Voltage and Ammeter - CW32

The following are photos of the finished voltmeter and ammeter based on the CW32F030.

Test images are also shown below. The first copper eyelet from the left is the common ground terminal, the second copper eyelet from the left is the voltage measurement terminal, and the third copper eyelet from the left is the current measurement terminal.

When measuring voltage, the two pin headers on the left need to be shorted; when measuring current, the two pin headers on the right need to be shorted.

The sliding rheostat on the left is for manual voltage calibration, and the sliding rheostat on the right is for manual current calibration.

The upper and lower rows of digital tubes are common cathode. The main controller is a CW32F030C8T6, and the four pin headers next to the main controller are for serial port debugging.

[Image 1]


[Image 2] [Image 3]
[Image 4] Considering heat dissipation and the measurement voltage range required for daily use, the LDO is an SE8550K2 in an SOT-89 package, along with a 1N5189 Schottky diode and a 10-ohm resistor in series for circuit protection. [Image
5 ] A TL431 circuit is used to provide a 2.5V reference voltage for calibrating the external voltage of the MCU's AD converter. [Image 6] The measurement circuit uses a 1N4148 for voltage clamping to protect the MCU's ADC pins. Specific images are not shown. Two parts failed this time: the control panel and the 3D casing. Both were due to the aluminum electrolytic capacitors being too tall. Pre-drilled holes were needed, or the casing needed to be raised, but this made it inconvenient to insert a multimeter and press buttons. Cost: Components + MCU, approximately 70 yuan.