Joule Thief

[Sprocket]

Here is a good site that should help with regard to capacitor capacities:

http://www.powerstream.com/battery-capacity-calculations.htm

Even a 400F low-voltage cap still comes nowhere near alkaline/nimh battery storage.  Also note the additional 'drawbacks':

As long as we are in the prelude, I might also mention that since the charge in a capacitor is Q=CV that a battery can be rated in farads as well. A 1.5 volt alkaline battery that stores 2 amp hours of charge (that’s 7200 coulombs) has the capacitance of 4800 Farads. Of course a battery makes an awfully weird capacitor because the voltage doesn’t drop proportionally to the stored charge, it has a high equivalent resistance, and etc.

Also, there is no danger from touching low-voltage cap. leads, irrespective of their capacities, as the resistance-path through the human body is far too high for significant current to flow - grab the terminals of a 12v car battery to prove it to yourself!  Shorting them together is another matter however!

[innovation_station]

i live in ontario...

so    sprocket

this does make good sence ... 

so this is still safe to play with ?   

just dont charge hv caps ..... that is where you can be hurt fast .....


ist!

[Pirate88179]

@ ArticKnight:

Thanks for the info.  I am using them exactly like batteries.  The 4,000 F super caps are expensive at this time (about $4,000 each)  I just hooked up a test circuit now with a toroid JT driving 2 superbright leds but I also tied in 2 10 F supercaps and one .47 F cap.  I will post a video later tonight or tomorrow but the cool thing is, I can disconnect the battery while lit and you can't see any difference at all in the light output....not even a flicker when connecting or disconnecting.  I have had it off the battery now and running for over 20 minutes.  I also used a potentiometer to tune the circuit which is also interesting.  So, 1 amp = 1 Farad.  I believe someone else posted the same thing.  (I like agreement) Thanks again.


@ Sprocket:

I read your quote from the article but have not read the article, but I will.  Thank you for posting it.  One thing that does not make sense to me, and I am not arguing with the article because I have not read it yet, nor do I really know much about these new caps at all, is that Sears now sells a cordless screwdriver using nothing but supercaps instead of lithium ion bats.  They said with the lithium the tool will run for 4 hours but takes 5 hours to fully recharge.  The supercap model runs for only 2 hours, but fully charges in 3 minutes!!!  You can google it if you want, I think Coleman makes one too.  Also, the use these now in electric and hybrid vehicles to capture and store the regenerative braking energy.  They will one day replace the drive batteries in vehicles but they are not cost effective for that as of yet from what I have read.  it would be great to recharge an electric vehicle in like 10 minutes instead of overnight.  And, these caps do not wear out even after millions of cycles of charge/discharge as other batteries do. If they outperform high tech batteries in these applications, I can't believe that a regular battery can compare.  But, like I said, I appreciate your posting the article and I will go and read it.  Thank you.


Bill

[Pirate88179]

@ Sproket:

Great article!!  I saved it for future ref.  A lot of good formulas in there.  Thanks.

Bill

[jeanna]

Hi everyone,

I have a report for your consideration tonight.

I continued the test to see if there is any difference or advantage to use thicker wire when wrapping the secondary.

What is required is to push the circuit to its limit and see if I can get more out of it by using a thicker wire for the secondary.

To that end, I restructured the array to be all in a parallel arrangement. I snaked the lights out and back 10 times arranging the jumpers to keep it all parallel. I checked each row before continuing. I have had the 10 ohm (9.5) resistor in series with the battery at the positive end.

The basic circuit is the basic hand made joule thief as follows:

2n3904 transistor
1k ohm at base
no actual led in || with the transistor, but just in the initial set up to be sure the ckt is set up correctly.
Toroid wrapped with 11 bifilar turns wrapped and twisted as described by evilmadscientist.com
1 battery 1.2V
10 R resistor at the pos end of battery.

30 leds in || with this not connected to anything.

Then I wrapped ONE turn around the toroid using various gauge wires:
22 gauge mag wire
24 gauge telephone wire single strand plastic coated - good for jumpers.
30 gauge mag wire
30 gauge kevlar wire coated with teflon.

and tested with the bridge rectifier to see the voltage of the toroid with the 1 turn running off the battery and through the toroid system.

Then I touched either side of the first led and turned on the whole array and tested.

They are so close to the same thing that there is no real difference.
The difference is so small, that it is less than the resolution of the meter.

Each gauge of wire when turned 1 time around the toroid showed 0.88Volts rectified
Each gauge of wire drew 0.19Amp when tested by E=IR with 10 ohm resistor in series with the circuit. In other words, the voltage across that 9.5 ohm resistor was 0.18volts in all cases today with 30 lights. Then I put a fresh battery in the holder still lower, but closer to last night's battery.

There was really no difference between last night's 12 light and today's 30 light array,
On the 12 light array, the voltage through the resistor to measure amps was 0.22V
On the 30 light array, the voltage through the resistor to measure amps was 0.21V

the same.
given a slightly deader battery today.

12 lights or 30 lights the same amperage. being seen in the whole circuit.

So, I have not yet taken this circuit to its limit. I will try putting a resistor of higher value in series with the battery to see if I can lower the incoming voltage enough to make the lights blink. At the place where they blink, I will check the various gauge secondaries to see if a thicker secondary has any advantage or disadvantage.

more tomorrow!

jeanna