Solar Joule Thief Circuits

[Seumas]

This might explain the circuit better, I found the site where I got it from:

How to Build Small Solar Circuits (Wiring & Diagrams) | Renewable Energy

[Matthew Jones]

YA the panels go negative in the dark and thats what switch's the PNP on.

Matt

[Seumas]

I tried to design a circuit to do the same thing but I was using npn transistors and though the circuit worked it did the opposite of what I wanted, it turned the led on when the panel was in the sun and off when the panel was in the dark LOL, I didn't know that the panel would go negative in dark (I'm still trying to grasp all of this) so now it makes sense to me, pretty simple and cleaver design. Thank you for the explanation the positive going to the base was confusing the heck out of me.

[Seumas]

Quick Follow up, I put the circuit together on a breadboard and hooked it to a small panel, here's the circuit in action:

http://www.seumas.org/pnpsolarswitch.zip

Also, I hit the local Harbor Freight store today, for those who are messin around with small solar circuits they have a discontinued item that used to sell for over 20 bucks now for 9.99 + tax so around 11 bucks. It is their Solar powered fountain pump item # 66093. I personally do not care about the pump, but the roughly 4.5x4.5 inch solar panel all mounted nice and neat with a 16' cord is not too shabby and is rated max output 7V at 1.2 watts.

http://www.seumas.org/spanel.jpg

[SkyWatcher]

Hi Seumas, i wired up that circuit you posted and checked that website and it seems you need at least a 4.5volt solar panel to bias off the pnp transistor, which is not useful for scavenged old solar panels from garden lights that only have around 2volts output at least thats what i'm seeing with a 60 watt bulb right next to one. And if that is the case which it seems it is based on my tests, it may need less parts, however, the solar panel has to fight against the 2.4 volts or whatever volts the rechargeable batteries are outputting. Since I can see how the pnp transistor is biased on, the battery negative voltage it seems flows through the solar panel and puts a negative on the base as Matt said. Unless I'm interpreting this incorrectly, i think the first circuit i posted is more efficient. Thanks for your contributions so far Seumas, I'm learning more about these circuits and sharing ideas is the key. My dad just gave me two solar garden lights he had that died out and it's obvious their building some of these not to last very long, things were very rusted and the plastic plates over the solar panels were so fogged up, there is no way much light was going to get through and then the AA cell is not going to charge and will have to be rejuvenated. I will be fiddling with these garden circuits and making a few more useful lights, then I am going to focus on the Bedini type cap discharger powered by something similar to these solar garden light circuits to fill the caps and charge batteries.
peace love light
Tyson
edit: nice video and solar panel you got there. what do you plan on doing with the panel.

[Seumas]

The panel in the video or the panel I just bought with the pump? The one in the video came off of another product from Harbor Freight, their 36 led solar powered motion sensor light. I bought it and messed up the unit by leaving it outside with the face down. Yes it is supposed to be water proof etc, but I left it out in a manner not consistent with how it is supposed to be mounted so I salvaged the solar panel. Next I am going to take the bundle of AA rechargeable batteries out of the unit and see if I can get that circuit to work with a bunch of led's powered by the solar panel and the batteries from it. This is what I got the panel from:
36 LED Solar Security Light
It is even nicer than the ones that come with the water pump, it has a nice adjustable base that can be mounted anywhere.

Can the resistor value be changed to accommodate a smaller panel? When I shine that flashlight on the panel like in the video, it reads just over 3 volts. Now I am tempted to hit Home Depot and pick up one of those garden/walkway lights and rip out the solar panel and test it on this circuit. I think I just might do that

[SkyWatcher]

Hi Seumas, thanks for reply and links to that site. I didn't use the joule thief in my test, i just used 2 AA in series to power the led. Though, i didn't find any different resistor values to get it to work with the lower voltage solar panel. Like i said, i think based on how i see the circuit working, the panel has to exceed the batteries voltage to apply any positive voltage to the base of the pnp to turn it off. So with a 1.2 volt AA, which is around 1.35 volt fully charged and an output from the panel of around 2 volts and there would be a voltage drop from that, i mean it's possible that in real sunlight and not a light bulb test that it might work with the circuit you've pointed out.
peace love light
Tyson

[SkyWatcher]

Hi folks, I took the ferrite bead out of the solar joule thief and decided to run some tests with it and see how many leds i could get to light at decent brightness. I managed to light 19 so far off the standard emitter collector with an amp draw of 40 milliamps at 1.32 volts. The leds are too painful to look at for very long, so they are probably fairly close to full brightness, at least by appearances. The photo is a little bloomed from camera, but the leds are quite bright.


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peace love light
Tyson
edit: oh and the leds are all in parallel

[Lidmotor]

Replication of simple on/off circuit

I am a bit confused on the switching with the 2 npn transistors, would it not be simpler to just use one pnp to handle the switching between the solar panels charging the batteries during the day and the batteries powering the joule thief at night/in darkness?

Here is an example, a simple circuit I found online and it seems to work pretty good:

The resister value should be higher around 5k, batteries could also be in parallel.

@Seumas and All
I replicated this simple On/Off circuit with good success. I was actually surprised at how well it worked. The solar cell (panel) I think is critical to making this work. Electronicgoldmine sells them. This circuit coupled to a Joule Thief worked really well. I took it one step further and linked it to my Stubblefied coil pulse motor in a series arrangement as a power booster. I replaced the battery with a 10 Farad/2.7 volt supercap for this video to show the power flow. The only problem that I had with the circuit was the light sensitivity on/off adjustment. Controlling the base resistance should have worked but I didn't have any luck there.
I would like to make something that would turn a Slayer Exciter into an automatic light. Lots of work to be done to get there.

