Modify Your Composite LCD to Work at 5v

To purchase a 4.3″ LCD with the following process already completed, visit the store.

Most of the available composite LCDs are made for 12v supplies. Some of them work at 5v, but most only work properly between 6-12v. The ones that do work at 5v usually work very inefficiently.

This tutorial will show a method of adapting the driver to work at 5v, matching the operating voltage of the Raspberry Pi. It applies to the drivers with a 1509 buck converter only. LCD’s with other buck converters function a similar manner, but the pinouts may be different. Please do research before proceeding if you have a different component.

sam_0401circledHere is a typical driver board for a composite LCD. This the driver for the 4.3″ LCD that’s used in the PSPi projects. It has 4 inputs: +in, GND, composite 1, and composite 2. The +in is usually 12v, which then routes through a buck converter, and this converts it to 5v.

The component that’s circled is the buck converter, and it usually has some variant the number 1509 written somewhere on it.

Remove this component entirely, while avoiding damage to the surrounding components. I normally use a rework unit to accomplish this.

 

 

 

ap1509

Once the component is removed, the buck converter circuit has to be bypassed. So we first have to determine the location of Pin 2 (the 5v output of the component we removed) on the board, which is pretty easy using this image from the AP1509 datasheet (available here). One side of the component has Pins 5-8, and all four pins connect together to GND. This means that the traces on the board will all be connected to each other.

Now that you determined where Pins 5-8 are, you can see that Pin 2 is on the opposite side. This is where we will now be connecting the +5v power input.

 

 

 

sam_0401line

On my driver the left pin was the original +in, and I wanted to keep it this way. I was able to easily do this because there was a second +in solder pad above the original one. All I had to do was solder a wire from the pad to the Pin 2 location. This is shown here with the red line. Obviously the component will be gone at this point, but this should give a good representation of what needs to be done. If you don’t have a driver with the 2nd solder pad, then just connect the +5v directly to the Pin 2 location and everything will work exactly the same. Be careful not to bridge any connections or damage surrounding components in the process.

8 thoughts on “Modify Your Composite LCD to Work at 5v

  • November 8, 2016 at 5:39 pm
    Permalink

    Hi,

    In your “install lcd composite tutorial” you don’t mention any “hardware modification” to the driver board. And when i look at your pspi v2 pictures, the driver board hasn’t been modified.
    I’m new at this and i was wondering if the component have to be desoldered in order to work with pi zero for instance.

    Thanks for your answer

    • November 8, 2016 at 5:58 pm
      Permalink

      The LCDs I purchased in the past had a different voltage regulator and worked fine at 5v, but the new ones had a design change and no longer do. I’ve tried a dozen different vendors and everyone is selling the one shown in the picture (or one very similar).

      You might get lucky and find one that works out of the box, but it’s unlikely. The one I link to in the LCD Product Page has much lower power usage than any other one I’ve used, so that’s why I chose it.

      • November 8, 2016 at 7:04 pm
        Permalink

        Thank you for your quick answer!

        Do you think it’s possible to remove the buck converter without a rework station?
        This component is really tiny and close to other smaller components.

        • November 8, 2016 at 7:21 pm
          Permalink

          Yes, as long as you’re careful. Holding a soldering iron on each pin and then bending them up would work. You could also cut the pins with some small side cutters and remove the chip.

          • November 8, 2016 at 7:31 pm
            Permalink

            Just tried it with a hobby knife^^
            I cut just 4 pins on one side and then gently bent the buck converter with tweezer.
            The result seems pretty nice to me, hpe it’s still working…

            Keep up the good work, your projects and tutorials are really great !

  • December 29, 2016 at 9:17 pm
    Permalink

    I purchased a very similar board of amazon, except instead of the AP1509 my board had a XL1509-5.0E1. The two chips have the same pin configuration so I went ahead with the modification, removing the chip and adding a wire connecting the positive pad to the output. Except this doesn’t seem to have worked as my screen will not light up at all. Any thoughts?

    • December 30, 2016 at 1:18 am
      Permalink

      Will you post a picture of this board and the chip in the forum? You have me curious.

Leave a Reply