PC-based serial I/O controllers and analog samplers are hardly new. However, this 10-bit unit has some special features that are normally hard to come by in a DIY unit, including closed loop control (as in a thermostat), spread-sheet logging, programmable I/O logic control, and temperature and light sensing. It also includes real-time system timers that can be used to control two on-board relays.

Speaking of relays, you can also define "less than" or "greater than" values in the software to control them. This can be done for any of the input variables – temperature, LDR resistance, analog voltage inputs and digital inputs. For example, you could set one of the relays to switch on if the temperature goes above say 20°C and this could then control a fan or some other item of equipment. In short, there are lots of possibilities, especially as the unit can also be directly interfaced to other CMOS circuits.

You can also quite easily create your own software to control the heart of this project which is (of course) a microcontroller – in this case a PIC! This particular PIC is a 40-pin 16F877A "power plant", boasting 8K of flash memory, 256 bytes of RAM, eight analog inputs, 256 bytes of EEPROM memory and lots of other features.

In operation, the PIC communicates with your PC via a serial port. You can connect it to the PC using either a serial cable or a USB-to-serial adaptor.