The module generates waveforms: rectangular, sawtooth, triangular and sinusoidal. The limitation is the ability to work only with one pre-selected frequency. The advantage is the ease of making the device. The basic application of the presented device is to work in the electronics workshop as a stationary or portable generator.
• Frequency 1 kHz
• Output waveforms: rectangular, sawtooth, triangular and sinusoidal.
• Duty cycle of the rectangular waveform: 50%.
• Output voltage: adjusted within range 0…supply voltage.
• Power supply: 9 VDC / 10mA (6-10 VDC).
• PCB dimension: 41×64mm.
• Electronic Kit – soldering required.
The schematic diagram of the generator is shown in Figure 1. The US1 chip generates a square wave with a duty factor of about 50%. The frequency of the waveform generated depends on the capacitance C1 and the resistance R1, and R2. Using elements with the values given in the diagram, a rectangular signal with a frequency close to 1 kHz will appear on the pin 3 of the US1 chip. Then, the rectangular waveform is converted by several RC filters into signals of other shapes. At the connection point of the resistor R6 and the capacitor C3 a sawtooth waveform is obtained. Then, after passing through a filter composed of R7 and C4, the shape of the waveform is close to that of the triangular one. Further, the signal is fed to the integrator circuit with transistor T1. The signal has a sinusoidal shape on the T1 collector.
Then, the rectangular waveform is shaped by several RC filters for signals of other shapes. At the connection point of the resistor R6 and the capacitor C3 a sawtooth waveform is obtained. Then, after passing through a filter composed of R7 and C4, the shape of the waveform is close to triangular one. Further, the signal is fed to the integrator circuit with transistor T1. The signal has a sinusoidal shape on the T1 collector.
All these signals are fed to the inputs of the analogue multiplexer US2. With its help, one of the four input signals is available on pin 3 connected to the base of transistor T2, which acts as an emitter follower.
The amplitude of the output signal can be adjusted using the potentiometer P1. The voltage of the output signal depends on the type of signal shape and the supply voltage. Generator works properly powered with voltage from the range of 5 V to 10 V. Due to low power consumption (approx. 10 mA at 9V), the generator can be powered by battery.
Assembly and test
The generator assembly diagram is shown in Figure 2 in the user manual. It is assembled on a single-sided printed circuit board. The assembly should start with soldering resistors and a rectifying diode. Then, it is necessary to solder elements of larger dimensions and finish them on the block terminals. After completing the assembly, the polarity of the elements should be carefully checked. The generator should work immediately after switching on the power supply. Figure 3 in the user manual presents the configuration of the signal selector jumpers.
R12, R13: 100kΩ
PR1: Trimmer potentiometer 50kΩ
C5, C6: 10nF
C7, C8: 1µF
T1, T2: BC547
JP1: goldpin connector 2×2pin + jumper
X1, X2: 2-pin terminal block connector