This project is to design and build a fuel bowser for refueling the tractor at the farm. It will need to be able to refuel approximately 40 L of diesel in about a minute, at a height of around 2 m. It will save time and energy awkwardly trying to pour diesel into the tank. It might also help with calculating fuel efficiency for various vehicles.
Having had a quick chat with the client, the basic design has been decided. A 40 L/minute pump, connected to a switch/button, attached to a pipe, with a screen readout to show number of liters. So, the bowser will also need a main container to attach to, a 12 V battery supply for the pump, and a relay. The capacity measurement device should be independant of the switch and relay, I think that a hardware interrupt would be appropriate to remove the need for a main switch, though that would also limit the ability of the device to accurately measure the fluid. I think that even a 65 ms startup time would be very unlikely to miss out on any useful information. A Nokia 5110 screen would be appropriate here. Cool, so that plan is coming together nicely.
It looks like it's around $4 for a flow rate meter that goes up to 30 L/min, but it's $16.25 for the 100 L/min version. The battery would be the usual price, around $23. The button is free, as is all of the wire. Relays are $1 each. An Arduino is $3. The screen is another $3. Maybe this would be best set up as 2 seperate projects which can be connected as required. A 12 L/min pump is $13, and a 30 L/min pump is $14.36. A pump suitable for diesel has been bought, once it's arrived, I think it just needs a it of pipe and some system for connecting it to the tractor battery, and job done!