7812&7912 12 Vdc Dual Power Supply Circuit

12 Vdc Dual Power Supply circuit with IC 7812&7912

Voltage Regulators low power consumption IC 78W series used in our instrumentation is now so cheap they are an economical alternative to simple regulators NPN-stabilizers. In addition, they offer the benefits of better regulation, current limiting / short circuit protection to 1000 mA shunt and heat down if the electricity disperses too. Indeed, is not the only way for these drives can be damaged polarity is incorrect or excessive input voltage. Regulators Series 78W to kind of stay 8V input voltage of about 35V, while the type 24v withstand 40V. Of course, of course, that regulators will not work with such an important input differential output as it would lead to excessive power is dispersed. All controllers will deliver the 78W series 1000mA current maximum expected input differential voltage output of less than 7V. Otherwise, too diffuse power, thereby bringing the fire extinguished.
Two transformers were used to step voltage 230-250V AC input power. It manufactures power transformers 6-0-6V secondary terminals. This output is fed into the rectifier and filter capacitor. Filtered IC6 that served 3-pin voltage regulator that provides a regulated output + 5V. It is used to enable the DPM system. It also comes as the network voltage source temperature accuracy.
Other manufactures transformers with a capacity of 12-0-12V at its secondary terminals. The center was established as a fountain in the previous case. The other two secondary terminals are fed bridge rectifier constructed using diodes. Output recovered is filtered using a capacitor C5 and C6 for food and IC7 IC. In-8 IC7, which are 3-pin regulators provide output voltage of ± 8V. These two voltages are signal generator. TO-8V power source is applied to the temperature of the network, and the reference voltage. It is also necessary to +12 V and-12V supplies for the implementation of operational amplifiers. This can be easily done using a 12V zener diodes. The output of bridge rectifier is attached to the +12 V and-12V, respectively, using two zener diodes. In the zener output is fed to the terminals of the operational amplifier supply. For supply
for operational amplifiers must not be very effective in regulating + 12V, the use of Zener diodes be costly.
For the testing of electronic components voltage above 50 V is required. This can be achieved through quadruple the chain tension. It consists of four diodes and four electrolytic capacitors. Unreasonable Administration Secondary 12-0-12V is connected to quadruple string. Quadrupled output of the circuit is 68V to ground.

7812+2N3055 High Power Supply Regulator

Using a single 7812 IC voltage regulator and multiple outboard pass transistors, this power supply can deliver output load currents of up to 30 amps. The design is shown below:
Notes:
The input transformer is likely to be the most expensive part of the entire project. As an alternative, a couple of 12 Volt car batteries could be used. The input voltage to the regulator must be at least several volts higher than the output voltage (12V) so that the regulator can maintain its output. If a transformer is used, then the rectifier diodes must be capable of passing a very high peak forward current, typically 100amps or more. The 7812 IC will only pass 1 amp or less of the output current, the remainder being supplied by the outboard pass transistors. As the circuit is designed to handle loads of up to 30 amps, then six TIP2955 are wired in parallel to meet this demand. The dissipation in each power transistor is one sixth of the total load, but adequate heat sinking is still required. Maximum load current will generate maximum dissipation, so a very large heat sink is required. In considering a heat sink, it may be a good idea to look for either a fan or water cooled heat sink. In the event that the power transistors should fail, then the regulator would have to supply full load current and would fail with catastrophic results. A 1 amp fuse in the regulators output prevents a safeguard. The 400mohm load is for test purposes only and should not be included in the final circuit. A simulated performance is shown below:




