Layout of positive grounded pedal

[frogman]

I am soldering up a tonebender mkii clone inside of an enclosure. The only pedals I have done thus far have had negative grounding schemes and wall jack plugs. This one has positive grounding and is battery power only.

I think I have all of the kinks ironed out.... The positive battery terminal goes to the middle lug of the stereo jack input and negative battery terminal goes to the -9v on the circuit board.
(please correct me if I am wrong)

My main question is about the LED... This is the 3pdt wiring that i have been using.

http://3.bp.blogspot.com/-EU_2EXapXLY/T5_wCJnN9YI/AAAAAAAABDU/xkOXlkmzruY/s400/EZ_3PDT_WIRING.gif

Would the positive end of LED go to the 3pdt and the negative end of LED go to the negative battery terminal/-9v on circuit board?

[GibsonGM]

Yup.  With PN junctions, polarity is absolute.  Good call.

[frogman]

Another quick question.

Ive asked this before but I worded it wrong and it was a confusing mess. READ THE WHOLE QUESTION.

Do I need a resistor between the power supply and LED (POWER SUPPLY --> 10K RESISTOR --> LED --> 3PDT SWITCH) or will a resistor in between the LED and 3pdt switch (POWER SUPPLY --> LED --> 10K RESISTOR --> 3PDT SWITCH) have the same effect on the brightness of the LED.

I've heard that they both have the same effect. However, I think I didnt understand the person's explanation they didnt understand my question and I stupidly wired the pedal this way and I dont want to do any unnecessary soldering, so I'm asking ya'll.

I ask because it seems odd. To limit current flowing to the LED, the resistor would need to be before the LED right? Not after the led.

[greaser_au]

in a series circuit, the current through all elements will be the same.  The current will be the same in either arrangement (all other things being equal).  See Kirchoff's current law : the sum of the currents entering a node will equal the  sum of the currents leaving the node. In this case the nodes (node = a point where one component joins another) have one entry point and one exit point - and thus all nodes have equal current through them.

e.g (assume the switch is closed,  has near-zero resistance, and thus is irrelevant to the discussion)
PS(+9v)----(node)----LED(2.0Vdrop)----(node)----10k(7.0Vdrop)----(node)----GND(0v)
PS(+9v)----(node)----10k(7.0Vdrop)----(node)----LED(2.0Vdrop)----(node)----GND(0v)

david

[antonis]

As "teacher" David analyticaly explained, it doesn't matter whether you'll place the current limiting resistor..

Designers often place it on PCB so you see on drawings only the cathode of the LED going to switch..

[GibsonGM]

I used to get ALL messed up over that - which side of the LED to put the resistor on, ha ha!   

It's part of learning to think in terms of current, as David laid out...series = same current, parallel = different currents, same voltage (until it 'goes series' again anyway).

Once one can break thru the 'barrier' of thinking in terms of voltage only, things seem to get a LOT easier!  Current is what is doing the work, after all; voltage is the pressure.   Blame all the talk and labels on products re. voltage, I think.

[frogman]

I used to get ALL messed up over that - which side of the LED to put the resistor on, ha ha!   

It's part of learning to think in terms of current, as David laid out...series = same current, parallel = different currents, same voltage (until it 'goes series' again anyway).

Once one can break thru the 'barrier' of thinking in terms of voltage only, things seem to get a LOT easier!  Current is what is doing the work, after all; voltage is the pressure.   Blame all the talk and labels on products re. voltage, I think.

All messed up indeed. I'm just beginning to read through a basic electronics manual so I am kicking myself for not knowing this. I think the term current "flow" is what makes it so confusing.

[antonis]

I'm just beginning to read through a basic electronics manual so I am kicking myself for not knowing this.

Don't kick yourself until you'll be an electronics specialist...
(then you'll have plenty of time and chances to come under childishly simple mistakes..)

I think the term current "flow" is what makes it so confusing.

You don't have to worry about it because current is so clever that it doesn't even try to access an unreachable path...