Quote:
Originally Posted by dcb
After researching it a bit more (hint: we could use more researchers), I did see that some of the arduino crowd add a 12v regulator prior to powering the duino, i.e. http://www.arduino.cc/cgi-bin/yabb2/...num=1191452682 , the claim is that bits were randomly inverting without it? |
I run a 6.5V-40V to 5V DC/DC converter on my front end now. I also put TVS's on the input to protect against surges. I installed the reverse polarity diode on the input of the DC/DC with surge clamp and gigantic bulk capacitance in an attempt to handle cranking brownouts. I think if a surge doesnt kill the 7805, your problems are going to be due to a brownout. Mine runs great but I fully admit it is complete overkill.
I wouldnt use an optoisolator. There are multiple other ways to level clamp a voltage that dont involve opto's. In my experience an optoisolator is used to establish / maintain isolated grounds. We're obviously sharing the same ground. They also arnt the cheapest things in the world.
I still maintain a simple diode bridge will be adequate. And in DCB's defense the zeners although low on the knee and not fully in breakdown are working on my and many others cars.
Hopefully with the scope you will be able to track down the IC count problem. I know the base pulse of the backlight PWM is running at 500Hz if you want to wire off of that for counting.
Unfortunatly I took the fun car out of town this weekend so I didnt get to do any decent calibration of the MPGuino.