Author Topic: Automobile power conditioning?  (Read 4989 times)

dougal

  • Sr. Member
  • ****
  • Posts: 289
Automobile power conditioning?
« on: December 31, 2013, 11:54:13 am »
Eventually, I'd like to do a couple of projects involving my car. My understanding is that the power system in a car can be quite noisy, and I think you can get pretty big voltage spikes, depending on where you try to tap in.

Besides using a cigarette lighter style power plug in a car, where is a good place to tap in? What is a recommended way to clean the power up for 5V/3V3 parts like microcontroller boards and components? Keep in mind that some projects would be interior, others might be exterior (say, in the engine compartment/front grill area).

Suggestions?

danowar

  • Newbie
  • *
  • Posts: 12
Re: Automobile power conditioning?
« Reply #1 on: December 31, 2013, 09:56:32 pm »
A 12 volt "cig plug" adapter for cell phone charging will give you clean power.  You can purchase the receptacles at any auto parts store, plug in your adapter and wire it in wherever is convenient.  I have also in the past soldered wires directly to the metal bits of the charging adapter, wrapped with electrical tape, and wired it in that way.

Any decent quality cell phone charger will give you very clean 5 volt power, typically in the form of a usb plug.

As for where to tie in to 12 volts, this can get tricky with newer cars. In the last 5-10 years, manufactures have tried many different approaches at reducing the amount of wire, or the gauge of wires used in cars.  While it seems CAN-BUS has become somewhat of a standard, many other techniques where used, including 12volt "logic" signals.  It is common to find a wire that sits high (+12v) and to trigger some action when pulled to ground.  Applying a load to those wires will cause issues.

My recommendation is to look up wiring information for remote starters, as it will point you to "good" +12v wires to tie into.  Check out "the12volt.com".  It is a community driven site that provides wiring information.  I have found it to be accurate in the past.

Another word of advice when looking up wiring diagrams, models vary drastically from year to year.  If the year of a specific make/model is not listed, there is a very good chance the diagrams for the previous and/or later year is no where near the same.

I am relatively new to Arduino development, but I have years of experience in automobile wiring.  I would be happy to collaborate, or offer my advice on any questions that arise.

dougal

  • Sr. Member
  • ****
  • Posts: 289
Re: Automobile power conditioning?
« Reply #2 on: January 02, 2014, 08:13:54 am »
Thanks for the pointer to the12volt.com. They don't seem to have any info on my 2012 Kia Soul at the moment, but I can keep an eye out, in case someone adds it later.

Mark

  • Full Member
  • ***
  • Posts: 196
Re: Automobile power conditioning?
« Reply #3 on: January 03, 2014, 01:41:49 am »
dougal

Don't be too sure about the 'clean' signal for some USB car chargers.
One of mine destroys the FM radio, so I suspect its not very well made, but wasn't a cheap one either.
They also have very little in the way of filtering.

The voltage in a car ranges from 8v when cranking to 14.2v when its charging.
The closer you get to the realllllllllly big capacitor (ie the battery) the cleaner it will be.

I prefer to use an 8v linear regulator (LM3808) with a filter capacitor (4700-20000uF plus a 0.1uF) to ensure the voltage is clean, before feeding it into an arduino or similar device with an on-board 5v regulator, that way the worst that happens is the regulator gets toasted rather than the board.

For 99% of cars, the main power feed comes into the ignition switch, and is then fed to the accessories, of which the cigarette lighter is usually 10A or more.

You'll be fine

Mark

RickiePabs

  • Newbie
  • *
  • Posts: 1
Re: Automobile power conditioning?
« Reply #4 on: July 25, 2014, 04:55:05 am »
Eventually, I'd like to do a couple of projects involving my car. My understanding is that the power system in a car can be quite noisy, and I think you can get pretty big voltage spikes, depending on where you try to tap in.

Besides using a cigarette lighter sold by
e cigarette wholesaler style power plug in a car, where is a good place to tap in? What is a recommended way to clean the power up for 5V/3V3 parts like microcontroller boards and components? Keep in mind that some projects would be interior, others might be exterior (say, in the engine compartment/front grill area).

Suggestions?

Well I know power conditioning is very important.. Sorry for posting in old thread but correct measures have you taken?
« Last Edit: July 27, 2014, 01:29:50 am by RickiePabs »