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Author Topic: Lasersaber strikes again. A joule thief king ?  (Read 412357 times)

d3x0r

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Re: Lasersaber strikes again. A joule thief king ?
« Reply #120 on: May 19, 2014, 07:47:16 PM »
My first coil had a short between the foil windings and the case; it's also the only one that worked alright.  Wound with 24 ga widings, and aluminum sheet for foil.
I made another coil without foil, with 32ga wire, it barely works.
I made another coil, this time with thin copper foil tape for the foil windings, 24ga wire; slightly higher drive coil inductance; and it doesn't work like at all... if I use my fingers and short from positive power to the high side of the LEDs, then I can get it to oscillate, but it has very very short runtime.


I tried to insulate the edges in the first coil, but then it's too thick to fit in a pot core... so I have nothing at this point :( :(

conradelektro

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Re: Lasersaber strikes again. A joule thief king ?
« Reply #121 on: May 19, 2014, 11:12:45 PM »
Please see also these two postings (circuits and scope shots):

http://www.overunity.com/14591/lasersaber-strikes-again-a-joule-thief-king/msg403065/#msg403065
http://www.overunity.com/14591/lasersaber-strikes-again-a-joule-thief-king/msg403087/#msg403087

I was mistaken, the transistor switches as long as the base stays positive (during the positive half wave of the signal from the secondary winding). See the detailed scope shots. The scope shots become less and less detailed to show the small and the big picture.

I can pull the core of the coil apart a bit to make it less inductive. Less inductance makes the amplitude of the signal at the base (from the secondary winding) smaller.

If the inductance is highest (the signal on the base has a high amplitude) the primary winding is even pulled below zero (there seems to be some negative current leakage from the base to the emitter), which then causes a rather long period where the winding goes above supply Voltage and feeds back current into the cap.

If the inductance is lower (the signal on the base has a lower amplitude) the primary winding is not pulled below zero (no leakage of negative current from base to emitter), which causes a shorter  period where the winding goes above supply Voltage and feeds back current into the cap.

So, there is no mystery switching (the transistor switches as long as the base is positive), but there is a mystery leakage of negative current into the emitter (and consequently into the primary winding) if the signal on the base has a high enough negative component.

It is just pure luck that my coil was just right enough to show this phaenomen. If I reduce the impedance of the coil slightly the phaenomen goes away.


Note, the base has to go to -15V in order to cause the phaenomen. If the base only goes to -12V the phaenomen stops.

What does it mean for my coil:

The ratio of 1 : 3 (primary / secondary) should go up a bit, may be 1 : 4. And it needs more turns (on both windings, which means thinner wire) to have a bit more current specially through the secondary winding (which hopefully will leak from base to emitter while the base is very negative).

There will be a limit of "possible leakage of negative current from the base to the emitter" when the transistor will break or at least will block.

So, a bit of negative current from the secondary winding leaks into the emitter pulling the primary below negative rail, which then causes a higher back EMF of the primary which will leak from the primary (while it is above positive rail) back into the cap.

LaserSaber has found a feed back mechanism:

The negative half wave of the secondary (which normally is lost as heat in the transistor or in a safety diode) can leak back into the cap (via emitter and back EMF of the primary). This only works with certain transistors.

There is also the extremely short pulse which reduces power draw. The effect of copper strips could be to make the pulse shorter (but I have not yet seen that).

Please look a the scope shots an tell me what you see.

Greetings, Conrad

conradelektro

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Re: Lasersaber strikes again. A joule thief king ?
« Reply #122 on: May 20, 2014, 02:49:36 PM »
Please also see:
http://www.overunity.com/14591/lasersaber-strikes-again-a-joule-thief-king/msg403109/#msg403109 (more scope shots)
http://www.overunity.com/14591/lasersaber-strikes-again-a-joule-thief-king/msg403065/#msg403065 (circuit)
http://www.overunity.com/14591/lasersaber-strikes-again-a-joule-thief-king/msg403087/#msg403087 (circuit)

I tried to see "power draw" and "power feedback" to the 1000 µF cap. Therefore I measure with AC coupling over the cap (only the AC component is visible, the 9 V DC Voltage is not visible).

