Time base circuit 555 various application circuits
The 555 touch timing switch IC 1 is a 555 timing circuit, which is connected to a monostable circuit here. Normally, because there is no induction voltage at the P end of the touch pad, the capacitance C1 is discharged through the 7th foot of 555, the third pin output is low level, the relay KS is released and the electric lamp is not on.
When the light is needed to be turned on, touch the metal sheet P with your hand. The human induced clutter signal voltage is added from C2 to the triggering end of 555, so that the output of 555 changes from low to high level. The relay KS is absorbed and the electric lamp is on. At the same time, the 7th pin of 555 is cut off, and the power supply will charge C1 through R1, which is the beginning of timing. When the voltage on capacitor C1 rises to 2/3 of the power supply voltage, the 7th channel of 555 discharges C1, which makes the output of the third pin change from high to low level, the relay releases, the electric lamp goes out and the timing ends. The timing length is determined by R1 and C1: T1 = 1.1r1 * C1. According to the value in the figure, the timing time is about 4 minutes. D1 can be 1N4148 or 1N4001. The photo exposure timer attached circuit is a photo exposure timer made of 555 single stable circuit. The single stable circuit is manually started. Working principle: after the power is turned on, the timer enters the steady state. At this time, the voltage of the timing capacitance CT is: vct=vcc=6v. For 555, the equivalent trigger, both inputs are high, i.e. vs = 0. Relay KA does not engage, normally open point is on, and exposure lamp HL is not on.
After pressing the button switch sb, the timing capacitance CT will immediately set to zero voltage. So the input of 555 circuit equivalent trigger is: r=0, s=0, and its output will be high level: v0=1. Relay KA is actuated, normally open contact is closed, and exposure lamp is on. The button switch is released immediately after pressing, so the power supply voltage is charged to the capacitance CT through RT, and the stable state starts temporarily. When the voltage on the capacitance CT rises to 2 / 3vcc, the timing time is over. The input of 555 equivalent circuit trigger is: r=1, s=1, and the output is turned over to low level: v0=0. Relay KA is released and exposure light HL is off. The transient state is over, and there is a return to steady state. The formula of exposure time is t=1.1rt*ct. The delay time of the parameters provided by this circuit is about 1 second to 2 minutes, which can be adjusted and set by potentiometer RP. The relay in the circuit must be the product with the suction current no more than 30mA, and the contact capacity of the relay shall be selected according to the capacity of the load (HL). In the attached circuit of single power supply to double power supply circuit, time base circuit 555 is connected to a non steady state circuit, and the output frequency of 3-pin is 20kHz and duty cycle is 1:1 square wave. The 3-foot is high power, C4 is charged; C3 is charged at low power level. Due to the existence of VD1 and VD2, C3 and C4 only charge in the circuit without discharging. The maximum charging value is EC. The b-terminal is grounded and the double power supply of + / -ec is obtained at both ends of a and C. The output current of this circuit exceeds 50mA.
The simple hypnotic time base circuit 555 is a very low frequency oscillator, which outputs short pulses, making the speaker emit a sound similar to raindrops (see the attached figure). The speaker is of 2-inch, 8 ohm small dynamic type. The speed of raindrop sound can be adjusted to a proper degree by 100k potentiometer. If a simple timing switch is added to the power supply end, the power supply can be cut off in time after the user enters sleep.
The DC motor speed control circuit is a pulse oscillator with adjustable duty cycle. Motor M is driven by its output pulse. The larger the pulse duty cycle, the smaller the electric drive current and slower the speed; the smaller the pulse duty cycle, the greater the motor electric drive current and faster speed. Therefore, the speed of motor can be adjusted by adjusting the value of potentiometer RP. If the current of electrode electric drive is not more than 200mA, CB555 can be used for direct driving; if the current is greater than 200mA, the driving stage and power amplifier level shall be added.
VD3 in the figure is a continuous current diode. During the power amplifier cut-off period, the circuit is provided for the current of the electric drive, which not only ensures the continuity of the current, but also prevents the self induced and negative EMF of the electric drive coil from damaging the amplifier tube. Capacitance C2 and resistance R3 are compensation networks, which make the load resistive. The pulse frequency of the whole circuit is selected between 3-5 kHz. The motor will shake too low frequency, and the motor speed regulation range will be reduced due to the small duty cycle range when the frequency is too high. Class D amplifier made of 555
100kHz controllable multivibrator is composed of IC 555 and R1, R2, C1, etc. the duty cycle is 50%. The control terminal inputs audio signal with 5 feet. The pulse signal with pulse width proportional to the input signal amplitude is obtained by 3 feet. The loudspeaker is pushed after L and C3 connection and filtering. The circuit of fan cycle speed regulation is coming in summer, and the electric fan has to be used again. This paper introduces an electric fan analog gust cycle speed regulating circuit, which can add a practical function to the old fans in our family, and it is also a preparation for the summer. The working principle of this system is described below.
