Is that a joule thief?

[Groundloop]

My JT battery voltage is now [01.05.2013 1630] at 0,949 Volt. This is a drop of
0,021 Volt during 11 hours. The LED is light very very dim, almost off.

GL.

[TinselKoala]

Have you considered making a light-level sensing instrument? I am impressed with the performance of the NTE3037 phototransistor; it would be fairly easy to make a light output meter with this as the sensor and a regulated supply from a 78L05 mini-regulator.
There are also some complete lightlevel sensors-on-chip like the TSL235R that would make a neat addition to a JT workbench setup.

[Groundloop]

Have you considered making a light-level sensing instrument? I am impressed with the performance of the NTE3037 phototransistor; it would be fairly easy to make a light output meter with this as the sensor and a regulated supply from a 78L05 mini-regulator.
There are also some complete lightlevel sensors-on-chip like the TSL235R that would make a neat addition to a JT workbench setup.

TK,

It would probably be nice to have a a light-level sensing instrument, but in this test I do not need it.

This test is to see if is it possible to fully drain a battery down to zero Volt. My theory is that this
is not possible, not even with a short. The battery will always go back to some low voltage. So my LED
is there to see if the circuit runs or not. But if I find a way to light a LED to some higher level,
using "dead" batteries, then a light meter could be used to measure the output.

Do you know any IC that can light a ultra bright LED to a reasonable light level from a very low
input voltage, say 0,1 to 0,5 Volt or so?

Added: I just found one. The LTC3108 can operate down to 20mV input. Data sheet attached.

GL.

[Groundloop]

My JT battery voltage is now [02.05.2013 1030] at 0,931 Volt. This is a drop of
0,018 Volt during 18 hours. The LED is light very dim, almost off, and is flickering.

If I touch almost any parts of the circuit, then the LED goes off. Yesterday [01.05.2013 2300]
the voltage was 0,925 Volt. So the voltage has increased somewhat during the night.

GL.

[conradelektro]

Do you know any IC that can light a ultra bright LED to a reasonable light level from a very low
input voltage, say 0,1 to 0,5 Volt or so?

Added: I just found one. The LTC3108 can operate down to 20mV input. Data sheet attached.

GL.

@Groundloop: a poster named magpwr showed a circuit and the transistor 2SK170 which lights a LED dimly down to 30 mV input power, I could do it with 50 mV.

Attached you see the circuit based on this transistor.

Greetings, Conrad