Ball detector module.
Can be used to count or detect the number of balls. Works with a hall chip built into the module. A small Neodym magnet is built into a rotating anchor. In order to measure a series of balls properly, a brake zone is built in. Without this braking zone the anchor will otherwise not have time to move back. The anchor has 2 extra holes of 4 mm. They can be used to place small steel axles as extra counterweight. However, I have tested it even without these extra weights and it works perfectly. The first hole of 4mm also serves to pull out the small magnet if you have the wrong polarity. I made a reference setup so that I have the correct polarity before pressing the magnet.
In the module extra height has been kept free to use Fischertechnik blocks. These are indicated on the drawing. Original Fischertechnik parts are always easier to connect with other parts. These extra parts are also shown in the drawing. The output of the module can be made via a straight connection or a 180 degree connection. All necessary blocks are also shown in the drawing.
For the hall connection I use a 3 pin female connetor. The wires of the hall can be easily connected without additional PCB. I swapped the 2 power pins of the hall output to the connector so the connector would have a standard connection: Output, +VCC, GND. This wiring then corresponds to that of a servo connection. The hall has an open collector output so it can easily be used on any kind of interface. Its power supply itself can be between 4V and 24V. The most commonly used voltage is 5V.
A drawing is also included with the timing results for a burst of 5 balls. You have to take into account that sometimes the speed can be quite high (pulses about 25 msec). You may need to sharpen the brake zone ( adjusts the input so that the ball can just pass) if your controller cannot handle this speed. This is the case for the TXT Controller Fischertechnik. I use my FPGA controller to read the pulses and it never has speed problems.
All parts are printed with the Flachforge Finder 3D printer. The filament used is PLA 1.7mm, 210 degree, Raft and Brim enabled, Infill 25%.
I had forgotten some details. As a pivot shaft I use a part of a nail, this nail has a diameter of 2.15mm. In the body I drill the hole on D2.2 mm in the cover plate I use D2.3. This way the nail clamps in the body and you can easily remove the cover plate again. If you want to add counterweights to the anchor I drill them out with 4mm. This size is the same as the Fischertechnik steel shafts. I make the pins 13mm long and can easily press them in. The small spacers rings are 0.5mm thick and must be securely mounted so that the anchor can move freely. There is still enough clearance left in the body. Of course, you can use a different diameter for the spindle. You just have to adjust the drill diameter.
The Neodym magnet in the side of the anchor is D2x3mm. I drill it out first with D1.9 and then on D2.0 1.5mm deep. This makes it easier to press the magnet in. If you don't have a D2x3mm Neodym magnet you can also use D3x3mm. Then adjust the holes. I have a series of drills from 1 to 10mm incremental per 0.1mm. This makes adjustments easy!
Added "a181106 cover 3pin.stl" file for cover 3 pins connector.