How to measure 3phase L-L 440 volt using STM32 ADC?

[parth kothiya]

i want to build circuit that can measure AC voltage 0-600V AC using STM32 it there any sample

circuit and example code of it..

i have try some circuit ...

• 1) 0-400v ac --> stepdown transformer --> 0-15v ac --> dc --> resistor divider --> adc pin MCU but in this case bridge rectifier drop some voltage(0.7v) so it can not measure lower voltage
• 2) 0-400v ac --> stepdown transformer --> 0-15v ac --> resistor divider --> add dc offset --> ADC pin MCU but in this case result is not very accurate compare to multi meter voltage

so how can i do this...?

[Vangelis Fortounas]

Hi.

0-400v ac --> stepdown transformer --> 0-15v ac --> resistor divider --> connect one end to ADC input, Divide the VDDA using two equal resistors to VDDA/2 and connect the other end to it. Connect also a capacitor (in tens of microfarad scale) between VDDA/2 and VSSA (Analog Ground)

[Vangelis Fortounas]

0-15 vac transformer gives 15x1.414 =21.15 AC p-p voltage for 400V max ofcourse. For 600V, Vpp is above 32 volts (peak to peak)

So the resistor divider you mention (not to have conversion saturation) must have a divide ratio at least Max_AC_Vpp / VDDA.

[AvaTar]

> 1) 0-400v ac --> stepdown transformer --> 0-15v ac --> dc --> resistor divider --> adc pin MCU but in this case bridge rectifier drop some voltage(0.7v) so it can not measure lower voltage

You could use a smaller transfer ratio (i.e. higher secondary voltage) and a higher resistive divider ratio, to minimize the voltage drop over the rectifiers. Perhaps use shottky diodes (Vd is about 0,25V).

Consider a galvanically isolated measurement (primary) unit with digital transfer to the MCU. Back EMF could easily kill the whole system. Not a hardware guy, but speaking from experience here.