Robot wireless remote control transmitter circuit

Wireless remote control has high requirements for operating equipment. This section takes a three-channel IC wireless remote control with a remote control distance of 1000m as an example to
introduce the wireless remote control transceiver device. It can control three kinds of electrical equipment at the same time. The circuit is simple and reliable, and it is easy to make.
    (1) Wireless remote control transmitter circuit 7-15 is the transmitter circuit. It consists of a main oscillator circuit and a high-amplification circuit. DF-27 is a dedicated transmitting device for wireless remote control .
It adopts a single-row packaged 9-pin integrated circuit. It allows a maximum power consumption of 600mW, a maximum no-load current of 18mA, and a 9-12V DC
power supply. Under the control of the external switch, a high-frequency 27MHz intermittent wave signal modulated by a square wave with a certain corresponding duty cycle is generated. DF-27 is internally composed of
five parts: width adjustment (duty cycle) circuit, square wave generation circuit, high-frequency oscillation (osc) circuit, modulation circuit and high-frequency power amplifier circuit
. The width adjustment (duty cycle) circuit is composed of a current Miller circuit (internal to DF-27) and a switch circuit. Pins ③ and ④ are connected to external push button switches
Sl and S2. The state of the internal switch circuit is changed according to different operations of the switch. , thereby changing the charging and discharging current ratio of the external timing capacitor C2 connected to pin ②,
and the timing resistor ruler connected to pin ① externally.
    The high-frequency oscillation frequency is determined by the parameters of the external frequency-selective component crystal oscillator (B) connected to pins ⑥ and ⑦. The crystal is usually used to oscillate at a 127MHz carrier
signal. The modulation circuit is a switching circuit. The carrier signal is controlled by the square wave, and then sent to the high-frequency power amplifier for amplification, and then
the high-frequency signal is emitted through pin ⑧.
    When the button switch S1 and phase S2 are in the off state, the square wave generating circuit outputs low level "O" and there is no modulation state. The carrier signal passes through
the hybrid circuit switch to the high-frequency power amplifier circuit, so at this time pin ⑨ outputs a high-frequency transition with equal amplitude. Corresponding to the other three switch combination states, pin ⑧ outputs
duty cycles of 5%, 75% and 50% intermittent high-frequency wave group signals respectively.