Voltage transformer (12/∼220В) with audible and visual indication

Presenting DC converter circuit 12-volt battery to AC 220 AT. For many readers, at first sight this scheme seems very complicated and expensive, but it turns out, that the creation of this type of transducer is not difficult. The most expensive component of the converter: network toroidal transformer and two MOSFET. Maximum output power depends almost exclusively on the size of the transformer.Преобразователь напряжения (12/∼220В) со звуковой и световой индикацией

Schematic converter 12V / 220V circuit shown in Figure 1.

Voltage transformer (12/∼220В) with audible and visual indication

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The circuit consists of core elements:

  • transformer
  • two MOS-transistors
  • integrated circuit series 4047.

Part of circuits with components T3 … T6, U2C, U2D performs only a supporting. Unused inputs U2C and U2D should be shorted to ground or to an additional power source. In the simplest embodiment can be dispensed with gateways U2A, U2B and output signals from chip U1 directly with the FETs T2 and MOSFET T1. The energy source is a battery 12 The capacity of several tens of ampere-hours. The transformer TR1 has a key role. This is a normal toroidal mains transformer with two secondary windings (220In / 2h9V). The transformer operates with two MOSFETs T1 and T2, are alternately switched at a frequency 50 Hz. To be stable frequency, It uses the popular chip CMOS 4047, which operates as a generator. The oscillator frequency is equal to 100 Hz, and outputs (legs 10 and 11) are inverted signals with frequency 50 Hz. In practice, the oscillator frequency (100 Hz) determined by the elements R1, PR1, C1, and you can set it carefully using the PR1. At the exit, that is, the winding of the transformer, It presents a rectangular waveform. When operating on battery power due to various types of losses and reduce the battery voltage using the power transformer secondary voltage with a nominal 2×9AT, instead of 2×12AT. Transformers can also be used in the circuit with a voltage 2×8AT…2×10AT. The output voltage depends primarily on the battery voltage and the transformation ratio, load but also has a certain influence.

elements D1, PR2, T4, T3, D3 operate in battery voltage control circuit. Since the current consumption from the battery will usually high, the battery can be drained quickly. a deep discharge of the battery in said chain, signaling buzzer Y1 and the voltage drop across the diode D3 below, installed via PR2. Excessive voltage drop and clog an already opened transistor T4 and T3 opening. This will enable D3 and diode, Besides, low condition 12 withdrawal U2D gate lead to a high state at the output. This will start the generator to the gate U2C, and piezo (zummyer) Y2 will give intermittent audible warning. The threshold voltage of a siren can be set using PR2. The circuit elements with R14, D5 … D8, T5, T6, D4 with sound and illumination of the diode D2 – inform the overloading and excessive output current. The resistor R14 there is a voltage drop, proportional to the output current. The voltage across this resistor is rectified by a diode bridge D5 … D8. a delay circuit R11, C3 prevents false alarms, resulting instantaneous current pulses. Only when the average current exceeds the set level, transistors T5, T6 open, Signal diode D4 lights up and the buzzer sounds.

Installation and commissioning

Driving-control signaling can be mounted on the board, shown in Figure 2.

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In the present scheme, large currents will flow in some circuits. Suffice it to calculate, that when 12 The power 100 W is obtained at a current, exceeding 8 BUT. Such a high value means a current, that key connections must be made of thicker conductors, at least, cross section 1…1,5 mm2. On the concept of the parts drawn with thicker lines.

Particular attention should be paid to the installation of the power transistors. Guides, leading to them, should be as short as possible, to 10 Cm. It is better, after the printed circuit board assembly, before connecting the power transistors and Transformer, should check whether the control system produces a square wave with a frequency 50 Hz and filling 50%.

If you do not what to measure frequency, one resistor may be used instead PR1 R1 (or two successively) with a value 45,5 k. In this case, the frequency will not deviate from the nominal value, Besides, deviation in 5, 10 or even 20% not important. In the exemplary apparatus used power transformer 100 W, and transistors T1, T2 even when the output load 80 W not much heated. You can use the transformer with one rated, greater or lesser. The control FETs are open only resistance 0,03 … 0,04 Ohms and can handle currents of several tens of amperes. In this way, scheme can try to work with a much higher power transformer, even 300 W at output load 250 W, using fuse B1 with the appropriate rating.

The inverter has not been tested with all possible types of load. Due to the shape of the output signal, resembling a rectangular, Some devices may malfunction or even be damaged.

Attention! The scheme is not safe for voltages. Minors should be started and administered circuit operate only, if they are under the supervision of qualified adults.


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