These are a collection of model railroad circuits I designed for the Raspberry Pi. All but two use the "HAT" footprint and are meant to be stacked onto a RPi. The other two are "generic" and expect to be connected to 3.3V GPIO pins.
These projects were created using Kicad 2013.06.11 (https://launchpad.net/kicad) under CentOS 6. Each subdirectory is one project, and contains a schematic and PCB design.
There are eight problems, six of them are "HATs" and the other two generic boards meant to be connected to 3.3V logic GPIO pins (typically a batch of 8 with a 3.3V power and ground connection).
The projects are:
- DualUncouplerHAT This a dual driver for a electromagnetic uncoupler coil. It features a pair of 555 type timers (in the form of a 556 dual timer) driving a TIP120 power darlington. It uses GPIO pins 21 and 22 (BCM 5 and 6, physical pins 29 and 31).
- DualUncouplerHAT1 This is the same as DualUncouplerHAT, except it uses GPIO pins 23 and 24 (BCM 13 and 19, physical pins 33 and 35).
- MCP23017Hat This is a 16 pin I2C port expander using a MCP230017.
- SMCSenseHAT This is a dual stall motor driver and point sense circuit. The stall motor driver uses a MPQ3725A transistor to allow driving either multiple Tortoises in parallel (eg for a crossover) or newer Switchmaster or Torquemaster which draw more current than the LM324 can handle. Also included is a point sense circuit built from a RS Flip Flop made from 2-input NAND gates. The point sense circuit expects to be connected to a single pole double throw switch, either a built in one in the Tortoise or an external one attached to the points themselves. Uses GPIO 0, 1, 2, and 3.
- SMCSenseHAT1 This is the same as SMCSenseHAT, except uses GPIO 4, 5, 6, and 7.
- SignalHAT This is a hat containing a MAX7221 driven off level shifted SPI. It can drive up to 8 common-cathode signals of up to 8 LEDs each.
- QuadSMC This is a generic quad verison of SMCSenseHAT.
- QuadUncoupler This is a generic qad version of DualUncouplerHAT.