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Hi All, i am currently using a voltage divider to bring the voltage down from 140V DC to +5V on the pin of RA0 in a pic micro. My resistors are getting very hot (100W resistors). Is there perhaps another way of measuring 140V DC on a the pin of the micro?
Use a high resistance voltage divider then use an opamp follower to buffer it to an impedance the PIC A2D likes (around 2k load on opamp output).
Hi Mike
Many Thanks what would be the divider resistor wattages?
i will then put both a 5W then it should run cool
do you know of any voltage regulator to operate at that voltage as well down to around +12V?
Use R1 180k and R2 1.2 k. Add 220k series resistor at A/D input.
Microchip Datasheet said:The
maximum recommended impedance for analog
sources is 2.5 kΩ.
My resistors are getting very hot (100W resistors)
If those really are 100W rated resistors (wow!) then you have something wired incorrectly.47K R1 and 1K for R2