Electronic counter circuit analysis

Electronic counter can be used in mechanical or manual counting way into electronic counting, and LED digital display, simple and intuitive, can be applied to many industries, to meet the needs of modern production and life style.

Working principle circuit, including power, photoelectric counting and counting display three parts.

Photoelectric counting part: when the photosensitive triode tube VT1 received to the infrared light-emitting diode VD1 shot to infrared light, the light current increases, reducing the internal resistance, collector output low level. This low level is applied to the inverting input of the voltage comparator IC2-B 6 pin, and the same time as the IC2-B input terminal 5 pin is R4, the voltage is 4.5V, and the 6 pin voltage is less than 5 feet. IC2-B 7 pin output high. This high level is also added to the inverting input of the comparator IC2-A pin 2 pin 2 pin voltage higher than the input 3 pin voltage comparator IC2-A 1 pin output is low, the low level of the photoelectric coupler inside the hidden tube light, corresponding to the photosensitive tube, transistor VT2 is also on the low level of VT2 collector output. When an object is passed through an infrared light emitting diode VD1 and a receiving tube VT1, the infrared is blocked, and the VT1 is not illuminated, and the dark current is less than 0.3 A, and the collector output is high. Due to the IC2-B 6 pin voltage greater than 5 pin voltage, the comparator's 7 pin output low level, the same comparator IC2-A 2 pin voltage is less than 3 pin voltage, so that the 1 pin output is high, the photoelectric coupler cutoff, the transistor VT2 also cut off, VT2 collector output high level. From the above visible, when the object through the VT1, then the VT2 collector on the output count pulse signal.

Counting display part: the CD4518 is used to make the 8421 Code Synchronous decimal counter, and the VT2 collector output pulse signal is reduced along the counter. In order to meet the requirements of falling edge count, the CP CD4518 is required to be grounded, and then the EN input terminal is counted. Because the CD4518 contains two identical electronic counter, the first level of Q4 output can be connected to the second level of the EN, which constitute the serial number of the two level, and realize the counting of 0 ~ 99. CD4518 seventh, 15 pin for the zero Cr, R12 through the resistance to zero level, with the capacity of the C4 to achieve a clear role. The decoding circuit uses two pieces of CD4543 to form the BCD7 segment decoder, which drives the LED digital display. Resistance to R26 ~ R13.

Components selection: voltage comparator for low power consumption, low offset LM393; photoelectric coupler with 4N35 or TIL117; VT2; 2SC218; IC3; CD4518; IC4; IC5; CIM543. Digital display uses a common cathode WD506C. VD1 is an infrared light emitting diode SE303; VT1 is a 3DU12 photosensitive transistor. Resistance all adopted (1 / 8) W metal film resistance.

Production and commissioning requirements of the light emitting tube and receiving tube is right, at the same time in order to avoid the natural light interference caused by false count, should be in the receiving tube on a black cylinder for the shielding tube. The counter can be achieved by the count of 99 to 0, if you want to increase the count, can be directly to the display part of the expansion.

Want to know more about electronic counter, electronic meter related information, please sustained attention www.hjelectronic.com Wuxi Huajian Electronic Instrument Research Institute official website