Garland switch on a unijunction transistor. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Garland switch on a unijunction transistor. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Color and music installations, garlands

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The unijunction transistor garland switch consists of a trinistor power regulator operating in the key mode and a control device based on an analogue of a unijunction transistor.

unijunction transistor string switch

The operation of the device is based on a change in the phase shift between the beginning of the half-cycles of the mains voltage and the pulses arriving at the control electrode of the trinistor from a relaxation generator assembled on an analogue of a unijunction transistor (transistors V6, V7). The pulse repetition rate can be set roughly trimming resistor R5 and smoothly variable resistor R3.

unijunction transistor string switch

To adjust the device to the desired light effect, the engine of the tuning resistor R5 is set to the upper (according to the diagram) position, and the variable resistor R3 is set to the middle one. A garland is connected to the device and included in the network. By moving the engine of the tuning resistor R5, it is installed approximately in the middle of the section corresponding to the modes of smooth ignition and smooth extinction of the garland. After that, resistor R3 can select the desired mode of operation of the device.

In the presence of a unijunction transistor, such a switching device can be assembled according to the circuit shown in the following figure.

Establishing it comes down to the selection of the resistor R4. To do this, the slider of the resistor R2 is set to the middle position, and the resistor R4 * is replaced by two series-connected ones - constant at 5 ... 10 kOhm and variable at 33 ... 47 kOhm. By rotating the variable resistor slider, they find the middle of the section between the modes of smooth ignition and smooth extinction of the lamps, after which the resulting total resistance of the chain is measured and a constant resistor with such resistance is installed in the device.

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