The prototype for the mini pinball machine has a 16x2 LCD display, audio amplifier, 16 switches in, 16 lights out, 4 MOSFET controllers, and 4 servo ports. In today’s episode, Ben translates this prototype into an Eagle design.
Ben puts together the PCB for the mini pinball machine in Eagle. He starts with some of the more cumbersome areas first, namely the lights and switches. He’s going to use these molex 2.54 or .1 inch pitch headers. He puts in the 16 switch molex connectors in and 16 for the lights. He’s got to think about how to orient the circuits in relation to the 16 switch molex connectors. He creates spacing so that they are able to make an adapter board that can attach for testing. He won’t run the traces until he has the main components on the board. There should be enough space between these.
He lays out placement for the power, the microcontroller, the screen, and input/output plugs on the lower-left. He shows the schematic of the constant current LED driver. Ben reuses a layout of an eagle file for the schematic of the constant current LED driver. They used the TLC59282 constant-current sink driver in the persistence of vision episode and Super Space Shuttle. You source the LED with current and then it sinks into the device.
Ben uses a schematic of an LCD display that fits his requirements but lacks an Eagle file so he’ll have to do his own. When working with schematic design software it is often necessary to either hunt down a library or make one. For rare parts it can be quicker to make one. For the schematic, the symbol is representative of the part, whereas the package detail comes from the datasheet. Ben creates a package that matches the physicality of the hardware.
After laying out a lot of the parts for the board to run the digital signals Ben needs to attach the SPI signals between the Teensy/Arduino and the I/O chips. At this point he’s added 2 MOSFET packages, headers for the solenoids, voltage regulator, p
