A practical automatic electronic welcome circuit

The circuit is shown in the figure, which is composed of pyroelectric infrared sensor, interlocking monostable trigger and analog voice circuit. IC1 and IC2 use integrated pyroelectric infrared sensor BH9402 , whose internal sensor is P2288-02 , chip model is SN9210 , working voltage is 2.5V-5.5V, static current is ≤100mA, output high level signal amplitude is ≥0.9VCC, working temperature is -10℃～+50℃, and detection distance is 6m.

In order to improve the anti-interference performance of electrical appliances, the original Fresnel lens (horizontal angle 1200, vertical angle 80°) can be replaced with a horizontal thin-film SC-62 lens. The detection range is a narrow plane with a horizontal angle of 100° and a vertical angle of 2°, that is, high-precision, wide horizontal angle detection, thereby avoiding interference caused by the activities of small animals on the ground.

The dual D flip-flop CD4013 is connected to form two monostable flip-flops. The transient stable time is determined by the values ​​of R4 and C2. When the component parameters shown in Figure 1 are used, the transient stable time is about 3.3s. The set terminal D of one flip-flop is connected to the inverting output terminal of another flip-flop to form an interlocking monostable circuit. IC4 and IC5 use voice circuits CIC5603 and CIC5604 respectively . When a positive pulse or high level triggers IC4 pin②, the speaker BL1 emits a "welcome" sound; when IC5 pin② is triggered, BL2 emits a "thank you for coming" sound. Adjusting the oscillating components R5, C3 or R6, C4. The pronunciation tone can be changed. When C3 and C4 are small, soprano is produced, and when C3 and C4 are large, tenor is produced.

Normally, the interlocking monostable triggers are in a steady state, that is, the 1Q and 2Q terminals of IC3 both output low levels, and IC4 and IC5 do not work. When a customer comes in from outside, IC1 detects human activity, and the ② pin outputs a positive pulse of about 2s (determined by the external timing resistor and timing capacitor of the ③ and ④ pins of the internal chip SN9210 ). The 1CP terminal of IC3 inputs the rising edge of the pulse, and the first monostable circuit is triggered to enter a transient state, and the IQ output terminal flips to a high level. The ② pin of IC4 is triggered, and BL1 plays "Welcome", and the playing time is about 3.3s (tl). During this period, the low level output by the ② pin of IC3 is added to the 2D terminal, locking the second monostable trigger to prevent the customer from being detected by IC2 when he continues to move forward, so that 2Q outputs a high level and triggers IC5. Therefore, when a customer enters the door, only "Welcome" is played, and "Thank you for coming" will not be played. In the same way, when the customer leaves, IC2 provides a positive pulse to the 2CP of IC3, and 2Q triggers the ② pin of IC5, and BL2 plays "Thank you for coming". The transient stable state time must ensure that the voice signal can be played just enough.
　　
Component selection and debugging

To simplify the circuit, IC1 and IC2 use the integrated pyroelectric infrared sensor BH9402, which can also be replaced by other similar products, but the vertical angle of the Fresnel lens should be smaller to prevent interference from small animals. IC3 uses the double D (rising edge trigger) trigger CD4013 or CC4013 (domestic). IC4 and IC5 use the PCB (printed board) soft package voice circuit CIC5603 , CIC5604 or KD5603 , KD5604, etc.

VT1 and VT2 use low-power transistors such as 9013 and 9014, and require β=120~180, so that the speaker can sound loud and clear.

IC1 is installed near the door, and IC2 is installed at the exit of the room. The distance between them is 1m to 1.5m, and the height from the ground is about 1.2m.