hello all,
iam designing a digital speedometer foe my two wheeler.
the speed iam getting in the form of 12v pulse sequence.

my doubts are:

1. can i give the 12v pulses directly to mc without opto couplers?
2. can i expect the output logic of magnitude 12v?
3. what is the maximum supply voltage i can give to mc?


thankyou

 

Maximum recommended voltage that AT89C51 can withstand is Vcc+0.5 where Vcc = 4v-5.5v

Check datasheet

http://atmel.com/dyn/resources/prod_documents/doc2487.pdf

 

maximum voltage that can be applied to any pin of 89c51 is -1.0 V to +7.0 V
Maximum operating voltage is 6.6 V

from data sheet
http://www.datasheetcatalog.org/datasheets/134/411652_DS.pdf

hope this helps...