This setup is very suitable to gain experience with the construction of Fischertechnik parts. Some parts are made with the 3D printer. Because of this they are better adapted which gives a better stability and a more compact construction. However, most parts could also be made completely with original FT building blocks.
There are some points you should pay attention to during the build. The rotors are quite high, so you need to pay extra attention to stability. The 4 rotors are centrally driven by 1 XM motor. This makes controlling these rotors easier. Because 4 balls are picked up and delivered at the same time, you have some pulsating loads on the drive shaft. Each rotor is driven over a gear and worm gear. The gears on the worm shaft have 30 teeth. I made these via 3D print so they would have less backlash on the worm shaft. The original FT gears would have more backlash.
I have chosen to use a feeder that indicates the balls. A chain takes care of this circulation. The chain is synchronized by an IR detector. The rotor contains a magnet that sends a pulse when it comes in front of a hall detector. Through this pulse I can control the feeder to transfer the marble to the rotor. Now the chain can be started again so the next marble will be ready when the rotor rotates further.
The software runs under Robopro via the TXT-Controller. Only the servo is controlled externally over an I2C line. All other signals run over the original TXT. This is a nice application for multitasking programming. I have provided 4 tasks for this. The main program controls the rotor motor1 and processes the pulses from the hall chip. A second task is the chain control. It controls motor2 and gets info for this from the IR sensor. Task 3 is the emergency stop control. In case of problems he stops both motors and also takes care of a safe possible restart. Task4 is the I2C service. This is necessary because the TXT still has a heavy software bug on the I2C line. It should never be interrupted for more than 5 seconds once started. By regularly reading back the servo position this requirement is met.
There are still some small sub routines. In the init routine we first wait 8 sec to control the chain. At a start or restart any balls that might still be present in the feeder are pushed through.
HD picture: https://www.flickr.com/photos/fotoopa_hs/49930149831
HD picture: https://www.flickr.com/photos/fotoopa_hs/49930149816
UHD picture: https://www.flickr.com/photos/fotoopa_hs/49930754197
Video on Flickr: https://www.flickr.com/photos/fotoopa_hs/49930162446
Frans.