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Backlit Marquee/ 12V Power setup

If you bought the add-on marquee upgrade, or are curious how to impliment your own, here are some helpful points. We will focus mainly on how power the backlight and the changes this makes down the line. 

This section's main goal is how to setup your arcade with 12V power. A needed upgrade when adding on accessories, say a trackball.

if you followed the Porta Pi Arcade manual, you should have everything running on a single 5V supply like so:

To add the backlight, we are going to pick a standard LED strip, which usually run on 12V. Since running on one supply makes things convienent, we need to change how power is distributed in the cabinet; specifically the voltage. The LCD and amplifier I supply in the Porta Pi Arcade can be powered with 5-12V DC. Knowing this, 12V DC will now be the main supply for the entire cabinet ( LCD, AMP, and LEDs). We must add a stepdown converter so the RPi can recive it's 5V DC. A common name for this stepdown converter is also "DC-DC buck" circuit, which you can build your own or buy a PCB that does this. These devices take incoming DC and convert it to a lower DC voltage. For our use, we will use it to step-down 12V to 5V.

NOTE: In my personal cabinets, I stepdown the output for the RPi to ~5.15V since the Pi2 likes to give me the 'under voltage' rainbow square in the upper right display sometimes.


If you buy one of these PCBs on ebay, do note three things: 

1) Make sure the DC-DC converter can supply enough amps for the Pi (1.5amps is a safe minimum requirment for the Pi2)

2) Most of these DC-DC converter in the wild [ebay] are adjustable via a ~5-10 turn potentiometer. Check the output voltage with a trusted meter BEFORE connecting your RPi.

3) Many 'cheap' sellers of these converters [intentionally or unintentionally] lie or round up on their ratings. So cross reference if you have doubts about the power ratings. 


Installing switches are optional, but a nice touch.

I use this guy, which you can find almost anywhere on ebay. I have had no problems with it powering the RPi.

It's an adjustable DC-DC stepdown converter. I found these stats online, note their accuracy varies with the quality of the components on the PCB. Take with a large grain of salt.

Input voltage: 4-35V DC

Ouput voltage: 1.23-30V DC

Input Current: 3A max (some sellers say heatsink req'd above 2A draw)

Switching Freq: 150kHz

Based on LM2596 IC

DC-DC Step down converter in action, Pictured to the right of the Pi
Another inside view.
What the 12V/5V wiring looks like + two switches installed.

You can find LED strips just about anywhere. They are pretty handy around the home/workshop/arcade.

Stick the LEDs strips to the extra wood panel, and fasten to the speaker assembly as shown. 

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