How to design a circuit

Hai
I want to design my own circuit using some IC' s and micro controller, some i have made but they works some days after they start giving some trouble so what is the problem? is there the problem with design or power or component grade am unable to find it can any body help me.

there may be many circuit is not working.
unless you post the circuit and tell the problem seen , it wil be difficult to give a solution.

---------- Post added at 18:12 ---------- Previous post was at 18:06 ----------

there may be many circuit is not working....

please read it as:
there may be many reasons why a circuit is not working.

My first design (35 years ago) failed for 2 months with tons of calculations and it was just a 2-transistor astable oscillator!
In my case, it was a silly mistake... the electrolytic capacitor at the voltage supply output was connected with the wrong polarity!
At that time I didn't have yet an oscilloscope, so anytime I measure Vcc I read about 5V but I couldn't see the large ripple since the capacitance of reversed capacitor was reduced greatly. Of course, now one can see (actually detect) the presence of ripple by measuring Vcc by an AC voltmeter.
What I mean from all this... is that don't expect your circuits malfunctions are due to big errors because we usually take care of the serious analysis first. So try to prepare yourself to find some silly mistakes in the hardware or software which can hide themselves because they are so obvious for one to check them carefully.

For example, the simple RC that resets an MCU could be the origin of many unexpected problems if not designed carefully... And this was my other silly mistake in my early designs :wink:

I think getting useful answers for what may confuse you, depends on how much details you are able to give to describe your problem. It is like in math problems, 4 unknows with one equation... many anwers can satisfy it... with 2 or 3 equations the number of answers decreases... but with 4 equations ... there will be just one answer :smile:

yes. it is usually silly things or mistakes and we spend lot of time in finding the source of problem.

if you have breadborded the circuit connection , then all such problems will appear intermittently.

yes. as said , it is 'n' unknowns with one equation.