Joule Thief

[kooler]

conrad
pretty kool setup i might have to try it..
is the cap needed or is it for a higher freq..

robbie

[conradelektro]

conrad
pretty kool setup i might have to try it..
is the cap needed or is it for a higher freq..

robbie

Robbie,

the 2 nF capacitor is very essential (and also the capacitance of about 2 nF; 100 nF would be way too much). It influences the switching of the transistor.

I learned this way of switching a Joule Thief from posts of a person calling himself "groundloop". It should reduce the base current and therefore the power consumption of the Joule Thief. But one has to test for the right capacitance and resistance. It also restricts the functioning of the Joule Thief to a quite narrow band of supply voltage. In this case 1.8 Volt would be already too high.

The high frequency is a result of the air core. In case you use a toroid, all values change (frequency achieved, capacitance and resistance needed).

Greetings, Conrad

[freepow]

  Hello All,  Attached is a diagram of a charging light circuit (hope i have it right ! )
               
                  Just say I charge this 200F cap with the solar cell when the switch is on of course,
                  I now need some help with adding a green LED, so when the cap is fully charged to
                  say 2.4v + the green LED will light up, then I want to be able to switch the charge switch
                  off and then I can use the 200F cap on my Joulethief, but I also want the green LED to
                  go out as soon as I switch the charge switch off.

                  The green LED is just to show me when its fully charged. I dont want the Cap consuming
                  current with the green LED when I'm powering my Joulethief !
                  Can someone help me with that green LED added to the diagram in the right way with
                  what ever else I need, Thanks.

[crowclaw]

Hello All,  Attached is a diagram of a charging light circuit (hope i have it right ! )
               
                  Just say I charge this 200F cap with the solar cell when the switch is on of course,
                  I now need some help with adding a green LED, so when the cap is fully charged to
                  say 2.4v + the green LED will light up, then I want to be able to switch the charge switch
                  off and then I can use the 200F cap on my Joulethief, but I also want the green LED to
                  go out as soon as I switch the charge switch off.

                  The green LED is just to show me when its fully charged. I dont want the Cap consuming
                  current with the green LED when I'm powering my Joulethief !
                  Can someone help me with that green LED added to the diagram in the right way with
                  what ever else I need, Thanks.

Hi freepow, Have you tried out your existing circuit, or is it just an idea on paper at this stage? I need to know the output voltage and current your solar panel can deliver. If your panel is capable of delivering well above the current limit of your LED say 20 mA into your cap to charge it, then the LED will be destroyed without a current limiter resistor in series!!  however, if your panel consists of a just few cells you should be ok... can you let me know. I'll try and devise a simple circuit that will light a green LED when cell reaches 2.4volts, and at that point will shut off the charge voltage. Is this what you want to do? Regards Merv

[freepow]

@  Merv, thankyou,  the solar cell will put out say 2.5v for the Cap and the current say about 200mA,
                            the diagram is only on paper at this stage, can you help ?