SOLAR CHARGER

1. SOLAR CHARGER   - this page - using a ZTX 851 transistor 2. Solar Light 3. Power Supply 5v Solar - Circuit 1 4. Power Supply 5v Solar - Circuit 2 5. Solar Charger - Push Pull circuit  This is another kit in our self-sufficiency range. We also have a 12v fluoro inverter kit for those who need to operate 20watt to 40watt fluorescent lamps from a 12v supply.  We will be introducing a number of kits for those who have opted to live with 12v energy. With nearly everything electronic capable of operating from a 12v supply, there is no reason why anyone opting to live with a low voltage supply cannot enjoy all the electronic pleasures of those who live in the city.  Some products are not yet available for 12v operation but inverters are available from 100watts to 4kw.  HOW THE CIRCUIT WORKSThe circuit is a single transistor oscillator called a feedback oscillator, or more accurately  a BLOCKING OSCILLATOR. It has 45 turns on the primary and 15 turns on the feedback winding. There is no secondary as the primary produces a high voltage during part of the cycle and this voltage is delivered to the output via a high-speed diode to produce the output. The output voltage consists of high voltage spikes and should not be measured without a load connected to the output. In our case, the load is the battery being charged. The spikes feed into the battery and our prototype delivered 30mA as a starting current and as the battery voltage increased, the charging current dropped to 22mA. The transistor is turned on via the 1 ohm base resistor. This causes current to flow in the primary winding and produce magnetic flux. This flux cuts the turns of the feedback winding and produces a voltage in the winding that turns the transistor ON more. This continues until the transistor is fully turned ON and at this point, the magnetic flux in the core of the transformer is a maximum. But is is not EXPANDING FLUX. It is STATIONARY FLUX  and does not produce a voltage in the feedback winding. Thus the "turn-on" voltage from the feedback winding disappears and the transistor turns off slightly (it has the "turn-on effect of the 1 ohm resistor). The magnetic flux in the core of the transformer begins to collapse and this produces a voltage in the feedback winding that is opposite to the previous voltage. This has the effect of working against the 1 ohm resistor and turns off the transistor even more. The transistor continues to turn off until it is fully turned off. At this point the 1 ohm resistor on the base turns the transistor on and the cycle begins. At the same time, another amazing thing occurs. The collapsing magnetic flux is producing a voltage in the primary winding. Because the transistor is being turned off during this time, we can consider it to be removed from the circuit and the winding is connected to a high-speed diode. The energy produced by the winding is passed through the diode and appears on the output as a high voltage spike. This high voltage spike also carries current and thus it represents ENERGY. This energy is fed into the load and in our case the load is a battery being charged. The clever part of the circuit is the high voltage produced. When a magnetic circuit collapses (the primary winding is wound on a ferrite rod and this is called a magnetic circuit), the voltage produced in the winding depends on the QUALITY of the magnetic circuit and the speed at which it collapses. The voltage can be 5, 10 or even 100 times higher than the applied voltage and this is why we have used it. This is just one of the phenomenon's of a magnetic circuit. The collapsing magnetic flux produces a voltage in each turn of the winding and the actual voltage depends on how much flux is present and the speed of the collapse. The only other two components are the electrolytics. The 100u across the solar panel is designed to reduce the impedance of the panel so that the circuit can work as hard as possible. The circuit is classified as very low impedance. The low impedance comes from the fact the primary of the transformer is connected directly across the input during part of the cycle. The resistance of the primary is only a fraction of an ohm and its impedance is only a few ohms as proven by the knowledge that it draws 150mA @ 3.2v. If a battery is connected to the circuit, the current is considerably higher. The 150mA is due to the limitation of the solar panel. Ok, so the circuit is low-impedance, what does the 100u across the panel do? The circuit requires a very high current for part of the cycle. If the average current is 150mA, the instantaneous current could be as 300mA or more. The panel is not capable of delivering this current and so we have a storage device called an electrolytic to deliver the peaks of current. The 10u works in a similar manner. When the feedback winding is delivering its peak of current, the voltage (and current) will flow out both ends of the winding. To prevent it flowing out the end near the 1R resistor, an electrolytic is placed at the end of the winding. The current will now only flow out the end connected to the base of the transistor. It tries to flow out the other end but in doing so it has to charge the electrolytic and this take a long period of time. These two components improve the efficiency of the circuit considerably. You will notice the battery is receiving its charging voltage from the transformer PLUS the 3.2v from the solar panel. If the battery voltage is 12.8v (the voltage during charging) the energy from the transformer will be equivalent to 9.6v/12.8v and the energy from the solar cell will be equivalent to 3.2v/12.8v. In other words the energy into the battery will be delivered according to the voltage of each source.                                                      MADE BY,                                                                             CHRISTO                                                                               IX-B                                                                     THSS VAZHAKKAD