For setting up, inspection and testing of electronic circuits and, if necessary, recharge battery offers power supply test station consisting of two stable and one adjustable channel.
The power supply is made with the use of electronic components from decommissioned monitors and power supplies computers. The diagram of the power supply (Fig.1) consists of:
- input noise filter on the transformer T1 and the capacitor C1…C2;
- step-down transformer T2;
- rectifier with VD1 smoothing capacitor C3;
- two analog voltage regulators on the circuits DA1 and DA2 (output voltage for DA2 recharging the batteries 12 V increased using a diode VD2);
- e the voltage regulator on a composite transistor VT1;
- scheme protection of the power transistor against overloads and short circuits in parallel the stabilizer DA3.
The stabilized voltage from the output of the chip is also used for DA2 the power circuits of the voltage regulator on a composite transistor VT1. Transistor the controller has a gain of at least 400 and the output current is more than 5 And that eliminates additional amplifying stages.
To protect VT1 from the failure in case of short circuit in the load in the circuit there is a feedback loop from the sensor load current R8 to the base of VT1 through parallel stabilizer on the chip DA3. The voltage at the sensor R8 leads to the opening of parallel stabilizer DA3, which bypasses the base of transistor VT1 and limit the current. The current installation limitations of a resistor R7 Is parallel stabilizer you can set any low-power transistor of opposite conductivity. Indication the output voltage is performed on the led HL2 green glow. To reduce fluctuations of the output voltage of the capacitor is installed large capacity C6.
The device is assembled on the PCB size mm 72x51 (Fig.2) which is placed in the housing of a computer power supply.
The switch SA1 and the fuse FU1 together with ammeter and voltage regulator installed on R3 the front wall of the housing, the ammeter is mounted in the box after the removal of the fan. The voltmeter in the circuit shown conventionally, as it will fit any the tester is measuring voltage.
Ammeter RA1 made on the measuring head type M2003 with a current total deviation of 100 μa. The shunt RS1 made of 10 turns of copper wire of 0.8 mm, is wound on the mandrel the Calibration of 0.8 mm. shunt sequentially for inclusion with ammeter tester mode measurement of large currents.
Step-down transformer with a capacity of 120…150 watts used industrial, type TN-58(59) or CCI-292(293,294,303), with a total voltage of the secondary winding 18…24 V and the allowable current of 3…5 A. the diagram does not indicate the Pinout conclusions it can be done on the basis of the voltages of the secondary windings and their connections. Mains filter taken ready-made from computer power supply.
Instead of a bridge the rectifier can VD1 apply 4 diode DB or D, D. The radiators on the diodes is not set definitely. Electrolytic capacitor C3 in the circuit taken at a voltage of 35 V to reduce leakage and possible overheating when working power supply for large load currents.
Integrated stabilizers DA1 and DA2 are fixed on the metal case via the mica strip. Display the enabled state of the power supply is made on the led HL1. Transistor VT1 is mounted on the housing through the strip with mounting from the outside of the radiator. The resistor R8 can to perform nichrome wire 01 mm and a length of 50 mm, is wound on a resistor type MLT-2.
Special adjustment scheme does not require power. Just connect to the output (0…16 B) load in the form of automotive light bulbs (50 candles) and regulator R3 to set the desired output voltage. The resistor R7 is set in such a situation, in which the voltage at the load stops growing when the rotation of the engine of the resistor R3.
Authors: V. Konovalov, A. Vanteev, Laboratory Automation and remote control", the Irkutsk center "Energy saving technology", Irkutsk.