Hi Dear members of 8052.com

I am having new problems with my DCCS project which disscused earlier here : http://www.8052.com/forum/thr...read=72808 .problems appeared mostly after changing the spark plugs and some other hardware upgradings . (resistor spark plugs has been changed with no resistor plugs)

after all of this i decided to implement the LC filter on the input line of the three board (Relay driver board , 7 segments driver board,Main board).

The problem that i didn't implmented this so far was the trouble i've had to find a frrite bead like BL02RN2 which is mentioned http://www.8052.com/faq.phtml?FAQ=93 by dear Prahlad , everytime i go to the electronic market here, they want me to tell them a number based on Hanry and the amperage rating of the inductor.(this is all about buying a wound inductor ,i don't have all of the suitable instruments to wound one myself)

1- so here is my question , what type of inductor is suitable for filtering supply noise .(Toroidal ,EI core ,Axial ,Radial ,Etc)

2- how should be the value of inductor calculated ,above of what frequency should be filtered , is it have to be calculated like this (based on Dear Kai's suggestion here : http://www.8052.com/forum/read.phtml?id=53375 ):
T=5 mH * 200 uF = 1 uSecond
F=1/T= 1 MHZ
if i was right,this should filter frequencies above 1Mhz ?
here is the picture of the ferrites which i've bought yesterday , maybe these could be helpful :
http://www.8052.com/users/farshidjh/IMG_3883.JPG

3- i cannot summary a final answer in my mind , in this project 'where the +5v enters the board' should be right after the LM7805K regulator ,didn't i have also to use a filter on the Car Baterry input to the board ?

4- i have 15V varistors in my components. does adding this component has a benefit in noise suppresion ?

i have read every discussion related to noise and ground potnetial problems and random resetes since i've membered here (2001), but due to my lack of knowledge in analog design and loosy electronic market here,i wasn't able to implement all of them to my designs.
my big thanks to everyone who spend their valuable time and share their experience with us.

P.S. : Still no Boom releated to the fuel tank gauge ! ;)

Wish you all a good weekend
Farshid J.H.