This is a basic circuit of a step up DC-DC converter which the output voltage is more than the
input, the circuit could be used to power a 9v or more devices from a 6v or even a 1.5v battery, charge batteries (3-12v) with 1.5v solar cell...
The circuit uses an oscillator using Schmitt trigger, all types of oscillators works, one transistor (Ex: BD139 or similar), resistors, coil (many different
types of coils work even a small DC motor works! or you can wind 60 turn on ferrite)
R1 and C1 determine the oscillation frequency, different types of coils perform differently at frequencies changes.
I used 5v input and toroid ferrite, the output exceed 60v (no load). The output voltage will drop as the load go higher.
Other types of oscillators can be used:
Other one to use see here: Simple rectangular oscillator
7812 or 7805 regulators can be used to stabilize the output voltage. (remember not to exceed the maximum input voltage)
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Joule thief is a simple step up converter, that converts DC to DC, for example you can drive a 3.4V Led with single 1.2V battery, even if the battery is almost dead. It extract all the energy stored in batteries.
You need:
- 1Kohm resistor.
- small NPN transistor ( for example 2N3904 ).
- ferrite toroid, (can be found on power supplies, radio), and wire to wrap around the toroid, ( big toroid and more turns = more output power and voltage you get ) the method of wiring is shown under, (if you don't have the toroid try the other methods under).
- and Led or anything you can't drive with one battery like: leds, lighting a neon lamp, charging capacitors with high voltage, charging other batteries Ex: charging 3.6V batteries with 1.2V battery...
you can change the 1.2V battery with 9V to get high voltage output that can drive neon lamps...
you can charge batteries...
A demostration:
A different types of coils can be used
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This circuit shows how to build a simple flasher that can flash Leds, lamps, motors...
To make this circuit you need:
To make this circuit you need:
- 4 Resistors, two 470-560 ohms and two 2.2K-10K ohms.
- 2 Capacitors, 47uF (or approach values ).
- 2 identical Small/power NPN transistors (any type will work), by using hig power transistors we can drive high power bulbs...
- Battery 3-4 V ( for 5V increase the resistors values).
- And leds 2.4V or any.
- A variable resistor of 1K-10K ohms can be used (in place of one 2.2k resistor) to change number of flashes per second ( from 1 to 10 Hz ).
One led or two can be used
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This circuit is a rectangular oscillator, that generates a square wave form, the circuit uses NAND logic gates, using CD4011 (contain 4 nand gates), the generated signal can be used as an audio alarm (by connecting a speaker directly to the output), or amplified and used as an inverter...
The enable input should be (+V) so that the circuit oscillates, if it's low, the output will remain at High (+V), If you do not need a controlled input, you can connect the two inputs of the two gates together and remove the connection between the first and the second gate. (like the picture)
This may simplify the wiring.
Caution: the common point of the resistors and the capacitor is not grounded.
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We thought that limiting the current of recharging the batteries did the trick, but no! the electrolyte leaks from the end of the negative terminal, when the battery leaks, it loses in the best case 50% of its capacity. more leakage always ends with a small explosion, so another method is needed!!!
The technique of a discontinuous contact: thanks to this technique the battery could suffer much less stress when recharging but on condition of leaving the battery two times longer to rest than to recharge (2 seconds of 6) 2s charging, 4s resting, And it works! batteries recharged without problems!
weather when recharging AA, AAA or 9 volt, no problem it works and it does not leak. In the worst case we can always limit the intensity.
The circuit consists of a simple oscillator that charges the batteries for 2 seconds and stop for 4 seconds.
The oscillator drives the Mosfet that charges the batteries.
Choose any mosfet Type, and any small transistor, that handle the charging current, if you want to charge a lot of batteries choose a high current transistors.
Another transistor and a potentiometer control the charging current, to charge all types (AAA AA 9V):
I recommend:
- AA: maximum 250mA
- AAA: 110mA max.
- 9V: 70mA max.
To recharge the batteries you must inject a voltage greater than the batteries voltage by X1.5.
This charger can charge as many batteries as you want! with 12 volts can be up to 6 (with more than 12 volts but in this case consider increasing the value of some resistors).
To make sure that your batteries are full charged and not damaging them, monitor their voltage, it should not exceed 110%, for example: a battery of 1.5V, maximum charge voltage is 1.65V.
(considering regeneration 80%), a 2Ah battery needs 20h for a complete recharge, Long? not really if you're not pressed.
Notes:
Before charging the batteries try to select them: never take that are not alkaline, leaking already, which are rusty, which are of a mark "cheap", that give "0.00 volts" or supposed to be "outdated "for too long. Remember that alkaline batteries can be recycled. no saline lithium or any non alkaline battery it won't work and it's dangerous.
The source video from youtube (but in french!):
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