Design of an IR sensor for the Fischertechnik ball track.

thingiverse

Designing an IR Sensor for Fischertechnik Ball Track.\r\nThe sensor module boasts a 15mm grid, perfectly suited for Fischertechnik, and adds only 15mm extra length. This sensor is designed to operate flawlessly in strong ambient light conditions without any issues. It handles fast burst mode with ease. The IR diode TSHA6203 uses a small opening of 12° to prevent being disrupted by ambient light. Similarly, the phototransistor receiver SFH313FA features a narrow viewing angle of 10° and an internal IR filter. The mounting of both components is inline built in and shielded from the environment. Light first passes through a 4mm opening on both sides, preventing side lights from entering. The light beam is low at the ball's surface, allowing the sensor to detect between two burst balls with a signal ratio of about 50%. If sunlight hits the ball, the reflection angle prevents it from entering the light channel. Without a ball present, extra ambient light acts as positive feedback, enhancing the control signal.\r\nThe sensor operates on both 5V and 9V power supplies. At 5V, resistors are set to 390 and 820 Ohms, while at 9V they are 820 and 1800 Ohms, as shown in the pictures. The sensor has been thoroughly tested with the Fischertechnik TXT Controller, working perfectly even for fast burst cycles. I connect the TXT Controller's 9V output to VCC and digital inputs to 10V. The necessary current is 13.2mA when light is present and 8.8mA in darkness. Phototransistor load requires about 4.5mA.\r\nA curve180° has been created, enabling the balls' trajectory to be quite close together. The sensor's sides feature slots for connecting additional Fischertechnik blocks.