Joule Thief Notes

Random related thoughts.

The amperage to the load depends on the load's impedance and the input voltage. $I_{load}={V_{input}/R_{load}}*efficiency$

Making Meters

Making some meters. http://campus.udayton.edu/~physics/gkm/p207ch28.htm

Ig=250 uA galvanometer max deflection current
Rg: galvanometer resistance

Imax: desired current for ammeter max deflection
RA: Shunt resistor in parallel

OpenDocument spreadsheet to calculate RA

Ig Rg = (Imax - Ig) RA

Vmax: desired voltage for max deflection
RV: Series resistor

Vmax = Ig(Rg + RV)

Expand These

Try using a germanium transistor to decrease operating voltage, perhaps as low as 0.15V. ¹⁾, AS127?²⁾, ³⁾
Also, try using a Schottky or germanium diode to increase efficiency.⁴⁾ Even a tunnel_diode would be worth investigating.
In fact, replacing the charge pump diode with a zener or tunnel diode should obviate the need for a separate zener diode to shunt excess voltage.
This circuit will also drive at least two LEDs in series.
What about limiting the LED current? (Red LEDs typically have an internal resistance of 22 ohm.)
Use a shake-magnet coil and rectifier in parallel with a very low voltage power supply (such as a manure fuel cell) to provide a jump-start voltage.
Use the shake-magnet coil and rectifier to recharge the battery.
Solar LED Throwie: AAAA NiMH batteries typically 200-400 mAhr. .(Find these inside rechargeable 9V batteries sometimes.) 200mAhr: Flat top, 1.626” tall, .276” diameter, .19 oz. ( 5.2 gms).

Some questions

How to reduce the minimum power supply voltage?
How to increase efficiency?
What effects the oscillation frequency?
Can I make it flash?
19 to 56 W/mÂ² @1V is 1.9-5.6 mA/cmÂ² total area of two cells in series. 4-6Â² cm should be safe for trickle charging a NiCd/NiMH cell. Adjust area larger to account for efficiency: 6-9cmÂ²?

                            //
Flasher?                 +-->|--+
                         |      |
                   +->|--+--||--+
                   |            |
+------------------+    _+------+
|                 C \   / E     |
|                   -----       |
|  =======            |B        |
+--UUU+UUU--+--/\/\/--+         |
A2    |    B1                   |
      |                         |
      +----||-------------------+
      |                         |
      +---/\/\/---+1V          ---
                                -

References

¹⁾ Transistor Biasing 1 by Harry Lythall

²⁾ http://forum.electronicwerkstatt.de/phpBB/topic68719_f34_bxtopic_timexDESC_by1_bz0_bs30.html

³⁾ http://64.233.179.104/translate_c?hl=en&u=http://www.b-kainka.de/bastel36.htm&prev=/search%3Fq%3Dgermanium%2B%2522joule%2Bthief%2522%26num%3D50%26hl%3Den%26newwindow%3D1%26safe%3Doff%26client%3Dopera%26rls%3Den%26sa%3DG

⁴⁾ Topic: circuit modification on YaBBSE