Characteristics of Batteries vs. Wall Warts

Hey guys - and sorry for the semi-long post,

I'm building (copying) a couple builds from others here on LPF. For testing my first crude test builds, I've been using variable voltage wall warts, but my final builds will use 2 Li-Ion 10440. I've stopped my work, as I'm unsure if there will be differences between the Li-Ion's and constant DC power supplies.

The builds are two ST phasers, LM317 driver for the PHR on 2x Ultrafire 10440 3.6v. The original sound board will be run from a 3v button cell, and the LED output will be tapped and run to an SCR (2n5060) acting as the switch for the 317. One of these phasers is a gift for my brother (big trek fan) for being my best man a few weeks ago, so I don't have time to blow up parts and re-order... (yes I bought him safety glasses)

As I'm still waiting for my battery order to arrive, I've stopped working on them. I'd like to start it up again, but am hesitant on the differences between the 2 power sources... Does anyone have experience switching safely from one to the other without having to re-test the driver current/voltage?

Cheers,

Zen

If you're using the good old LM317 driver, I'd say you're quite safe.
That IC will always put out the current you set it at with the resistor between
'output' and 'adjust', as long as it has enough voltage on it's input.
Some drivers deliver different amounts of current, depending on the diode's forward voltage
and/or the input voltage to the driver, but not so the LM317.

Only two things can throw it off:
1. you don't have enough extra voltage (Diode's Vf + ~2V for the LM317) on the input,
in that case the driver simply delivers less current that it's supposed to, so it's safe.
2.When the input voltage is much higher than what the diode needs, the LM317
can get quite hot, which can be countered by heatsinking the IC, and/or adding
silicon rectifier diodes (the 1N40xx kind, for example) before the input, lowering
the voltage by about 0.7V each diode.

If anything, the batteries are safer than the wall transformer, because they are a quite 'smooth' power supply.

The problem with some wallwarts is that their output voltage drops significantly with load, and that can sometimes create an unstable situation. If its a good quality one and the same voltage as the batteries will be, they're fine for testing purposes.

The best solution is to put a capacitor to ground on the input lead of the lm317. You can leave it in place when power it with batteries, but also remove it or replace it with a smaller one if space is limited.