In Car PIC MCU Flash Memory get damages in few days

[vigyanabikshu]

Dear friends,

I am developing an In Car security system using PIC16F886 but facing random failure

I am new to automotive design and I am using a traditional 7805 regulator to power up a PIC16F886 mcu and some sensors.

Everything works fine but after running few days, randomly crashes the PIC16F886 due to failure of flash memory. Again programming works fine. It is noticed that sometimes the PIC's EEPROM memory also losses.

Did I need some filtering and protection in my power supply ?

I think, it crashes while starting car. Did I need to power up PIC MCU after Ignition using some circuit ?

Thanks in advance

 

[KlausST]

Hi,

Did I need some filtering and protection in my power supply ?

Definitely yes. The supply is noisy. With supply gaps at starting and high voltage spikes.

But there are additional possible prblem sources.
* high voltage spikes on signal lines (wired). Very likely. --> Install HF filters and overvoltage protection circuit.
* EMI (wireless)
* missing or wrong reset circuitry (make sure - with pullup, reset circuit, capacitors - that the uC does not ccidentally enter programming mode)
* Pcb layout. Especially: GND plane and current path for transient spikes at I/O and power supply lines.

Klaus

 

[vigyanabikshu]

Thank you very much for your kind suggestion Klaus.

Got a filter circuit from another thread https://www.edaboard.com/threads/341214/
https://obrazki.elektroda.pl/2437872500_1437359410.png

and a buck converter circuit with protection diode from https://www.edaboard.com/threads/256116/



I think to replace 7808 circuit with the above one and apply filter circuit above will solve my problems

Expect your suggestions

Thanks

 

[FvM]

Adding TVS diodes for the power supply is always a good idea. Although the circuit will probably work in your car, it won't necessarily survive a surge test according to IEC automotive standards.

KlausST mentioned that the overvoltage often enters the circuit through signal lines rather than supply. I presume a "security system" has external signal lines. How did you protect it?

 

[dick_freebird]

In more tropical areas it might also be heat related, what
is your flash memory's retention rating upper temp limit?
Certainly underhood would be bad but black interior is no
pleasant climate either. Add internal temp rise to an already
elevated case temp, what do you have?

 

[vigyanabikshu]

Dear dick_freebird, I tried both Industrial grade (80 degree) and Extended (125 degree). And was monitored for weeks, and think it is not a heat related problem.