Hey Karen,
Yes as the polling time decreases so does the accuracy. Having it poll for 1 second is acceptable for this project but I may move down to .5 seconds as I will have a total of 4 hall effect sensors to poll data from.
The RPMs we see from PC fans and water pumps are pretty high. Fans are around 1600-2000 rpm and most water pumps run in the 3600-4000 rpm range. My hope is to have the project sound an alarm if the rpm drops below 2800 rpm or stops completely.
I am working with a friend on a completely new code for the fan and pump RPM. We are having to work in a multiplexer to switch between hall effect sensors because the ATMega 128 and 328 both only have 2 interrupts. I am expecting project completion to be some time in July.
The only thing I have not deved is the water flow rate. I do have some Water Flow Sensors on the way from Seeed Studio though. They will not be hard to set up, I will just have to modify my existing code and convert their rpm into liters per hour flow.
Here are a few photos and a schematic of my development setup. The pump is a CPX Pro from Dangerden.com. Temp sensors are from Bitspower and contain 10k thermistors, the fan is a generic NZXT 120mm
