Structure and composition of infrared photoelectric rangefinder
Infrared rangefinder is mainly composed of modulated light emission unit, receiving unit, phase measurement unit, counting display unit, logic control unit and power converter and other parts. Its light source is usually arsenic crop (GaAs) semiconductor light-emitting diodes. When a considerable amount of current forward through the GaAs diode P-N junction, P-N junction will be emitted in the wavelength of 0.72 μm, 0.94 μm of near-infrared light, which is due to the doped GaAs semiconductor in the electron-hole composite, the excess energy in the form of photons released and produced. And the intensity of the light emitted changes with the injection current. Therefore, it will be used as a rangefinder light source, you can change the size of the feed current on the intensity of the light emitted directly to the amplitude modulation, that is, this semiconductor light-emitting device both "radiation" a "modulation" dual function.
Used to receive modulated light infrared photoelectric detection conversion device is usually a silicon photodiode or avalanche photodiode, these devices have a "photovoltaic effect". When the external light irradiation to its P-N junction, due to the effect of photoelectric energy conversion in the P-N poles to produce a potential difference, the size of which varies with the intensity of the incident light.
The size of the difference will vary with the intensity of the incident light, thus playing the role of "demodulation".
Ultrasonic rangefinder composition and structure
The ultrasonic generator circuit is an ultrasonic generator circuit. Double timer EN556 (U2b) monostable trigger. R6 and C6 constitute a differential circuit, its role is: when the key S2 is pressed, the low level into positive and negative spike pulse, after VD1 to get the negative spike pulse, triggering the monostable trigger flip-flop. Monostable flip-flop output high level lasts about 1 ms, that is, tw ≈ 1.1R5C5 ≈ 1 ms. EN556 (U2n) composed of multi-harmonic oscillator, ground resistance tester oscillation frequency f1 = 1/T1 ≈ 1/{0.7 [(R1 + R2) + 2 (R3 + R4)] C3 ≈ 40 kHz. the oscillator oscillator by the output level of the monostable trigger control. When the monostable trigger output goes high, the polytuned oscillator oscillates and pin 5 of the EN556 outputs about 40 rectangular pulses with a frequency of 40 kHz and a duty cycle of about 50%. Considering the instability of the start-up phase of the polyharmonic oscillator, the design is designed to lose m a larger number of pulses. If the number of output pulses is too small, the emission intensity is small and the measurement distance is short. However, if the number of pulses is too many, the firing duration is long, and the pulse string is not yet fired when it is close to the measured object, which results in the echo generated by the pulse fired first will reach the receiving end, affecting the ranging results and causing the ranging blind zone to increase. (U1) of U1a ~ U1e ultrasonic pulse drive circuit, can increase the amplitude of the pulse voltage driving ultrasonic transmitting transducer, effective electrical/acoustic conversion, enhance the ability to transmit ultrasonic waves, increase the measuring distance. 40 kHz pulse string all the way through the inverted by U1a, and then by U1b and U1e parallel inverter inverted; another way through the South U1c and U1d parallel inverted by U1c and U1d inverted. The other one is inverted by the parallel inverters of U1c and U1d.
