Outline · [ Standard ] · Linear+ current 5V, 500mA

Hello, can someone help me with this... I need to find current with 5V and 500mA, to connect my GPS inside the car, I have 2005 Logan, Laureate. The thing is... I have a bluetooth gps receiver which connects with my phone for navigation. And I do not want wires running inside the car, even from the cigarette lighter, so I though that I connect the unit somewhere in the car and keep it on all the time while the car is engaged, and when I need a navigation just connect my phone to the gps. But the question is where to get a stable 5V 500mA current.

Hello,

can someone help me with this...

I need to find current with 5V and 500mA, to connect my GPS inside the car, I have 2005 Logan, Laureate.

The thing is... I have a bluetooth gps receiver which connects with my phone for navigation. And I do not want wires running inside the car, even from the cigarette lighter, so I though that I connect the unit somewhere in the car and keep it on all the time while the car is engaged, and when I need a navigation just connect my phone to the gps.

But the question is where to get a stable 5V 500mA current.

LM2596 is a 3A switching voltage regulator, so you have less power dissipation on higher current consumption. it comes n 12V output, 5V output or adjustable output.
it only needs a few external components: 3 capacitors, 2 resitors and one coil, the values of theese components can be found in product datasheet.
it`s cheap and reliable.

LM2596 is a 3A switching voltage regulator, so you have less power dissipation on higher current consumption. it comes n 12V output, 5V output or adjustable output.
it only needs a few external components: 3 capacitors, 2 resitors and one coil, the values of theese components can be found in product datasheet.
it`s cheap and reliable.

I did a little googling about this LM2596... and I see that this is simple switcher power converter.

So where should I connect this semi conductor, and how should this electric circuit look like?

i posted a picture with the schematic for LM2596-5V output and the complete datasheet.
you just need to connect it like in the schematic, on the input line you feed it 12V from car socket and on the output you have the +5V regulated.
cheers

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Thanks for your help, I really appreciate.

Will try to find this LM2596 these days, and see to connect it right.

5V sound exactly like the tension used for various sensors by the ECU, but I wouldn't tamper with that. The solution above is much better.

5V sound exactly like the tension used for various sensors by the ECU, but I wouldn't tamper with that. The solution above is much better.

You've just qualified for "Bula daciotului".

On the schematic above it is stated that input voltage is UNREGULATED 12V, but since the car battery as a voltage source can be considered (highly) regulated, you can eliminate that first condenser on the input from the design, and save a bit (veeeeeery little, though O:))

wrong! the car battery voltage isn`t well filtered. it has lots of spikes from the electric windows, fan or even alternator. It is recomended that you use the minimum filtration wich is provided in that schematic.
In this case "unregulated" means the input voltage, wich is different than the regulated 5V output

Don't!
That capacitor filters the noise produced by various inductive elements.
I would suggest even its replacement with a larger capacity one...

The greatest spike the car battery must sustain comes from the electric starter (order of magnitude 100+ Amps), and compared to that any other electric motor in an average car is insignificant.

As for the EMI noise, the biggest source is high voltage ignition/spark plugs.

Has anyone actually measured those ripples, spikes and noise on a battery in a working car? I mean, besides specialized laboratories, unavailable to the ordinary public...

After all, the man does not need high specs, and even if the voltage on the output isn't 99.999999....% pure, it is used for charging battery in another device, which has it's own regulation, + at least 2 more levels of filtration, etc, etc...

Let's not go academic about simple things!

This post has been edited by g100sic: 17 Jun 2010, 15:59

The riple is big enough to be seen with an osciloscope. How much could you be saving by dispensing with an ordinary capacitor?

The spikes from the electric motor that opens the window fried some transistors and microcontrollers that were filtered according to the technical documentation of the stabilizer. I had to put 7 diodes to protect my device and make it reliable.
I can`t understand why people don`t respect the technical datasheet that comes with a product. Then if the prodct malfunctions or fries another device you`ll say that the step down converter is faulty?
If the manufacturer says "put at least that value there" that`s what you should do. If you don`t you cand have trouble.
I`d understand if that condenser was expensive but the most expensive costs 0.1 Euro

I would try something simpler: a 7805F (isolated package) linear regulator, mounted somewhere on a large piece of metal, under the dashboard, eventually with a 5.6 ohms, 5W resistor in series with its supply. You don't even need a pcb, and is cheaper.
http://www.datasheetcatalog.org/datasheet/...hild/LM7805.pdf

If you can't find isolated version, make sure to electrically isolate it's mounting terminal from the chasis.

For non switching step down voltage converters the power dissipation is greater. 14.4V - 5V = 9.4V voltage drop on the regulator. And even this regulator needs capacitors between input-gnd and output-gnd.
If you supply a heatsink you can use the LM7805 with satisfying results.
Cheers

psychoo's suggestion seems to be right.