Now is the time to plan your new projects for 2022 and select the best Raspberry Pi hardware. This guide is based on real experience across real projects, both successful and ones where the hardware was not ready for the workload.
Who would use a Raspberry Pi computer? Anyone with an interest in hardware configuration, detailed programming, light weight computers, low power computers, or direct interfacing of computers for control of robots, machinery, irrigation systems, almost anything.
The Raspberry Pi range used to be limited and now has both smaller, more powerful and capable models, plus bigger better options. You need to look at the range again before deciding what you might use.
The top end Raspberry Pi models compete with the lighter weight options from Intel and AMD. The lightest weigh models are too small for project development and may be ideal for the end product.
Raspberry Pi Pico
The Pico is a controller chip, not a regular computer. You could use a bigger Pi to develop some code to go on the Pico for something like controlling a water irrigation system. You need the Pico, connecting wires or header pins, and a microUSB power supply. The example code is written in a special version of Python.
The advantage is a cheap way of controlling things that accept a 3.3 volt digital signal. The disadvantage is the lack of grunt to run any sort of display or feedback direct. You have to send data to something else, like a Pi Zero W, to connect to the network.
What you might do is run your project on a Pi 3B, or 3B+ or 4, and run digital lines out to the Pico as a kind of switch. Using the irrigation example, you interact with the 3B. You install a Pico in each area of your garden. One wire from the 3B to each Pico. Multiple wires from the Pico to water sensors and irrigation control solenoids.
With the low cost of the Pi Zero W, described below, I would use a Zero W instead of a Pico just to save development time and wiring.
Raspberry Pi Zero
The Raspberry Pi Pico is the smallest option and needs lots of add-on hardware for development work. The Raspberry Pi Zero is a good choice for something small, low power, and low cost. In many cases it is best to learn and develop on something bigger, like the model 3B, then move to the Zero for beta testing then optionally down to the Pico if the Pico is suitable.
The Zero has a single core running 0.5 GB, GigaBytes, at 1 GHz, GigaHertz, and is enough for command line work. You can just squeeze in the desktop version of the Raspberry Pi OS although the interaction is slow. I usually do the desktop stuff on a model 3B then move to the Zero when the project is ready to run by itself or for management through a network without a screen attached.
The Zero has a processor that does not run everything you can use on the 3B. Both use an ARM processor. There are dozens of versions of ARM processors. The 3B runs an ARMv7. The Zero uses an ARMv6. Some software depends on the extra instructions in the ARMv7. Those programs crash in the Zero. If you run one of those programs in the command line, you might get a message like "illegal instruction".
The Zero has a camera socket for input using a special Raspberry Pi camera and a mini HDMI socket to run a permanent display. There is a single USB style socket for power and a USB 2 socket for connection to a keyboard or hub. You could use a Logitech style wireless wireless connection to a keyboard and mouse. A powered hub would let you connect a backup disk.
The Zero has no network connection built in, just a USB port where you can attach a USB hub containing a network adaptor. There is the newer Zero W for Wifi.
The Zero is painfully slow for most things you do during development. Using a fast microSD card helps with some things but not many. That really fast microSD card will make a bigger difference in a Pi 3B, 3B+, or Pi 4. You can then transfer that card to a Zero for the final tests.
The Zero is slow to boot so use the Zero for things that are on all the time or that can be switched on a couple of minutes before you need it.
The Zero is slow to update a GUI, a Graphical User Interface, so choose things that run will not display or in a simple text window.
The Zero W is a Zero with an added Wifi connection through a tiny surface mounted antenna. The Wifi range is impressive when compared with low cost plug in devices. The Zero W also includes Bluetooth plus Bluetooth low energy, BLE. You could start with Bluetooth mouse and keyboard then work towards remote management over Wifi.
The Zero W is also limited by an ARMv6 instead of an ARMv7.
For many projects, the Zero W would be better than a Zero with a plug in Wifi option. There are exceptions.
A Zero W inside a metallic container would have problems, something you could avoid by using a regular Zero with a Wifi antenna you can mount outside the box.
