Monthly Archives: October 2016

Build Solar Powered Robots

Your initial thought might be, “Simply add solar panels for free energy!” Not so fast. As I alluded to in Chapter 3, “Rolling Robots,” it’s not that simple. Even if you have a panel big enough to power your rig the way you like it, there’s no guarantee the sun is out. Furthermore, even if the sun is out, the earth’s orbit makes it appear to move across the sky, meaning the voltage generated will fluctuate.

All that being said, there’s a lot to like about solar-powered robots. You can store them away for a couple years and they’ll still work. You don’t have to buy new batteries periodically. Finally, you can do some intriguing things with robotics, like create autonomous crawlers that creep around your yard like a friendly robo-insect. However, even if you do use batteries in your robot, you can have a solar panel as well, to continuously charge the batteries. The best of both worlds!

In this chapter, you’ll learn about how to use these panels in your projects. Then you’ll bone up on breadboarding, which is a cool way of temporarily constructing circuits. Finally, you’ll build two sweet projects. The first is a solar-powered battery charger, and the second is a simple robot that is entirely powered by sunlight .


How Do Solar Panels Work?

Solar cells are layers of semiconductive materials (shown in Figure 4.2) that create an electrical current when exposed to light. The earliest recorded observation of the photovoltaic effect took place in 1839 when Alexandre-Edmond Becquerel’s experiments with silver chloride produced voltage and current when exposed to light. By 1959, all satellites launched into space bore solar panels, and a little more than 50 years after that, we’re using them to power robots.

You often hear different terms associated with solar technology. A solar cell is a piece of photovoltaic material, usually crystalline silicon. Solar cells are often connected into groups on a support structure, and these are called panels. A group of panels is an array.

Solar cells are rated for direct current (DC) output under certain test conditions—a sunny June day in San Francisco, for instance. Measurement is in watts as well as photovoltaic efficiency. Finally, because the output is DC, you’d need an inverter to run household appliances off of it.

There are two kinds of solar cells. The most common are the crystalline silicon wafers I’ve been describing, which are covered in glass or plastic to protect the fragile cells.

The other kind of solar cell is flexible plastic. Called thin film solar cells, or TFSC, these consist of photovoltaic material deposited on a substrate. Originally used for solar-powered watches, flexible-film solar cells are more expensive than crystalline silicon and have a lower efficiency. However, they’re useful for situations where the panel needs to flex, or the weight of the panel becomes a consideration.

Local radio station on your computer or smartphone

You may not know this, but many, if not most, local AM and FM radio stations stream their broadcasts over the Internet. That means you don’t need a radio to listen to your favorite radio station. All you need is a computer or smartphone and an Internet connection.

Although many stations stream their broadcasts from their own websites, it’s often easier to use a streaming radio service or app that can access feeds from multiple radio stations. These services/apps, such as iHeartRadio or TuneIn, let you listen to practically any radio station in the United States, and many more globally. This way, you can keep in touch with your local stations when you’re away from home—or listen to the best of the best from anywhere in the world!


Using TuneIn

My favorite streaming radio app and service is TuneIn. This service streams live broadcasts from more than 100,000 radio stations around the world for free, to any computer, smartphone, or tablet. TuneIn is also available on “smart” TVs from Samsung and Panasonic, and on Roku and Sonos streaming media boxes.

What I like best about TuneIn (as opposed to iHeartRadio, discussed next) is that it’s truly a global service. You can find local stations from virtually every country around the world, which enables you to listen to the best music of any type, anywhere. You’re not limited to primarily U.S. stations, nor to stations owned by a single media conglomerate. (And, yes, TuneIn includes all the Clear Channels stations that also make up the bulk of iHeartRadio’s options.) You get the most stations of all genres from all countries, period.

To listen on your smartphone or tablet, you need to download the TuneIn mobile app. It’s available (for free) for iOS, Android, Windows Phone, and Blackberry devices. On your computer, you listen in by pointing your browser to

After you sign up or sign in to your free account, the TuneIn website displays some recommended stations, based on your past listening experience, along with playback controls for the currently selected station at the bottom of the page (see Figure 1). Use the menu bar at the top of the page to access stations by location, format, or name. (To search for a specific station, enter the call letters into the search box at the top of the page.)

Personal Photos from Being Hacked

It’s all over the news: Somebody hacked into the iCloud accounts of Jennifer Lawrence, Rihanna, Ariana Grande, and other female celebrities and posted their nude selfies out on the Internet for the entire world to see. Now, this sort of activity is not just an invasion of privacy; it’s also theft, and whoever did it (if he gets caught) could face some serious jail time.

But the fact remains that the hacker did do it. Somehow, he was able to access these celebrities’ private iCloud accounts, where all the photos and files from their iPhones are automatically backed up to and stored. Just how did this character break into these private accounts? And how safe are your smartphone photos?


Where Are Your Digital Photos Stored?

Just about everyone these days uses their smartphones to take and share digital photos. These photos are stored on your smartphone, of course, but also end up in lots of other different places.

For example, any smartphone can back up all your photos to your desktop computer. This may happen automatically when you physically connect your phone to your PC, or you may have to initiate the backup manually. Apple’s iPhone goes one step further, activating an automatic wireless backup whenever your phone is on the same WiFi network as your computer. In addition, your iPhone may back up or transfer your photos to other Apple devices in your household, including an Apple TV unit, if you have one.

