====== Joule Thief Notes ======

Random related thoughts.




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

====== 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 {{galv-ammeter.ods|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. (([[http://web.telia.com/~u85920178/begin/bias-00.htm|Transistor Biasing 1 by Harry Lythall]])), AS127?(([[http://forum.electronicwerkstatt.de/phpBB/topic68719_f34_bxtopic_timexDESC_by1_bz0_bs30.html]])), (([[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]]))
  * Also, try using a Schottky or germanium diode to increase efficiency.(([[http://older.4hv.org/index.php?board=5;action=display;threadid=241|Topic: circuit modification]] on YaBBSE))  Even a [[wp>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?
  * [[wp>solar_power|19 to 56 W/m²]]  @1V is 1.9-5.6 mA/cm² total area of two cells in series.  4-6² cm should be safe for trickle charging a NiCd/NiMH cell.  FIXME Adjust area larger to account for efficiency: 6-9cm²?

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











===== References =====

  * [[http://www.emanator.demon.co.uk/bigclive/joule.htm
    | Make a Joule Thief. ]] by [[bigclive1@gmail.com]]
  * [[http://cappels.org/dproj/ledpage/leddrv.htm
    | White LED Drive Circuit ]]
  * [[http://www.wppltd.demon.co.uk/WPP/Batteries/Charging_Methods/charging_methods.html
    | Charging Methods]]
  * [[http://www.solorb.com/elect/solarcirc/aacharge/index.html
    | AA Battery Solar Charger]]
  * [[http://www.axeonpower.com/chemistries.htm
    | Cell Chemistries]]