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

[conradelektro]

I made a little play thing which can be leaned against my ceramic stove and drives magpwr's circuit.

Greetings, Conrad

P.S.: I know there are units on sale which put out 2 Watt http://biolitestove.com/campstove/camp-overview/tech-specs/#sub , my lean-to Peltier Gadget is just for fun.

[gyulasun]

Hi Folks,

In the data sheet of the 2SK170 you can read that this type is selected into 3 groups when manufactured and these groups are identified with different suffix in the type name.  The selection is based on the drain current,  I_DSS measured at zero gate-source voltage.

These are  2SK170GR  which has  I_DSS = 2.6~6.5mA   
                  2SK170BL  which has  I_DSS =  6~12mA
                  2SK170V    which has  I_DSS =10~20mA

I wonder which suffix you guys happened to purchase because obviously the 2SK170V has the smallest R_DSON  and the highest Y_fs forward transfer admittance. 

I remembered a Design Idea from the Electronic Design News Magazine, see this link: http://www.edn.com/design/power-management/4320557/JFET-based-dc-dc-converter-operates-from-300-mV-supply   
The writer of the article works (or worked) for Linear Technology and most probably he established the base circuit for the later creation of the LTC 3108 type DC-DC converter family.  The circuit shown in the Design Idea works from 300mV DC as a minimum input and includes several components, so it is rather complex compared to magpwr's circuit but the reason I mention it is that it may serve as a "food for thought" for anyone here wishing to experiment with these setups, showing certain solutions with discrete components.

@Conrad      Very nice build, thanks for showing your setup with the stove.

rgds, Gyula

[magpwr]

Hi gyulasum,


This is a interesting finding which shows current handling capability 3 different version of  2SK170.

Just noticed the 10 pieces of (2SK170 BL  6~12mA version) which i purchased from www.futurlec.com for $0.20 ea .It's found through search "2SK170" for that site.

It's unknown if slightly higher current handling capability would have impact on "input voltage  detect sensitivity".

Unknown if the 2SK version is similar like those for transistor eg:BC547A,BC547B,BC547C which have different gains.

I noticed that base on datasheet BF862 and J105 does have better RDS/Lower on resistance than 2SK170.
But unfortunately  the startup voltage for BF862 and J105 is not really impressive at around 300mV.There maybe relationship between current capability and voltage\current detect for JFET base on current technology.

To increase current output\input at low voltage it would be more sensible to use transistor EG:ZTX1048A with 2SK170.

I have tested the J105 this afternoon which was disappointing which could not start at 0.1v but does start oscillation at 0.3.. 0.4v

[conradelektro]

@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

[acmefixer]

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 gyulasum,


This is a interesting finding which shows current handling capability 3 different version of  2SK170.

Just noticed the 10 pieces of (2SK170 BL  6~12mA version) which i purchased from www.futurlec.com for $0.20 ea .It's found through search "2SK170" for that site.

It's unknown if slightly higher current handling capability would have impact on "input voltage  detect sensitivity".

Unknown if the 2SK version is similar like those for transistor eg:BC547A,BC547B,BC547C which have different gains.

I noticed that base on datasheet BF862 and J105 does have better RDS/Lower on resistance than 2SK170.
But unfortunately  the startup voltage for BF862 and J105 is not really impressive at around 300mV.There maybe relationship between current capability and voltage\current detect for JFET base on current technology.

To increase current output\input at low voltage it would be more sensible to use transistor EG:ZTX1048A with 2SK170.

I have tested the J105 this afternoon which was disappointing which could not start at 0.1v but does start oscillation at 0.3.. 0.4v