Homemade wireless remote control circuit diagram

As shown in the figure is the circuit diagram of a homemade wireless remote control ;

1. Working principle of motor remote control circuit

Wireless remote control transmitting circuit

The picture shows the remote control transmitter circuit. The 555 integrated block and R1, R2, RP1, VD1, VD2 and C1 form an astable large-range variable duty cycle oscillator. The oscillation frequency of the parameters shown in the figure is about 50Hz. By adjusting the resistance of RP1, the duty cycle can range from 1% to 99%. The 50Hz square wave signal is output from pin ③. VT1 and peripheral components constitute a crystal frequency-stabilizing capacitor three-point oscillator, and the resonant frequency of the quartz crystal is 27.145MHz. This circuit uses quartz crystal to stabilize the frequency, so it works reliably. The high-frequency carrier wave generated by VT1 oscillation is modulated by the square wave signal at pin 3 of the 555 circuit and is emitted by the antenna.

Wireless remote control receiving circuit

The picture below shows the receiving driver circuit. In order to simplify the receiving circuit, a super regenerative detector is composed of VT2 and its peripheral components to detect the original square wave modulated signal. C12 and R7 are added to the ③ pin of IC 2 for amplification. The amplified signal is multiplied and rectified by VD3 and VD4, and a smooth DC voltage is output by the VT3 emitter follower. The size of this voltage is related to the different duty cycle signal waveforms sent. If the duty cycle is large, the voltage is high. The bias current provided by R11 for VT4 is large, and the motor speed is high. The duty cycle is small, and the voltage is low. R11 is The bias current provided by VT4 is small and the motor speed is slow. When the duty cycle is small enough, VT3 is cut off and has no output, VT4 does not conduct due to loss of bias, and the motor M stops. It can be seen that the motor speed is directly proportional to the duty cycle.

2. Selection of components

L1 can use a 10K type mid-circumferential bobbin, wound with 9 turns of Φ0.15 high-strength enameled wire. L2 can be wound with 3 turns of the same type of enameled wire on the outer layer of L1. No shielding cover is needed, but the magnetic core needs to be screwed in. L3 is produced in the same way as L1. B uses a metal shell resonator such as JAl2, with a frequency between 27-29.8MHz. VT1, VT2, and VT3 all use 3DG130D NPN transistors, β>100. VT4 uses 3DD15D high-power tubes. RFC uses 18uH color coded inductor. The model number of IC1 is NE555. The model number of IC 2 is LM386. Except for the marked electrolytic capacitors, all capacitors use CC1 type high-frequency ceramic capacitors. The resistors are all 1/8w carbon film resistors.

3. Circuit debugging

First adjust the transmitter carrier frequency oscillator, and leave the high-frequency choke coil RFC and crystal oscillator B temporarily uninstalled to short-circuit C4 to ground. Adjust the resistance of R3 so that the collector current of VT1 is 12mA, and then install crystal oscillator B. At this time, the current will increase to about 15mA. Otherwise, the magnetic core of L1 should be carefully adjusted until the circuit starts to oscillate, and the C4 short circuit should be removed. The debugging method of super regenerative detection is to use an 800Ω high-impedance earphone in series with a 10uF capacitor across the emitter and collector of VT2, and use a non-inductive screwdriver to fine-tune the potentiometer RP2 and the magnetic core of the coil L3 until there is Until there is an obvious loud "rustling" sound. Next, bring the transmitter antenna close to the receiver, turn on the control switch S, and fine-tune the magnetic cores of the coils in the transmitter and receiver until clear industrial frequency sound can be heard in the headphones, then distance the two machines, and then Further fine-tuning. The remaining circuits do not need to be debugged and can generally work normally after installation.