My supervisor like to see a circuit diagram. I can draw it but I like to do it in a software way.

Eagle...

its free, you can download it it from Element 14

not only is it free, but there are tutorials on the element 14 site.

Not only is it free, and for drawing circuits, once you can use it, it lays out / routes your PCB's too its a proper PCB package.

One word of warning, it will take longer than 10 minutes to learn.

If they are simple circuits, nothing beats a pen and paper.

Eagle is free for non-commercial projects.

Their official URL is http://www.cadsoft.usa.

The program is okay,and there are LOTS of parts available, especially if you download their libraries, and the Sparkfun parts library.

Eagle is relatively easy to use, especially if you keep to a 0.1 inch grid and design with through-hole components. Going to surface mounted designs leads to complications, such as a higher probability of having to build your own library for parts which do not have an existing library.

Good luck!