Joule Thief

[freepow]

@ ALL, from Freepow !

I have'nt been on here for a while...

Can someone give me a simple diagram on these...

1 - I have a small solar cell that charges my super cap up, and I want it to stop charging when cap is almost full, at around 2v, need a simple circuit to stop cap being charged when it reaches about 1.5-2.0 volts !

2 - a very simple joulethief that charges a capacitor any HV cap with only microfarads  up super-fast, just like a disposable camera...

[nul-points]

[...]
Can someone give me a simple diagram on these...

1 - I have a small solar cell that charges my super cap up, and I want it to stop charging when cap is almost full, at around 2v, need a simple circuit to stop cap being charged when it reaches about 1.5-2.0 volts !
[...].

hi freepow

this basic schematic may do the job for you


if the voltage o/p of the solar panel (SP1) is greater than around 3.5V, then it will charge the Super Cap (SC1) up to approx 1.8V and hold it there until you either discharge or remove the cap

you'll need to choose R1 to suit your panel min & max o/p voltages:

let's say that the minimum useful o/p voltage of the panel is 3.5V
and we want the zener to have a minimum 'holding' current of 5mA

R1 = (3.5-3.2)/0.005 = 60 ohms approx (use 62 ohms)

with 9V max panel o/p, the zener would dissipate ((9-3.2)/62)*3.2 = 0.3W, which would be acceptable

so, with a 0.5W 3.2V zener, you could use panels which provide a max o/p in the range, say, 4 to 9V


12V max panel o/p would be close to the power limit for the zener - ok for occasional short-term peaks - but unwise for long-term average (in case the panel overvolts)

so for max panel o/ps in the range 9 - 18V, increase R1 value to, say, 120 ohms, and increase R3 to 20 ohms (double up Watts ratings for R1 & R3, also)

but why use a panel which is regularly generating max o/p >9V, if you only want to collect 1.5 - 2V in your Super Cap?


so parts list looks like:-

Z1 - 3.2V 0.5W Zener
R1 - 62 ohm 10W (for panel max o/p in range 6-9V)
R2 - 10K ohm 0.2W (default load)
R3 - 10 ohm 1W (inrush current limiter - 20 ohm for 9-18V panel)
Q1 - medium-power, medium gain NPN transistor, eg BFY51 (with 'star' heatsink)
D1 - low-leakage current rectifier diode (ie. not schottky), eg, try 1N4007 initially


hope this helps
np


http://docsfreelunch.blogspot.com

[electricme]

@Stefan,

I just went and visited this web address http://peswiki.com/index.php/Directory:Les_Kraut to see more about this new JT.

Yes, Les has replicated the Prof Stevens device and he states he got energy 8 times out of it.

There is a video some where taken by a Sterling D. Allen of it, he visited the Prof and Les so if the info has been removed from YouTube then perhapse if the Prof or Sterling reads this, they may consider sending a copy directly to you.

My congrats to the Prof, well done.

Hope this helps us all.

jim

[freepow]

@ nul-points,  Thanks very much !

The reason I am using actually a 4.0v solar panel outside feeding in to the house, I have to switch it on to charge the super cap.
The power from the solar panel go's through a Red charge indicator LED and onto the super cap, as soon as the super cap reaches around 1.5v the green LED comes on to show me that I have reached what I want in the Cap (depending on the resistor I use for this).

I need to hook a simple circuit between the solar panel and super cap, so it will automatically charge the cap up to the limit I want (around 1.5v) then automatically switch off charging !

[nul-points]

@ nul-points,  Thanks very much !

The reason I am using actually a 4.0v solar panel outside feeding in to the house, I have to switch it on to charge the super cap.
The power from the solar panel go's through a Red charge indicator LED and onto the super cap, as soon as the super cap reaches around 1.5v the green LED comes on to show me that I have reached what I want in the Cap (depending on the resistor I use for this).

I need to hook a simple circuit between the solar panel and super cap, so it will automatically charge the cap up to the limit I want (around 1.5v) then automatically switch off charging !

hi freepow

nice idea!

now that high brightness LEDs (and sub-assemblies) are becoming more available at lower cost, i'm also thinking about possibilities of using a 'modest' solar panel to provide some LED indoor lighting


your 4V panel may just be a little on the low side for faster charging but  the schematic above should still do what you asked - although you should move any inline 'indicator' LED and resistor to be in parallel now with the panel

you could leave the supercap in place and connect to your load when required, or disconnect (& move?) cap to connect to required load elsewhere.  Its ok to leave the cap connected once it's reached charge, because the circuit will just keep it at the charged voltage

if you want some indication on this circuit, you could try connecting a Red (because its lower voltage than Green) LED (with same direction as D1) across R3 to see if you get some indication of charging - the brightness will decrease as the cap charges from empty to full (you might need to experiment with larger values for R3 tho' - maybe in the range 20-100 ohms?)

if this works, you could use your Green LED (with resistor) as the 'ON' indication in parallel across the panel o/p

let us know how you get on

all the best
np


http://docsfreelunch.blogspot.com