Hi alll.....

The front end design of my project deals with detecting a 30v dc. I am planning to do the detection part by a microcontroller. So, I need to isolate the microcontroller from the the high voltage DC circuits and then down convert 30v DC into a low voltage (3.3v) for the microcontroller.


Please give me suggestions/clues for designing the circuit.

Thanks

 

30Vdc → (27K + 3K) → V_3K → Voltage follower (Op Amp LM358), 3Vdc max → ADC0804 → Mcu

Use 27K + 3K to divid the 30V input voltage, and then you will get a Vamx = 3V, following the above process, you will get 1/10 from 30V.

In your Mcu that you must multiplied the input voltage by ten.

 

You could use an opto coupler to isolate and detect the 30Volt, the circuit below the 30 volts is set by the R1/R2 combination, and the output of the opto into your microcontroller, so when the supply gets to the desired voltage, the opto coupler works, and triggers your micro.

http://www.google.co.uk/imgres?q=tl...8&start=16&ndsp=21&ved=1t:429,r:11,s:16,i:162

if you use a TL431 as the reference diode then R1=110K and R2 =10k

If you dont need the isolation, then use the two resistors method as posted by scott.