My arduino, used in my car, freezes when ever i give the car heavy acceleration

It works find while it is idling, or mostly cruising, but as soon as i drive the car hard it freezes and reboots (thanks to the watchdog code for reboot)

Now I'm not sure if my circuit could use some protection of some trick that would stop the interference (suspected) or whatever is causing the hang.

(link to malware site removed)

Remember I'm an amateur, be kind :)

Two things...

  1. Use a different repository for images. I suggest attaching the image to your post then creating a link to the attachment.

  2. Your 78XX regulator (whatever that is) has no capacitors. I suspect that violates the manufacturers constraints.

Try a 1000uf capacitor from the input of D2 to ground. Then place a .1uf ceramic cap from the input of D2 to ground very close to the regulator.

I would put the relay kick back diode close the the relay terminals (that is connected to FET 2)

Why do you have Vin 5v and 3.3v on the nano all connected together? I would get rid of the relay zeners.

LarryD: I would get rid of the relay zeners.

A 1N4001 doesn't make a very good 5.1V Zener anyway. :D

The 12V supply from a car can be very dirty with lots of high voltage transients. Have a look at this application note:


Hard acceleration means the HT lead voltages increase substantially due to the higher pressure in the cylinders - you are picking up HT interference I therefore suspect. This could come in on any of the wires connected to the Arduino - or even be picked up directly by the reset pin.

Is there any way you can put a DMM on the 12V input of the 5V regulator and monitor the voltage during acceleration and then move it to the 5V output of the regulator and repeat the test ?

Wow lots of answers. I'm already feeling the smartness rubbing off on me. Now to my replies:

  1. The 5v and 3.3 are not connected, the diagram only appears that way
  2. I'm using the 7805 replacement (switching) I ordered some 2200uf. Would one 2200 be enough here? Also, I ordered an isolated power component to replace that. I'm thinking I'll still use the capacitor with it as well
  3. OldSteve, I'm using a different zener , I just placed the 1N4001 there for the drawing.
  4. Larry, I overlooked that one. Thanks.
  5. Russel & Mark: I just ordered a pack of TVS. Hopefully that can handle the power side of things along with the caps. But what about analog signals? Will putting a zener on each input pin prevent input spikes?

Raschemmel, I could try that as well.

Hi, Can you attach your drawing please so I can see what everyhbody else did?

Thanks... Tom... :)