speedometer with 18f2420 for motorcycle error

[aratti]

On top of Ramius wise suggestions, please ground pin 1, which is an unused floating input working as an antenna for incoming noise. The same apply for all the other unused pins that you show in your schematic. If they are set as input then ground them if they are set as output turn them to zero, and you can leave them floating.

"Never leave input pins floating"

Cheers

Al.

[Ramius]

Thank you Al for the compliment!
AndrijaD, one other "common" technique is to make all unused areas on your board as a "ground plane". The picture below shows one of my double sided PC boards and both the top side and bottom side with all the traces (circuitry) have all unused areas as a ground. I know the picture is not great and at least you see the idea. The ingition coils and spark plugs in any motorcycle or automotive application produce what is basically a "Spark gap" transmitter much like what was used in for radio in the early 1900's. Each time the spark plug "fires" it produces an electrical spike and a lot of digital electronics see this spike as a "valid signal". Since these spikes occur at different frequencies at certain RPM you will find the same signals used to run you PIC. You can take any portable AM radio and as you get next to your motorcycle you will start to hear this noise. Again, I hope this will assist you in getting your project to be a big success! Best, Ed