Power consumption

Using nRF Power Profiler PPk2, the power consumption of the PCB can be measured. Follow a simpler ESP32-C3 dev board tutorial to learn how to use PPK2.

Power consumption with no optimisation

The average power consumption of the PCB no optimisation:

• with 2 power LEDs
• no firmware optimisation
• radio is on

The average power consumption is:

• 3.87mA in deep sleep mode
• 25.69mA for 30s during the timeout after the bell is pressed and the Ding Dong sound is played
• 31.94mA for 34s during the entire cycle of the bell press and going to sleep
• 70.62mA for 6s during the Ding Dong sound

Download nRF PPK2 file

Power consumption with optimisation

Firmware and hardware optimisation can be done to reduce the power consumption:

• remove the power LEDs, TX and RX LEDs
• optimise the firmware to turn off the WiFi and radio as soon as the function is done: WiFi.disconnect(true); and WiFi.mode(WIFI_OFF);
• optimise the firmware to not blink the user LED

The average power consumption of the PCB with optimisation:

• 73.04uA in deep sleep mode
• 17.11mA for 30s during the timeout after the bell is pressed and the Ding Dong sound is played
• 24.93mA for 34s during the entire cycle of the bell press and going to sleep
• 63.99mA for 6s during the Ding Dong sound

Download nRF PPK2 file with no LED

Download nRF PPK2 file with no LED and radio/WiFi

Battery life calculation

Based on the above values, the battery life can be calculated with this python code:

Estimated battery life: 410.14 days or 1.12 years

# Constants
number_of_doorbell_rings = 5  # Number of doorbell rings per day

battery_capacity_uAh = 1200000  # Battery capacity in µAh, converted from 1200mAh
consumption_high_uA = 24930  # High consumption in µA, converted from 32mA
consumption_low_uA = 73  # Low consumption in µA
high_consumption_duration_s = 34  # Duration of high consumption in seconds
total_day_seconds = 86400  # Total seconds in a day

high_consumption_duration_s = high_consumption_duration_s * number_of_doorbell_rings  # Multiply by the number of doorbell rings

# Calculate the total consumption in µAh for each period
high_consumption_total_uAh = consumption_high_uA * high_consumption_duration_s / 3600  # Convert seconds to hours
low_consumption_duration_s = total_day_seconds - high_consumption_duration_s
low_consumption_total_uAh = consumption_low_uA * low_consumption_duration_s / 3600  # Convert seconds to hours

# Calculate the total average daily consumption in µAh
average_daily_consumption_uAh = high_consumption_total_uAh + low_consumption_total_uAh

# Calculate the battery life in days
battery_life_days = battery_capacity_uAh / average_daily_consumption_uAh
# Calculate the battery life in years
battery_life_years = battery_life_days / 365

# Echo out the values
print(f"Estimated battery life: {battery_life_days:.2f} days or {battery_life_years:.2f} years")

Battery measurement simulation

The battery measurement circuit is simulated in Falstad.

$ 1 0.000005 5.023272298708815 78 5 50 5e-11
172 224 240 176 240 0 7 0 3.3 0 0 0.5 Gate Voltage
w 352 224 352 176 1
f 288 240 352 240 33 1.5 0.02
R 352 176 352 144 0 0 40 4.2 0 0 0.5
c 224 240 288 240 0 0.1 0.000999999998577626 0.001
r 288 192 336 192 0 1000000
w 336 192 352 192 0
w 288 192 288 240 0
g 352 352 352 368 0 0
r 352 256 352 304 0 100000
r 352 304 352 352 0 100000
w 352 304 256 304 0
o 2 64 0 4099 0.001220703125 0.00009765625 0 2 2 3

With a p-channel MOSFET, when the gate voltage is 0V or LOW, the battery voltage is measured. When the gate voltage is 3.3V or HIGH, the battery voltage cannot be measured.