My observatory controller hardware, this is based on the Teensy3.5, 3.6, or 4.1 microcontroller with W5500 Ethernet module.

Relays (most have screw down terminal provision) there are:
4 x 0.5A rated optically isolated solid state relays (RE1 to RE4.)  I use these for switching
2 x n-channel 50A rated MOSFET transistors for switching my DC roof motor.  These are driven by optically isolated SSR's.
4 x 15A 230V rated mechanical relays.  These are driven by optically isolated SSR's.
1 x 10 position header with 5V or 12V power and ground and digital control signals for an 8 channel mechanical relay board typically available from eBay.

Input signals (all have screw down terminal provision) there are:
4 x current limited diode clamped analog inputs.  These are 10:1 voltage divided for measuring up to 33V max.
4 x current limited diode clamped digital inputs (3.3V max) with pull-up resistors.  These are typically used for sensing (roof) limit switches or light switches.
4 x "shared" current limited analog or digital inputs (3.3V max.)  Two of the four are diode clamped.  These are typically used for analog sensors (temperature or windspeed for example.)

Digital I/O:
2 x TTL Serial connections with 5V power on screw-down terminals.
2 x I2C connections with 3.3V (or optional 5V)  poly-fused (0.5A) and 12V on RJ45 connectors.
1 x I2C pin-header for optional BME/BMP280.  Typically used for inside temperature and humidity.
1 x SPI pin-header for optional DS3234RTC clock.

Power (all have screw down terminal provision:)
2 x 3.3V power (0.5A poly-fused.)
2 x 5V power (0.5A poly-fused.)
2 x 12V power (protected by main fuse.)