Electronic toy dog

This is a relatively simple toy, a dog sound and vibration detection alarm. The condenser microphone in the picture is used as the ears of the toy dog, the speaker is used as the mouth of the toy dog, and the two LEDs are used as the eyes of the toy dog. When the condenser microphone detects sound or vibration, an electrical signal is generated. This weak electrical signal is amplified and rectified to become a DC voltage. It is sent to the switch circuit for further processing. There are two NE555 timers in the circuit. One is connected as a low-frequency oscillator, mainly used for the flashing of LED1 and LED2; the other is connected as an audio oscillator, mainly used to simulate the barking of dogs.

Circuit working process: If any sound occurs near the microphone, the sound signal is amplified and converted by transistors T1~T6 to generate a 12V DC voltage on the ④ pin of IC1. The output of IC1 becomes high potential, and LED1 and LED2 flash and last for a few seconds. Under normal circumstances, the ④ pin of IC1 maintains a low potential due to the grounding of R13. When the microphone detects sound or vibration, a DC voltage appears across R13, and the potential of the ④ pin of IC1 becomes high. As a result, the speaker emits a dog barking sound, which lasts for a few seconds, and the LED starts to flash. Adjusting VR1 can change the pitch of the dog's barking. But be careful not to put the speaker in the toy dog's mouth too close to the microphone in the ear, so as not to cause acoustic feedback.

Place the circuit in the toy dog's belly. Place the condenser microphone in one of the toy dog's ears. Place LED1 and LED2 in the two eyes. Place the speaker in the mouth. The 12v can be powered by a battery or a 12V, 250mA AC adapter.