Again the left scope shot is with the high inductance core and the right scope shot is with the low inductance core (cores are pulled apart a few millimeters). The feed back with the high inductance core is higher because I think that in this case the negative current leakage through the transistor from the secondary winding on the base is happening.

I also tried to measure power consumption and as TinselKoala suspected, this is tricky. It seems to work with my Multimeter at 9 V, the result is about 20 µA. At lower Voltages (the circuit works down to 0.5 Volt) the measurements become unreliable (varies between measurements from 7 µA to 20 µA).

So, I did the calculation by help of time and capacitance.

 Q = As = C * U    (Q = charge or Coulomb or Ampere-seconds, C = capacitance in Farat, U = Voltage over the cap)

 1000 µF  *   9 V = 0.009 As (charge at start Voltage)
-1000 µF * 0.5 V = 0. 0.0005 As (charge at stop Voltage)
 0.0085 As in 420 seconds (7 minutes) --> 0.0085 / 420 = 20 µA on average

 4700 µF * 9 V = 0,0423
-4700 µF * 0.5 V =  0.00235
 0.04 As in 1800 seconds (30 minutes) --> 0.04 / 1800 = 22 µA on avarage

The caps have some leakage and power draw is about 20 µA at 9 V and goes down when Voltage drops slowly to 0.5 Volt. The calculated 20 µA average power draw is not unrealistic given the 20 µA measurement at 9 Volt.


LaserSaber's circuit: 3000 µF cap

 3000 µF  *   9 V = 0.027 As (charge at start Voltage)
-3000 µF * 0.5 V = 0. 0.0015 As (charge at stop Voltage)
 0.0255 As in 18000 seconds (5 hours) --> 0.0255 / 18000 = 1.4 µA on average

The cause for the 14 fold difference (20 µA versus 1.4 µA) should be the core and may be the MPSA18 is even better than the 2N1304. (I will get some MPSA18 next week.) His pot core should have a higher inductance than my conventional core and therefore there should be more current on the base of the transistor (which would allow more feedback). It could also be that LaserSabers ceramic capacitor has less leakage than my old low grade electrolytic capacitors.

Greetings, Conrad

conradelektro

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Re: Lasersaber strikes again. A joule thief king ?
« Reply #123 on: May 20, 2014, 02:53:10 PM »
Wrong post, deleted.

Vortex1

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Re: Lasersaber strikes again. A joule thief king ?
« Reply #124 on: May 20, 2014, 03:37:34 PM »
You can configure a standard blocking oscillator circuit to perform in a similar manner and with nearly identical waveforms by lightly coupling the base of the transistor to the second winding with about 100 to 200 pF coupling capacitance. A high value resistor is also needed to bias up the transistor.

What you get is an extremely narrow pulse of around 400uA into the LED, but the average is closer to 4uA, the apparent brightness of the LED being being equal to one being operated at a steady current of around 10 to 100 uA.

So we are talking about a duty cycle of around 1% or less.

I have simulated this and the LS circuit in LTSpice where exact measurements can be easily had.

A fresh PP3 will put out about 10 volts with between 150 to 300 milliohms internal impedance and if touched to the 3500 for 4 milliseconds, the cap will charge to 98% of the applied voltage. Then it should have about 175 mJ available.

If dissipating 10uW with 175,000uJ, 4.86 hours are possible but this is best case not real world.

A good question to ask: Of what utility is such a device if you can hardly see it and it is unusable as a torch? I already have a clock that produces micropower ticks and runs for better than a year on a tiny battery.

conradelektro

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Re: Lasersaber strikes again. A joule thief king ?
« Reply #125 on: May 20, 2014, 05:34:42 PM »
You can configure a standard blocking oscillator circuit to perform in a similar manner and with nearly identical waveforms by lightly coupling the base of the transistor to the second winding with about 100 to 200 pF coupling capacitance. A high value resistor is also needed to bias up the transistor.

