Joule Thief

[nievesoliveras]

This is the circuit that when you touch the positive of the 1.5v battery with the coil output diode it gets charged instantly. If you let the wire connected the motor stops.

A circuit that make the touch automatically is needed.

Any ideas?

[electricme]

@nivesoliveras and others

The flip flop sends a high (which is a positive voltage) from it's output, which can be used to switch on a transistor. After a preset time, it will then cycle off, the on-off times in the circuit are generally fixed, but it is possible to have it adjustable for the mark space ratios (the ON times and OFF times) to be made longer or shorter.

Here is a link to a site that gives a very good explanation for those who don't know what a Flip Flop thingie is all about. It has a PCB that has been populated, there are very few parts involved and this one is very basic, it has no way to control the times when the LED is on or Off, these have been are fixed by the designer via the chosen resistor and the capacitors. They are chosen because they give reliable starting of the circuit which can be tricky sometimes

The circuit can also be used as the main section to drive a iron core transformer to make a UPS, but that's for another day

http://electropart.info/schematic-diagrams/led-flip-flop-project.html
   
To alter the times that the LEDs are On and Off, you need to increase or decrease the value of the resistors or the capacitors separately, or you can change all of them.
You cannot alter the 470R resistors as these are required as a current limiter for the LEDs, but you can change the values of the 10K ohm resistors, I would change the 10K resistors to a 1000 ohm resistor and insert a 10k pot between the top of the resistor and the positive voltage supply rail. The 1k ohm resistor serves as a buffer between the transistors base so it won't be fed too higher a voltage.
You could also place a 10k ohm pot across the electrolytics, setting the wiper to the high or low side will either make the LED be on for shorter or longer times.
You could instead use a BC548 or a 22222 etc etc transistor.

The circuit as seen switches ON and OFF the two leds alternatively, what we need to do is use the circuit to feed pulses to a larger transistor (BD139) to switch on and off two circuits, the first one being the supply powering the CFL battery, the other switching the charging circuit.

So if the CFL can be made to turn on and off faster than we can see it happening it will give the impression it is always ON, during the OFF times the back EMF from the collapsing magnetic fields in the coil can be used to recharge the battery driving the CFL, this should be able to extend the time that the CFL can be driven by the battery.

One thing to remember though, this circuit is designed to work with 9v DC, we need to make it work with 1.5 volt DC.
That's the challenge.

Suggestions,
The LEDs could be removed, and a wire link be inserted in it's place (takes care of the 3v that is necessary to make the LED fire up). Without the LEDs it should be possible to make this circuit perform at a much lower voltage, the transistor turn on at .6 of a volt, use geraniums to bring this lower to .2 volt if necessary.
Make sure the transistor chosen can handle hi spikes though.

Take the Hi at the base of each transistor (leave the transistor in circuit) by soldering a wire from it to the base of another transistor, or solder a wire from the collector to go to the base of another transistor (BD139)

Feed the 1.5 volt through the collector of the BD139 and take the switched Hi (1.5v) out to drive the CFL

Do bacilly the same with the 2nd transistor from the flip flop that drives another BD139 whose Collector is soldered to the output coil and the emitter is soldered to the Pos of the 1.5 volt battery supply.

I haven't done this as I haven't got the bits here to see if it works, but it may or may not work, only one way to find out is to give it a go.

Testing the flip flop
A scope (CRO) connect the earth clip to the Negative side of the battery, the tip to the base of the small transistor/s will show you if the Hi pluses are on the output, connect the probe to the BD139 emitters and you should see the same pluses there also, that tells you the FLIP FLOP is working and the BD139's are firing (switching) OK, and you would be able to see the mark space ratios as well.

jim
     

[electricme]

Here is the circuit, only the modified Flip Flop.
The LEDS are removed, the resistors that used to be used for the LEDs can now be of a lower resistance value.

There are 2 parallel outputs marked in Green and Blue, you can select either to drive the bases of the BD139s that are not seen here.
Take the Negative and common it to the CFL

jim

[electricme]

A small modification to my last circuit.

I have now shown the POTs which are placed "across" the electrolytics, adjusting the settings to the left will make the capacitor take longer to discharge, moving the wiper to the right will shorten the times of discharge.

Setting either wiper differently will allow you to switch on and off the BD139s at what ever times you wat them to be on and off for.

jim 

[nievesoliveras]

Thanks @electricme!

I bought one of those flip flop flashers last year and have not assembled it waiting to get some transistor sockets, so I can change different transistors.
Also I will get sockets for the caps. The frequency can be changed using different capacitor values too.

Jesus