http://projectguitar.ibforums.com/index.ph...=39451&st=0

It may be also as you say that the clicking would be due to the timer. I ran into this while developing the variable kill switch. I was able to minimize the clicking, but not totally eliminate it.

On the converse side, I have aclipping circuit that uses LED's to clip. It is mounted in the pickguard and the LED's light when clipping occurs. This circuit does not click or pop, but this may be because it is masked by the distortion tones... but I don't think it's the case.

Anyway, only 1 way to find out what's going to happen! Try it.

[mammoth guitars]

Isolate your LED power and ground connections from the rest of the guitar electronics and there should not be a problem.

[cukaracha]

ok, fantastic!! totally answers my question!!

now just one more. how do i make the LEDs glow at say regular breathing pace? what hardware would i need that would make the LEDs turn brighter and back down automatically?? is there anything special about the way its wired??

thanks in advance

[Prostheta]

This is the issue raised by Donovan - if the LEDs change state quickly, ie. blinking then it's possible that click/pop crosstalk noise could be introduced to any signal lines nearby. If you want the LEDs to fade in and out, then it shouldn't be a problem.

I think that a steady fading in/out pattern could be acheived with a simple 555 timer circuit charging/discharging a resistor/capacitor arrangement which would provide a simple AC voltage to the LED, thereby varying the intensity.

This is what i'm thinking. The circuit is an astable multivibrator - the LED on the left shows the state of the timer, and the LED on the right fades in/out as the timer charges/discharges an RC arrangement.

[cukaracha]

ok, i saw the video and a few other more explanatory ones.

now my question is lets say i want the LEDs to light up, and fade down ONCE every 3 secs. what values of resistors and capacitor do i have to use?

also, is it necessary to use a breadboard? can i just wire all the components directly? and if i do, how do i ground it? if not, is there a smaller alternative to the breadboard?

thanks

Edited April 2, 2009 by cukaracha

[Donovan]

I suggest doing some research and learning how these things work. It shouldn't take too long as the questions you are asking are pretty fundamental.

I would do some reading. Read about 555 timers. Google the 555 timer and you will find a bilzillion sites explaining how to set them up, many with convenient little calculators that you punch in some numbers and they tell you what the blink frequency will be.

Also go to www.allaboutcircuits.com and read as much as you can handle about everything that is the world of electronics, including LED circuits.

[billm90]

ok, i saw the video and a few other more explanatory ones.

now my question is lets say i want the LEDs to light up, and fade down ONCE every 3 secs. what values of resistors and capacitor do i have to use?

also, is it necessary to use a breadboard? can i just wire all the components directly? and if i do, how do i ground it? if not, is there a smaller alternative to the breadboard?

thanks

I have never used bread boards. I just wire the stuff up. but I have not had to do any hardcore diy stuff without a supplied board.

but for something like this you may want to just find something that is made to do this function.

IC chips can be programmed to run a function.

this may be modded to do what you want. email the guy. he helped me out with my project.

http://www.bakatronics.com/shop/item.aspx?itemid=579

as for grounding. you will not be grounding your LED's to the guitar. your leds will be a complete spereate circuit.

Edited April 2, 2009 by billm90

[Prostheta]

There is that possibility, ie. making it a seperate circuit. It could also be used as part of the same circuit by joining the grounds, and using a stereo jack socket to break the 0v rail continuity of the LED circuit thereby turning it on/off when plugged in, same as how EMG pickup circuits work. I would pop a small electrolytic cap across the +v and 0v rails to clean up any noise which might otherwise be introduced through them. Not sure if this would work in practice, as i've not done much active electronics work for a few years now.