Detect 72 V with a PIC 3.3V controller

[nusliqiang]

Hi,

I want to design a circiut can detect a 72 V DC supply using PIC controller which is using 3.3 V supply.

Is there any good method/ safer other than just put a voltage divider there?
The concern is to reduce the possibility of the Microcontroller be damaged by the high voltage.

Thanks for any suggestion

 

[budhy]

One of the alternatives

 

[nusliqiang]

Thanks so much,

What is the R1 R2, R3 suggested?
may I put:

R1 = 100k
R2 = 1K

R3 = 1K

The port shrink current is Maximum 4mA

 

[budhy]

R1 = 100k
R2 = 1K

R3 = 1K

R3 = 10K

 

[IanP]

Another option is ≈47kΩ resistor and 2.7-3.3V zener diode .. similar safety level as version with transistor ..

If you use 100kΩ/1kΩ as input voltage divider (version with transistor) it may not work .. Try 100kΩ/2kΩ ..

Regards,
IanP

 

[nusliqiang]

thanks,
I will try