Here is the video of last night's experiment:

YouTube - Solar On-Off circuit---Stubblefield coil and Joule Thief.ASF

Lidmotor

[Seumas]

I'm glad you got it to work Lidmotor, I however have run in to a little problem with the circuit. By themselves the on/off solar circuit and my joule thief circuit work perfectly, I even replicated SkyWatcher's multi LED setup but with only 10 LED's. I could of done more but I wanted to see how long 1 AA would power them through a joule thief. But when I take the output from the on/off solar circuit to the input of my joule thief I get nada. The output from the solar circuit is 1.5V when I am using just one AA and 2.75V when I have 2 AA's (old AA's) and an LED on the output. I was wondering if you could post a quick scribble schematic of how you had it all hooked up -the stubblefield and super cap, just the solar and joule thief.

pic of one of my joule theifs:
http://www.seumas.org/joulethief.jpg

Hooked up to 10 leds and powered by one button battery:
http://www.seumas.org/jt1.jpg

Same as above but with no flash:
http://www.seumas.org/jt2.jpg

and when I hook that same circuit up to the solar switch output I get nada

[SkyWatcher]

Hi folks, since ou site is down, figured I'd post my promising results here. I recently converted a 12 led lantern that is normally powered by 4 D cells and is now running off 1 AA rechargeable cell in standard JT emitter/collector connection. you'll notice in the pic showing the JT circuit inside the lantern that it has a 1" diameter toroid with 18 gauge insulated solid wire. Now this 1" toroid yielded about 4 hours run time using the 1- AA 2000mah rechargeable cell and the JT had a 150 ohm base resistor, since any higher ohm base would not light the leds very brightly. Then I decided to try a smaller diameter toroid of 1/2" diameter, this using 24 gauge magnet wire and with the same 150 ohm base resistor, run time was 8 hours at same brightness level. Now as we speak, I am running a duration test with the same 1/2" toroid and 24 gauge, though with a 1.5kohm base resistor and run time so far is 14 hours and still going at same brightness level. Many more experiments to be run, until I achieve the longest run time at same brightness level possible. Here are the pics. In the pic showing the various toroids, the 1/2" toroids are marked (1) and the 1" diameter toroid is marked (2). I'd like to hear your thoughts.
peace love light
Tyson


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[Lidmotor]

Auto on/off and Joule Thief

I'm glad you got it to work Lidmotor, I however have run in to a little problem with the circuit. By themselves the on/off solar circuit and my joule thief circuit work perfectly, I even replicated SkyWatcher's multi LED setup but with only 10 LED's. I could of done more but I wanted to see how long 1 AA would power them through a joule thief. But when I take the output from the on/off solar circuit to the input of my joule thief I get nada. The output from the solar circuit is 1.5V when I am using just one AA and 2.75V when I have 2 AA's (old AA's) and an LED on the output. I was wondering if you could post a quick scribble schematic of how you had it all hooked up -the stubblefield and super cap, just the solar and joule thief.

pic of one of my joule theifs:
http://www.seumas.org/joulethief.jpg

Hooked up to 10 leds and powered by one button battery:
http://www.seumas.org/jt1.jpg

Same as above but with no flash:
http://www.seumas.org/jt2.jpg

and when I hook that same circuit up to the solar switch output I get nada

I hooked the Joule Thief up just like in the diagram, only for an interesting effect, I ran it through the Stubblefield coil in series. The super cap could have been a rechargable battery. It was pretty simple. The light sensitivity adjustment was the only problem that I had with it.
If your Joule Thief circuit will not run off this then maybe you need to play around with it and get it to run on less power??? Just a guess.

Lidmotor

[SkyWatcher]

Hi folks, the tests continue with the 12 led lantern, i was able to get 17.5 hours run time with the 1/2" toroid/ 24 gauge/ 1.5kohm base JT. I am now running a duration test with the 1/2" toroid/ 26 gauge/ 1.5kohm base JT. Next tests will be with different base resistance, then 30 gauge wire and different base resistances, then I will be testing the larger 1" diameter toroid with different gauge magnet wire to compare. Also all tests maintain approximately same brightness levels tapering slightly as battery discharges, then brightness falls off at end. Any comments welcome.
peace love light
Tyson

[SkyWatcher]

Hi folks, well my experiments with these JT pulse circuits are revealing more and more to me. I picked up a couple strings of led christmas lights, each have 20 leds and a nice warm white color, which is much better and more like regular white bulbs. Well I can say that while using the normal JT output at collector and emitter is ok, though the most promising results I'm finding are with using a secondary pickup coil powering series strings of leds. So far, it seems that when using the right frequency and high gauge wire for secondary, that these led strings can put out a surprising amount of light and give good run times. Maybe it's because of the phosphors in the white leds that take very little current to run, either way it's useful light and that's all that matters. I'm focusing on getting strings of leds to light bright for long periods at this time and then plan on working out a solar/wind and any other recharging method to keep batteries running these lights for free. I sure am thankful to jeanna and others for lighting the way to the knowledge of using secondaries on joule thief type circuits. Anyone else working on similar circuits now. I'd love to hear about any other experiments folks are doing. thanks.
peace love light
Tyson

[SkyWatcher]

Hi folks, here is the 20 led string from biglots lit powered by a large ferrite bead, though it's wrapped on the outside like a solenoid, it has 6 layers of 30 gauge with one layer of bifilar 24 gauge on top for JT circuit. It is working a little better than the 1" toroid and may give longer run times, duration testing at this time. Any thoughts welcome.
peace love light
Tyson


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