Fun with a Raspberry Pi

It's almost an overused statement, that there's more computational power in your <insert common electronic device here> than it took to put a handful of men on the moon.

Never has this been more obvious to me than when the Raspberry Pi was first released.

However, the moon landing happened over 50 years ago. So I sometimes wonder the relevance of such comparisons. Computers have exponentially increased their power since their almost quaint beginnings back then, while coming down in cost at nearly the same rate. Nonetheless, when you have a fully functional desktop computer, (sans the keyboard, mouse, and monitor) the size of a credit card, that costs less than $200, even $100 (for older lower spec models) which truly does have more computational power than the Apollo 11 spacecraft I can't help but appreciate the progress we've made in the last half-century or so.

So what is a Raspberry Pi, really?

It is a computer in the truest sense of the word. Only it is the size of a credit card due to an amazing feat of technological origami. The circuit board, includes the CPU not unlike those found in a mobile phone or tablet, video card, stereo output sound card and RAM. These are soldered to the board, and as such are not upgradeable or repairable. Newer models boast Wi-Fi and ethernet connectivity as well as Bluetooth included "on board", as well as better specs in both CPU and RAM. However, they also require more power to run reliably. Older models may need accessories to add WiFi/Ethernet/and Bluetooth functionality.

You might be wondering; "what about the hard disk?".

Well you might be surprised that the hard disk role has been effectively... an SD Card, or micro SD card, depending on the generation of Pi. Given the low power requirements (16W for the 4th gen, less for older models), and modest speed requirements of the Pi, this has been a very effective option.

The most modern release of the Pi (which at the time of writing this article is the Pi 4) has also been used with USB3-connected solid state drives to increase the performance even further. However, that still needs a bit of a "kick start" by booting from a SD card to get the SSD to work, then the SSD can take over and turbo-charge the Pi. (at least at the time of writing this article).

So, it's a low-spec computer (by todays standards)...

The computer side of the Pi offers a cheap, low power, but still effective means to run a computer system, and all that it implies. It's possible to check emails, play older games, browse the web, read, write and modify documents and even stream videos from online sources. However, older models may struggle a bit with some of these tasks if they're typically done with "better" hardware.

In classrooms across the planet, Raspberry Pies are used to teach basic computing, electronics, and even programming to children and adults alike.

The Raspberry Pi isn't just a stripped-down computer. Its low power requirements, size and weight have been used in countless applications where larger, more powerful (and power hungry) computers cannot go. Ranging from drone mounted wildlife radio tracking equipment to DIY telescope tracking and control systems for serious hobbyist astronomers. A Raspberry Pi can be found anywhere a mobile, programmable controller can be used, and has the ability to connect and control an incredibly wide variety of devices.

Going beyond the mere computer features, the Raspberry Pi has a convenient general purpose input/output (GPIO) port designed to connect any number of circuits, sensors, motor controllers, and displays. In short, it is a computer that has the connections to build, and test your own electronic devices.

While electronic enthusasists will make their own DIY circuits to do any number of weird and wonderful things. From creating a barbecue controller that will email you if the flames go out, to robots. You don't have to spend hours with a soldering iron to get going with a Raspberry Pi.

There are alternative, pre made circuit boards (usually the same size as a Pi) which are called "Hats", which basically just plug into the Pi and sit on top like a "Hat". Hats come in all shapes, sizes, and purposes. Some stand alone like a small screen, while others enable you to connect even more elaborate circuits to the Pi. Sometimes, hats even pass the pins through the circuit board, so you can literally stack hats on top of one another. However, you have to make sure that you don't try to use the same GPIO pins for two different hats.... well maybe you can get away with sharing power/ground connections. :-)

Some fantastic hats include:

• High quality audio hats such as:
  
  • HifiBerry DAC
  • Amp hat, DAC hat, and Digi hat by Justboom
• TV hat: Yes, you can plug in your TV antenna and watch digital TV channels.
• Uninterruptible power supply hats:
  • Uptime UPS hat. Adds battery backup for powering the Pi during power loss.
  • PiJuice hat. Does the same thing, but can have solar panels, and shuts the pi down properly before the battery is utterly exhausted.
• Robotics/Sensors
  • Sense Hat, has a lot of really interesting sensors, accelerometers, magnetometer, air temperature/humidity sensor, gyroscope, a little joystick and a colour LED matrix display.
  • Servo Hat: Can connect up to 16 servo motors.
  • Automation Hat: can connect a series of relays, and sensors to the Pi, but does not include the sensors themselves.

There are many others, of all kinds. GPS, Power of Ethernet, Long range radio links, microphone arrays for making voice activated devices, analogue to digital converters (ADCs), realtime clocks (RTCs), serial connection interfaces, various break out boards (BOBs) which provide more ports than you probably know what to do with.

No matter the type, hats basically save you a ton of soldering and fiddly wiring. However, there are "prototyping hats" are largely blank to begin with, and they enable you to design and solder up your own circuitry, and simply plug that into the Pi.

