Week 3: May 22nd - June 1st

Individual Log - Prem

As requested from Dr. Ejaz during our previous meeting, adding a circulation pump to allow the product to produce instant hot water was explored. Initial concerns were the power requirements of the pump since it was assumed that it would have to produce similar pressure present at the tap (50-80 PSI). However, further research revealed that the pump would only have to produce a few PSI in order to create a differential pressure between the lines. I then purchased a low current 12V pump (fig. 1) to test the its efficacy as a circulation pump.

Figure 1: 12V 1/2" Pump

The pump initially worked well and was purging the hot water line, but it only lasted around 30 seconds before it tripped the power supply protection circuit. It appears that the pump received was either defective or damaged during initial testing because further diagnostics revealed that the motor was pulling excess amounts of current and spinning abnormally. A new pump was ordered and will be tested for the upcoming week when it arrives, but adding a circulation pump appears to be a viable addition to the project given the testing didn't damage it.

Progress was also made to the logic controller, which can now accept battery and generator input at the same time, and will create an active low signal whenever the generator is producing any amount of power. The leak detection circuit was also integrated into logic controller, and will produce an active low signal if water is present. It was calibrated to be as sensitive as possible, and will currently detect at least one drop of water.

Figure 2: Logic Controller with Generator and Leak Detector Integration

Simulations of the generator detector circuit are shown below, with the output going to 0V if the generator voltage exceeds the battery voltage. A diode was used for current detection because it produces a consistent voltage drop, and also allows the system to dynamically accept power from the generator or battery at any given time.

Figure 3: Generator Detector Simulation

Lastly, an SOC to bit value table was generated once a ratio of 4.3 was determined for the voltage divider, which will produce exactly 3V at the ADC for a battery voltage of 12.89V. The bit-rate of the ADC was then multiplied by the ratio of the ADC value from 3.3V to generate the corresponding bit rates for each percent.

These values can be stored in the MCU, and an IF loop can be used to determine the closest estimated percentage of the battery's state of charge.