12V Simple Power Supply Help, please!

[mindctrl]

Hi,

I'm building a circuit that runs off of 12V power. It's going to be for automotive use, so it will be powered off the 12V socket in cars(cigarette adapter), and I know that the voltage in cars isn't exactly at 12V in most cases. How can I keep things at a steady 12V?

Thanks in advance,

--mindctrl

 

[Nigel Goodwin]

Hi,

I'm building a circuit that runs off of 12V power. It's going to be for automotive use, so it will be powered off the 12V socket in cars(cigarette adapter), and I know that the voltage in cars isn't exactly at 12V in most cases. How can I keep things at a steady 12V?

You need to provide far more details of what you are wanting to do, does your project require 12V?, if so, why?. Can it work off less?, does it require a stable supply or not?.

Providing a stable 12V supply in a car isn't trivial, and it's very rarely done, most portable TV's run off 10.5V or so for this very reason!.

 

[mindctrl]

Hi again,

Sorry for the lack of details - that post was a tad rushed. Anyway, down to business. In answer to your question, yes, my project requires 12V. I am powering LEDs off of a transistor that will have the supply voltage of 12V, so that it can sustain a bright enough light when wiring them in series. I could wire it to 10.5v, but what would be the purpose of that? Why not just stick to 12v?

I will also be using a PIC to drive this all. I got a few PIC16F628A's, and I haven't had a chance to take a look at the pin diagram yet, but I'm guessing they require a 5v supply. I'll just drop a 5v regulator. I was taking a look at your WinPicProg page, and I was wondering, what exactly is PortA and PortB? You didn't really explain what they were... Are they just what one side of the PIC is connected to, so you can make another external board with the LEDs or LCD display or whatever you want to use to connect the main board to.... an expansion port?

But I digress. I'm guessing that the whole thing should probably run off a stable 12V supply, I don't know how sensitive the transistors are, I'm guessing they don't like voltage fluctuations too much. I know for sure that the PIC doesn't appreciate voltage spikes and sags, so the regulator is a must.

What do you think? I've never done this before, so any help is greatly appreciated.

Thanks again,

--mindctrl

 

[Nigel Goodwin]

Hi again,

Sorry for the lack of details - that post was a tad rushed. Anyway, down to business. In answer to your question, yes, my project requires 12V. I am powering LEDs off of a transistor that will have the supply voltage of 12V, so that it can sustain a bright enough light when wiring them in series. I could wire it to 10.5v, but what would be the purpose of that? Why not just stick to 12v?

Because it's complicated, and far more expensive, to regulate a car supply to 12V - your project doesn't seem to specifically require 12V for any reason, more just an arbitary figure plucked out of the air.

I will also be using a PIC to drive this all. I got a few PIC16F628A's, and I haven't had a chance to take a look at the pin diagram yet, but I'm guessing they require a 5v supply. I'll just drop a 5v regulator. I was taking a look at your WinPicProg page, and I was wondering, what exactly is PortA and PortB? You didn't really explain what they were... Are they just what one side of the PIC is connected to, so you can make another external board with the LEDs or LCD display or whatever you want to use to connect the main board to.... an expansion port?

PortA and PortB are the two 8 bit ports on a PIC16F628, PIC's with more than one port are labelled A, B, C etc.

But I digress. I'm guessing that the whole thing should probably run off a stable 12V supply, I don't know how sensitive the transistors are, I'm guessing they don't like voltage fluctuations too much. I know for sure that the PIC doesn't appreciate voltage spikes and sags, so the regulator is a must.

What do you think? I've never done this before, so any help is greatly appreciated.

The PIC needs a stable 5v supply, this is easily arranged with a 5V voltage regulator - I would suggest that you either feed the LED's and transistors from the unregulated supply, or from a regulated one less than 12V. There's nothing critical about the supply for the LED's.