For a project destined to use a Pico or equivalent, you will have to add Wifi somehow and should start development with the potential Wifi add-ons so that you can test their working range.
Automation can often use low speed one or two wire protocols in areas where Wifi suffers interference.
The cheaper plain Zero would be a better start point for anything not using the Zero W built in Wifi.
The 3B doubles the memory, 1 GB, when compared to the Zero, and bumps processing up to four cores at 1.2 GHz. You get Wifi and Bluetooth the same as the Zero W. You get four USB 2 ports making the device comparable to a Zero with a USB hub plugged in. There is an Ethernet port, although only 0.1 Gigabit.
The power connection is the same, you just need more amperage to tun the USB ports. The HDMI socket is full size saving you a special cable or adaptor. This is the initial development machine you can use with everything, keyboard, mouse, screen, network, and backup disk until development settles down to the point where remote operation is viable. You can pull the final microSD card from the 3B and plug it straight into your Zero.
The 3B+ adds a little speed to the 3B with processing bumped up to 1.4 GHz. The 0.1 Gigabit Ethernet is upgraded to 1 Gigabit but internally is limited to 0.3 Gigabit as it is connected through the USB 2 component. The 3B+ is not worth the replacement cost if you already have a 3B.
The 3B uses an ARMv7 chip and the 3B+ has an ARMv8. Currently all the Pi software runs on both versions, it is only the ARMv6 in the Zero that causes problems.
Given the current tiny price difference, I would buy the 3B+ instead of the 3B when I need an additional device. There is also the model 4 when you need extra Ethernet or USB speed.
The Pi 4 bumps up the core speed a tiny amount to 1.5 GHz and doubles the memory to 2 GB. Now you can run applications Like LibreOffice on the same machine to document your development process.
You get the choice of 2 GB, 4 GB. or 8 GB of memory, enough to run all sorts of weird development tools. The main advantage is running all the tools together instead of stopping one to start another.
The processor has the extra grunt to run two HDMI displays and can run them both at 4Kp60, a good option when you want to do something like look at code along side the working application.
Two of the USB ports are pushed up to USB 3, a big advantage when you want to process video files on external disks. The same speed increase lets the 1 Gigabit Ethernet port run at full speed, making the Pi 4 better for file and media servers.
You can choose one of the Pi 4 options to run your development project on the same machine as your email and everything else. When development is close to the end point, move the project across to the target Pi so you are not blinded by the model 4 speed.
Raspberry Pi 400
The Pi 400 has the chips from a Pi 4 spread out on a long circuit board inside a cute keyboard. The different board shape places all the ports and pins along the back of the keyboard. This could be fun for teaching very young children.
The actual keyboard is a cramped notebook keyboard and should be avoided for any serious work. You want a real keyboard for full speed typing. I think they should have the option for a keyboard with real key movement, space to separate out the frequently used keys, and a touch plate like some full size keyboards. They would then have space for an optional battery and an SSD.
Project development can be divided into design, alpha, beta, release, and maintenance phases. The design phase could use a Pi 4 with 8 GB connected to two 4K screens. Repeat once for each designer. The big speed limitation will be storage so attach top end USB 3 SATA III SSDs. Given the uptake of NVMe SSDs, there could be a few discarded SATA III SSDs on sale real cheap.
Alpha testing is less demanding and can reuse the Pi 4 with, perhaps, the 4 GB version. The difference in cost of different choices in screens and keyboards is fifty times more than the minor cost difference between a 4 GB and 8 GB Pi 4.
Beta testing requires realistic performance. Let the developers keep their Pi 4s for documentation and coding. Move testing on to the slower cheaper board selected for the final product.
Release and maintenance phase require lots of online interaction. The minimum for a Web server would be the Pi 4 with 8 GB and two fast SSDs in the USB slot.
If we insert a learning phase, your investment of time is the big factor. Cost is next as you have no money and no investors. The model 3B or 3B+ is an excellent learning tool without pushing up the cost. The 3B would match the cost of any cheaper model when optioned up with a USB hub and Ethernet or Wifi.
