udhay_cit
Full Member level 6
Dear friends,
I need to measure a DC voltage range from 0-30V using microcontroller ADC. For that i am using potential divider value of R1=12K, R2=1.5K. My MCU operating @ 3.3V so with this resistor combination i can get 3.3V output @ 29.7V input. I am using 3.3V zener to protect overvoltage.
I can get 3.3V output for 29.7V input, without using zener diode... But if i connect zener diode the voltage never reach 3.3V for even 35v-40v range.
I know the zener will start conduction little bit before reach the Vz, But how can i avoid this problem... Please give me the solution...
Notes: R9=150E is not involving in this circuit & it is optional for 4-20mA current measurement, so please don't consider this...
Thanks & regards
Udhay
I need to measure a DC voltage range from 0-30V using microcontroller ADC. For that i am using potential divider value of R1=12K, R2=1.5K. My MCU operating @ 3.3V so with this resistor combination i can get 3.3V output @ 29.7V input. I am using 3.3V zener to protect overvoltage.
I can get 3.3V output for 29.7V input, without using zener diode... But if i connect zener diode the voltage never reach 3.3V for even 35v-40v range.
I know the zener will start conduction little bit before reach the Vz, But how can i avoid this problem... Please give me the solution...
Notes: R9=150E is not involving in this circuit & it is optional for 4-20mA current measurement, so please don't consider this...
Thanks & regards
Udhay