25mV Joule Thief powered by peltier merely using our body heat -Free energy 24/7

[magpwr]

Hi Acmefixer,

The 2SK170 absolute lowest possible voltage still remains at 25mV for oscillation to start&continue.It's not about the coil turns ratio anymore.Already tested it.
At 24mV it's no guarantee.

My latest discovery J210 N-channel JFET will work very well with ZTX1048A transistor.But lowest startup voltage is at "35mV" for JFET to kickstart transistor (Collector connected to drain,emitter&source).If ZTX transistor kick started manually on it's own lowest supported voltage is 30mV for oscillation to continue.
Secondary coil to gate of "J210" must be 330KOhms and secondary coil to ZTX1048A must be 330 Ohms at 35mV input.If resistor goes 150k or below to the gate the JFET will not work at all unless it's around 0.3volts .One more thing the J210 series JFET doesn't do oscillation on it's own at  voltage <100mV it merely produces alot of spike provided using resistor 330kOhms to it's gate...to automatic kickstart transistor.
I was surprise base on above configuration the voltage could exceed 10volts output for 35mV input(10v/0.035V =285 x voltage boost) input at around 6mA current draw ,circuit output capacitor using 100nf.Current still remains sufficient for led to be lit.

2SK170 and ZTX transistor combination still produce the best result.

[acmefixer]

The lowest I've been able to get a JT to go is 80 millivolts, however I didn't really try to optimize the circuit. You may be able to do better.  I used a button cell to get the bias voltage I needed to get it to work at low V.  I used the TN0702, and you can see the circuit here.  But click on the image several times to get it to enlarge.  You may be able to get yours to do better by using the bias voltage method I used.

@gyulasun: you are finding interesting circuits.

The two circuits shown in this publication http://www.edn.com/design/power-management/4320557/JFET-based-dc-dc-converter-operates-from-300-mV-supply derive the output Voltage from the primary (the coil with the few turns) at the Drain (Collector) of the transistor.

An then, according to the block diagram (you have to look up the data sheet), in the http://www.linear.com/product/LTC3108 the output Voltage is derived from the secondary (the coil with the many turns) at the base of the transistor (like in magpwr's circuit).

That might explain the low 20 mV supply Voltage limit in the LTC3108 (and the 25 V in magpwr's circuit) and the 300 mV in many other circuits.

I got the 2SK170 BL transistors from Reichelt (Germany) and Mouser (have a subsidiary in Germany, but usually deliver from the USA).

Greetings, Conrad

[conradelektro]

An experiment with two 30 mm x 30 mm Peltier Elements (inexpensive Peltier Elements):

The heavy brass mortar (big strong walled cup) stays at room temperature a long time. One can fill cold water, ice or snow into the plastic container placed on top of the brass mortar (which stands up side down on the table).

A rectangular hole at the bottom of the plastic container is covered by an aluminium flat bar.

The two 30 mm x 30 mm Peltier Elements are glued to the outside of the aluminium flat bar.

Greetings, Conrad

[gyulasun]

If you make the coil that it has a greater turns ratio, the JFET will start oscillating at a lower voltage.  Remember that at zero gate voltage, the JFET will conduct current, so it's a matter of getting the loop gain above unity with the supply voltage that you have.  Also I believe that with a supply at a few dozen millivolts you will not be able to get the output to a useful level unless you use two stages - one to get it started and another to switch high supply current.

Also, remember that "An hour in the library is worth ten in the lab".

See atttachment.

Hi acmefixer,

I would be interested to read the patent you show a schematic from in your attachment. Could you give the patent number?

I have read your blog, seen your schematics with the button cells to create gate bias for the TN0702.  I believe you could include in the same circuit a JFET oscillator like magpwr has shown with the 2SK170 and the only purpose for this oscillator would be to produce the 2-3V DC bias voltage.  By using a third coil next to the needed two coils for this oscillator, you could galvanically isolate the output of this oscillator so the biasing of the TN0702 (or other MOS or JFETs) should not be a problem. And then you could run the whole circuit from as low as your 80mV DC without the bias cells, and without a significant input power increase.

rgds, Gyula

[magpwr]

hi conradelektro,

Nice work.

I wonder if we use hot water against room temperature into a small pot.Maybe it could be turned into a small dinner's light on the restaurant table with green concept in mind.
It would make environmentalist happy since there is no candles to burn this time.Maybe like a led candle floating on hot water in small pot.

To Acmefixer,
Unfortunately mosfet is not the solution for input voltage below <100mV.Noticed you are using button cell in your circuit. I'm aware mosfet need to driven with higher voltage unlike transistor.
Please do try with Junction-FET which it's the only workable\self starting solution for voltage below <100mV.