LED Current Draw

[kurtlives]

Working on a power supply. Figured I should know just how pedals my 200mA transformer can supply.

I first hooked up a super bright blue LED and a 16K (those are the two components I always use for my indicators) onto the breadboard. Measured the current draw with my DMM on the 200mA setting and I get a reading of 0.40mA.

Weird...
But I do the math
6.25V DC across LED / resistance (16000) = 0.00039  Again 0.40mA approx

Then I see Danos current draw chart
Common analog transistor/opamp designs ZVex Box of Rock 3mA
  Ibanez Tube Screamer 6mA
  Boss BD Blues Driver Overdrive 13mA
Digital/DSP based single pedals Boss PS5 Super Shifter 50 ma
  Boss DD-5 Digital Delay 65mA
Multi Pedal/Effects Boss ME 50 multi-effects 140mA
  Boss Twin Pedals (i.e. DD-20 delay, etc.) 200mA


What? The analog pedals themselves are drawing more than the LED??? Maybe that chart includes the LED indicator?

I am missing something here? Right now it looks like my 200mA transformer could power 500 LEDs, is this right?

Thanks...

[slacker]

That all looks right to me, not sure why you're surprised that the pedal draws more current than the LED.
I know people sometimes say for a simple fuzz a LED will draw more current than the pedal but I think that's for normal LEDs and small resistors where the current draw of the LED might be 10 or 20ma. If you use superbrights then as you've found you can get the current draw much lower. 

[kurtlives]

That all looks right to me, not sure why you're surprised that the pedal draws more current than the LED.
I know people sometimes say for a simple fuzz a LED will draw more current than the pedal but I think that's for normal LEDs and small resistors where the current draw of the LED might be 10 or 20ma. If you use superbrights then as you've found you can get the current draw much lower. 

Huh? You would think brighter means more current being drawn???

So basically can I consider the LED current draw neglible seeing as it draws less than 1mA per effect.

[waky]

Huh? You would think brighter means more current being drawn???

So basically can I consider the LED current draw neglible seeing as it draws less than 1mA per effect.

it does,  for example: A regular led drawing 10ma will not be as bright as your super-bright led using up the same amount of current,
so basically for a super bright led you need less current to be as bright  as the standard type, thus giving you more battery efficency

[slacker]

Superbrights, ultrabrights or whatever are much brighter than normal LEDs drawing the same current. At the rated 20ma the ones I've got are usable as a torch, they're that bright. You don't need them that bright in a stompbox though so you can use much bigger resistors than normal LEDs and get the same brightness, I use 51k with mine and they are still plenty bright enough.

[kurtlives]

Ok cool...

How does a regulator affect things? I have this 200mA transformer and its going to have a bunch of 9V regulators on it. Do they draw current?

[waky]

i think they do, as they dissipate some energy in form of heat... thats current consumption right? xD well im not too sure 

[earthtonesaudio]

Check the regulator datasheets, there's a spec called "quiescent current" which is how much current they need while just sitting idle.

[composition4]

In addition to the quiescent (idle) current, which I think is around 5mA for 78xx series, you also have to consider the current used in dropping the voltage.  For example, if your power supply is 18v and you have a 9v regulator, you will be losing 50% of the current drawn to heat. In that example, if your regulator is supplying a constant 100mA, you will be drawing 205mA from the power supply

Jonathan

[Mich P]

Liteon have some drawning only 2mA
in red,green or yellow 3 or 5mm
that's what i use.
Mich P.