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Doppler effect sensor and its application RD9481

Published on Jan 20 2011 // Doppler Effect Sensor

 Doppler effect sensor and its application RD9481 1

Abstract: This paper introduces a Doppler effect sensors RD9481 works and pin functions, and in the lighting application example.
  Keywords: Doppler effect; sensor; RD9481
  1. Overview
  RD9481 is a new type of Doppler effect sensors for integrated module that includes microwave transmitter and receiver circuits, gating amplifiers, voltage comparators, state controller, delay timer, the timer and reference power supply latch circuit. New modular structure, stable performance, adjustment range, only a small amount can constitute a variety of external components to test circuit. Can be used in anti-theft alarm, automatic lighting, automatic doors and other automated equipment.

 Doppler effect sensor and its application RD9481 2

2. Internal structure and Pin Description
  RD9481 block diagram shown in Figure 1, the package is 14 pin dual in-line plastic packages. The pin function as follows:
  1,2 feet: antenna.
  3,4 feet: gain adjustment side, adjusting external resistor can adjust the sensitivity, that is, adjust the detection distance.
  5 feet: the control side ban triggered when the 5 pin voltage <0.3UDD, the ban is triggered; when the 5 pin voltage> 0.3UDD, to allow the trigger.
  6 foot: then the power filter capacitor terminal.
  Pin 7: Power supply negative terminal USS.
  8 feet: repeat triggering control side, 8 feet high, allowing repeated trigger; low, not allowed to repeat the trigger.
  9,10 pin: Output Delay Timer external resistor side.
  11 feet: control signal output, active high.
  12,13 feet: Timer external resistor output terminal block.
  14 feet: Positive power supply UDD.
  3. Work
  Work, first RD9481 transmitter circuitry within the power of microwave emission by the antenna connected to 1,2 feet outward emission microwave, moving objects encountered by the reflected microwave signal from the antenna RD9481 1,2 feet. The microwave receiving circuit, the Doppler pre-amplifier OP1 to enlarge, and then amplified by a gated amplifier OP2, the composition of the comparator to the way the amplitude discriminator to identify an effective trigger signal UB. COP1 as a comparator, when UC <0.3UDD time, COP1 output low, output is usually low and the gate also prohibit the transfer to the lower UB; a moving object, UB goes high, and the gate is also is high, start state controller, UO output high.
  RD9481 8-foot connected low, the trigger for the work can not be repeated in the delay of any moving object within the time signals are not working, until the delay ends. Delay the end, UO goes low, while blocking the timer starts, the block time period, not to make any mobile UO signal goes high, thereby enhancing the reliability of the module work. 8 pin connected high, the trigger for the work can be repeated, moving objects can be repeated UB trigger signal, so that UO goes high, and the delay time has been maintained.
  4. Application Circuit
  RD9481R typical application circuit shown in Figure 2, the circuit automatically senses lighting circuits, light does not shine during the day, when walking at night is not no bright lights turn on automatically when people move.
  220V mains transformer by transformer, after rectifiers (V1 ~ V4), the filter capacitor C4 and the voltage regulator circuitry 7812 receive DC power supply voltage. Photoresistor RG R1 connected in series with the supply voltage to form the voltage divider circuit. Exposure to light during the day on the photosensitive resistor RG, RG showed a low resistance, RD9481 5 feet low, blocking the trigger signal, the circuit does not work; at RG was high resistance, RD9481 5 feet high, the circuit to work properly . Working mode selection switch S, S is closed as a duplicate trigger work, S turn on the trigger for the non-duplication of work. Regulation RP1, the sensitivity of the circuit can be adjusted to change the detection range, adjust the RP2 can change the output high delay time, adjust the RP3 timer can change the timing closure time.