Calculations:
This circuit is a fine example of Kirchoff's current and voltage laws. To summarise, the sum of the currents entering a junction, must equal the current leaving the junction, and the voltages around a loop must equal zero. For example, in the diagram above, the input voltage is 24 volts. 4 volts is dropped across R7 and 20 volts across the regulator input, 24 -4 -20 =0. At the output :- the total load current is 30 amps, the regulator supplies 0.866 A and the 6 transistors 4.855 Amp each , 30 = 6 * 4.855 + 0.866. Each power transistor contributes around 4.86 A to the load. The base current is about 138 mA per transistor. A DC current gain of 35 at a collector current of 6 amp is required. This is well within the limits of the TIP2955. Resistors R1 to R6 are included for stability and prevent current swamping as the manufacturing tolerances of dc current gain will be different for each transistor. Resistor R7 is 100 ohms and develops 4 Volts with maximun load. Power dissipation is hence (4^2)/200 or about 160 mW. I recommend using a 0.5 Watt resistor for R7. The input current to the regulator is fed via the emitter resistor and base emitter junctions of the power transistors. Once again using Kirchoff's current laws, the 871 mA regulator input current is derived from the base chain and the 40.3 mA flowing through the 100 Ohm resistor. 871.18 = 40.3 + 830. 88. The current from the regulator itself cannot be greater than the input current. As can be seen the regulator only draws about 5 mA and should run cold.

source: http://www.mitedu.freeserve.co.uk/

1000W Inverters 120 -220VAC

1000W Inverters 120 -220VAC Circuit

This inverter will sufficiently power any of your 115VAC (or 220VAC)small appliances. T1 choice of amperage is yours to make, but if you can salvage a heavy-duty unit from somewhere, use it.

The least expensive method to get a larger transformer would be to remove the old 2000v primary and then re-wind an old microwave transformer. Most of these transformers are rated 1KW or better.

Your local TV or Electronics repair shop may have one or dig one up from the dumpster. Just in case you don’t know, micro-wave transformers can keep their charge (via the connected electronics) for a long time, so be careful! R1 and

R2 are 10 ohm, wire-wound, and at least 5 watts.



Wattage/cooling should be increased accordingly if you decide to beef up the output. For D1 and D2 you can use any power diode like the 1N4002 to 1N4005. If you live in Europe, Australia, or any other country with a 220VAC system, the only different is the transformer. This particular circuit can be constructed to handle up to 1 KiloWatt (1000 watt). If there is enough interest, I can modify this circuit to include a crow-bar circuit, battery backup, or more output in watts, or everything.

The power output is determined by transformer T1, and power transistors Q1 & Q2. Assume a transformer of about 15A and the chosen transistors of 2N3055 (15A) type, the inverter can supply about 300 watts with the parts shown. If you are good with electronics all you have to do is replace the 2N3055’s and T1 accordingly for more output. It is imperative to mount Q1 and Q2 on large coolribs. If you intend to beef everything up with a couple kilowatts a standard (5″) cooling fan will also be required. If this is the case, the 2N3771 power transistor is a good choice at 30Amps.

NTE’s replacement, NTE181, is an improved version of the 2N3771 and carries 90volts instead of the 40 volts and can dissipate 200W instead of 2N3771’s 150W. It is mandatory to include at least one suitable fuse and enclose this project in the correct casing. To be really safe you may want to include a primary and secundary fuse for your own protection. You are dealing with 120VAC or 220VAC at respectible amperage so be careful. The powercord also needs to be secured to prevent accidents.

The 68uF Tantalum capacitors were chosen for their endurance. Normal electrolytic capacitors would overheat and explode. Somesort of cooling fan inside the project case may be a good choice, I myself use a ball-bearing cpu-fan from an old computer. New they don’t cost that much either, about 3 bucks or so.
Since T1, and Q1/Q2 are NOT part of the PCB, these few parts can easily be used on a piece of Vero or experimenters board. Radio Shack and Tandy have these boards also available at a very reasonable price (in Canada $3.50). The receptacle(s) on T1’s output will be part of the case (obviously). I Just a small note about the 12 Volt battery, this circuit and others similar can draw huge amounts of current and will drain your battery in hurry so don’t let your battery go dead! That’s why a wind/solar power combination would be an excellent future addition. For those interested in a PCB, I have included one below with a layout. As soon as I get my digital camera I will include pictures of the finished project