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In this episode The Ben Heck Team takes a look at the original pinball machine so they can rebuild it as their final long term project for the year. The original Mini Pinball machine was built to a 1:2 scale of an actual pinball machine but there wasn't very good control to prevent the ball from flying all over the place.
The original mini pinball machine used a Teensy 3.2 MCU and a lot of hand-soldered components. The major parts in the original unit are a battery, an audio SD card that could be replaced with the 12-bit DAC built into Teensy 3.6, a volume knob that can be removed, and a start button that can be removed as well. After analyzing the original pinball machine, Ben and Felix test out 8 different sizes of balls. The original ball they used for their pinball machine was too light and floaty.
The surface mounted MOSFET Ben looks at is n-channel 80 volts and 39 amps which should be plenty for this project. A MOSFET is a metal oxide semiconductor that can switch powerful loads. After that Ben and Felix take out there meter to measure the charge on various battery packs. Felix breaks out a breadboard to do some solenoid testing. The hope is that they can use one size of small solenoid for everything on the mini pinball. Felix goes over a circuit diagram of everything they’ve wired up. It has 12 volts coming in, the VVD has 12 volts coming in, a diode, a solenoid that goes into the drain of the MOSFET, a switch that’s going to 5 volts, 5 volts comes into the gate, and there is a 10K pulldown resistor on the gate as well that goes to ground, and then the source of the gate goes to ground. The MOSFET allows them to control high current loads with regular TTL level signals (like a MCU).
While Felix mocks up a MOSFET test, Ben works on physical stuff such as what type of ball will work best. In the earlier project Ben was really hung up on making it to scale like a pinball machine but comes to realize that was a mistake because the physics didn’t scale correctly. The original mini pinball was 1:2 scale of a real machine. By rigging up a foam core mock-up they can scale for much more than just size. Ben scales the ball up, scales up the angle, and then uses a weaker solenoid.
Karen helps Ben with the models for the flippers to test for the mini pinball game and uses this experience to learn how to use Fusion 360 because she wants to get into 3D modeling. She starts by creating a couple of different circles in her sketch. They want the flippers to be approximately an inch and three quarters. She gives an overview of what she’s doing and how Fusion 360 makes calculations. After she’s done designing, they will 3D print her flippers, put it on the game, and see how it works. Before they do that, Ben takes Karen’s basic flipper design and turns it into another body and adds additional features. Meanwhile Felix is wiring up MOSFET controls so they can try out both flippers and put some things on the mock-up playfield to get an idea for what size is best. They’ll look at the strength of the flippers, the size of the solenoid, the length of the flippers, the size of the ball, the tilt of the playfield, and how deep it is. They’re going to mix all those together and try to make a playfield that is not too big but one that is more playable and has more control and weight as opposed to the original version where the ball is just flying all over the place.