ADC In a micro controller

[hansika]

Hi,
i want to monitor 12V supply health status in my project i am using PIC micro controller which is having in built ADC, but the ADC range is 0-5V so can any one tell me how to do this. with resistor divide network if i use 1k and 2k can controller detect the same range because in this case current is so much less.please suggest me what to do

 

[lockman_akim]

u can use voltage divider concept..
it simple..

Voltage divider - Wikipedia, the free encyclopedia

 

[betwixt]

The input current to the ADC is usually very small and if you are only measuring a fairly constant voltage you can almost ignore it. This means you can make the resistors quite a bit higher in value without losing accuracy. I would use values of 18K to the 12V line and 10K to ground, this gives you a range up to 14V before the ADC input reaches 5V so you have a safety margin in case the 12V is higher than expected. The voltage you are measuring is then 2.8 times the reading from the ADC. For example, exactly 12V would give an ADC reading of 4.286 V

Brian.

 

[lockman_akim]

yes it is..all the calculation is in the link..
you can use higher resistance value if you want..as long as u satisfied with the current value..

 

[Tahmid]

Hi,
Current value is not all that important as a VERY small amount of current is required. You can use 1k and 2k resistors as you mentioned with no problems. Vout = (Vin*Z2)/(Z1+Z2). Here Z2 has to equal the 1k resistor and Z1 the 2k resistor in the arrangement:
**broken link removed**

You might think about adding a filter and voltage protector at the output although it's not absolutely required, just in case.

Hope this helps.
Tahmid.

---------- Post added at 21:00 ---------- Previous post was at 20:56 ----------

*You could even use 10k and 20k and it wouldn't make a difference.