#The 7th Lichuang Electric Competition#Power consumption monitor

Note: * is a required field,
please fill it in during the registration stage↓
 
* 1. Introduction to project functions
In a laboratory environment, it is very convenient to monitor voltage and current. Through some adjustable power supplies, multimeters, or high-end monitoring equipment, it is very convenient to monitor the input and output power consumption of the equipment in real time. However, these devices are relatively large in size, poor in portability, complex in measurement methods, and single in connection terminals. In order to more conveniently monitor the power consumption of some devices outdoors, or quickly measure the power consumption of devices indoors, a power consumption detector with an optional range is designed. By welding current sampling resistors with different resistance values, it can adapt to the measurement of high-power or low-power devices. In addition, in order to improve the measurement accuracy of low-power devices, the device comes with a battery to independently power the measuring device, which can reduce measurement errors and improve measurement accuracy.
*2. Project attributes
The project is open to the public for the first time; the project is original; it has never won an award; it mainly refers to the USB ammeter case provided by National Technology.
* 3. Open source agreement
GPL3.0 open source
 
* 4. Hardware part
1. Only one of the R2 and R12 resistors is pasted. If the current flows in the forward direction, R2 is welded. If it is reverse power supply, R12 is welded. The two resistors cannot be welded at the same time.
2. In order to adjust the resistance value of the current sampling resistor, you can choose to weld the resistor R*. The purpose of this is to target different current measurement ranges. The default 10mΩ resistor R1 is more suitable for large current measurement (up to 6A). When it is necessary to measure the power consumption of low-power devices, you can choose to weld a higher resistance resistor R*, such as 100mΩ, to improve the measurement accuracy of small currents.
3. Switch SW1 is used to switch the power supply of the power consumption meter. This is very necessary - it can avoid the extra current consumption of the external power supply, and it can also avoid the high voltage of the external power supply from burning the power consumption meter. When measuring the power consumption of a 5V powered USB device, the power meter can be powered directly by the TYPE-C port and output power at the same time without connecting VIN+ and VIN-; when measuring the power consumption of a higher powered device (voltage>6V), it is necessary to connect the power supply through the VIN+ and VIN- ports, and output through VOUT+ and VOUT-. At this time, the switch SW1 needs to be switched to lithium battery power to avoid damage to the device.
4. After testing, the maximum external power supply voltage is 30V, which is mainly limited by the ratio of the voltage divider sampling resistor R10/R11. If you need a higher voltage measurement range, you can increase the ratio of R10/R11, and accordingly, the voltage conversion value in the program also needs to be modified accordingly.
5. An additional IIC interface is added to the right side of the power meter, which can be connected to the temperature sampling module (AHT20) of the IIC interface to realize the function of ambient temperature calibration, but this function is not currently implemented because the selected sampling resistors are basically low temperature drift resistors, and the current use environment is not so bad that additional ambient temperature calibration is required.
 
*5. The software part
is fully compatible with the program in the USB ammeter case provided by National Technology. Although there are some differences in circuit design, including the power supply part, interface part, sampling circuit, and the display module uses a 0.96-inch OLED, it does not affect the display. The program only fine-tunes the error ratio during sampling, which can significantly improve the error in a larger measurement range. It should be noted that the software design provided by National Technology also uses an internal crystal oscillator source, that is, no external crystal oscillator is required.
 
*6, BOM list
No.
Quantity
Designator
Footprint
Supplier Part
Comment
1
4
C1,C3,C6,C9
C0603
C412628
4.7uF
2
10
C2,C4,C5,C7,C8,C10,C11,C12,C13,C14
C0603
C385971
100nF
3
1
CN1
CONN-SMD_1251SMT-2P
C132528
W-1251M02P-0400
4
2
H1,H2
Power supply pad
C49661
 
5
1
H3
HDR-TH_4P-P2.54-VM
Program burning port
Do not solder
6
2
H4,H5
HDR-TH_4P-P2.54-VF
Display screen interface / external IIC port
solder according to demand
7
1
R1
R2512
C500718
0.01Ω
8
2
R2,R12
R0603
C2909476
0Ω
9
2
R3,R4
R0603
C136596
10Ω
10
2
R5,R6
R0603
C23025
300Ω
11
1
R7
R0603
C23186
5.1kΩ
12
2
R8,R 9
R0603
C25804
10K
13
1
R10
R0603
C136946
91kΩ
14
1
R11
R0603
C136139
10kΩ
15
1
R*
R2512
C500718
0.1Ω
16
1
SW1
SW-SMD_JS202011JAQN
C221664
JS202011JAQN
17
1
U1
SOT-23-5_L3.0-W1.7-P0.95-LS2.8-BR
C82942
ME6211C33M5G-N
18
1
U2
MSOP-10_L3.0 -W3.0-P0.50-LS5.0-BL
C99652
CH340E
19
1
U3
SC-70-6_L2.2-W1.3-P0.65-LS2.1-BR
C59135
INA199A1DCKR
20
1
U4
LQFP-48_L7.0-W7.0-P0.50-LS9.0-BL
C3032170
N32G430C8L7
21
2
U5, U6
short terminal
does not need to be welded
 
22
1
USB1
USB-C-SMD_TYPE-C16PIN
C393939
TYPE-C16PIN
 
*7, Competition LOGO Verification
By comparing the measurement data with the power analyzer, it can be found that the power consumption meter has higher measurement accuracy, with an average voltage error of 1.2% and an average current error of about 1%.
* 8. Demonstrate your project and record it as a video and upload it