Arduino Protection circuit

I am trying to build a protection circuit for my Arduino board ( planning to make for Arduino mega 2560 and Pro mini) as a part of a project that I am working on. I read about the Ruggeduino here and would like to incorporate similar protection circuits. I don't think implementing the design of ruggeduino as it is would be feasible. I would be really grateful for any suggestions, advice .


What in particular are you looking for protection from?

Maybe describe your project a little? You only need to protect pins that are exposed to the outside world. What is on those pins defines how to protect it.

Extremely sorry for the incomplete information in the previous post!

Actually, in the project, arduino is being to drive large motors.The project is basically on building an autonomous vehicle . So it will also include brake , reverse etc.

I have a 24V DC supply. I am passing this supply to the arduino Vin via a buck converter (that results in 12 V supply to arduino). Voltage spikes on switching on the circuit, reverse polarization etc have resulted in damage to the microcontroller.
There are some basic ways of going about protecting my I/O pins (like in figure1(attached)). I was wondering if this is the best possible way or is using an opto-coupler or MAX16013 IC a better method ? Also, I read that there is some restriction on the diode that I take,i.e, it seems the breakdown voltage matters in such cases . So, this circuit(figure 1) will not hold for very large surge of voltage ? Also, i have included capacitors here. Will the inrush current be a problem ?

I was planning to use varistors. But the V-I characteristics above its breakdown voltage rises much slowly than that of a TVS diode (please correct me if I am wrong here). Therefore, it will pass on much higher voltage to the subsequent circuitry. Then I will have to place an additional heat sink or design the circuit following the varistor.

So , I am kind of confused here.

This was for voltage spikes , reverse polarisation.
The link here
talks about other ways in which I can possibly destroy my arduino. The solutions that have been given are there in ruggeduino.
So, is it good enough to implement these as it is or how should I go about it? I am not using all the I/O pins of arduino mega 2560 (I think we are using a max of 6-7 pins).

Its true that I can always buy an arduino board if they get damaged. But my task here is to try and make arduino rugged. The method should also be cost efficient!

Thanks !