Joule Thief

[Pirate88179]

@  ALL, thanks for your help, but I need someone to give me a simple diagram of a LED that will light when there is a LOAD,  however, there will be more than one LOAD and each LOAD is seperate and has a on/off switch.
each LOAD is powered by the same 2.5v
See my diagram...

Maybe I am missing something basic here but I don't see why this would not work?  The led should light if either one or both of the JT's are operating.  Resistor value would need to be zeroed in on by experimentation.

Bill

[freepow]

@ Bill, Thanks for diagram, I've tried what you said, the LED light up when JT turned on but JT does'nt work,
so there must be another way...
any idea's

[crowclaw]

Hi Freepow... this circuit should  do what you're looking for. The two unmarked rectangles represent your switched JT circuit blocks. D1, D2 provide circuit isolation between JT's. Current load through LED approx 20Ma. 22ohm resistor can be increased or decreased to suit trial. Kind Regards

[freepow]

@  Crowclaw,  Thanks a lot !!!

Please have a look at this picture, The LED will turn on when the 2.5v Solar panel is on, But I want to put a  Red LED in circuit for when A or B (battery) is turned on, however I dont want the Red LED to come on if the battery switch is in the off position and the Solar panel is on !  only if I switch A or B is on !

Any idea's please.

[crowclaw]

Hi Freepow... Well pushing the old grey matter now!!  lol... ok try this circuit, you will have to duplicate it for battery "B" and use two red leds for each battery circuit. You could use just one red LED but would have to be powered off battery "A" rather than off it's own battery "B" when selected!! The red LED should draw approx 11mA with the 22R resistor. Any NPN small high gain signal transistor can be used. I've selected component values to minimise base currents etc but you can experiment with values yourself based on my design. This circuit should give you what you are looking for. Regards