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

[itsu]

You could always simulate a design.

The design can be anything by the way; one of your own, something from an application note from Linear Technology, something COTS off ebay, you name it. Perhaps itsu has an idea of his own, and you two could collaborate on it?

Any circuit (within reason) is fine by me, a joule thief like circuit comes in mind first to ramp up the 1.5V to something that will light the leds, or a switching PS like concept for higher efficiency.

Itsu

[MileHigh]

You could always simulate a design.

The design can be anything by the way; one of your own, something from an application note from Linear Technology, something COTS off ebay, you name it. Perhaps itsu has an idea of his own, and you two could collaborate on it?

In another time or another era, I may have been interested.  But unfortunately not this time.

I figure you could emulate the DC-to-DC converter strategy of high-frequency switching to stay away from the resistive losses in the main coil.  However, there are switching losses also so perhaps slower switching with a big low-resistance coil would work also.  After all, you don't have to worry about any size or cost constraints for the coil or any other components for that matter.

I actually think sticking to a Joule-Thief-style architecture makes it more interesting.  Then you are constrained with the Joule Thief feedback mechanism and the inherent disadvantages associated with it.  So that pushes the designer to try to optimize the switching and the timing when constrained within the "box" of the Joule Thief architecture.

MileHigh

[MileHigh]

MH

I have to say that i do understand what you have stated above,but at the same time,i am a little confused. Was it not you that stated that the pen was mightier than the bench?,but now you say you need the bench before you can put pen to paper

Brad

You are just being your pain-in-the-ass imp character and I am not amused.  The pen is mightier than the bench and the pen comes first.  It's time for a smack-down.

Let me translate that for you in the context of this discussion:  You learn knowledge in the classroom or by yourself or on the job.  That is "the pen."  Then you apply that knowledge by going on the bench.

I will give you an example:  You want to design a circuit to energize an inductor and then discharge the inductor into a load.  If you don't have the slightest clue how the inductor responds when you energize it by applying a voltage across it, how can you possibly make intelligent decisions and component choices when you are working on the bench?  Sound familiar?

You are also trying to conveniently forget something.

What is your test procedure for your supercapacitor?  You have said almost nothing, and in fact, much to your chagrin and loathing, your first response was pretty much junk.  Yes, I am pressing the button because the button had to be pressed.

Where are your "bench smarts?"  You say you have learned nearly everything on the bench.  How would you test a supercapacitor to measure it's size and any other parameters that you want to mention?  I am asking for a test procedure from you, not one lousy sentence.  Are you up to the challenge?

The whole world is watching Brad.

[TinselKoala]

While it is very amusing to see you mates arguing back and forth, it has been a long time since anyone has actually posted any real empirical results. Some of the arguing and conjecturing (hand-waving, or maybe ****-waving      ) has to do with the Joule Thief circuits and their efficiency. So I decided to make up a test bed and do some testing.

The results so far are to be considered preliminary, but it looks like Circuit 2 is the efficiency winner, by a thin margin. It produces less brilliant light but on a lux per watt basis it wins.

I am running short on suitable toroids so I wound the inductor on a small pot-core setup. This is probably even better than using a toroid, and a heck of a lot easier to wind. Both L1 and L2 are 20 turns of #34 magnet wire.

I couldn't get my power supply to set precisely at 1.5 volts; the voltage monitor showed 1.62 volts for the tests I have run. I checked input voltage and current both with DMMs and with oscilloscope and got essentially the same results. The output ran one LumiLed super-efficent LED in my lightbox, with the ExTech LT300 lightmeter, with sensor 18 inches away from the LED. As you can see from the image of the test circuit below, all I had to do to change between the circuits was to flip the LED connector over and attach it to the other output pins. The actual position of the LED in the lightbox is exactly the same in both cases, there is absolutely no difference in the two setups except how the LED is connected to the board.

So, Circuit 1 ran at an average input power of 90 mW and produced 63.9 lux at the sensor, for an efficiency of 710 lux per Watt.
Circuit 2 ran at an average input power of 40 mW and produced 30.0 lux at the sensor, for an efficiency of 750 lux per Watt.
By eye, there was little difference in the brightness of the LED, even though in real terms #2 was half as bright as #1. Both circuits ran at a little over 12 kHz, but with very different waveforms (Collector wrt Emitter). I'll show the waveforms later on, perhaps also with a video of the testing.

So the efficiency winner in these preliminary tests is Circuit 2, by a thin margin. Brightness winner is #1 but will definitely drain the battery much faster.

(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)

Brad

[TinselKoala]

A second set of results at a lower input voltage of 1.52V:

Circuit 1 gave 49.3 Lux at an average input power of 54.6 mW for an efficiency of 903 Lux/Watt.
Circuit 2 gave 26.1 Lux at an average input power of 28 mW for an efficiency of 932 Lux/Watt.
Operating frequency is between 10 and 11 kHz.

Again, Circuit 2 is more efficient on an electric power to light basis, while Circuit 1 is brighter.


ETA: I've used 20 turns for both windings in the inductor. If anyone has suggestions as to different turns/turn ratios which might give different or better results, please let me know and I'll wind up a new coil set. The pot-core makes this easy as it has an internal bobbin that is easily replaced.