What you get is an extremely narrow pulse of around 400uA into the LED, but the average is closer to 4uA, the apparent brightness of the LED being being equal to one being operated at a steady current of around 10 to 100 uA.

So we are talking about a duty cycle of around 1% or less.

I have simulated this and the LS circuit in LTSpice where exact measurements can be easily had.

@Vortex1: could you please publish the circuit diagram (of this standard blocking oscillator which performs in a similar manner) here. I have great problems understanding "verbal circuits".

I would like to try it for example with a standard Joule Thief or with my MAX931 circuit (shown here http://www.overunity.com/14591/lasersaber-strikes-again-a-joule-thief-king/msg402853/#msg402853 )

Because you ask about "utility": What is useful? What do we really need? May be it is just a mental exercise like playing chess. If you ask about utility for everything you do, you end up staying in bed all day, because in essence, nothing is useful. Usefulness is determined in the brain of the observer with very subjective criteria. "Objective usefulness" is a group exercise namely a convention, and also the group can be wrong.

Greetings, Conrad

NickZ

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Re: Lasersaber strikes again. A joule thief king ?
« Reply #126 on: May 20, 2014, 05:55:39 PM »
  The point is that there are some oscillator devices that do keep a useable amount of light on for a long long while, or possibly even longer. Also, finding the way to do this, even with only a single led bulb is a start in the right direction, as we must learn to walk before we can run.

Vortex1

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Re: Lasersaber strikes again. A joule thief king ?
« Reply #127 on: May 20, 2014, 06:23:00 PM »
Greetings Conrad

Tell me what inductance and ratio you would like me to simulate in each of the coils, maybe something similar to what LS is using. I already have a circuit that has a 1:1 ratio, 50 mH each, but it can be changed. See attached.

green =collector V
blue=baseV
red=LED current

TinselKoala

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Re: Lasersaber strikes again. A joule thief king ?
« Reply #128 on: May 20, 2014, 06:38:23 PM »
Dark Alchemist's circuit meets with my approval.

DALM, using MPSA18 or BC337-25.

Vortex1

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Re: Lasersaber strikes again. A joule thief king ?
« Reply #129 on: May 20, 2014, 08:30:35 PM »
Using the prior (simulation) circuit and substituting a 50 to 350 pF variable mica capacitor for the fixed 200 pf, I can tune the drive capacitance to look just like the LS circuit on the bench with a real circuit. I wound the pot core  using 15 mH each, winding on a split bobbin to minimize inter winding capacitance. The circuit then draws about 20 uA and delivers about 15 to the LED.

The aim was to prove that by  minimizing inter winding capacitance, I could simulate it external to the pot core winding capacitance and get the same waveform. So nothing special about the LS circuit, it is a current starved blocking oscillator.

TK: DALM, but what is the LM? Lamp for Miners?

scratchrobot

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Re: Lasersaber strikes again. A joule thief king ?
« Reply #130 on: May 20, 2014, 09:31:33 PM »
My take on Lasersabers circuit, running on a 100uf cap at 9v.
https://www.youtube.com/watch?v=nDP1XuUUZf8

conradelektro

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Re: Lasersaber strikes again. A joule thief king ?
« Reply #131 on: May 20, 2014, 10:32:46 PM »
My take on Lasersabers circuit, running on a 100uf cap at 9v.
https://www.youtube.com/watch?v=nDP1XuUUZf8

@scratchpot: I guess you used a MPSA18 transistor and the circuit as given here http://laserhacker.com/?p=410 ?

Trivial calculation for your circuit:

 100 µF  *   9 V = 0.0009 As (charge at start Voltage)
-100 µF * 0.5 V = 0. 0.00005 As (charge at stop Voltage)
 0.00085 As in 150 seconds (2 minutes 30 seconds) --> 0.00085 / 150 = 5.6 µA on average

Great achievement, congratulations. I saw the coil specs in your video info, thank you for specifying the details.

Greetings, Conrad

scratchrobot

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Re: Lasersaber strikes again. A joule thief king ?
« Reply #132 on: May 20, 2014, 10:44:43 PM »
@scratchpot: I guess you used a MPSA18 transistor and the circuit as given here http://laserhacker.com/?p=410 ?

