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Index 24

555 trigger and long time delay circuit

Published:2011/6/12 10:58:00 Author:nelly | Keyword: trigger, long time delay

555 trigger and long time delay circuit
As shown on the figure 6-7, this circuit adopts the dual time base circuit 556. The half of the 556 and R,C make up of a monostable delay circuit and putting it to cascade. Then the trigger and long time delay circuit will be constructed. According to the program, we need to design the every delay time: td=1.1RC. If R1=R2=R3=R4=R, C1=C2=C3=C4=C, the total delay time: T4=4td=4.4RC. If it has n grades, Tn=1.1nRC. (View)

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555 Sine wave Generator Circuit

Published:2011/6/23 22:39:00 Author:Zoey | Keyword: 555sine wave, generator, circuit

555 Sine wave Generator Circuit
As shown in the figure 5-13, the astable multivibrator is composed of IC1, Rp1, R6 and C3, and f=1.44/(RP1+2R5)C3. Oscillation frequency of the parameter in the figure is 20Hz~20khz, which can be adjusted by RP1. Figure5-13 Sina wave Generator Circuit Both IC2 and IC3 use Double BCD up counter for obtain four-stage cascaded frequency. IC4 is a new switched-capacitor filter, it filters the frequency signal sent and output standard sine fundamental. While IC5 uses JEFT to input theoperational amplifier, which is used to butter the amplifier stage, and the value of amplitude can be adjusted by RP2, the magnification K≈RP2/RHo. (View)

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Crystal oscillator Circuit composed of 555

Published:2011/6/23 21:48:00 Author:Zoey | Keyword: Crystal oscillator, Circuit, composed of 555

Crystal oscillator Circuit composed of 555

With the composition of a 555 circuit, a quartz crystal oscillator circuit can be formed. As shown in the figure 3-7, after jointing point A and point B or clamping and jointing a small resistance, an astable multi-vibrator is formed and its oscillation frequency f is 1.44/R1C1. Choose a fixed R1C1 oscillation frequency close to f, and then joint the different parts as shown in the picture, tract the circuit to crystal oscillator or to its oscillator on the harmonic. If it does not starts-up well, we can adjust the variable capacitor. If the time constant is multiplied N times, the oscillator frequency will turn to be 1/N of the crystal oscillator frequency. (View)

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555 Photosensitive oscillator circuit

Published:2011/6/27 3:08:00 Author:Zoey | Keyword: 555 Photosensitive oscillator, circuit

555 Photosensitive oscillator circuit

As shown in picture 3-11, this oscillator constitutes an astable multi-vibrator along with a 555, R1, R3, C1 and a photosensitive audion, and its oscillation frequency can be calculated by this formula: f=1.44/(R+2RVT+2R3)C1 The internal resistance in photosensitive audion VT changes as light change. When exposed in a strong light, is will have a low resistance, vice versa. Therefore, the oscillation frequency changes as sensitivity of light changes, oscillation frequency can change from 1Hz to 6.5Hz. This oscillator can be used as the leader to explore the way for the blind people, or as the harbinger of dawn or can be used in other situations. (View)

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555 Square wave Generator with a Large-scale Changeable Duty cycle

Published:2011/6/30 0:04:00 Author:Zoey | Keyword: 555 quare wave Generator, Large-scale Changeable, Duty cycle

555 Square wave Generator with a Large-scale Changeable Duty cycle

Figure 3-5 Square wave Generator Circuit with a Large-scale Changeable Duty cycle As shown in the figure 3-5, 555, R1，R2, RP1, D1,D2 and C1 constitute an astable multi-vibrator. D1 and D2 refer to the guide tubes on the charge and discharge loop respctively. tc=0.693(R1+RPleft)C1 td=0.693(R2+RPright)C1 t=tc+td =0.693(R1+R2+RP)C1 Dmin=tc/T=(R1+R2+RP)≈0.01% Dmax=tc/T=(R1+RP)(R1+R2+RP) ≈99.99% From the formula above we can conclude that, no matter how RP1 is adjusted to, the oscillation period won't be affected. Oscillation frequency of the parameter in the figure is about 20Hz. (View)