This generator is powered by a 2..3 batteries (accumulators) with a total voltage of 2..6 Volts. It allows to generate pulses of frequency 1 to 100 kHz with a stable duty cycle not frequency-dependent. Fixed values of duty cycle are set using combinations of the four switches, and can take values from 6 to 93%.
The scheme can be stability of output parameters, low consumption and its simplicity (only two chips). The output of the generator X2 is designed to control a transistor key.The following is a list used in the unit circuits, diodes and two modes. In parentheses are possible replacements:
- DD1 — 74HC00 (1564ЛА3)
- DD2 — 74HC393 (1564ИЕ19)
- VD1 .. VD4 — 1N4148 (any low-power ultrafast)
- SA1 — DS-04B, SWD1-4 (any DIP switch in 4 sections)
A master oscillator assembled according to the standard scheme — in two logic elements DD1.1 and DD1.2, which as a driving circuit uses a RC-chain (R1R2C2). You need to specify that instead C2 may be involved, and the quartz resonator. The capacitor C1 performs the correct startup of the generator at low supply voltages. Signal generator is divided by the counter DD2.1, and the contacts of the switch SA1 is served control the combination of the outputs of this counter in the feedback of the second counter DD2.2. As soon as this combination allows to put the positive supply at the 13th output DD1.4, the second counter resets, and you can adjust the duty cycle of the output X2.
The table below shows the duty cycle at the output of X2 depending on the numbers of closed switch contacts SA1:
The diagram does not show the power pins of chips, they are standard: 7 — negative supply (common), 14 — plus. All the cons need to connect and be connected to the common wire. All positive findings — to +V.
The generator can be assembled in an hour on the breadboard 3x7 cm and does not require further configuration.
One of the variants of connection of the generator is shown to the right. The device is powered by two AA batteries, the output stage is assembled on n-p-n transistor and the load inductor is used. Such a scheme can be used to study OADS.
At low supply voltage transistor output stage it is best to choose germanium, type AC176.
Vyacheslav Gorchilin, 2016
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