I developed this system back in 1997 for Roche Pharmaceuticals - Vitamins and Fine Chemicals Division.
The brief was to design, build, install and maintain a liquid dosing system for a drugs trial across 5 farms. The system was to deliver 25ml of biotin solution onto cow cake in milking parlours with a tolerance of 10% maximum.
The system would need to log its operation and give the herdsman a simple and clear interface to operate it.
I designed the main control box using the guts of a PC which would do all control via the PC parallel port. Using 16:1 decoder chips and an opto-isolated output, this would drive control relays that would operate the valves, pumps, heaters and power.
The herdsman control panel used a small alphanumeric keypad connected to a keyboard encoder which was in turn connected to the PS/2 port on the PC. The num lock, caps lock and scroll lock LEDs formed the top bar of the display. The side LED's were controlled by using one of the digital lines of the parallel port connected to 8-bit shift registers whose output was connected to the LED's.
The system also had a client package which could be used on a laptop for interrogation, configuration and maintenance of the system. This could all be done via an RS232 serial port. Here are some screen shots.
The entire system was written in Microsoft Quick Basic 4.5 which was compiled and deployed on DOS 6.22.
The system worked extremely well after a few tweaks. It met the tolerance requirements adequately hitting an average tolerance of 1%!! Results could be exported in CSV format for analysis.
I produced this system with almost no help. Someone gave me a crash course in plumbing and I had some help from a fluid dynamics professor when I encountered a strange anomaly where doses were inconsistent due to fluid pulses in the pipework. This was solved by stirring the liquid in the pipework between doses by activating the aquarium pump whose main purpose was to circulate liquid through the pipework to prevent freezing and keep it at a constant temperature to keep doses the same.
I wrote all software, designed and built all the hardware including circuit boards and installed all of the systems with a bit of extra labour. I also maintained the systems for a period of 18 months.
Despite the very harsh environment and the extremely cunning nature of cows, the system was very reliable and performed admirably. I also got it to send results by email from DOS!!
The only downside - I discovered fairly quickly that I am very allergic to cows!! I had to complete all the work in a hazmat suit!