12 Volt Geräte im Auto | Posts 16+

My WRT54GL router has been running flawlessly at 15V.
If you want to be absolutely sure, use a well-cooled 7812. That's perfectly sufficient.

Bertil wrote:

If you want to be on the safe side, use a well-cooled 7812. That's perfectly sufficient.

A 7812 voltage regulator will definitely be sufficient to prevent the voltage from becoming too high. But what is the minimum voltage of the access point?

The problem with the 7812 is that it has a typical dropout voltage of 2V (the minimum voltage difference between the input and output). This means that even with 12V at the cigarette lighter socket, only 10V is available for the device. And if the voltage also drops to 9V when starting, then it's only 7V.

However, it's also possible that the access point internally further reduces the voltage in multiple stages (e.g., 3.3 or 5V for the microcontroller, and 9V for the transmission module), allowing it to handle a higher voltage (as mentioned by Bertil). But to do that, you'd have to take it apart or be brave ;o)

Greetings.
Guste.

If you're going to open it up anyway, you can also provide the desired supply voltage yourself and make it available. 5V internally is often higher than most of us would assume. Providing these 5V with sufficient power is no longer necessarily a problem. There are plenty of ready-made solutions for this, or enough components that you can cobble together something with minimal effort. 8 or 9V internal operating voltage would certainly not be a problem either. Everything is far enough away from the 12V source and therefore can be implemented using voltage regulators.

What is the actual power consumption of the devices you plan to connect? A backup solution for the moment of startup could be built yourself using a suitably sized capacitor and a diode, which would disconnect the device from the main power supply in the event of a voltage drop. For a duration of one to three seconds, something like that is easily manageable.

guste100 wrote:

But what is the minimum voltage of the access point?

The WRT54GL can drop down to 9V.

I've switched to a 3G access point that runs on a battery now. The question is not whether...

guste100 wrote:

... It has a typical dropout voltage of 2V. ...

I just remembered something related to that.
The LM2940-12 is the low dropout version of the 7812 (approximately 500mV).
http://www.national.com/ds/LM/LM2940.pdf

Hi,

What kind of power supply does it need?
Otherwise, I would choose something like that.
[url][/url]

SGhttps://www.distrelec.at/dc-dc-wandler-6-w-smd/traco-power/thl-6-2412wism/365853{MARKER}

servusssss wrote:

Hi, What kind of power does that thing need?

1A... the 6W DC-DC converter isn't sufficient with its 0.5A output.

Good evening!

Sure, here is the translation of the text from German to English:

"Fa." translates to "Company" or "Firm" in English. Mascot DC/DC Converter 8862 12/12.
Technical specifications: Input voltage 10-16 volts, output voltage 13.2 volts, and current 6 amps.
Input and output are galvanically isolated, purchased from Company X. Farnell price: approximately €95.
These devices (approximately 100 units) are all operated in vehicles under the most demanding conditions, 24 hours a day, and some for over 10 years without failures.
Purchased from Farnell. Price: approximately €95.

Sure, here's the translation:

"Best regards."

tdi-Erwin (siehe Fehlerdatenbank)

What actually happened to that project?

I'm already thinking about planning my vacation.

- What goes in the roof box?
- Does it work with both a bike rack AND a roof box?
- Where does the Bobbycar go?
- How far can Wi-Fi reach between cars?

and how exactly do I power all of this?

Let's participate in your installation as soon as it's finished...

It's probably too late, but I wanted to add a few thoughts:

'So-called 'true' 12V devices don't actually run on 12V; they internally generate their actual operating voltage (e.g., 5V or 3.3V) using buck regulators (or linear regulators for low power). As long as their input circuitry (e.g., bypass capacitors, Zener diodes) functions correctly, there are usually few problems even with higher voltages.' I have often operated WRT54 routers without any problems using 14.4V or similar power supplies.
This also applies to SSDs, which only operate on the 3.3V and, at most, 5V power rails. For magnetic disks, a tolerance of +/-10% is specified, and I wouldn't dare to predict what happens outside of that range.

'For devices that truly require exactly 12V, one can sometimes use diodes as a workaround. A diode connected in series will reduce the voltage by approximately 0.6V, and multiple diodes will reduce it by a corresponding multiple.' The power dissipated in the process is generally manageable and within acceptable limits for slightly thicker diodes under typical current conditions.

3) As previously mentioned, achieving a truly regulated voltage in a car's electrical system within the 12V range is difficult because the input voltage can be both below and above that level. With the 'diode trick,' the voltage would then be significantly lower than desired, for example, when the device is idle.
You really can't avoid using a buck/boost solution in that case.
Alternative: Use a 'true' 12V power source (e.g., a lead-acid battery or 10 NiMH batteries) and charge it with a constant voltage charger, and optionally discharge it. Or, even better, operate a UPS (Uninterruptible Power Supply) with an inverter. Then you also have power for laptops, etc.