Joule Thief

sm0ky2 · July 26, 2009, 08:30:05 PM

Quote from: xee2 on July 26, 2009, 07:29:43 PM
@ sm0ky2

I think you ae having same problem as jeanna - you need to reduce the current draw of JT by increasing the base resistor value. Pirate uses really big capacitors and charges them overnight. That way he has enough power saved up to run the JT for a while.

kind of a catch-22, i had to reduce the base resistor to make JT work with my big red LED-diodes

xee2 · July 26, 2009, 08:36:05 PM

@ sm0ky2

Quote from: sm0ky2 on July 26, 2009, 08:24:45 PM
i believe this will adjust your current. the voltage (minus the drop across the resistor) should stay relatively the same.

It will change both. You will need to change both base resistor value and variable resistor values until you get the desired voltage and current.

xee2 · July 26, 2009, 08:39:45 PM

@ sm0ky2

Quote from: sm0ky2 on July 26, 2009, 08:30:05 PM
kind of a catch-22, i had to reduce the base resistor to make JT work with my big red LED-diodes

Sometimes there are limits to what you can do with what you have.

jeanna · July 26, 2009, 09:06:53 PM

Quote from: sm0ky2 on July 26, 2009, 08:30:05 PM
kind of a catch-22, i had to reduce the base resistor to make JT work with my big red LED-diodes

Hi sm0ky2,
I think this is only a method to find the best resistor value for the lowest possible input voltage.
I am pretty sure the battery voltage pot is just a tool to simulate the lower voltage of the EB.
I think the cap is what will address the turn-on current need of the system, but once oscillating, this optimizing of the base resistor for low current draw may keep it on. I am hoping.

I totally forgot that Bill left his in place for a while.
I believe I have not given it enough time.

Soon, it will be cool enough to venture out. After my coffee.

jeanna

sm0ky2 · July 26, 2009, 09:55:29 PM

Jeanna,

( i know this is the wrong thread for this, but they seem to be kind of intermingled anyways)

i managed to stretch my EB apart from 1.5ft out to 7ft apart.
the voltage pretty much stayed the same. but my current dropped back down to 2.5ma. i may have to let it get settled in again to see if it goes up higher than before, but my preliminary tests dont show much diference, if any, between 1.5ft spacing and 7ft.

i guess i dont have any 3055s, so i have to go transistor-shopping to find something that will turn on with .6v