Electronic bird repeller for crops

During the period when crops and fruits are ripe, in order to prevent birds from damaging the fruits of their labor, many large grain growers and fruit farmers often organize people to blow gongs at the edge of fields and in orchards to drive away birds. This is not only hard work, but also time-consuming and labor-intensive.

To this end, the author has made a simple and practical AC/DC crop electronic bird repellent, which can detect the calls of birds in the fields and orchards, and then make beeps, clicks, whistles or human voices to scare away the birds in the fields and gardens. Its output power is more than 5W, and the bird repellent effect is good.

The working principle of the circuit is shown in Figure 1, which consists of sound pickup amplification, frequency selection amplification, triggering, language recording and playback, audio power amplifier circuit and power supply.

When the microphone BM does not detect the bird's call, VT1 is in the cut-off state, the relay K does not work, its normally closed contact K1 is connected, the normally open contact K2 is disconnected, the voice circuit and the audio amplifier circuit do not work, and the speaker B2 is silent.

When birds make sounds, microphone BM converts the detected bird sounds into electrical signals. After preamplification and frequency selection amplification, they are added to the gate of VS through C5. VS is triggered and turned on, relay K is energized and attracted, and its normally open contact K2 is connected, so that the voice circuit and audio amplifier circuit work, and speaker B2 makes a loud bird-repelling sound. After K is attracted, its normally closed contact K1 is disconnected, but because C6 is discharged through K, K can still maintain attraction for a certain period of time (about 2 minutes). After C6 discharges, K is de-energized and released, and K2 contacts are disconnected. The voice circuit and audio amplifier circuit stop working, and speaker B2 stops making sounds. When there is a bird call again, the above process is repeated.

Changing the inductance of L and the capacity of capacitor C4 can change the resonant frequency of the frequency selection circuit. The smaller the capacity of C4, the higher the frequency; the larger the inductance of L, the lower the frequency. The purpose is to make the circuit more sensitive.

A1 is a fool-proof voice recording and playback module, which features a unique two-way I/O voice transcription technology. The module's recording input and playback output are combined into one, with very few peripheral components, making it very easy to use. The recorded information will not be lost after a power outage.

A2 is an audio power amplifier, which is used to amplify the voice signal output by A1, so that the speaker B2 can emit the pre-recorded bird-repelling sound. A3 is a three-terminal voltage regulator integrated circuit.

When the recording button SB1 is pressed and not released, the ⑥ pin of A1 is triggered by a low level, and the LED lights up, indicating that the circuit enters the recording state. At this time, A1 can record the sounds of beeps, firecrackers, and whistles. When SB1 is released, the LED stops emitting light, and the recording ends. This module can record people for up to 30 seconds.

When you need to play sound to drive away birds, just press the play button SB2, and the ⑧ pin of A1 will get a negative pulse trigger, and its ② and ③ pins will output the stored voice sound signal. One way is directly through the speaker B1 (for monitoring), and the other way is coupled through C8, R7 and C9, R8 to the in-phase and inverting input terminals ③ and ② of the power amplifier integrated circuit A2. The A2 power amplifier drives the speaker B2 to make a loud bird-repelling sound. If the SB2 button is always on, B2 can continuously play the recorded human voice. RP is a volume adjustment potentiometer, which can control the volume of B2 output. The output power can reach 5W, which can meet the needs of bird repelling.

Component selection and production requirements: R1 and R2 use sealed variable resistors, R3~R9 use 1/4w carbon film resistors, R10 uses 2W winding resistors, C1-C3, C6, C10, C11, C13 all use aluminum electrolytic capacitors with a withstand voltage of 16V, C4, C5, C7~C9, C12 use polyester capacitors or monolithic capacitors. VT1 and VT2 both use 9013 silicon crystal triodes. VS uses MCR100-1 type unidirectional thyristor with a small trigger current. K uses JRG-21F type DC relay with a working voltage of 12V. BM uses electret microphones for recorders. L can be wound 200-350 turns on the "I" shaped ferrite core with Φ0.15mm-Φ0.8mm enameled wire.

A1 uses the PT-8830 fool-style voice recording and playback module, with a recording and playback time of 30 seconds. It uses soft packaging and patch technology and is made on a double-sided small printed circuit board with a size of 22mm×18mm. Its tube pin arrangement and internal circuit function are basically the same as the PT-8820 integrated module. The difference is that the recording storage time of PT-8830 is 30 seconds, while the recording storage time of PT-8820 is 20 seconds.

A2 uses LM386 audio power amplifier integrated circuit. A3 can use 78L05 low power consumption 100mA fixed three-terminal voltage regulator integrated circuit. LED uses ordinary red round light emitting diode.

RP uses WH15-K potentiometer, SB1 uses 6mm×6mm small horizontal touch key switch, SB2 uses small 1×1 self-locking push button switch. B1 uses 8Ω, 0.1VA small speaker, B2 uses 8Ω, 5VA propaganda car special speaker.

S1 is a 2×2 toggle switch, S2 and S3 are 1×1 toggle switches, and K uses a JRG-21F DC relay with a working voltage of 12V. VD is a common light-emitting diode, VD1 uses a 1N4007 silicon diode, and T1 uses a 220V/12V, 15W high-quality power transformer, which is required to work for a long time without heating. In order to save costs, G can also use 8 No. 1 rechargeable batteries. If a small battery is used, the voltage is 12V.

When debugging, turn on S1, turn it to gear 1 to connect the DC power supply, then turn on S3, the whole circuit is powered on and manual debugging is carried out. First, solder the pins between A and B of MB, then press SB1 to make a sound to speaker B1, A1 can record the sentence, and press SB2 to play it. Because SB2 is a self-locking key switch, only need to press it once, the recording circuit will work continuously. At this time, turn off S3, re-solder the A and B wires of MB, and the circuit will enter the fully automatic working state. In farmland orchards with mains electricity, AC power can be used, turn on S1 to gear 2, close switch S2, and charge while working. In farmland orchards without mains electricity, turn gear 2 to 1 to use batteries or rechargeable batteries for power supply.

Figure 2 is the printed circuit board of this machine. The size of the printed circuit board is 780mm×350mm. The A1 module uses 7 short wires to fix it to the self-made circuit board. When soldering A1, the soldering iron shell must have a good grounding wire to prevent the AC voltage induced by the soldering iron from breaking through the A1 chip. The power plug of the soldering iron can be unplugged and the residual heat of the soldering iron can be used for soldering to ensure that A1 is not damaged.

Put the finished circuit into a small plastic box of suitable size. Make holes on the box surface to fix RP and S1-S3 and extend them out. Install B1 inside the box and make some sound release holes at the corresponding positions on the box surface. Lead B2 out of the box through 2 wires and connect it to the speaker outside.

This circuit can work normally after power-on as long as the wiring is correct and the circuit is simply debugged.