In my case, I had some old USB 2 hubs left over from upgrades to USB 3. I had old 2.5 inch USB disks and small mSATA SSDs left over from upgrades. I bought a Pi Zero before the Zero W arrived. I reused lots of parts to make use of the cheapest Pi. Now I do most of the work on the Pi 3 and move the result over to a Zero or Zero W only when the result is stable.
The Pi models are low power compared to their performance and a great choice for locations where power is limited by a solar array or operation from a battery or the summer trickle of water through your hydro power. The Pi devices do not need fans, making them the quiet choice and the device you can build into something else. With no moving parts, you can walk away from the installation and forget physical maintenance.
To complete the quiet maintenance free operation, you would use SSDs instead of disks and make sure the power supply has no fans.
Experimenting with a Raspberry Pi is fun and relatively low cost. Now that the range has expanded, you are no longer limited by where the project may end up. Just choose one big fast model for faster easier development then look at the smaller models for the final product.
You could start your Pi choice from a current desktop perspective or a notebook or begin with the end, what you need when you mass produce the product. The earlier comparison of models should help.
The minimum end point is a Pico but the Pico is not suitable as a full development environment. If the Zero is your end point, life is easier because microSD cards from bigger models plug straight into the Zero.
The Pi 3 can replace a notebook and a Pi 4 can replace a small desktop. For a desktop, you can unplug everything from the computer and plug it into a Pi 3 or 4. The only bit you have to change is to move internal disks into USB enclosures. A notebook will already have magnetic disks in 2.5 inch size ready for inserting into a USB 3 enclosure.
Any disk can go into a USB enclosure. The total power from USB 2 is limited which means choosing low powered devices or enclosures with external power. The Pi 4 has USB 3 for extra power to run any 2.5 inch disk.
Desktop operating systems and applications do not transfer direct from the Intel/AMD architecture to the Pi ARM chip. You install operating systems and applications compiled for the Pi ARM architecture. Life will be easier if you can configure your Pi while the predecessors are still in use to provide Internet access.
With your old system still active and a new keyboard/mouse/screen for development, you can learn in real time with all the documentation and examples online. My Pi projects started with the leftovers from a desktop that could no longer be maintained in a useful way. I had the best mouse for my hand, an excellent full size keyboard, a decent screen, plus both wired and wireless networks. I also had a working desktop and a great notebook for reference.
The other resources were required when the Pi 3B was the top of the range. The Pi 3B USB 2 could not search my really big disks at sufficient speed. For those projects, the Pi 4 with USB 3 would be the perfect match. The Pi 4 would have also solved the two screen problem for some projects.
Operating system installation
The Raspberry Pi OS is downloaded as a compressed image. Expand the downloaded file to the image then write the image to a microSD card. The image on the card will be something like 4 GB until you first boot from the card. During the first boot, the OS will expand the last partition, fsroot, to use all the space on the card. You cannot add anything to the empty space or the boot will fail. You can add things to the fsroot partition after writing the image and before the first boot.
I write the image with my notebook. I then copy in some configuration scripts and run the scripts after that first boot. An 8 GB microSD card was recommended then 16 GB and now, for the Pi 4, a 32 GB card. I use some old 16 GB cards for my Zero and Zero W. For the 3B and up, I use 32 GB with, perhaps, a USB SSD.
The installation sets a password, the screen, and asks if you want to update all the packages. The package update is a waste of time on a Zero and still too long on a 3B. I perform the initial boot on a 3B, skip the update, then run a script to configure the machine the way I want. After everything is working, I start an update script and walk away to do something useful. The update runs several steps, package list update, install useful utilities, upgrade packages, autoremove, and purge.
The low cost of the Raspberry Pi devices means that most projects are limited by the cost of everything else, the screens and disks. My best keyboard cost more than a Pi 3B.
The cost of cables, adaptors, and a USB hub on one project cost more than the difference cost between a Pi Zero and a Pi 3B. I proceeded with the Zero purely because I had the USB hub and most of the other parts left over from other projects.
Some local shops have the Pi 3B and 3B+ within a dollar of each other, making the 3B+ the logical choice out of those two. Then you see the Pi 4 for just a few dollars more.
