I'm interested in making a data logger for a vehicle with an Arduino Mega 2650, but am realizing the power supply is very important in this application. Filtering is just as important as protection.
Has anyone used the Pololu D15V70F5S3 before? Is it sufficient protection in a vehicle? This project could be wired to the car's ignition as to not be switched on during starting.
it looks good except for the 10R resistor, that seems like it would just create unnecessary voltage drop and help with nothing. something else you might look into is just using one of those 12 volt cellphone chargers, it would be alot cheaper, i see them at walmart all the time for5$ at the registers. the ripple is pretty small and they can usually supply around 500-600 mA.
ouch, load dumps seem like they're quite the electronics killer. seems like it'd be pretty hard to protect against that. maybe a tvs diode and a fuse but if it happens often itd be a hassle.
Fortunately it's a common problem and the big boys have devices to help.
Google
"RBO40" , TVS + reverse polarity etc protection.
"Littelfuse AUML", varistors designed for auto voltages.
Putting either in front of the Pololu PSU would probably do the trick.
I'm currently designing a circuit to be used in cars and I'm either going to use the AUML varistor followed by a diode bridge (for rev polarity) or just the RBO40 by itself.
so apparently most newer alternators have load dump protection. i've had 2 arduinos in my car for quite a while, and my battery terminals are not the best, but i've never seen this problem before. makes me want to take it apart and check.
Yeah I've got a gadget in my truck at the moment, it's just connected to the nearest 12v wire I could find. It's also got about 10 metres of unshielded wire from a sensor directly into a uC pin.
It's all been working just fine for a year or so.
So i guess you can be luckly, but anything new I design will have more protection.
I built a GPS power supply with a standard 7805 + 2 caps design. I didn't even have a reverse protection diode. It was in my old truck for 5 years (until I sold the truck), and still works.
I also have an APO, which also uses a 7805, and it too was installed in there for years, and is still working.
I'm not saying to forget about protection, just throwing out a data point or two...
IMO, it depends on how long you plan to have it installed.
This is interesting. I never knew about "load dump". I always thought the best way to go was a switching "cigarette lighter" power supply. (I still might.)
In any case, it makes me wonder about car radios and such. It would seem they would have the protections talked about here. If so, maybe I wont pass them by at the thrift store next time.
Thanks, pretty new to all this, I'm really grateful for the help.
Seems RBO/TVS is simple and cheap, $3,...I would think almost anything with an IC in the car must have something similar...I'll grab a couple of radios when I'm at the junkyard, maybe ABS systems too.
I also switched to the 3.5A version of the Pololu DC-DC convertor instead of the 7A version.
I've looked at 7805 based 5V PS circuits, but they aren't they going to limited to around 18V input and about 1A? That just seems too tight. Plus, a little bonus, with 3.5A available I can add an external DC jack to power another small device (or another Arduino ) without building another power supply.
Is an LED necessary to drain the caps when off, or will the devices do that?
) without building another power supply.