Popularity Four Logic Level Detector ----- Power Level INDICATOR

Keywords: LM339, level indicator circuit diagram Be Author: 贵荣荣 The popularity of the logic level detector is displayed with yellow (Y), red (R), and green (g), the LEDs of the three colors showed high resistance, low level, high level and clock pulse. The circuit consists of three voltage comparators A, B, and C in tetracycore comparator LM339. The principle is shown in the drawings. R4, R5, R6 pairs 5V supply voltage voltage dividing, provides 2.36V reference voltages for the inverting input of comparator A. A 0.61V reference voltage is supplied to the in-phase input terminal of the comparator B; R8, R9 partial pressure provides a 2.5V reference voltage to the same phase input terminal 5 pin of comparator C. VD1, VD2 is the probe T input protection diode. C1 is a high-frequency anti-noise capacitor and should be close to the LM339 3, (12) foot mount. X1, X2 end is connected to the positive power supply VCC and ground terminals of the subject with the crocodile clip. LED1 is red, green two-color LED, LED2 is yellow LED. When the probe T is detected at a certain point in the TTL digital circuit, the four states and LED display may be shown in Schedule. 1. After the high-resistance (Z) state X1, X2 is turned on, T is not detected or detected by the opening, and R2 (1 MΩ), R3 (560kΩ) is divided into a group of phase input 7 foot and B in-in-phase input terminal 8 foot 8 Give a 1.8V signal voltage. According to the working principle of the voltage comparator. A of the 1 foot and B (14) foot output of 0 (low), the LED1 G, the R tube is turned off. At this time, the inverting input of C is dropped to 0 by R7. C 2 pin output 1 (high). LED2 burns yellow light. Indicates that the measured point is high or open. Be Be 2. Low level (0) state When t is detected at a low level point. 7, 8 foot signals. 1881.0.6V, A 1 pin output 0, LED1-G tube cutoff, B (14) foot output change 1. The LED-R tube is transmitted red light, indicating that the measured point is low. Since the LED1-R is turned on, the pressure drop is 1.2V to 2V. The current limiting resistor R7 voltage drop is greater than 3V. So the C's 2 foot output 0. LED2 is off. 3. High Level (1) Status When t is detected to high power flat point, 7, 8 foot signals. 1882.3.2V, A 1 foot output 1, LED1-G is turned on green, B (14) The foot output is 0, the LED1-g is turned off, and the 2 foot output of C is 0, and the LED2 is turned off. Indicates that the measured point is high. 4. Clock pulse (CP) status Since the clock pulse is 1.0 constantly alternately changed, the clock signal is detected when t is detected. If the clock oscillation frequency is very low (10 Hz or less), it can be seen that LED1 red and green alternately; if the clock frequency is high, it is difficult to distinguish red, green color, red, and green tube approximately simultaneously. Two-color composite made of orange light, indicating that the measured point is a clock pulse state. At this time, C 2 foot output is 0, and the LED2 is turned off.