Design of handwriting drawing board based on common copper clad laminate

Abstract

Handwriting drawing board is not only a subject which can be used to write and draw, but also a method to measure and process weak signals. This design adopts 8051 single chip microprocessor as the main controller. It applies a constant-current source[1][2] to copper plate and collects the voltage value according to the resistance divider effect. Then it amplifies the signal with low-noise and high-precision amplifier[3] AD620 which is placed in the low impedance and anti-interference pen. It converts analog signal to digital signal by an 11-channel, 12-bit A/D converter TLC2543. Adoption of average filtering algorithm can effectively improve the measuring accuracy, reduce the error and make the collected voltage signal more stable. The accurate position can be detected by scanning the horizontal and vertical ordinates with the analog switch via the internal bridge of module L298 which can change the direction of X-Y axis signal scan. DM12864 is used as man-machine interface and this hominization design is convenient for man-machine communication. This collecting system has high accuracy, high stability and strong anti-interference capability. It's easy to control and has very large development space in the future.