how to add LED's to each of these mods?

[Bandwagonesque]

hi everyone and happy weekend. My switching woes befall me and I am having some trouble in getting a simple thing to work in adding LED indication to both of these mods for a silicon fuzz face I am working on. I am wanting to add a simple feedback 'flaming howl of death' oscillation mod with the input jack tip going to a momentary 2 pole arcade switch, then to a b100K 'tune' pot, then to the output jack. can someone tell me how I would go about adding a regular led to the side for indication when its on?



im also trying to do the same with an on/on DPDT switch in cutting off this tone circuit and having an LED on when tell me when the tone control is on and then off when its off. could someone show me as to how I would get this done? any help would be greatly appreciated as im stuck and not sure how to get over adding LED indicator's to simple switching mods. thanks again folks and take care.

[antonis]

[Bandwagonesque]

thanks a bunch antonis! But is there an easier way sans the transistor and extra resistor? Ive been trying to make a work-alike wiring layout like this one work for my tone control needs but for a DPDT instead of the 3PDT like on the layout, but I keep burning up my breadboard and wafting smoke out of my face so im not sure what im doing wrong. do i need to do anything with the vacant 2 terminals on my switch? my fuzz is npn negative ground. any help would be greatly appreciated. had an easy enough time adding a switch to bring the tone control in and out, but adding an LED to let me know if its on or off has been deceptively difficult and i keep burning through things. 

[kaycee]

You do know that you always need a current limiting resistor on an LED, don't you? Otherwise they burn up. Antonis' example, only adds a transistor to the essential resistor, you could solder it up flying off of the LED legs, or use a finger nail size vero.

[ElectricDruid]

You do know that you always need a current limiting resistor on an LED, don't you? Otherwise they burn up. Antonis' example, only adds a transistor to the essential resistor, you could solder it up flying off of the LED legs, or use a finger nail size vero.

+1 this. Sounds a lot like you're not limiting the current through the LEDs. An LED is a diode (yeah, yeah, you knew that) and that means that one way around it looks like an open circuit and the other way around it looks like a short circuit. So imagine that LED as shorting your power supply to ground. Now you see where the smoke is coming from and why a resistor to limit the current is important!!

[Phend]

Why the transistor, why not just a 3k (1k) resistor and led from 9v to grnd. Please explain, thanks in advance any comment(s).

[idy]

I'm thinking Bandwagonesque hasn't been "read in" on what that transistor LED switching or "millennium" bypass is.

If you have an unused pole on your switch (i.e. the circuit mod requires one pole and you've got two, or the mod requires two poles and you've got three) you just use a mechanical switch and (very important!) a Current Limiting Resistor. Just like regular footswitch.

If you don't have an extra pole on your switch (the circuit requires three poles and you haven't got four, the circuit requires two and a three pole switch won't fit, etc.) but you do have a "half used" pole (i.e something is either connected to the circuit or its disconnected and one terminal of that pole is unused) you can use that, if it is a "path to ground," as a control terminal for that fancy transistor switching gizmo. Sometimes called "Rat" bypass cause that's what the Rat makers used to get true bypass and LED out of a DPDT. The improved version is called "millennium" bypass and our thanks go to R Keen.
http://www.geofex.com/article_folders/millenium/millen.htm

In the Rat and Millennium the "unused" terminal connects to the output of the circuit in bypass. A resistor to ground is either already there, or adding one doesn't mess things up too much.

[antonis]

Why the transistor, why not just a 3k (1k) resistor and led from 9v to grnd. Please explain, thanks in advance any comment(s).

If you read carefully my quoted schematic (kudos to Joe Davindson), transistor acts as a slightly ON switch in the mean of Base voltage controls Collector-Emitter current..
In case of a "classic" LED switch (fully ON), it should definately need a current limiting resistor in series with the LED..

[Bandwagonesque]

hi everyone. I managed to get an LED working for my tone bypass switch by using the following method, but connecting the bottom pins together.


The only issue is that im still having problems with my breadboard smoking up. But I narrowed it down to the voltage sag pot that is smoking up , but its for some reason that escapes me and its getting killed in the process. I have a b10K pot as the voltage sag and a 100uF electrolytic cap across the 2 and 3rd lugs (negative to center lug/2nd lug) and a 3.9K resistor to ground. this usually with all my other fuzz face circuits, gets me to around 4.5 volts when rolled all the way back to feel just like a battery before death. but this is the first time ive ever experienced a sag circuit smoking up on me.

its a npn fuzz face circuit and the only other weird stuff is a b250k pregain pot and a tone control and a 1.2K vs 470ohm switch. does anyone know what could be the matter? when I bypass the voltage sag circuit/pot, it works justttt fine but its a real drag I have to sacrifice the sag pot as I kind of need it in this instance. thanks everyone so much for your help so far as 

[antonis]

OK.. Let's take it once more..
(in the mean time, a bucketful of water should be essential..)

