Low-cost voltage and current meter with dual-channel electronic potentiometer

Voltage and current meter with electronic potentiometer that can be modified for TL494 Mean Well and other power supplies. Multifunctional voltage and current meter with electronic potentiometer function. If used to modify the adjustable power supply, it is best to use an encoder to control it, so I spent some time redesigning the circuit and writing the program. It is an improved version of the key version.
 
It should be possible to use the encoder to control the 12864 serial port screen compatible with ST7567. If you have a similar 12864 screen, you can use it by changing the pins in LCEDA.
20220824 latest version, you can adjust the maximum PWM output voltage in the software.
Dual-channel electronic potentiometer. The encoder can be used to control the controllable 0~6.6 volt voltage at DV and DA outputs. It can be used to replace those two-way precision multi-turn potentiometers plus a voltage and current meter head modification kit for TL494 chip power supply to change to an adjustable power supply. The output of the post-stage has been amplified by the operational amplifier lm358. If a larger voltage is required, the amplification factor can be increased by modifying the operational amplifier amplification factor resistor to output 0 to 10 volts.
      In the normal interface, short press the encoder, and then rotate the encoder left and right to adjust the size of the electronic positioner output voltage. After about 10 seconds, no operation will exit the adjustment. Long press the middle button of the encoder to enter the menu, select the corresponding module to implement the function, and after entering the module, long press the encoder to exit. 1. There is a charge and discharge control function. After setting the voltage, current and timing conditions, press Run, the P37 control port outputs a high level, and stops running and outputs a low level after reaching the set conditions. The control output port can be connected to an external relay to control the on and off of the charging circuit, and can control the rechargeable battery. If it is not used as a power modification kit, this function can also measure the battery discharge capacity. The battery is connected to a dummy load through this meter. After setting the cut-off conditions, the battery capacity can also be measured.
It is designed for TL494 power supplies such as Mean Well power supplies to transform adjustable power supplies. Of course, some communication power supply modules can also be used. As long as the reference voltage is adjusted to control the voltage and current, it should be theoretically usable, but the kind that adjusts the output voltage sampling cannot be used. Replace the mechanical dual potentiometer and voltage and current meter, and remove some useless functions. Only one voltage and current display is retained. For specific modification methods, please refer to the tutorial on mechanical potentiometers. For friends who do not understand Mean Well power modification, please be cautious, success is not guaranteed. The software is not perfect yet, the firmware was updated on 20220823. The problem of inaccurate voltage and current display in the charging control module has been corrected. This error is caused by changing the reference. Because the internal reference was changed, and the charging and discharging module was not changed synchronously, the voltage and current display in the charging and discharging module was inaccurate, which has now been corrected.