So right away you see that your photos are spread out all over the house, not just on your phone but also on your computer and other devices. But the photographic migration doesn’t stop there; most smartphones are configured by default to back up your photos online. This type of online backup is referred to as cloud storage, because your photos and other files are stored somewhere in that amorphous cloud of servers on the Internet.

A robot via the Web to perform some activity

Radio control of a robot is one thing, but what if we built a robot that connects to the Web, so we could control it from around the world? It doesn’t get much cooler than that!

Chapter 7, “Harnessing Infrared,” in my book Robot Builder: The Beginner’s Guide to Building Robots shows how to build an Arduino-equipped dart gun that detects intruders with a passive infrared (PIR) sensor and blasts them with a foam dart. In this tutorial, I’ll show you how to give the dart gun (shown in Figure 1) the ability to send you a message via Simple Notification Service (SNS) whenever the gun fires. Talk about intruder detection!


Types of Web-Interacting Robots

What exactly can you do with a web-connected robot? As it turns out, quite a lot! This section covers some of the possibilities.



Sniffer robots search the Internet collecting keywords, and then their programming does something with that collected information. For example, some gumball machines dispense only if a certain keyword appears on Twitter. Some organizations have an LCD screen scrolling with recent keyword mentions.

One advantage of a sniffer system is that it can be controlled remotely with no need for additional hardware—merely a Twitter account. The downside is exactly the same—in that anyone can hijack your robot.



Autotweeter robots send out a Twitter message (tweet) when certain events take place. The classic example is a kegbot that monitors and controls a beer keg. It dispenses beer and measures its temperature, accepts payment, and sends out a tweet when the keg pours a pint.

Recently Twitter changed the way it interacts with external devices, and some old methods of sending out tweets no longer work. However, as long as Twitter continues to be popular, there will be a way to interact with it.



As an introvert, I always dreamed of a robot that could go to family functions and school dances in my stead. I could sit back and direct the robot to roll around, with a camera and screen allowing me to interact with guests. One category of robots actually does that—telepresence bots.

At its simplest, a telepresence robot rolls around carrying an iPad or other tablet, with videoconferencing running on the computer. The home base could include a desktop PC that controls the robot remotely. Some clever hacks have piggybacked the control functionality on top of the videoconferencing feed—one bot creator used black-and-white cards to trigger a light sensor positioned at the corner of the screen.



Some robots, like the gumball machine I mentioned in the sniffer section, are designed to be controlled remotely. Robot arms can be directed from websites, with webcams positioned to show what’s happening. A whole subcategory involves pet toys that let you play with your cat or dog from a remote location.

Some interactive bots are games, such as chessboards with players separated by miles; others are much simpler, the equivalent of robot soccer. Typically interactive robots (like a lot of robots I’ve described here) are designed for fun rather than to accomplish a serious task, but it doesn’t have to be that way!


Home Automation

One category of serious web-connected robots is for home automation. Imagine being able to adjust your window blinds with your smartphone, or having a program that varies lighting schemes when you’re on vacation. These robots can send you data on the status of your alarm system, tell you whether your home’s furnace is running, and more.

This category also includes agricultural automation such as greenhouse controllers, which turn on fans and trigger water valves, measure temperature and soil moisture, and turn on grow lights as needed.


Sensor Net

One of the most intriguing aspects of all these devices connected across the Net is the possibility that you could have all of them measure the same thing and publish that data to the Web, giving you a real-time map of an area.

Virtual Currency Before Bitcoin

Although Bitcoin is the best-known virtual currency, it wasn’t the first. In fact, Bitcoin is just the latest of a multitude of schemes designed to supplement or replace traditional money.



One of the first virtual currencies was E-gold, founded in 1996. E-gold was unique in that its virtual currency was backed by real, honest-to-goodness gold bullion. In essence, trading E-gold was basically the same as swapping gold ownership, but anonymously.

At its peak, in 2008, E-gold claimed more than five million user accounts. However, the anonymous nature of the currency made the service very attractive to crime syndicates looking to launder their dirty dollars into cleaner cash. Weak security systems also contributed to an influx of hacking and fraud from these same crime syndicates.

All of this led the U.S. government to get involved, and in 2008 the company’s management pleaded guilty to money laundering and operating an unlicensed money transfer business. The Feds froze all user accounts, amounting to more than $86 million in E-gold. The company itself closed its doors the following year.

By the way, E-gold was just one of several similar virtual gold payment systems back in the day. Competitors included GoldMoney and e-Bullion, which appeared equally shady. (E-Bullion’s owner was eventually arrested on charges of running an illegal money transfer business and of paying three hit men to stab his wife to death. Good folks there.)


Beenz and Flooz

In 1998, an interesting new website called was launched. The idea behind is that you could earn virtual currency (called Beenz) for performing a variety of online activities, such as visiting certain websites or shopping online. The Beenz you earned could then be spent on various online goods and services.

The site tried to position itself as “the web’s currency” that would challenge the world’s traditional currencies. That it didn’t succeed is now obvious. In fact, Beenz had a very short life, closing its virtual doors in 2001. It never got past the challenge of convincing governments around the world that it really wasn’t establishing a new currency, or of convincing users that it wasn’t all a big scam.