Voltage, current and power meter

Description:
This is the first current, voltage and power hybrid detection instrument I made. It uses the STC15W408AS microcontroller with the TM7707 analog-to-digital conversion IC. After the voltage reference TL431 (LM385) is welded, debugged and calibrated, it can measure voltage, current and power in real time, and also adds load impedance test.
The PCB design power supply voltage is directly connected to the microcontroller and A/D sampling and the 1602 LCD screen to ensure the stability of the input voltage. It supports 5~30VDC wide voltage power supply. If it exceeds this range, please power the meter head independently.
If it is used to measure the capacity of the battery, please make sure that the battery has a protection board or other low-voltage measurement protection device. The meter head does not have a low-power stop function. Pay attention to the positive and negative poles of DC measurement to prevent the risk of fried chicken. I have informed the measurement risk. If there is an accident, it has nothing to do with me. I will be responsible for it.
 
1. Basic parameters of voltage, current and power meter
1. Supply voltage: 5-35Vdc
2. Voltage range: 0-60V
3. Current range: 0-10A4 Power statistics: 0-4KW
5. Resistance calculation: 0-10K
6. Ah statistics: 0-1000AH7 Stopwatch timing: 0-100 hours
 
2. Wiring diagram
Note: When connecting the thick wires in the diagram, try to use thick enough wires that can pass a large enough current. Thin wires are generally signal wires, and generally PVC or silicone soft wires are sufficient. If it is used for a long time, I generally recommend soldering the wires directly to the PCB board to reduce the contact resistance and the possibility of poor contact caused by terminal oxidation.
 
3. Introduction to the functions of each mode (please see the attached current, voltage and power meter manual for details)
Mode 1: Power resistance display mode √
Mode 2: Ampere-hour statistics mode √
Mode 3: Fine-tuning mode √
Mode 4: Correction mode √
 
4. Key points in the production process
When designing the PCB, the voltage reference is designed with TL431 and LM385. When welding, please choose one of the two. You don't need to weld two.
The contrast of the 1602 LCD display can be adjusted. Please buy a vertical one. Of course, I also added pads when designing. The horizontal one can also be installed, but considering that the 1602 display cannot be adjusted after installation, you need to buy a vertical one. The 2mR mark on the PCB is a constantan wire current-sensing resistor (pin spacing 10MM diameter 2.5MM) CN1/CN2 terminals are brass stretched welding PCB-9M3 or PCB-9M4 can be used to ensure the accuracy of the current, voltage and power meter. The resistors and capacitors on the PCB are as high-precision and low-temperature drift as possible (stacking rule: what electronic strange rule, when your own PCB is very LOW, use very expensive components to stack materials, and some gold-plated pins are not impossible to improve the work. )
 
Five, there are several small problems (deficiencies, and I also hope that the replica group friends will help to improve)
There is no design and production of a shell.
When designing the DC power socket, the size was not considered well. The display screen will be blocked when inserted into the mother socket. Later, it was forced to be installed horizontally. The aesthetics is not very good and can be barely used.
Due to limited conditions, I do not have a power supply with particularly high accuracy, that is, my voltage and current meter is calibrated with a general adjustable power supply. The accuracy may be accurate when calibrated by a good power supply. I hope that the creators who have the conditions will boldly help me try. Thank you! 6. About proofing and welding
1. Proofing can be directly opened with the attachment editor for proofing, the default proofing option.
2. For welding, first solder the patch and then plug it in directly. There are not many components, so welding is more convenient.
7. Burning program calibration and debugging
1. Burning: This project provides program source code. (Those who are capable can directly improve the program, and those who don’t understand can directly compile and burn it) Download the latest ISP download software from the STC official website.
 
Note: The burner TXD is connected to the board RXD, RXD is connected to the board TXD, GND is connected to the board GND, click here to connect, insert the computer, find the corresponding COM port, open the ISP software, select the chip STC15W408AS, select the HEX file, check the options in the above picture, click download, plug in the board power supply for burning.
2. Calibration and debugging:
disconnect the load at the output end;
press and hold the button to power on and select "Mode4" to enter the calibration mode:
release the button when the screen prompts "Release key";
the screen prompts "Input 0.000A" to ensure that the current is zero, press the button once
to enter the next step: when the screen prompts "Input 5.000V", input 5V voltage, press the button once to enter the next step:
when the screen prompts "Input 3.000A", input 3A current (regardless of the voltage), press the button once to enter the next step;
the screen prompts "Finish" and the calibration is completed (save the value after completion, and you can power off to cancel the calibration during the process).
 
After the calibration is completed, the voltage, current and power meters can be used normally.
                                        Finished product effect diagram (without the shell, it seems like something is missing)
 
3. Voltage measurement (this is compared with the multimeter)
 
Eight, ending
1. The firmware source code, chip manual, and instructions for use are all in the attachments, which can be downloaded and used directly.
2. The voltage, current and power meters can only measure DC voltage. Be sure to pay attention to the positive and negative poles when measuring. Reverse connection may burn the meter head or fry the chicken. (My friendly reminder)
3. About calibration: This is just a psychological effect. It doesn’t matter if you don’t have a good power supply. The adjustable power supply can be calibrated together with a multimeter with good accuracy. After calibration, you can also achieve good results. If you have professional instruments, then after calibration, you can pursue the ultimate experience..........
Please take care of me as a newcomer. If there is anything wrong, please point it out! ! !