555 sound logic level probe
Posted on Mar 28, 2007 10767
As shown for the acoustic logic level probe circuit. The probe consists of a voltage comparator, multivibrator, piezoelectric ceramics HTD and other components. Wherein the com
position of the latter two audio circuit to the frequency of the sound level to determine the level of TTL or CMOS device level. Voltage comparator LM339 (IC1) in IC1-1, IC1-2 each 1/4 LM339. Divider network R2, R3 so that when VDD 6V voltage dividing point C is Vc F1.9V, which is lower than the reference voltage IC1-1, but higher than the reference voltage IC1-1, it usually diode D2, D3 are closing, oscillator IC2 does not work. When the probe contacts the high, low, or pulse, is used to detect high IC1, IC2 for detecting low-level output signal corresponding driven D2, D3 conduction, and through R9, R10, R11 C1 to be charging the IC2 start-up, promote HTD sound. When the probe contacts the high level, IC1-1 output signal so that D2 is turned on, and through R9, R11 on the C1 is charged. Oscillator start-up, the corresponding oscillation frequency fH 1.44/(R10 + 2R11) C1, the icon parameter corresponding frequency of approximately 4kHz. When the probe contacts the low level, the corresponding D3 conduction, C1 through R10, R11 for charging the corresponding oscillation frequency of the oscillation circuit after start-up is fL 1.44/(R10 + 2R11) C1, the frequency corresponding to the icon parameter is about to 700Hz. When a burst is detected, the corresponding HTD emit sound mixing two or given tremolo sound. The high-frequency sound judgment circuit is high; low frequency sound judgment low; fat vibrato said probe is a series of pulses, thus realizing the logic level detection.