Microchip Technology

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  • Four Digit Sensor Counter

  • Created: May 18, 2016

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This reference design is a simple four-digit sensor counter circuit that effectively detects objects that pass through the circuit where the counting will be displayed in the seven-segment display. This device has a count up and down mode, which counts object from 1 to 9999. It has also a low quiescent current linear voltage regulator that has an out of 5V. It specifically uses the MCP1702 voltage regulator of Microchip, which is a family of CMOS low dropout (LDO) voltage regulators that can deliver up to 250mA of current while consuming only 2.0µA of quiescent current. The input operating range is specified from 2.7V to 13.2V, making it an ideal choice for two to six primary cell battery-powered applications, 9V alkaline and one or two cell Li-Ion-powered applications.

The circuit is comprised of an 8-bit microcontroller, seven-segment display, voltage regulator and a slot optocoupler. The H21A1 is called a slot optocoupler that contains an infrared LED light coupled with an NPN phototransistor. Normally, the LED inside H21A1 IC is always ON making P3.3 of the microcontroller at logic “1″ at any time. If an object pass between the transmitter and receiver, port P3.3 will change its state at logic “0″ which this period may count the number up or down in steps of 1 depending on the switch S2. If Port P3.4 floats, it will count down otherwise, it will count up. Moreover, S1 switch will reset the time to zero.

Most counter circuits are found in industrial and commercial applications that are used for object detection and counting. This can be observed in malls for statistical scheme where people come and go will be closely monitored. Furthermore, this can provide ease in counting numerous products or people that the user aims to supervise.