Simple long delay circuit using 555 time base circuit
Compared with the general timing circuit, this circuit adds a diode VD1 to the 5th pin of the 555 time base circuit to prolong the timing time.
1. Circuit working principle
The circuit principle is shown in Figure 11.
When the button SB is pressed, the 12V power supply charges the capacitor Ct through the resistor Rt, so that the potential of pin 6 continues to rise. When the potential of pin 6 rises to the potential of pin 5, the circuit reset timing ends. Since a diode VD1 is connected to the 5-pin string to make the potential of the 5-pin rise, it has a longer timing than the general connection (suspension or grounding through a small capacitor).
2. Selection of components
555 circuit uses NE555, μ A555, SL555 and other time-base integrated circuits; diode VT1 and VT2 use 4148
silicon switching diodes; resistors R1 and Rt use RTX-1/4W carbon film resistors; capacitors Ct selects the electrolytic capacitor; The relay K can be selected according to the needs of the electrical equipment.
3. Production and debugging method.
The timing time of the circuit can be changed by adjusting the parameter values of the resistor Rt and the capacitor Ct to change the length of the timing time. The structure of this circuit is simple, as long as it is soldered according to the circuit diagram and the selected components are correct, it can work normally.
Double 555 time base circuit adjustable timing delay circuit
This circuit uses two 555 time base circuits to form a timing circuit with a long timing time and adjustable timing time.
1. Circuit working principle
The circuit principle is shown in Figure 12.
The IC1 555 time base circuit is connected as a self-excited multivibrator with adjustable duty cycle. When the button SB is pressed, the DC voltage of 12V is added to the circuit. Since the voltage of the capacitor C6 cannot change abruptly, the pin 2 of the IC2 circuit is at low level, the IC2 circuit is in the set state, and the pin 3 outputs high level, and the relay When K is energized, the contacts K-1 and K-2 are closed, and the K-1 contact is closed to form a self-locking state, and the K-2 contact is connected to the electrical equipment to achieve the function of controlling the electrical equipment on and off.
At the same time, IC1 555 time base circuit starts to oscillate, so pin 3 outputs high and low levels alternately. When pin 3 outputs high level, capacitor C3 is charged through diode VD3 and resistor R3. When pin 3 outputs low level, diode VD3 is cut off, and C3 is not charged, so C3 is charged only when pin 3 is high level, so the charging time of capacitor C3 is longer. When the potential of capacitor C3 rises to 2/3VDD, the IC2 555 time base circuit resets, pin 3 outputs low level, relay K loses power, contacts K-1 and K-2 are disconnected, and return to the initial state, which is the next step. Get ready next time.
2. Selection of components
IC1 and IC2 use NE555, μA555, SL555 and other time-base integrated circuits; VD1~VD4 use N4148 silicon
switching diodes, and light-emitting diodes can use ordinary light-emitting diodes; R1~R5 use RTX-1 /4W carbon film resistors; capacitors C1, C2, C5, and C6 use CT1 type ceramic capacitors, C4 uses CD11-16V electrolytic capacitors, and C3 uses tantalum electrolytic capacitors with very small leakage current; RP can be WSW type organic solid fine-tuning Varistor; Relay K selects JRX-13F small electromagnetic relay with two sets of changeover contacts.
3. Production and debugging method
During debugging, the variable resistor RP can be adjusted to change the duty cycle of the square wave pulse output by pin 3 of the IC1555 time base circuit,
thereby changing the timing time of the timer. The structure of this circuit is simple, as long as it is soldered according to the circuit diagram and the selected components are correct, it can work normally.