A Perspective On The B Type EESD - Robert Murray-Smith - Any issues?

[MileHigh]

Well, I can easily see Brad having a braingasm from TK's posting so I will get a few words in edgewise.

One of the classic weaknesses on the forums is to use the term "efficiency" without even defining what it means.  Brad is someone that does this all the time.

Take a look at a Joule Thief.   Are we talking about electrical power in vs. electrical power out efficiency like Poynt just stated?  Or are we talking about electrical power in vs. light power out like TK just stated?

What about the LED itself?  Are you doing your "burn" at the optimum efficiency point for the LED where you get the most light out per milliwatt in?

How flat or sloped is the current discharge curve across the LED when you are doing a burn?  Does this have an impact on the power in to light out efficiency?

What about the flashing frequency and duty cycle and human perception of brightness?

What about the human perception of the light level?   How do you define an "adequate" level of light output from the Joule Thief?  Is it just bright enough to be a panel indicator light?  Or do you want a practical amount of light like a small night light?  Is there a sweet spot for human perception of the light output from a Joule Thief?

How you define efficiency for a Joule Thief is a big enough question for such a little circuit.  But it is what it is.

Just saying, "Wow, that looks like an efficient Joule Thief!" is essentially meaningless if you don't qualify it.

(snip)
For instance,the schematics below.
You say !your! JT circuit(1) is the most efficient,and i say circuit 2 is more efficient
(snip)

Oh my god I must be wrong based on TK's data!  Brad is going to have a braingasm!

Why did I say that circuit #1 might be more efficient?

My line of thinking was as follows:  In circuit #1 when the LED is lit it is based on a discharge of the LED in series with the battery.  So the EMF from the battery is a "helper" to keep the LED lit.  So, it suggests to me that circuit #1 may be able to extract more energy from a nearly dead battery because it looks like it will run at lower battery voltages than circuit #2.  That will likely translate into a longer run time from the same battery.

How did I define "efficiency" for the "most efficient Joule Thief?"

The answer was the most efficient Joule Thief by my definition would be the one that has the longest run time and extracts the most possible energy from the nearly-dead battery.

I stated this to Brad multiple times but it never sank in.

Now we can go back into the holding pattern waiting for Brad's expected tsunami braingasm.

Brad:  I still would like to see your "bench smarts" measurement procedure for your supercapacitor.

[minnie]

   TinselKoala , with circuit 2 you could always strike a match to see if it's
   switched on!
    Warmest regards,John.

[poynt99]

Well there we have it Chet. It's a no-go.

MH and TM will just have to keep bickering at each other I guess...

[TinselKoala]

At even lower voltage, this time from a relatively fresh #357 button cell battery instead of the power supply, the efficiency reverses, with Circuit 1 being more efficient.

At 1.4 volts:
#1 gives 35.9 lux at 41.4 mW = 867 lux/watt
#2 gives 23.9 lux at 32.3 mW = 740 lux/watt

So, as usual... both TinMan and MileHigh are right, and wrong... depending.

[TinselKoala]

   TinselKoala , with circuit 2 you could always strike a match to see if it's
   switched on!
    Warmest regards,John.

No need for that! Both circuits make the LED I'm using "blindingly bright" when viewed by eye. I'm barely able to see the difference in brightness, but the lightmeter tells the tale.