Joule Thief

[Pirate88179]

@PhiChaser

you forgot to label the built-in self-destruct mechanism, that keeps us buying more of these things!!

I actually have one of my Cree bulbs (unmodded and running off mains) beginning to flash a bit.  I suppose this means that the driver board is on the way out.  If it gets too annoying or burns out totally, I guess I will just run it off a flash circuit like I do the others.

The weird thing is that this bulb has been run with my added heat sink since almost day one.  I suppose that driver board was not meant to last forever.
Still, this was way longer than any cfl I ever had.  Also, none of the Cree bulbs have burst into flames (yet anyway) like several of my cfl's did back a few years ago.

Bill

[MileHigh]

So many devices run off of low-voltage DC these days that all of these wall-warts become a pain.  They are shoving a form of wall-wart into an LED light bulb so it works in a standard socket.

Then you have homes with solar panels and battery banks that work off off DC, so this whole DC to AC back to DC is a pain in the butt and more expensive and less reliable.

I hope the consumer electronics industry and the housing industry is working in the background to solve this problem.  They need to launch some kind of universal home "smart DC power distribution bus" with new wall sockets and plugs just for DC power.   You need "smart DC power plugs" for electronics and "smart DC power wall sockets" in houses.  Sort of like a USB 3.1 for DC power where when you plug your DC device into the DC wall socket, there is a negotiation phase that takes place so it is transparent if the device requires 5 volts or 12 volts, etc.

[Pirate88179]

So many devices run off of low-voltage DC these days that all of these wall-warts become a pain.  They are shoving a form of wall-wart into an LED light bulb so it works in a standard socket.

Then you have homes with solar panels and battery banks that work off off DC, so this whole DC to AC back to DC is a pain in the butt and more expensive and less reliable.

I hope the consumer electronics industry and the housing industry is working in the background to solve this problem.  They need to launch some kind of universal home "smart DC power distribution bus" with new wall sockets and plugs just for DC power.   You need "smart DC power plugs" for electronics and "smart DC power wall sockets" in houses.  Sort of like a USB 3.1 for DC power where when you plug your DC device into the DC wall socket, there is a negotiation phase that takes place so it is transparent if the device requires 5 volts or 12 volts, etc.

That's a great idea.  The power company can just split off a dc (hopefully clean) bus that can run all of this dc stuff we now use.  Or, we can just find an efficient way to make our own dc at our homes...not to run our homes, but just to run all of our dc devices.

Hey, I ran across this old video from Lidmotor from a few years back about his resonant JT circuit: https://www.youtube.com/watch?v=850LpSRkL-A

Have you seen that one?  It makes for a very efficient JT it seems, unless something else is going on with his circuit design.  Obviously this is far different from what we would call a "standard" JT circuit but after reading some of the discussions on the other topic, I thought it was interesting.

Bill

[crowclaw]

We are seeing more AC power point mains outlets available with single or twin USB sockets incorporated...good idea. No doubt you guys over the pond have them also?

By the way how are you Bill haven't looked in for a while.

[MileHigh]

Here is a Joule Thief issue that has been in the back of my mind for a long time.  See the attached portion of a Magluvin scope capture of his Joule Thief collector-emitter voltage.  Of course the collector-emitter voltage is the voltage across the LED.  Naturally there is an unknown current waveform associated with the voltage waveform that will have a similar decaying waveform shape.

So the issue is this:  You can clearly see the declining voltage across the LED.  So how bright is the LED as a function of the voltage?  What if the LED is bright for the upper half and very dim for the lower half?  I don't know if this is true but it merits an investigation.

If if the lower half light output from the LED is very dim then presumably it does not contribute to the visible light output of the LED to the naked eye and there is a lot of "wasted energy" in the inductor discharge.  If that's true it is arguably an "issue" and it suggests you can build a better mousetrap Joule Thief.

So, what if, for the sake of argument, that half of the energy in the coil discharge is essentially wasted because it barely lights the LED?

MileHigh