## Simple timing circuit diagram (1)

The general timer shown in the figure can be timed for 5 minutes to 18 hours at a time; the cycle timing is from 5 minutes to 20 hours; the total time of timing on and off is 18 hours. The control power is less than 500W, and the power consumption of this circuit is less than 1W. The time base circuit NE555 and C3, W, R1, R2 constitute the time base pulse generating circuit. The pulse period can be changed from 5 minutes to 2 hours by adjusting W. R2 can prolong the pulse period. The maximum period of R2 pulse is 1 hour. The counter CD4017, d2-d10, k1-k10 and so on constitute the delay multiplication circuit. The circuit extends the pulse period by 10 times. K1-k10 controls the multiplication multiple, and has an integral relationship with the output pulse period of NE555. BG and bidirectional thyristor constitute the control circuit of AC power supply. BG base is on at high level, SCR is triggered on and controlled circuit works. BG base very low level cut-off, SCR cut-off, controlled circuit stop working. C1, DW, D11, C2 constitute a simple DC supply circuit to provide 12V DC power for the timing circuit. In the first timing, K12 is set at “1”, and K1 is open circuit. After NE555 outputs 10 pulses, the en of CD4017 stops counting for high level. At this time, click an, CD4017 counts again, and the maximum time is 18 hours. When the cycle was timed, K12 was set at “2” and CD4017 was counted. The maximum time of each cycle is 20 hours. Timing opening and timing closing are controlled by k1-k10.

## Simple timing circuit diagram (2)

In this circuit, after closing the switch SA, the 220 V AC voltage is reduced by C5 and R4 (discharge resistance of C5), rectified by VD4 and vd5, and stabilized and filtered by vs, R3, C3 and C4 to provide a relatively stable DC voltage to IC555. When SA is just closed, because the voltage at both ends of C1 is zero and can’t change suddenly, the 2 and 6 pins of IC555 are at low level, the 3 pins output high level, the relay K is closed, the socket XB is powered on, and the controlled electrical apparatus starts to work; at the same time, because the 3-pin of IC555 is high-level, its 7-pin is also high-level, the diode VD1 is on, VD2 is cut-off, and the power supply charges C1 through RP1 and R1, with charging speed Regulated by RP1. When the voltage on C1 is charged to 2 / 3 of the power supply voltage, pins 2 and 6 of IC555 become high level and 3 pins become low level correspondingly, relay K is released, socket XB loses power, and controlled electrical apparatus stops working; at the same time, because 3 pin of IC555 becomes low level, its 7 pin also becomes low level, diode VD1 is cut off, VD2 is on, capacitor C1 is discharged through R2 and RP2, and discharge speed is adjusted by RP2. When the voltage on C1 is reduced to 1 / 3 of the supply voltage, the 2 and 6 pins of IC555 will become low level again, and the whole circuit will repeat the above working process.

## Simple timing circuit diagram (3): basic application of 555 cycle timing circuit

When the circuit is powered on, C2, R1, C3 and R3 generate a differential sharp pulse to reset the counter cd4518 and the D-type trigger CD4013. At this time, the Q of type D flip-flop is high level, the triode is on and the relay is closed. 4sv838 electronic – technical data – electronic components – circuit diagram – technical application website – basic knowledge – principle – maintenance – function – parameters – Symbols of electronic components

The timer consists of 555 integrated circuit, resistance RA, Rb and capacitor C to generate 1 minute time base signal. After 1 / 2cd4518 frequency division (10 frequency division), the falling edge of q4a triggers the next frequency divider. At the same time, Q1A, Q2a, Q3A, q4a output BCD code into CD4511 seven segment decoder to drive LED digital tube. When the counter receives the 100th pulse, Q1b, Q2B, Q3B, q4b (0101), the NAND gate cd4011 outputs a descending pulse, which turns into a rising pulse after being reversed by the inverter, triggering CD4013, so that the circuit turns over and turns Q into a low level. The relay is de energized and released, and the counter is reset naturally. When the counter starts to count again, the relay remains disconnected. Only when the counter counts 100 pulses can the relay pull in. Therefore, this timer is powered on for 100 minutes, and then powered off for 100 minutes, in a cycle. 4sv838 electronic – technical data – electronic components – circuit diagram – technical application website – basic knowledge – principle – maintenance – function – parameters – Symbols of electronic components

Because the time base signal here is 1 minute, the value displayed by LED nixie tube coincides with the delay time. If the time base signal is not an integer, then led digital tube can only display the progress of timing.

## Simple timing circuit diagram (4): countdown timing circuit diagram

As shown in the figure is a countdown timer timing circuit diagram, which is composed of preset reversible counter CD4029, double BCD synchronous plus counter cd4518, quad-2 input or not gate cd4001, high-precision time base circuit bh1908 and cl002. The circuit has high timing accuracy, is convenient to use and is very common in daily life.

Countdown timing circuit

The circuit consists of five parts: second time base circuit, preset circuit, timing decoding display circuit, audio prompt circuit and timing output circuit.

(1) Time base circuit. It is mainly composed of high precision time base integrated circuit bh1908. In this circuit, three gears of 1s, 1min and 1H are selected as timing time base. When the oscillation start / stop control terminal en is low level, the oscillator starts to vibrate, and when it is high level, the oscillator stops oscillation. R is the reset terminal. When connected to high level, the internal frequency divider is cleared.

(2) Preset circuit. It consists of two pieces of double BCD synchronous adding counter cd4518 and preset buttons SB1 and SB2.

(3) Timing decoding display circuit. It consists of two pieces of preset reversible counter CD4029 and two pieces of digital display tube cl002. Cl002 has the functions of register, decoding and display. The working process of timing decoding display circuit is as follows: pulse signal is input to CP terminal of CD4029, after counting, it is output from output terminal, and then the result is displayed after cl002 decoding.

(4) Audio prompt circuit. It consists of kd253 and capacitor C7. When the timing is over, a prompt will be pronounced.

The following is a brief introduction to the whole workflow.

When the power is connected, cd4518 is cleared. When the start button is not pressed, the en end of the oscillator is in the high-level state. At this time, the oscillation is stopped, and the preset end PE of CD4029 is also high-level. The preset timing time can be set through SB1 and SB2 and displayed on the display.

When the start button is pressed, the second time base pulse generated by the oscillator is added to the CP terminal of CD4029 respectively. Since the U / D of the plus / minus conversion terminal is connected to the low level, the count down is started. After counting down until zero from high level to low level, carry output / C / O becomes low level and turns to high level after RS flip-flop composed of D1 and D3. The high level is added to carry input / C / I of the first chip CD4029, and the counter stops working and ends at fixed time.