Trivial calculation for your circuit:

 100 µF  *   9 V = 0.0009 As (charge at start Voltage)
-100 µF * 0.5 V = 0. 0.00005 As (charge at stop Voltage)
 0.00085 As in 150 seconds (2 minutes 30 seconds) --> 0.00085 / 150 = 5.6 µA on average

Great achievement, congratulations. I saw the coil specs in your video info, thank you for specifying the details.

Greetings, Conrad

Yes i used the mpsa18 and your calculations seem acurate :)
Thanks

conradelektro

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Re: Lasersaber strikes again. A joule thief king ?
« Reply #133 on: May 20, 2014, 11:04:04 PM »
Greetings Conrad

Tell me what inductance and ratio you would like me to simulate in each of the coils, maybe something similar to what LS is using. I already have a circuit that has a 1:1 ratio, 50 mH each, but it can be changed. See attached.

green =collector V
blue=baseV
red=LED current

@Vortex1: thank you for publishing your very interesting circuit. I am always impressed if something is done in a well documented way together with a simulation. I will come back to your nice circuit once I am done with LaserSaber's circuit.

If it is not too much work for you I would like to ask for the following:

Please simulate LaserSaber's circuit as given here: http://laserhacker.com/?p=410

- you could omit the three 1N4146 diodes if it is easier

- the MPSA18 would be important

- as coil please use my coil: see the attached drawing, the core is the following

http://at.farnell.com/ferroxcube/etd59-31-22-3c90/ferrite-core-half-etd59-3c90/dp/3056430?Ntt=3056430
FERROXCUBE - ETD59/31/22-3C90 -  FERRITE CORE, HALF, ETD59, 3C90
Farnell Order Code: 3056430
Manufacturer Code: ETD59/31/22-3C90

My goal:

- I want -30 Volt peak at the base, which windings ratio would achieve that (at 9 Volt supply Voltage)? (Now the ratio is 1:3 and the peak is about -15 Volt). In other words, the signal from the secondary should have an amplitude from -30 V to + 30 Volt (60 Volt peak to peak) at 9 V supply Voltage.

- What happens if I double the windings (while keeping the ratio) ? (I want more current in the signal, but the peak should stay at -30 V)

- I have enamelled wire with 2 mm diameter (31 Gauge) and 4 mm diameter (26 Gauge). If necessary I could get different wire.

So, my aim is to find windings which give me a peak of -30 Volt at the base (from the secondary) and a bit more current in the signal from the secondary as I have now (all at 9 Volt supply Voltage). I hope I specified the requirements well enough. I do not know how much current is in the signal now, but it seems a bit too weak.


My coil as it is now:

- now I have 29 turns (one layer) as a primary, 5.5 mH, the wire has 0.6 mm diameter but a very thick insulation, it has in total a diameter of 1 mm (the layer fills the whole width)

- now I have 145 turns (5 layers) as a secondary, 145 mH, same wire (1:5 ratio)


Planned new winding:


- 1 layer of 0.4 mm wire as primary (will have about 70 to 80 turns)

- 6 layers of 0.4 mm wire as secondary (will have about 420 to 480 turns) (1:6 ratio)

- a last layer of 0.4 mm wire which I can add in series to the secondary to get a 1:7 ratio

Could you simulate that (at 9 Volt supply Voltage)?  (I want to have a -30 V to +30 V and reasonably strong signal on the secondary)


Last question: I have to learn this simulation business, do you happen to know from where I can download a useful version of LTSpice (for Windows 7)?

Greetings, Conrad

conradelektro

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Re: Lasersaber strikes again. A joule thief king ?
« Reply #134 on: May 20, 2014, 11:37:37 PM »
Dark Alchemist's circuit meets with my approval.

DALM, using MPSA18 or BC337-25.

@TinselKoala: I know I could search for the DALM circuit, but do you have a link to the circuit or a drawing at hand?

What is the power requirement of your DALM inplementation (roughly)?

I saw the inductance measurement, thank you, that helps.

Greetings, Conrad