SparkFun Forums

[grcbyte]

Hello,

I made one project with my arduino, one lcd16x2, 4 led segments... and i want use the 12v from the car lighter to power the Arduino\circuit.. what is the better way to do this?

Its better if i buy something like this:

DC-DC Converter Board Voltage Regulator Stepdown Module [LM2596S]



Specifications:
Input Voltage: 3-30VDC
Output voltage: 1.21-18VDC
Max output current: 3A (Recommend use following in 2A, leaving a certain margin)
Built in LM2596S-adj
Dimensions: 37mm x 37mm
Step-down: The input voltage must be at least 1.5v higher than the output voltage.

Thank you

[thebecwar]

I don't see why that wouldn't work, but it doesn't sound like you need that much current. A LM7805CT takes 7-20vdc* and regulates it to 5v (1A), and costs less than a candy bar. Add a pair of small filtering capacitors and maybe even a protection diode, and you're still not talking about a lot of money. As far as where to tap in? The wiring harness for the radio would work fine, and you wouldn't risk anything vital to your safety.

*Keep in mind that the manual says the electrical system in your car runs at 12v, but depending on the make/model, I've seen as high as 14.8 while it's running, and as low as 11 when shut off.

[grcbyte]

Thank you

Something like this?



C1 \ C2 0 ==> 0.33uF and 0.1uF (i read on datasheet of 7805)
C3 470nF?

[thebecwar]

What I'd use:
C1 - 100uF 20v electrolytic
C2 - .1uF 10v electrolytic
C3 - Not needed.

The caps are really just there for smoothing the input and output, and exact specs are not necessary. Whatever you can find is probably fine, as long as you leave yourself a little safety margin in the voltage rating. (ie.- don't use a 12v rated cap on the input to the regulator.)

[jremington]

You will need a voltage spike protector between the cigarette lighter socket and whatever voltage regulator you use. Automobile electrical systems are nasty environments for electronics, with noise spikes as high as 40-50 volts when the engine is running.

[Mee_n_Mac]

What Arduino are you using ? Most already have some step down regulator onboard. Your usage doesn't seem to be drawing all that much current, you should be OK using that regulator if you add some additional "spike" protection as noted above.

[grcbyte]

Ok, what spike protector can i use?

Thanks

[magnethead]

Call me captain obvious, but I love car cell phone chargers. Just find one with theconnector that matches your board, or clip off the end and go straight to the 5V bus.