Design of Power System
Math
Power In = Power Out + Power Loss
Wattage = Amperage x Voltage
Efficiency: 0..100%
Energy = Wattage x Seconds
Battery Capacity = 2000mAhrs => 3.7V * 2000mA * 1h = 25kJoules = 1 milli liter of gasoline.
AC Based System
AC
Switch
Fuse
Light
AC-DC Converter
Power Supply
e.g. 60W 12V
Wires:
Ground G
Hot L
Neutral N
Wires
Ground G
Hot L
Neutral N
Raspberry Pi
5V 3A
Motor Controller
Stepper Motor
NEMA17 1.5A
Stepper Motor
NEAM17 1.5A
Buck Converter
Input 12V
Output 5V 3A
USB C Breakout
5V & GND to USB C Male Connector
15W
80% Efficient
17W
3A
0.1A
3.1A
40W
57W
70W
85% Efficient
70W
12V Consumer
5V Consumer
100% Efficient
100% Efficient
Example AC Based System: �SBC for Motor Control, plugged into Wall Socket
Have:
Need:
Power Specifications
Raspberry Pi 5
Volt
Amp
Nema 17
Resistance
Amp
Volt
Motor Hat
Volt
Amp
Buck Converter
Volt
Amp
Parts
AC-DC Converter / Switching Power Converter
Illuminated Rocker Switch Power Socket
AC – Power Cable
USB-C Breakout board
Wire 110V
Wire 5V
Spade Crimp Connector
Buck Converter
Example
AC-DC Converter 60W https://a.co/d/08PNSk6g
Switch https://a.co/d/0eShb2mY
Spade Connector https://a.co/d/0aCL6oB7
USB C male https://a.co/d/0eJUeQVX
Low Voltage Wire https://a.co/d/0ckxYKSG
Buck Converter https://a.co/d/08BVfdxg
AC Power Cable https://a.co/d/08BVfdxg
Battery Wireless System
3.3V Consumer
USB Connector
Wires:
Ground G
5V
10W
Battery Management System
When USBC is plugged in, charges battery and provides power to system.
When USB-C is unplugged runs off battery.
Battery
3.7V
2000mAh
ESP32
3.3V 0.3A
1W
Sensor
0.1W
Voltage Regulator
Input Any
Output 3.3V 2A
95% Efficient
300mA
30mA
330mA
3.3V
1.1W
1.25W/3.7V = 360mA
2000mAh/360mA = 5hrs
1.2W
95% Efficient
1.25W
Example Battery Powered Portable Sensor w Microcontroller
Have:
Need:
Power Specifications
ESP32–C6
Volt
Amp without Wifi
Amp with BLE
Amp Sleep
Amp Deep Sleep
AFE4490
Volt
Amp LED
Amp Controller
3.3V
200mA
3.3V
Negligible
Lithium Ion Battery Charging
100% Constant Current Charge until 4.1V
Constant Voltage Charge at 4.2V
@ 4.2V 100% Capacity and 500 Charge/Discharge Cycles
@ 4.1V 85% Capacity and 100 Charge/Discharge Cycles
Battery
Li PO Battery Example
Nominal Voltage
Voltage Full
Voltage Empty
Voltage End
Capacity
Discharge Current
Charge Current
Discharge Current Max
Charge Current Fast
3.7
4.2V
3.5V
3V
2000mAh
2C
0.5C
4A
1A
Parts
Battery Protection Circuit
Battery Management System
Battery FET on Resistance
Voltage Regulator
Efficiency
Runtime:
Continuous measurement with BLE
1 min measurement every hour with BLE
Not needed
BQ25185DLHR, Texas Instruments
TPS6282533DMQR Texas Instruments
5hrs
300 days
0.1 Ohm
95%
Runtime
Lets assume battery is 3.7V nominal and has 2000mAh capacity
Total Current = Current for ESP32 when BLE/WiFi is on + Current on AFE Driver + Current for LED
Battery Current: Total Current x 1/Voltage Regular Efficiency x 3.3V / 3.7V (Power in = Power out but at different voltages)
Runtime = 2000mAh / Battery Current