Taking Care at the time of Design a Circuit

hi to alll

i want to design a circuit using microcontroller and the name of the circuit is "Temperature Indicator using PIC16F84"

now what kind of care should be taken?...

what are the ways to design a circuit?

how can i get the idea that this much values are transistor or this much values of resistors that i have to use to make my circuit run?...

Plzzzzzzzzzzz help

NOTE: I donot want ready made circuit so dont send me a link in which circuit is given....I want to learn and try my level best and also wants support from the members....

Popatlal Panjarawala

1.u identified your PIC,so if you see its datasheet,you'll know what are its associated components and where it has to be connected.normally PIC relatives are a crystal,two capacitors,a resistor at the mclr pin and decoupling capacitor on its Vcc pin.
2.Next is you have to identify the temperature sensor depending on the application you use.Eg:- LM35(simple one) or PT100.U can even search for many more parts.
3.Take LM35,go to its site,check its data sheet.There they would have mentioned which pin is for what.and what are its asscociated components to be connected.
3.Now you need to integrate your PIC,sensor and the power supply and the display,if you have.
4.write your codes.
I told these assuming that you have some knowledge in electronics.If so,you wont find it difficcult in reading the datasheets and going ahead
if you are NIL in basic electronics,then its a tough nut to crack and make you understand how electrons flow.In either case,start up and come up with specific questions,people are there to help you out.

regards,