speedometer with 18f2420 for motorcycle error

[AndrijaD]

Pedja mozemo i na srpskom.I use schematic for power supply from lm2576 datasheet.MCLR is disable.


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[Ramius]

Hi AndrijaD,
It sounds more like you are getting interference from the spark plug. This can be a "challenge" to eliminate. First, I would hope you have your project in a sealed, metal box that is grounded? It may be necessary to use only "feed-thru" capacitors on any wires going into or out of the box. You could also add 3 capacitors as close to pins 19 and 20 (PIC power and ground), one of which is a .1mfd, and a 10 mfd tantalum, and 100 mfd tantalum. Why 3? Simple. Capacitors are like resistors (Called Xc) to AC (noise) and since the frequency of the noise will change with the RPM, you want to make sure one of the capacitors looks like a short to ground for the noise. Other techniques and tactics is to take your wires and twist them together in the end of an electric drill so they will "shield" each other. Hope this will give you a "start". Best, Ed

[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