So I have a motorized flip out lcd, it is much brighter when the motor isn't on, when i start it up, it gets dimmer significantly. Also, it states that it takes 12 votls +/- 10%, but i am at a constant 14.1 volts. What resistor would I use to lower that 14.1 volts to 12 volts, that would probably be my main question. I am thinking that if the voltage was lower, it would be brighter. I know putting excess amount of voltage in an lcd can ruin it. Thanks for the help

 

Not enough information - you need to measure the current load of the screen in order to calculate the required resistor to drop the load. With the current and voltage across the screen known you can calculate the equalivant resistance of the circuit and then put an external resistor to drop the extra 2.1 volts you think you have.

But all that is wrong anyway.

What you really want is a voltage regulator which are pretty common and easy enough to find at 12 volts.

But that's wrong anyway.

The LCD screen, assuming that it's designed for car use, is designed to operate at 13.6 VDC nominal. Just like the common home uses 120 VAC the common car voltage is said to be 12 VDC. Really the home's AC voltage is 117.5 VAC and drifts up and down - I read 112-122 VAC. The car's battery ought to be providing 13.6 VDC from a fully charged battery not under load.

Your 14.1 volts is well within an accepted tolerance - assuming that you're meter is calibrated properly.

What happens to the screen when you turn on the headlights on high beam with the car off?

What happens when the high beams are on with the car is running and you raise the RPMs to +2500?

Watch the high beams on a surface like the back of a garage - do they get brighter and dimmer as the RPMs change from idle to +2500 RPM?

These are questions probing the correct operation of your car's voltage regulator which is likely built-in to the alternator if it's like the one I just changed out in my Honda.

 

What LCD Unit do you have? Check your settings on the lcd as that may have to do with why its dimming. If you have an 'auto dim' setting try turning it off to see if that helps.

My apologies if you've already tried that. I have an lcd that dimmed & I wasnt aware that it was default to 'always on'. Also check your wiring. Make sure your power & battery connections are spliced in correctly & solid.

 

Wow, paul350z, all of that was probably just over my head, lol. I will give those a try and see what happenes.

As for what LCD, i have an innovatek, i know its a cheap one, but it works for what i need. I don't think there was a menu setting to set auto dim. Was it a menu setting for yours pgh2atl?

 

What happens to the screen when you turn on the headlights on high beam with the car off?

What happens when the high beams are on with the car is running and you raise the RPMs to +2500?

Watch the high beams on a surface like the back of a garage - do they get brighter and dimmer as the RPMs change from idle to +2500 RPM?

I've tried these and nothing changes the brightness of the screen. Only thing that does make it brighter is if I turn off the car. What is this voltage regulator? Do I just put it between the 12v power line?