The circuit is shown in Figure 1a. NE555 is connected to a square wave generator with adjustable duty cycle, and the duty cycle can be changed by adjusting RW. During the high level of NE555 output, the zero on-off photoelectric coupler MOC3061 initially gets about 10mA positive working current, which makes the internal gallium silicide infrared emitting diode emit infrared light, and turns on the photosensitive two-way light in the zero crossing detector when the electricity is over zero, and the power of the electric fan motor is turned on, and the fan is running and supplying air. During the low output of the 3-pin of NE555, the two-way switch is off and the fan stops. MOC3061 has certain driving capacity, and can directly control the operation of electric fan motor by using the internal bidirectional switch of MOC3061 without power driving element. RW is the duty cycle adjustment potentiometer, that is, the air supply time adjustment of the electric fan unit time (the circuit data is about 20 seconds). Changing the value of C2 or RW can change the control period. Fig. 1b circuit is a typical power expansion circuit of MOC3061. When controlling the motor with high power, the power expansion circuit should be considered. When making, the device can be selected with reference to the parameters shown in the figure. Because the power supply adopts the method of capacitance voltage drop, please pay attention to safety when making the power supply, and the human body cannot directly touch the circuit board. The temperature controller of electric blanket has two levels of high temperature and low temperature. When using, it is set to high temperature, and always wake up after falling asleep; when it is set to low temperature, sometimes it will feel that the temperature is insufficient. This paper introduces a temperature controller of electric blanket, which can control the temperature of the blanket in a suitable range.
Working principle: the circuit is shown in the figure. IC in the figure is NE555 time base circuit. RP3 is a temperature control potentiometer, and its sliding arm potential determines the triggering potential V2 and valve potential VF of IC, and V5 = VF = 2vz. The AC voltage of 220V is reduced by limiting current of C1 and R1, rectification of D1, D2 and C2 filter, and DW voltage stabilization, and the voltage of about 9V is obtained for IC. When v2vz is adjusted and V6 ≥ VF, IC turns over, 3 feet turn to low level, BCR is off, heating of electric hot wire stops, temperature begins to decrease, ICEO of BG1 decreases gradually, V2 and V6 decrease. When the V6 component is selected: BG1 can choose the PNP germanium tube such as 3ax and 3aG; BCR uses small bi-directional silicon controlled silicon with more than 400V, and other components are selected according to the icon. Key points: the thermal sensor BG1 can be led out with a temperature resistant thin and soft wire and installed with the pin joint. A temperature probe is made by injecting heat conducting silicone grease into the aluminum shell of a capacitor. When using, the temperature probe can be placed in a proper position. The power supply of multi-purpose delay switch power socket home appliances, lighting lights and other power supply is often required to be carried out after different time delay. The power socket can meet this different needs. Working principle: the circuit is shown in the figure, which consists of step-down, rectification, filtering and delay control circuit. Press an and 12V working voltage to add it to the delay device. When the ② and ⑥ feet of NE555 are high level, the ③ pin output of NE555 is low level. Therefore, relay K is powered on and contacts K1-1 are absorbed upward. At this time, the “delay off” socket is powered up, while the “extended” socket is not powered.
At this time, the power supply charges C3 through capacitor C3, potentiometer RP and resistor R3 to “ground”. With the voltage rising on C3, the voltage of the ② and ⑥ feet of NE555 is decreasing gradually. When the voltage drops to 2/3vcc When the output of the ③ pin of NE555 changes from low level to high level, the relay will lose power and will not work. If its control contact is restored to its original position, the “extended off” socket will lose power, and the “extended open” socket will be powered up. In this way, different requirements are met, led and LED2 are given corresponding instructions. As long as the components and components are good and the assembly is correct, the circuit can work normally. The delay time is determined by the values of C3 and pr+r3, t ≈ 1.1c3 (pr+r3). RP is the effective part. C3 can be used for capacitors with dozens of PF to 1000 μ F, (pr+r3) values of 2k-10m Ω. The voltage withstand value of C1 shall be ≥ 400V, the power of R1 shall be ≥ 2W, the k-18 type can be selected for an button switch, and the relay model is jqx-13f-12v. Other components have no special requirements. The vd1-vd4, R1, C1 and C2 of the switch power supply of DC low voltage voltage stabilized power supply are novel and practical. NE555 and R2, R3, C4, vd6 and other components constitute a multiharmonic oscillation circuit with a frequency of about 20kHz. R4, C3 and vd5 constitute voltage reducing and voltage stabilizing circuit, which provides 12V working power for NE555. The high power tube VT1 and transformer t constitute the switch circuit. The working state of VT1 is controlled by the ③ pin of NE555, and the conduction time is determined by the pulse width. Adjust R3 to change the pulse width. The pulse width becomes wider, the output voltage increases, the pulse width becomes narrower, and the output voltage decreases. Vt2, R8, R9 and C6 constitute the over-current protection circuit. When the load is too heavy or the short circuit fault occurs, vt2 is on, forcing NE555 to reset and stop vibration, thus protecting VT1 from damage. C7 and R10 are used to protect the network and prevent the C-E junction of VT1 from being impacted by instantaneous pulse. The two secondary windings are output 20V and 12V respectively after rectification and filtering. In order to make the production simple, the switch power supply is designed to be unable to automatically stabilize voltage. Its function is similar to that of transformer, but only realizes the light-duty isolation and voltage reduction function. The voltage stabilizing function is realized by the voltage stabilizing circuit behind. 12V DC voltage output +5v voltage after 7805 voltage stabilization; 20V DC voltage is sent to adjustable voltage regulating circuit. The two are not common in order to add and subtract multiple voltages.