voltage sample for uC

[justinjohney]

i need a clarification
can i use resistive divider for taking samples from 3 phase.(i understand the risk if any shorting occur, :twisted
not much current consumption.only for uC adc reading current.
415V to 1.5VDC

 

[betwixt]

As long as you also understand the risk of the ADC being connected to a live source, yes you can. But be careful where you take your measurement across. If it's across phases, one side of the measurment will have to be referenced to another phase so your whole circuit, although measuring the correct scaled down voltage, will itself be sitting at 415V (remember that voltages are relative). If you are measuring to a 'neutral' in a star network you measure from neutral to each phase which is probably much safer.

Beware that most resistors are rated to no higher than 250V (check their data sheets) so you may have to use several series resistors in the HV side of the divider to reduce the chance of them flashing over.

Brian.

 

[mathespbe]

Dont use this idea ever with out using a transformer....

 

[justinjohney]

If you are measuring to a 'neutral' in a star network you measure from neutral to each phase which is probably much safer.

ofcourse brain.