Joule Thief

[kooler]

@all

On a standard JT circuit whats the best way to check for back emf?

Thanks!

stick a diode on the collector of the transistor

robbie

[jadaro2600]

@all

On a standard JT circuit whats the best way to check for back emf?

Thanks!

see image: ..since the collapse is in the opposite direction, it's actually proper to measure voltage like this..   

- - - - - - 

Does anyone know how to circumvent the cut-off voltage of the base; perhaps somewhere in the intricacies of the coil to base, the voltage can be boosted beyond the source? ( safely )?

[altrez]

stick a diode on the collector of the transistor

robbie

Thanks robbie!

[altrez]

see image: ..since the collapse is in the opposite direction, it's actually proper to measure voltage like this..   

- - - - - - 

Does anyone know how to circumvent the cut-off voltage of the base; perhaps somewhere in the intricacies of the coil to base, the voltage can be boosted beyond the source? ( safely )?

Thank you for the pic jadaro2600. I think I am getting back emf from my config. I put the scope on it and it went wild!

-Altrez

[xee2]

@ kooler

i just went back and checked the emitter for bemf and the scope doesn't show it but it will light 5 leds..

5 LEDs x 3V = 15V across coil. That is not from the battery, so there must be some bemf there.

It would be between the emitter and the negative terminal of battery with positive at the battery. Maybe the positive spike is just getting sucked into the battery negative terminal.