Design a system using a conductive water sensor (basically two metal probes that are very close together - when water is present between the probes it conducts) to detect when water level in a tank falls below 20% and when that happens, turn on a pump. The pump is a 3-phase 3-wire 1kW rated. This is for an industrial application where the water is being used for a chemical process. Design the system with some fail-safe such that the tank should never become empty.
2. Design summary:
Good approach. For reliability it is ok to say good quality components but beyond that how doyou ensure fail safe?
e.g. one way is to have redundancy - multiple sensors; bakckup alerts, etc.
for example, what if the relay fails? Or the motor is powered but the pump is blocked etc?
You need to close the loop from the circuit instructing the motor to be on but pump not working somehow.
What about over-rides? What if your box fails - is it possible to manually enable/disable the motor if needed?
3. Block diagram
your block diagram is a muddle of electrical, signal and mechanical items. Think a little about how to make a readable and clear diagram
4. Power supply design
Looks like your voltage level diagrams have some mistake. when tank is 100% full, all ABC lines should be ~12V.
Why are you realising gates through transistors? Can't you just use 74LSxx series chips?
5. Industrial Design:
Could have been more detailed - with mechanical details, specific material etc.s
