Need some help with system...

VWTronics · 12-14-2003, 08:27 PM

Well,
I got the ITPS and 70W-A set-up..... installed the power supply and every thing looked fine. Installed the system in the car every thing started up fine.... then I saw the screen flicker every once in a while.

I had the screen being feed from the power supply, so I thought I was drawing to much of the power supply.

Solution: Using a 7812 regulator chip (Takes +12-37 volts down to +12 Volts flat ) and a relay being trigered of the ITPS I powered the LCD. My problem now is that I can see my desk top, but only for a second then my screen turns white. If I keep truning the screen on and off, my desk top appears in the back ground then screen goes white????

I had the hole system up and running fine in the car when using a Arise power supply, so I know the system works. All I did was swap the power supply to the 70W-A and the ITPS????

Please Help........

System setup:

M9000
Laptop hard drive
USB DVD, GPS, Touch screen
TM-701L
WinTV PCI card
2 x 2" cpu fans (12 volt)

121603 Update:

It worked

!!!!, I ended up removing the 7812 regulator (did not read the fine print on required voltage input, that's what you get for that) and powering the LCD directly of the battery. I did keep the relay, so now when I turn on the system after x amount of time the LCD comes on when ITPS triggers the relay, and stays on for the 35 sec or so once I power down. I did conclude that the 70W-A can not survive the crank, but what the hell another project to work on......

shchua · 12-14-2003, 08:59 PM

The datasheets for the 7812 says it has a dropout voltage of 2.0V and requires a minimum of 14.5V input to regulate. Did you measure the output voltage of the 7812 under load ? It might be much lower than 12V.

If so, you might want to use a LM2940-12 or similar low dropout (0.5V) regulator.

VWTronics · 12-15-2003, 05:40 AM

Quote: Originally Posted by shchua

The datasheets for the 7812 says it has a dropout voltage of 2.0V and requires a minimum of 14.5V input to regulate. Did you measure the output voltage of the 7812 under load ? It might be much lower than 12V.

If so, you might want to use a LM2940-12 or similar low dropout (0.5V) regulator.

I'll give that a try......Thanx

VWTronics · 12-15-2003, 08:04 AM

Quote: Originally Posted by VWTronics

I'll give that a try......Thanx

Is this the one you referenced ?

http://www.digikey.com/scripts/DkSea...245879&Site=US

VWTronics · 12-16-2003, 12:03 PM

See Update

shchua · 12-16-2003, 08:21 PM

Glad it worked out for you. But I wouldn't recommend powering the LCD monitor from the battery, unless the monitor has a built-in regulator. The battery voltage may contain nasty stuff like load dumps and voltage spikes (albeit for very short durations) that could damage your monitor.

The Digikey link expired, but the Digikey part number that you want is LM2940T-12.0-ND.