Bar-code-scanner

Description: The circuit demonstrates a method for interfacing a HEDS-1000 emitter-detector pair with a HA-5144, intended for use as a barcode scanner circuit. The HA-5144 functions as an amplification system that transforms the widths of the printed barcode's bars and spaces into a pulse-width modulated digital signal. Amplifier A1 amplifies the current output from the detector. The output from A1 is directed to two precision peak-detector circuits, which identify the positive and negative peaks of the received signal. Amplifier A4 serves as a comparator, with its reference voltage set at the midpoint of the peak-to-peak signal through resistors R5 and R6. This configuration enhances edge detection accuracy and reduces ambiguity in bar width. Additionally, Amplifier A5 acts as an optional noise gate, permitting data to pass only when the peak-to-peak modulation signal exceeds one diode drop. The circuit operates on a single supply voltage with low power consumption, making it suitable for battery-operated data entry systems.

The circuit design employs a HEDS-1000 emitter-detector pair, which is essential for reading the reflective properties of barcodes. The HA-5144 amplifier is central to this system, converting analog signals from the detector into a digital format suitable for processing. Amplifier A1 plays a crucial role in boosting the weak signals received from the HEDS-1000, ensuring that subsequent processing stages receive a strong and clear signal.

The two precision peak-detector circuits connected to A1 are vital for accurately capturing the signal peaks, which correspond to the transitions between bars and spaces in the barcode. These detectors help in forming a reliable digital representation of the barcode, which is essential for accurate scanning.

Amplifier A4's function as a comparator is critical. By establishing a reference point at the midpoint of the peak-to-peak voltage, it ensures that the system can differentiate between the high and low states of the signal effectively. This precise edge detection minimizes errors in interpreting the barcode, especially in cases where the bar widths may vary slightly.

Furthermore, the inclusion of Amplifier A5 as a noise gate enhances the reliability of the data transmission. By allowing only signals that surpass a certain threshold, the circuit effectively filters out noise and irrelevant signals, ensuring that only valid barcode data is processed. This feature is particularly beneficial in environments with potential electrical interference.

The entire circuit is designed to operate efficiently on a single supply voltage, which is a significant advantage for battery-operated devices. The low power consumption characteristic of the design not only prolongs battery life but also makes the system more versatile for various mobile applications in data entry and barcode scanning. Overall, this circuit provides a robust solution for barcode scanning, combining effective signal processing with energy efficiency.The circuit illustrates a method of interfacing a HEDS-1000 emitter-detector pair with a HA-5144 for use as a bar-code scanner circuit. The HA-5144 is used as an amplifier system which converts the bar and space widths of the printed bar code into a pulse-width modulated digital signal.

Amplifier A1 is used to amplify the current output of the detector. The output of A1 is passed to two precision peak-detector circuits which detect the positive and negative peaks of the received signal. Amplifier A4 is used as a comparator whose reference is maintained at the midpoint of the peak-to-peak signal by resistors R5 and R6. This provides a more accurate edge detection and Jess arobiguity in bar width. Amplifier A5 is used as an optional noise gate which only allows data to pass through the gate when the peak-to-peak modulation signal is larger than one diode drop.

This circuit is operated by a single supply voltage with low-power consumption which makes it ideal for battery-operated data entry systems.