electronic Guru's needed ...

felix99 · 11-20-2002, 08:02 AM

Hi,
I currently have some projects running and some plans I found are not complete so what I need is:

A Stabilisation circuit (with filers if possible) to get 12V as proper as possible. ( sorry I dont know the english special term)
My dictionary says smothed - so I need a proper smothed 12V

.

Why this ? - I have some noise on my TFT , only in car , at home on a stabilzed 12V Power supply tehres no noise.
I also have a raw TFT where I have to build a controller for and I want to integrate the needed cicuit directly in it .

Any cicuits , hints etc.. that could help me ??

Thanks

Felix

Hope I expressed myself understandable .- sorry if not.-

Seanster · 11-20-2002, 12:21 PM

Can you power the screen off of the computer's 12v power? That's what I do. As a bonus, the screen shuts off with the computer automatically.

felix99 · 11-20-2002, 01:24 PM

Thanks for replying ,

Problem is that i need the screen also when PC is off-
And the other screen I' wanna buil a controller for is for stand alone use ( without pc) . Thats why I need this

Felix

Electronicsuk · 11-20-2002, 01:49 PM

A large capacitor(s) and a LM7812 regulator should make a good enough smoothing circuit. Try perhaps a few 2200uF capacitors in parallel, make sure they are rated at 25v minimum. Don't worry about your spelling, it's actually very good. I have seen english people who are much much worse!
Best regards,
Matthew

felix99 · 11-20-2002, 02:09 PM

Thanks

The capacitors before or after the LM7812 ??

Tnx

Felix

//edit

perhaps - an idea came to my head- i could take the 12v part from sproggy psu ??

\\edit end

Seanster · 11-20-2002, 06:20 PM

I checked out your site and I can't tell what you would be doing with the screen when the computer is off. And what is the other screen for? Just nosey...

If it was me, I'd just plug another power supply into the inverter :)

felix99 · 11-20-2002, 06:58 PM

the inverter just supports one - if i connect AT PSU it cuts off after 28min

I have a digital camera and i wanna look at the pics / videos i take via the tft and a friend of myself has one of those multimedia discmans which are playing mp3'cds vcds svcds - when we have long travels he alwas brings a good movie or new mp3s - ( the discman works via TVout gui .
I also planned a backview camera

The other TFT is for my parents car. will get them one of those discmans and build them a tv tuner - later a carpc

thats why

Felix

mp3hombre · 11-20-2002, 10:36 PM

Get yourself a 15 VDC 1 Amp adapter, a 4700 uF capacitor and a 12 V 1 Amp voltage regulator.
The capacitor goes before the voltage regulator, just make sure to wire them correctly and put them in a small plastic box.

Electronicsuk · 11-21-2002, 02:37 AM

Put 2200uF capacitors before the regulator and perhaps some smaller capacitors (10uF) after the regulator. The LM7812 is rated at 1A but you can put more of them in parallel for higher current.
Best regards,
Matthew

Mastero · 11-21-2002, 06:15 AM

insted of the LM7812 you can go for LM1084-12 its rated at 5amps and is linear ..

Mastero

PTCruiser · 11-21-2002, 06:58 AM

Salut Félix!

Bon je répond en angalais....

If you want to use a LM7812 you can go for LM1084-12 you will more than 12V to get 12V stab. (Drop out regultor)

It's will be ok with your engine running ~14-15V but not when your engine is off <=12V.

Use the 12V from your ATX power supply instead!

Try to eliminate the noise with a Ground loop...

Anyway throw away your 12V->220V converter and get a DC-DC converter (opus, Zootjeff, DIY...) (I don't like converter they introduce a lot of noise in the system)

But if you just want to use your CD/VCD/MP3 player check this:

http://www.mp3playerstore.com/buy_it_now__/mp-2003.htm

http://www.mp3playerstore.com/buy_it...ar-adapter.htm

Exactly what you want to do? less than 10$

Euclid · 11-21-2002, 08:43 AM

how necessary would this be?
I am running my screen straight off my battery. It takes 12v @ 0.7a. Should i do this? Should i fuse it for 0.7a?

PTCruiser · 11-21-2002, 08:49 AM

As the "12V" voltage in our car is unregulated (~8..15V)
Your screen can be damaged by the overvoltage.

But it's depend of your screen elctronic...

Check the datasheet of your screen.

felix99 · 11-21-2002, 09:02 AM

Hi ,
First thanks for all replys.
I think I'll take 2 L7812 and some 2200µF capacitors and some little ones.

Can I ground the EARTH GRD pin of my inverter to carosserie ( car structure) ?

The major things I want to eliminate with this circuits are:
- Noise on TFT
- Protecting my TFT against High voltages
- Getting rid of audio noise because this noise definately comes from 12V line
- Protecting some other devices from too much Voltage.

So;- many Thanks angain

Felix

concerning Inverter: ( DCDC PSU is not cheap enough for me )
- the inverter works very good and is far away from my PC so that there is no noise coming from it- tested!-

PTCruiser · 11-21-2002, 09:35 AM

Please note that with engine Off you screen will not work.

Drop-out regulator...you need higer voltage than 12V input to get 12V output regulated...

Quote:

the inverter works very good and is far away from my PC so that there is no noise coming from it- tested!-

So you where at home -> feeding the ATX power supply with 220V AC and you still get this noise?

Engine off with your inverter (the engine is stoped) you have noise?

What was your test?