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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING Simple designs on trinistor KU112A. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Beginner radio amateur [an error occurred while processing this directive] Relatively cheap and commercially available low-power trinistors KU112A can be used in a wide variety of amateur radio designs. This is discussed in the published article. This trinistor compares favorably with other similar ones by low turn-on and hold currents and the ability to control at high resistance of the load connected to it. In addition, it can not only be easily opened, but also closed without applying a negative voltage to the control electrode-cathode junction, which is important for such a threshold element. Consider several practical designs that use the specified trinistor. Relaxation generator (Fig. 1). It uses a piezoceramic sound emitter with a built-in generator as a load. When the supply voltage is applied to this device, the BF1 emitter starts emitting intermittent sounds with a frequency of 1,5 ... 4,5 kHz.
It happens like this. First, the trinistor is closed, the capacitor C1 is gradually charged from the power source through the emitter and the resistor R1. When the voltage at its terminals exceeds 9 ... 10 V, the zener diode VD1 will open. Following it, the trinistor will open, a sound will be heard from the emitter. With the opening of the trinistor, the voltage at its anode will not exceed 0,7 V. The capacitor C1 will begin to discharge through the resistor R1, the trinistor, the zener diode and the resistors R2, R3. When the control current through the trinistor is not enough to keep it open, the trinistor will close. The sound will stop abruptly, and the capacitor C1 will start charging again. The process will repeat. Thus, the device works as a generator of rectangular pulses with an amplitude close to the supply voltage, following at a frequency of approximately 2 Hz with a duty cycle of 3. The peculiarity of the generator is that it starts to work with a slight delay after the supply voltage is applied. And this, in turn, in some cases of its application can be very convenient. The generator is operational at a supply voltage of 11...15 V. Continuous Tone Generator (Figure 2). In it, in place of the emitter, a high-resistance dynamic head, for example, 0.25GDSH-2 with a resistance of 50 Ohms, or a high-resistance telephone capsule can be used. An interesting feature of this generator is the strong dependence of the sound frequency on the value of the supply voltage. When the voltage changes from 6 to 15 V, the frequency decreases from 4000 to 400 Hz. This effect allows you to create various sound simulators on the basis of this device.
A wider frequency range can be obtained if, instead of capacitor C1, several are installed, of different capacities, connected by a jack or push-button switch. By installing a more powerful one with a high base current transfer coefficient, for example, 6114SC2D, instead of the KT2500B transistor, you can connect a low-resistance head to the generator, say, with a resistance of 8 ohms.
The details of this sound generator can be mounted on a printed circuit board (Fig. 3) from one-sided foil fiberglass. Time relay for low power load (Fig. 4). It is assembled on the already known trinistor and a low-power bipolar transistor. The duration of the relay exposure is about five minutes. It controls the operation of the blinking HL1 LED, but it is permissible to turn on another low-power load instead.
With a short closure of the contacts of the button SB1, the capacitor C1 is quickly charged, the trinistor opens, the LED starts flashing. But the capacitor starts to discharge. As soon as the voltage on it decreases to 1,2 ... 1,8 V, the trinistor will close, the LED flashes will stop. Resistor R1 is designed to prevent the short circuit protection of the power supply at the moment the SB1 button is pressed. In addition, it prevents the button contacts from burning. The emitter follower on the transistor VT1 allows you to get longer exposures with a lower capacitance of the timing capacitor C1. Using an imported high-capacity oxide capacitor with a very low leakage current, as well as a transistor with a base current transfer ratio of at least 800 (2SC184V, 2N5089), you can get more than an hour delay to turn on the load.
The details of this time relay can be mounted on a printed circuit board (Fig. 5) also from one-sided foil fiberglass. Time relay for powerful load (Fig. 6). It uses a powerful p-channel MIS transistor (VT1) as a high-current switch. With the values \u1b\u2bof the elements C3, R1, R5 indicated in the diagram, the EL1 car incandescent lamp shines for about four minutes. Resistor R1 is installed in order to facilitate the closing of the trinistor VS4700. With a capacitance of capacitor C20 of 5 uF, the shutter speed reaches 12 minutes, but due to the feedback circuit that the resistor R15 creates, the process of the lamp going out is delayed for several seconds. However, during this time, the field-effect transistor does not have time to overheat at a supply voltage of 4 ... 5 V, even when operating with a maximum load current (in this case, XNUMX A). In most cases, the trinistor closes successfully even without the resistor RXNUMX, so it can not be installed initially.
The permissible power of an incandescent lamp connected as a load is limited by the maximum permissible direct and pulsed drain currents of the field-effect transistor, as well as by the size of the heat sink on which it can be mounted. It is desirable that the temperature of the transistor case during operation does not exceed 60 ° C. The details of the device are mounted on a printed circuit board (Fig. 7) made of one-sided foil fiberglass. The heat sink for the transistor can be an aluminum plate 2...3 mm thick and 60x40 mm in size. It is fixed with two MOH screws on the reverse side of the board at a distance of 15 ... 25 mm from it.
In all devices, it is permissible to use both foreign small-sized oxide capacitors and domestic series K50-24, K50-35. The blinking LED can be, in addition to those indicated on the diagrams, L36BSRD, L816BGD, L796BGD - all are round, but of different diameters. Zener diode - any with a stabilization voltage of 4 3 10 V, for example, KS147G, KS168A, D814A, 1N5998B. Instead of the KS520V zener diode, which protects the field-effect transistor from supply voltage surges (in the case of installing a time relay on a car), it is permissible to use KS522A, KS524G, KS527A. Instead of KT3102K transistors, any of the KT3102, KT342, SS9014, 2SC1222, 2SD1020 series are suitable, instead of KT6114B - any of the KT503, SS8050, 2SC5019 series, and instead of KP784A - KP785A. A piezoceramic sound emitter can be any with a built-in generator, designed for a supply voltage of at least 10 V - HPA17AX, HPA24AX, EFM-475. Dynamic head - 0.1GD-17 or telephone capsule with a resistance of 40-1600 ohms. When experimenting with designs and their manufacture, it should be borne in mind that the greater the current in the anode circuit of the trinistor, the lower the resistance of the resistor shunting the control electrode-cathode circuit should be. It is not recommended to use trinistors that have already worked in switching power supplies for ZUSST-5USTST TVs. Author: A.Butov, village of Kurba, Yaroslavl region
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