Varius Circuits

Low energy consumption audio signal generator

Low energy consumption audio signal generator

On those occasions when we want to see if an amp works, the best tool we can use is a source of acoustic signal with a frequency around the 1 kHz. These characteristics can be merely 'tolerated', because in cases of rapid tests rarely consider whether the amplifier is quality. We need only find that it works So, the deformation of the generator is a parameter without irrelevant, giving way to another more important: consumption. The design of the circuit discussed below has been done so that the generator is to fulfill the above requirements. ..

Tone Oscillator with 555

Tone Oscillator with 555

This is a basic 555 squarewave oscillator used to produce a 1 Khz tone from an 8 ohm speaker. In the circuit on the left, the speaker is isolated from the oscillator by the NPN medium power transistor which also provides more current than can be obtained directly from the 555 (limit = 200 mA). A small capacitor is used at the transistor base to slow the switching times which reduces the inductive voltage produced by the speaker. Frequency is about 1.44/(R1 + 2*R2)C where R1 (1K) is much smaller than R2 (6.2K) to produce a near squarewave. ..

1 KHz Audio Oscillator schematic

1 KHz Audio Oscillator schematic

This circuit consists of a CMOS square wave oscillator on a frequency of approximately 1 kHz. The RC filter, which has a roll-off frequency of 500 Hz, filters the harmonics, providing a sine-wave output. ..

Audio Oscillator schematic

Audio Oscillator schematic

The oscillator circuit (see Figure 1) involves two unity gain phase shift stages, A1 and A2, in tandem and a gain stage, A3, with back to back diodes and resistor network providing non-linear negative feedback. At a particular frequency (determined by RT and CT - the timing components) A1 and A2 provide 90 degrees phase shift each, 180 degrees in total and the circuit begins oscillating, since A3 and its non linear network has more than unity gain for small signals. As the oscillation level increases the diodes conduct and limit the gain of A3 stabilising the output at the desired level, in this case a little over 1V RMS. However, some distortion of the sine wave peaks is caused by the diodes...

Sawtooth generator circuit

Sawtooth generator circuit

Sawtooth wave generators using opamp are very common. But the disadvantage is that it requires a bipolar power supply. A sawtooth wave generator can be built using a simple 555 timer IC and a transistor as shown in the circuit diagram. The working of the circuit can be explained as follows: The part of the circuit consisting of the capacitor C, transistor,zener diode and the resistors form a constant current source to charge the capacitor. Initially assume the capacitor is fully discharged. The voltage across it is zero and hence the internal comparators inside the 555 connected to pin 2 causes the 555's output to go high and the internal transistor of 555 shorting the capacitor C to ground opens and the capacitor starts charging to the supply voltage...

38KHz or 40KHz signal generator

38KHz or 40KHz signal generator

The small 8-pin PIC12C508 is pre-programmed to generate our 38KHz carrier frequency by simply pulsing I/O-pin GP1 (shown above). The PIC will generate either 38KHz or 40KHz, depending on the state of GP3 when power is first applied. If you connect GP3 to ground, then apply power to the circuit, the frequency will be 40KHz. This was implemented for people using the older 40KHz style infrared detector modules. The default is 38KHz with pin #4 (GP3) left floating or (not connected to anything), Pin #7 (GP0) is to inhibit (stop) the carrier output. When GP0 is connected to ground, the PIC will halt generation of the carrier frequency. ..

Zener Oscillator circuits

Zener Oscillator circuits

These two circuits are interesting from an academic point of view. Their practical implementation is rather critical and it is not easy to get steady operation. Circuit (a) requires a "cooked" zener: connect it first to a constant current generator, then increase the current until the voltage across the zener starts to decrease. Reduce the supply current and wait a few minutes until it really warms up. The zener is now ready for the circuit: increase the voltage slowly until it oscillates (1KHz in the circuit shown). You may need to decrease the voltage once oscillation takes place. With suitable circuit components it will oscillate up to 20MHz. ..

