Multiple LEDs

[Josemitejam]

Hi all,

I'm building the Schumann floop clone from dead end fx, and  I was considering adding a few extra leds just for some visual fun. So I'm wondering, how will leds affect a pedal? Instead of just one, would ten start degrading tone, etc.

Thanks!


Joe

[GibsonGM]

Got a link to the schematic?

[Josemitejam]

Here's the link: 

https://drive.google.com/file/d/1kOqsQYWxK222AO_UmE2SFrxSq9b6eUMM/view

So it would depend on the pedal and it's schematic then?

[GibsonGM]

Well, things like 'adding LEDs' depend on what the LED is being used for, how much current it/they draw...what the power supply consists of and so on.  So yes, it does depend on what's going on.   Circuits can only operate within SOME defined set of boundaries. Adding things can exceed those bounds and let out the magic blue smoke

So, are you talking about the LFO 'rate LED', D2/R6 on the schematic?  I believe that if you keep the current draw the same, you won't affect the LFOs operation. If you try to put too much load on it, you will.  That means cutting the current to the existing LED in order to drive a 2nd one.   

Others have DONE this (and a search might give you more specific info)...you need to understand the output of the 4069 chip (what it can sink/source), and what voltage is present at the output there.   If you exceed the given parameters, you'd have to make a driver, perhaps from an NPN, or ruin the chip.   There's only so much 'adding on' to an IC that you can do without more of a modification...just offhand, I think you may need a driver to do anything 'worthwhile', which is not a hard thing to toss together, and would allow you do a FEW LEDs, rather than 'getting away with' just one more.  As long as you have room for it (like, 3 parts).

To see why I'm leaning that way, read this: http://lednique.com/parallel-leds/  and ALSO remember that the LFO has a job to do - asking it to supply more current for the LEDs may lead directly to circuit performance issues, and we don't want that...you could also look up "NPN LED DRIVER"  on the net.... HTH!

[iainpunk]

if you put multiple LED's in parallel, they all need their own current limiting resistor, otherwise, some(most) won't turn on at all.

cheers

[Josemitejam]

Ok that makes total sense, I'm gonna play this safe and stick to the schematic's two leds then!

Thanks a ton!!

[GibsonGM]

Ok that makes total sense, I'm gonna play this safe and stick to the schematic's two leds then!

Thanks a ton!!

Or, you can stick a transistor where the rate LED goes, and use it to drive multiples!   Something to try just on a breadboard if you want, as a 'learning exercise', and with any additional LEDs you place in parallel having its down R, as Ian picked up on...there will be a limit to how many 1 transistor can drive, it does have a power rating   If you're using super bright low current LEDs 'outside the circuit' with base tied to LFO output THRU A RESISTOR, that number may 'quite a few'.  Look up 'LEDs in parallel' to learn how to choose the resistors...this 'trick' is worth messing around with on the BB, learning about before attaching it to an LFO.  Many ppl do this.

http://www.learningaboutelectronics.com/Articles/LED-driver-circuit.php

[antonis]

Is there any particular reason, other than severely loading LFO output, for using multiple LEDs in parallel configuration..??
(in the mean of, there should be identical voltage drop across each LED + individual current limiting resistor..)

[GibsonGM]

Is there any particular reason, other than severely loading LFO output, for using multiple LEDs in parallel configuration..??
(in the mean of, there should be identical voltage drop across each LED + individual current limiting resistor..)

If I understand correctly, because the OP wanted to know if it could be done to 'look cool'?  Visual fun    I assumed parallel...would it be better to do it in serial? Purely academic discussion, I also am curious of the best way to do this if desired. 

I would plan to use an NPN as a driver and avoid loading the IC, thru a resistor to base (10k?), and would calculate the correct dropping resistors for each - and would consider how much current it will take to do each one.   This question comes up sometimes regarding Arduino outputs with multiple LEDs, for example.

[antonis]

I assumed parallel...would it be better to do it in serial?

It depends on available power supply headroom (n times forward voltage drop) and only for identical LEDs (of the same current rating)..

On the other hand (parallel), it's more like total current consumption matter..

[iainpunk]

i'd say parallel.

there are two LED's one controlled by a momentary switch and a circuit that is giving a ramp up and down signal. given the fact that its voltage controlled brightness, putting more LED"s in series would diminish the on time by ''gating'' the signal.
the other is controlled by the CMOS chip, this could be done in series so conserve a few mA, the LED's individual need not be that bright, since there are multiples of them.

cheers