+9V -> LED -> GND -> SMOKE ..

[Bandwagonesque]

I would hope it would be so simple that that would be my issue but everything seems right but i'm still cooking through voltage starve pots. Here is the schem to my npn fuzz on the breadboard exactly as it is. excuse the crudeness as its my first freehand schem in a long time. there are alot of pots and their pot lugs are numbered. but can anyone tell me if my switch for the 330ohm vs 1.2K,  or the tone circuit and bypass switch with LED placement is causing my trouble with the voltage starve circuit? when i jump the voltage starve circuit completely, everything works just great! but would really like to be able to sag the voltage a bit and admittedly clueless why i'm hitting a block. glad I have the LED working but this caveat isn't what I was expecting to face.

[kaycee]

I have no idea why you have the capacitor and resistor to ground off of your sag pot? You just need variable series resistance of the pot to simulate sag, no path to ground.

[antonis]

What is the value of voltage sag pot..??

[Bandwagonesque]

I have no idea why you have the capacitor and resistor to ground off of your sag pot? You just need variable series resistance of the pot to simulate sag, no path to ground.

ahh i was going off of this layout here but is this the incorrect way of doing things? this way, with a B10K pot and a 3.9K resistor to ground (instead of the 2.2k on the diagram) I was getting to 4.5volts at the end of its throw with a nice smooth taper. otherwise i was dealing with caveats, but is this wrong? the electrolytic capacitor i read around here (https://www.diystompboxes.com/smfforum/index.php?topic=76150.0). is this something i shouldn't be worrying about either? I did try it without the resistor to ground and cap and smoked another pot (ha...ha...).

What is the value of voltage sag pot..??

whoops! I used a B10K for the Voltage Starve

[antonis]

I used a B10K for the Voltage Starve

Does the LED glow when its Cathode is grounded AND pot wiper set at any posistion other than FCW..??

[Phend]

Reference:...Plus a Question for my education, What does a sag pot do for the effect, yes it adjusts the voltage, what benefit is there for the effect or sound ?

https://www.diystompboxes.com/smfforum/index.php?topic=113378.0

[kaycee]

Reference:...Plus a Question for my education, What does a sag pot do for the effect, yes it adjusts the voltage, what benefit is there for the effect or sound ?

https://www.diystompboxes.com/smfforum/index.php?topic=113378.0

In this case, it will make it more spluttery and gated the more the voltage is restricted. Supposed to simulate a dying battery, not actually as simple as just reducing the voltage as I understand it. Anyway, some players swear by a partially depleted battery.

[Bandwagonesque]

I used a B10K for the Voltage Starve

Does the LED glow when its Cathode is grounded AND pot wiper set at any posistion other than FCW..??

Bingo, its doing very nearly this. When the pot is all the way CW, it emits for a split second and then pitters out to nearly nothing at all but then emits when the voltage starve is turned all the way CCW. I got rid of the path to ground with lug 1 to resistor to ground, and instead put the lug 1 to board power, and then connected the 2nd and 3rd lugs and sent those 2 to +9V, but the problem still persists and not sure why this is doing this now as this has never been a bother in the past. do you happen to know what im doing wrong?

[antonis]

Let's see what Georg Ohm (with a little help of Gustav Robert Kirchhoff) says about it..



+9V - (Lug 2-3)*I_LED - CLR*I_LED - LED_{forward voltage drop} = 0 => +7V = (lug 2-3 + CLR)*I_LED, considering 2V LED drop..

You can see that LED glow is strongly dependent on lug 2-3 + CLR total resistance..
When pot is set FCW, plenty of current is availiable for LED glowing..
(it's only dependent on CLR value..)

What actually happens with your particular issue is the reverse Voltage Sag pot wiring..
(lug 1 instead of lug 3 placement..)
That's the reason for LED glowing when pot set CCW - you actually set it CW..!!

P.S.1
Instant LED glow is due to 100μF cap discharge..

P.S.2
100μF cap should be reverse wired - positive plate looking to +9v..

[kaycee]

Power the LED from the 9v source, not after the sag. I still have no idea what the capacitor is supposed to be doing, remove it.