Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Measuring 140V DC on RA0 on a PIC Micro

Status
Not open for further replies.

gavo4444

New Member
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?
 
What are the resistor values?
 
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 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).

Like this:

OpAmp has to be capable of pulling its output pin close to 5V rail. You must use a "rail-to-rail" OpAmp.
 

Attachments

  • Divider.gif
    Divider.gif
    44.3 KB · Views: 197
Last edited:
The only one that counts is the 100K. Look at the blue trace on my plot:D
 
do you know of any voltage regulator to operate at that voltage as well down to around +12V?

Do you want to convert 140VDC to 12VDC?
 
Make R2, 3k3, a standard value.
 
My resistors are getting very hot (100W resistors)
47K R1 and 1K for R2
If those really are 100W rated resistors (wow!) then you have something wired incorrectly.
 
Status
Not open for further replies.

Latest threads

Back
Top