Simple SCR oscillator

Simple SCR oscillator

Silicon controlled rectifiers (SCR) can easily oscillate if there is an inductor (a speaker coil in this case) which gives just enough extra voltage to completely switch off the sustain current. In this way a new cycle may start and oscillations set in. It operates over a wide range of supply voltage and components values are not critical at all. Operational frequency in this circuit goes from 100Hz at 11V to 10KHz at 100V...

Oscillators for Buzzers and telephone Earpieces

Oscillators for Buzzers and telephone Earpieces

In order to generate a single note you may try these simple circuits. With only three components you may implement some basic buzzers. You need a telephone earpiece for the first circuit. Any old telephone set has got one of those magnetic earpiece that is right for our purposes. Add an extra capacitor and a transistor and you have your buzzer. Frequency of operation is about 1800 Hz and the capacitor must be changed if you wish to have a different frequency. The second circuit is implemented with a ceramic sounder: its intrinsic capacity is used to make another simple buzzer. Working frequency is 800 Hz and power drain is really low. ..

30m Band Receiver

30m Band Receiver

The direct conversion receiver described consists of only a bandpass filter, mixer IC, VFO and audio filter. With only 22 parts, this simple circuit should take a few hours at the weekend to construct. For extra simplicity, eliminate L1 & C1 and connect C2 to the slider of P1. The oscillator section of the NE612 is configured as either a series-tuned Colpitts- or Clapp oscillator. Depending on the parts the receive range is from 10050 kHz to 10250 kHz. Due to component tolerances the number of turns and/or the capacity of L3 and C7 are adjusted to tune the required portion of the band. ..

7 MHz VFO

7 MHz VFO

A 7 MHz oscillator with a variable crystal oscillator (VXO) operates very stably, but it allows only a small frequency variation (approx. 5 kHz). In contrast, a VFO with an LC resonant circuit can be tuned over a range of several hundred kHz, but its frequency stability will depend upon its construction. The use of a ceramic resonator as frequency-determining component fulfills both requirements. The following oscillator circuit, which uses a ceramic resonator, offers a tuning range of 35 kHz with good frequency stability. The somewhat unusual resonant LC circuit at the collector of VT1 has two functions. It improves the shape of the output signal and at the same time compensates the amplitude drop starting at approximately 7020 kHz. ..

8 stages LFO analogue sequencer

8 stages LFO analogue sequencer

The CD4060 is a CMOS 14-stage binary counter with an internal oscillator on chip. The oscillator is controlled by the resistors and capacitor tied to the timing pins, 9-11. This oscillator runs the binary counter, and the various outputs count at the oscillator speed. In particular, pins 1, 2, and 3 count at 1/16384 th of the oscillator frequency. If we set the main oscillator to run from 16384 Hz to 163840Hz, then outputs 1,2 and 3 count at from 1 Hz to 10 Hz...

Function Oscillator using 8083

Function Oscillator using 8083

Built around a single 8038 waveform generator IC, this circuit produces sine, square or triangle waves from 20Hz to 200kHz in four switched ranges. There are both high and low level outputs which may be adjusted with the level control. This project makes a useful addition to any hobbyists workbench as well. The waveform generation is produced by IC1. This versatile IC even has a sweep input, but is not used in this circuit. The IC contains an internal squarewave oscillator, the frequency of which is controlled by timing capacitors C1 - C4 and the 10k potentiometer. The tolerance of the capacitors should be 10% or better for stability. ..

Crystal Clock Generators

Crystal Clock Generators

Here exist a small collection from three generators, what using crystal for basic production of oscillations. Each generator uses different topology of circuit for the production of oscillations. ..

Frequency Divider

Frequency Divider

This is a classic divider of frequency via two. It is achieved with a classic circuit T-flipFlop, round IC1 [ 4011 ]. In the circuit, the frequency of network, after are limit the negative half-s period of sine wave and transform in square wave, are divided via two. Thus for frequency50 HZ, we will take in the exit pulse of frequency 25 HZ. The supply of circuit it is + 5V and does not need high benefit in current. ..

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