With more hats being made every day, you are only limited by your imagination, and ability to come up with creative solutions to real world problems. :~)

Raspberry Pi Vs. Arduino:

Another popular (even cheaper) programmable controller is the Arduino. Unlike the Pi, the Arduino is more programmable micro controller than computer. As such, it offers no desktop interface, no typical PC keyboard support, and you can't just plug a monitor into it. It only has USB (for power/programming purposes) and it's own equivalent of the GPIO ports, with both digital and analog pins.

The advantages of the Arduino are:

• It handles analog signals natively (the Pi does not, without an additional Analog to Digital Converter, also known as an ADC),
• It's cheaper, and...
• While it can run a screen it doesn't do so with conventional computer monitor ports.

An Arduino, once programmed, is effectively configured to do one task in a continuous loop from the time it is turned on until it is turned off. Such a task might be monitoring temperature, or controlling an irrigation system, but it won't be able to do things like browse the web, or ever edit a Word document.

The disadvantage of the Arduino is that it is significantly more restrictive in the way that it works. You see, it only uses a variation of the C programming language, so to use anything else, you'd have to pass the signals/data onto a more capable device to use more elaborate functions on the data from there.

However, it is entirely possible to connect an Arduino to a Pi, and have the best of both worlds, as long as you work within the limitations of each and configure the effective communication between the two.

Finally, it is possible for the Pi to be connected to a cheap Analog to Digital Converter (ADC) such as the MCP3008, which is a simple chip and cheaper than adding an Arduino.. so if you only need a few analogue inputs, then this might be an easier option. There are many other ADCs out there, some have more inputs, or greater "resolution". If you're wondering what resolution means, the MCP3008 is a 10 bit, 2¹⁰or 1024 level ADC. That means there's 1024 levels between completely on, and completely off instead of merely on and off as digital signals would normally be transmitted.

Is it all about the electronics?

The Raspberry Pi, and other popular controllers like the Arduino aren't just about the electronics you can connect to them, what the Raspberry Pi offers the possibility of using multiple programming languages and frameworks (individually or collaboratively) to get the job done. This is something that the Arduino (and similar controllers) can't do. So the Pi is a great "brain" to the Arduino's leg and hand work.

For instance, you can run a full computer suite (including desktop, web server, database). Use a program written in Python to collect data from sensors and store it in the database of your choice, then use PHP, Java, Javascript, SQL, Ajax, Perl, Node Red and JSON (just to name a few) individually or collaboratively to depict that information and provide a control interface.

In short, you can do whatever you like, however you like, and make it as simple or complex as you desire. Within the limits of computational power than Pi provides, of course.

Common uses:

People use Raspberry Pies to teach/learn about electronics, build programmable robots (such as CNC mills/routers/plasma cutters), monitor environmental data such as weather stations, temperature and humidity in greenhouses, storage places, and food production. Another popular use is monitoring air quality and radiation in laboratories, industrial sites and cities. Raspberry pies can also be used in any number of home automation applications such as workshop dust extraction, lighting, solar power monitoring and door controls.

Why DIY with Raspberry Pis?

The truth is that many dedicated commercially available devices such as specialist temperature and humidity controllers, computerised home automation and building management, are actually more expensive than the Pi and Arduino. People with technical skills (or the desire to learn them) can build amazingly customized, efficient, and most of all effective devices that are not only a match to commercially available products, but surpass them. Better yet, once you build a system from scratch, you can easily maintain the device or modify it as your needs change. No licenses, no maintenace contracts, no terms and conditions, just complete freedom. Of course, you can also choose to buy licensed software if that is what you want to do.

Be warned though, there is a learning curve. But there are some amazing instructions on how to build Pi-based projects. You can find some of them here:

https://projects.raspberrypi.org/en/projects

So can I use a Pi instead of buying a new PC?

Having said the many wonderful things that a Pi can do, the Raspberry Pi models 1-3, and even the lowest spec Pi 4, haven't really been what I would consider a true alternative to a full-blown computer.

The Raspberry Pi's CPU is based on entirely different architecture to the common PC, and as such there are some compatibility concerns with popular software. However, the 4GB & 8GB RAM models of the Pi 4 can take advantage of both 64Bit operating systems, and run even Windows 10 reasonably well.  The 2GB RAM model Pi 4, and the previous 1-3 generations are not viable desktop replacements because they don't meet the minimum required hardware specifications.

However, if you plan to go down this route, I would strongly suggest adding a cooling fan to your Raspberry Pi. Also, please note that if you buy a Pi, you have to still buy an SD card (I recommend a UHS-II rated one for performance) or USB SSD card, keyboard, mouse and monitor. The Pi 4 uses MICRO hdmi ports, and so you'll need an adaptor to plug in a standard HDMI monitor.

Naturally, if you want to run Windows, you'll also need to have/buy a license and be ready to put in some serious time to install it. Online reports suggest that it is not a trivial or established process yet.

Conversely, if you're happy with the free Raspbian (or similar) operating system, you can run things very well, and build your own SD card easily using the instructions found on the Raspberry Pi home page. Raspbian even includes a free edition of Wolfram's powerful mathematics software, Mathematica.

I'm currently in the process of building a Raspberry Pi based weather station, and I'll include that in my next article.

I hope this helps you delve into micro PCs, electronics, and fun projects that teach you some interesting tech skills.

Have fun and stay safe!
Ham.