LED indicator VS. Battery Life: can it be better?

[any]

I wonder how long a led could be powered from a seperate small "button cell" lithium?
If you use a seperate battery for the led it will only add the cost of the battery and possibly a pcb mount battery holder.
I bet the lithium would last just as long as your 9v before it needs replacement.

Cheers

[Mark Hammer]

That's actually an excellent idea.  For two reasons.  One is the disaggregation of battery drain for the circuit as opposed to the LED.  Two is the elimination of any switch-related popping when the status LED and circuit share the same power.

Now the awkward side.  If one uses a separate battery for the power indicator and audio circuit, you'll either have to find a way to shut off BOTH batteries when you unplug, or else leave the coin cell permanently connected.  That latter move would require you to assure that the stompswitch is in, and remains in, the "off" position to avoid battery drain of the coin cell when not using the pedal.

[earthtonesaudio]

An update from me:

I did a bit of experimenting to try and come up with a low-current solution.  I tried constant current (using JFETs), big resistors, and even a cute little step-down switcher using a negistor.  So far the big resistor is the winner (0.1mA and adequate brightness).  However, the constant current source only consumed 0.2mA and you have the benefit of stable performance over a wide range of battery voltages.

I was really hoping the negistor switcher would do well, but it took about 0.4mA... the benefit of this one is it was putting out 6V pulses at about 25kHz, with about a 25% duty cycle and was able to drive many LEDs (I fed the negistor output into another transistor used to drive the LEDs).

I was somewhat impressed with the performance of these circuits, even though they weren't super-stingy with the power like I hoped.  There's still room for experimenting with all variations (I just easter-egged in parts pretty much blindly), so if I get it working better I'll let you all know.

That's actually an excellent idea.  For two reasons.  One is the disaggregation of battery drain for the circuit as opposed to the LED.  Two is the elimination of any switch-related popping when the status LED and circuit share the same power.

Now the awkward side.  If one uses a separate battery for the power indicator and audio circuit, you'll either have to find a way to shut off BOTH batteries when you unplug, or else leave the coin cell permanently connected.  That latter move would require you to assure that the stompswitch is in, and remains in, the "off" position to avoid battery drain of the coin cell when not using the pedal.

Hm, I bet you could switch it off using a combination of a switched stereo jack and some form of millennium bypass.