In one local shop, the smallest Pi 4 is only $2 more than the Pi 3B+ while another has the price difference at $9. $9 or $2 per unit might be important when you need hundreds but for your experiments and development, that small cost difference is silly, buy the Pi 4 for the faster USB. You will save many times more than $9 of your time.
When you add in the cost of an adaptor from mini HDMI to regular HDMI, the total cost mounts up. You can buy a mini to regular HDMI cable for almost the same cost. Using the right cable is often no more expensive and reduces time wasting mysterious incompatibilities. Little differences like that can change the cost of a project from $5 up to $70 or add days to the debug time.
For the USB hub on one project, I had the hub for free as scrap from a previous project but I had to buy an adaptor or a replacement cable of the right type. Both were stupidly expensive. The adaptor also made the result physically too big. A few days later, I accidentally found the right cable when shopping for something else and the cable just happened to be on sale real cheap. That coincidence chopped $6 off a project that should come in under $100 but had started at $140.
Books on projects
The people behind the Raspberry Pi create books full of projects and a monthly magazine full of ideas. You can download the magazines and many of the books for free, making Raspberry Pi experiments cheaper than those brands where you have to buy several books for $30 each.
The Speed, Quality, Cost question
Service companies may talk about speed, quality, and cost then ask you to choose two. Cheap components often fail in mysterious ways, blowing out your time and reducing the final quality. Start by investing your money in known good brands. After you have experience and something working, you can test cheaper options. When you have problems with a cheaper component, swap back to the known good component.
For one model Pi, the online cost in Australian dollars, before delivery, varied from $81.77 up to $189. Where should you look for Raspberry Pi products in Australia?
Start with Little Bird, littlebirdelectronics.com.au, with a Web site dedicated to the Pi, raspberry.piaustralia.com.au. Little Bird provide the official parts and the best support. They sometimes include free delivery and they often have excellent kits for beginners. This is the best place for first time buyers.
Core Electronics, core-electronics.com.au, is a company with a bigger range of products. They are sometimes cheaper than their competitors and at other times slightly more expensive. Their bigger range means you may be able to buy something with a better fit. Perhaps you can get a right angle cable for a tight spot. Core is the second place I look.
RS Components, au.rs-online.com, have a huge range of parts outside their Raspberry Pi products and might have all the components you need to complete a project. They have good prices on alternative brands for things like power supplies. They sell in bulk when you need a hundred items. If you have no experience with building computers, start with Little Bird, buy genuine Pi products as a reference and look at RS for the extra things not stocked by Little bird or Core.
Amazon Australia are way over the top too expensive for genuine Pi products but can be a good place to shop for USB items and storage devices.
While eBay, Aliexpress, and others occasionally have a good deal on something, you really have to know everything in fine detail about what you need. You then waste time sifting through all the junk. I sometimes use those sites to buy odd generic items like little plastic spacers.
Pi 4 memory
The Pi 4 is available with 2 GB, 4 GB, or 8GB of memory. I used the same software on a machine with 4 GB and rarely used 2 GB. 4 GB gives you the margin to add other things like LibreOffice to write documentation while developing on the Pi. When software needs more than 4 GB, you usually need a faster process which pushes you up into Intel land. For those projects, you might recycle an old notebook computer.
Notebook computers have everything, processor, USB ports, Ethernet, Wifi, and a battery. A six year old medium price notebook has as much speed as a Pi 4 and has a battery to keep the machine running when the power runs out. A Pi 4 fitted with an uninterruptible power supply, screen, keyboard, and an SSD for bulk storage, costs more than an equivalent second hand notebook.
Buying a used notebook is like buying a second hand car. Buy a model you know. Buy from someone you know or someone with a good reputation for service. Check how you replace the disk and battery if needed. You can then plug the notebook in, load Linux, the right software, and build many projects you might have put on a Pi. Things like file servers.
The notebooks do not have the GPIO pins but they can connect to a Pi through USB or a network. You might use the notebook as a central controller for a network of Pi devices.
Buy a Pi. Experiment. Have fun. Start with a Pi 4 with 4 GB. Add a Pi 3b+ then a Zero W.