Step 1: Choose Your Raspberry Pi
Step 2: Choose Your Screen
Not all screens are the same, and if it was cheap, it's probably not the best quality screen. If you're having problems with the raspberry pi detecting the right screen height and width, adjust the overscan settings in config.txt. To access the config.txt file, remove your SD or MicroSD card, plug it in your computer, and it's in the root directory (boot). Edit it with a program such as Notepad++.
Step 3: Installing Retropie and Drivers
Once that's done, flash it on to your SD card ( must be at least 4 GB). Now you have to install the Retrogame driver, to enable the use of buttons and joysticks wired to the gpio. Here's a download link with instructions on how to install it:
However, all this can be a hassle. So here's an image of Retropie 2.3 with everything installed, ready to use, compiled by Instructables user rbates4:
EDIT: New link
All you have to do is flash it.
Step 4: Test It Out
Step 5: Buttons and Joystick
First off, you're going to need a joystick. I found mine in a local electronics store in Spain. I also found one online which is nice and works perfectly with the arcade machine:
You're also going to need buttons. I decided that 6 buttons were good enough, but I'd recommend getting 10 if you want to easily play any game. These should work fine:
The picture above shows where each button and joystick pin must be wired. The (opt.) mentioned after a few of the pins means that it's optional. I use my arcade without them. Due to a small amount of ground pins, I soldered all the ground wires together from each button and joystick, and just used 1 ground pin, which is depicted on the image.
Now just go to Retropie, use your keyboard and to access the start menu, select configure input, and set your selected buttons to whatever you want.
Step 6: Building the Body
Since the monitors differ from one another, the casing for the arcade machine will differ. My dimensions would be useless, so here are a few pictures of the main design. I used a sliding back cover to easily access the electronics. I left a hole for the power strip inside, which I use to power the RPi, the monitor, and the speakers.
Step 7: Speakers
If you want sound, you need speakers. The minimum requirement is that they have a 3 (or more) watt amplifier, and that it uses the standard 3.5mm jack. I stuck mine in the area above the screen, and sound comes out well.
Step 8: Optional
I decided I wanted to make the logo glow, like in the real arcade machines. I just used a strip of LEDs, and wired one side to the 5 volt pin on the RPi, and another to a ground pin.