The power consumed by an electrical appliance is simply the product of voltage across the appliance and the current drawn by it. Voltage measurement is pretty straight forward. Using a resistor divider network, 120 V can be converted down to below 5 V, and can be read through ADC port. However, PIC cannot measure the current directly, it must be converted to voltage first. This is done by a low shunt resistance. This voltage drop across the shunt resistance is too small and requires a precision instrumentation amplifier to boost it to appropriate level.
The firmware for PIC is available to download.
|Read Rest of the Project|