UGN-3501T Hall sensor due to the composition of the counter circuit diagram UGN-3501T has a high sensitivity, it can feel very small magnetic
field changes. Thereby detecting the presence of ferrous metals. We use this characteristic can be made it count loading. When the ball rolled over the position of Hall sensor, the sensor outputs a peak pulse 20mV. After this pulse signal is amplified to drive the op amp A741 2N5812 transistor, so as to complete the on-off process. The counter is connected to the output terminal can constitute a 2N5812 counter.