3

I have some project ideas that would be targetted for use in a vehicle. I would like to consider the possibility of tapping into the car's 12V battery to power the projects, for example through the cigarette lighter port. I would put the input power from that port through a linear or switching regulator (e.g. a 7805 or similar), to give me 5V power. Am I likely to face any challenges in that approach? Are there front-end circuits that are a 'must have' for consuming automotive battery power in low voltage / low current embedded applications? Specific circuits and/or part recommendations are encouraged.

vicatcu
  • 22,499
  • 13
  • 79
  • 155

2 Answers2

2

I recommend using an Adapter from Cigarette lighter to USB (like a cell phone charger), to get your 5V. It is simple, cheap and effective. And if you tear it open you will find a linear Drop Out Regulator (for the lighter loads) or a switcher (for heavier). And they are typically already current limited and such. So I suspect they are perfect for your goal. I would readily run an Arduino such.

mpflaga
  • 1,345
  • 6
  • 10
  • your circuits should always have some form of protection. Where the adapter will do most of it. But I always put a TVS(5Vzener) clamp between VCC and GND, to protect against surges from handling, etc... – mpflaga Jan 30 '13 at 21:04
  • And depending on the quality of the adaptor, you may need additional filtering anyway to filter out spikes. – FarO Feb 02 '16 at 10:41
1

When designing your own vehicle based power supply, make sure to add enough filtering. When the vehicle starts, there could be voltage spikes that may go unfiltered. Manage your own filtration.

Not all cigarette lighter adapters are created equal. One of mine has a warning that says to connect only after the vehicle has been started or is idle. It implies that the charger should not be plugged into the lighter socket during vehicle starts. I'll post a picture when I could.

Chetan Bhargava
  • 4,612
  • 5
  • 27
  • 40