Build an Open Source Computer: Raspberry Pi

For under $150—including monitor and accessories—you can build a fully functional open source computer. This computer has a tiny footprint and is useful for all kinds of creative projects. This is also a great way to equip classrooms for learning at a reasonable cost.

What we'll build: Raspberry Pi 4 Model B with peripherals

This post shows step-by-step how to build a fully-functional open source computer called the “Raspberry Pi.” This walkthrough is for complete beginners. The entire process should take under an hour of hands-on time, including shopping for the parts.

This specific setup cost $246.62. Most of that was the new monitor ($90) and mechanical keyboard ($65)—both of which were purely for convenience and preference. Had I been frugal, the full thing would have cost closer to $130.00. If I was aggressively cheap, well under $100.

When you finish this post, you might try installing Ruby on Rails and start building web applications. Questions, comments, feedback? Email me.

Table of Contents - How to Build The World's Simplest Personal Computer: Raspberry Pi

  1. Introduction
  2. Parts
  3. Setup
  4. Operating system
  5. Turning it on
  6. Shopping list

A. Introduction ↑ Table of Contents

In the early 2000's, a group of teachers, academics, and computer enthusiasts created a miniature computer to inspire creativity in children (full story here). They called it the Raspberry Pi.

About a decade later, in 2012, a UK-based non-profit—the Raspberry Pi Foundation—began selling Pis to the general public at prices from $5 to $35, depending on the model.

At such a low price tag, and because of its kid-friendly roots, you might ask, “is the Pi a toy?” It's much more than that. The Pi is an excellent tool for a variety of programming, electronics, Internet of Things (IoT), and hobby projects. With the Pi as a launchpad, you can learn skills that fetch well-paying jobs in a variety of industries all over the world.

In addition to hobby uses, the Pi also occasionally pops up in higher-profile use cases. For example, earlier this year, two university hospitals in Bogota, Colombia tested the Pi in emergency-use Covid-19 ventilators. Pis have also traveled to space:

Northern Europe from low Earth orbit taken with Raspberry Pi (Source: Raspberry Pi via YouTube)

Below is a fully-illustrated, step-by-step post showing how to source, assemble, and start up a Raspberry Pi computer. Depending on your needs, this machine may be powerful enough to use as a basic home desktop computer. I chose something modest because simplicity is my primary goal.

The Pi runs entirely on open source software, including a Linux operating system. This means all of the source code is freely and openly available. This is possible through a large community of developers who build software together. Open source software is like public land: it's for everyone to share.

Building a computer on open source software is a valuable exercise for several reasons. You will better understand the interplay between community-powered computing and commercial computing. And you will always have access to computers and applications for a tiny fraction of the cost of retail computers.

B. Parts ↑ Table of Contents

I ordered everything on Amazon, both for convenience and so anyone anywhere could replicate this build. A detailed parts list (with product screenshots and purchase links) is at the end of this post.

The Boxes

We'll start with the parts arriving at my front door.

The packages arrived about three days after I placed my order. I live in a rural area. It's probably way faster in the city.

Here's what was in the boxes:


A 21” monitor was in its own box. It came with a VGA cable (pictured above, blue ends). The other two cables are the power unit. I chose this monitor because it was cheap, new, and had an HDMI input. It cost $90.

I could have saved about $60-70 by going to a thrift store and getting used peripherals and cables. I opted for a new monitor because this computer will live in my office. I wanted something that looks, smells, and works like new.

Raspberry Pi

This is the actual “computer.” This particular version is a Raspberry Pi 4 Model B. It's 8.5 centimeters wide, 5.6 centimeters deep, and 1.6 centimeters high. If you're interested, detailed measurements are here. (transparency is one joy of open source.)

I explain below what the various inputs and outputs do. For now, all you need to know is that this little thing is the computer.


To keep the Pi safe, I bought a metal case. A case is not strictly necessary. I wanted something that wasn't an open circuit board with loose wires that looks decent in my office (nothing but love for loose wires though!). A case also protects from dust and the elements, which is good for the long game.

Keyboard (with cables, extra keycaps, and key changing tool)

The keyboard was an optional upgrade. I enjoy mechanical keyboards and wanted this Pi to have its own look and feel.1

A cheaper option might be something like this. You can use pretty much any USB keyboard. I chose to upgrade the keyboard because it makes it more fun to use the computer, which makes me more likely to use it more often.


This is an entry-level wired optical mouse. I personally prefer wired mice and keyboards so I don't need to deal with batteries, charging, or wireless connection issues. If you prefer wireless accessories, the Pi has built-in Bluetooth.

Mini HDMI cable

This is the cable that connects the Pi to the monitor. Little end goes into the Pi. Big end goes into the monitor.

If you're using an older monitor (cheaper), you might need a VGA to HDMI adapter.

Power supply

To keep the cost down to a bare minimum, the Pi ships without a power supply. You can use a number of external USB-C power supplies. However, after skimming a few posts about power delivery issues with the Pi 4B, I decided not to risk it and just bought a Pi-sanctioned power supply. I didn't want to turn this post into an electronics tutorial, so I purchased something I knew would work right out of the box.

MicroSD (64GB, blank)

This MicroSD chip serves as a 64GB hard drive for the Pi. The tiny MicroSD chip (smaller than my fingernail) is the actual memory unit. How cool is that?

The larger piece is the adapter for an SD card reader, as described below.

You can also buy MicroSD cards that load via USB thumb drive, which may be a better choice depending on how you plan on downloading the operating system. Alternatively, if you don't have access to a computer for downloading and saving files to a MicroSD card, you can buy cards with preloaded operating system files.

I decided to go with a blank MicroSD card and load the necessary software onto the card myself. I describe the entire process below to show how simple and non-intimidating the process is.

C. Setup ↑ Table of Contents

Now let's turn these parts into a working computer.

First, the computer:

Here are the inputs and outputs you should understand: