{"id":10376,"date":"2023-10-29T12:07:25","date_gmt":"2023-10-29T16:07:25","guid":{"rendered":"https:\/\/dronebotworkshop.com\/?p=10376"},"modified":"2023-10-29T12:07:25","modified_gmt":"2023-10-29T16:07:25","slug":"ir-remotes","status":"publish","type":"post","link":"https:\/\/dronebotworkshop.com\/ir-remotes\/","title":{"rendered":"IR Remotes Revisited – 2023"},"content":{"rendered":"\n

\"Download<\/a> \"Parts<\/a> \"View<\/a> \"Download<\/a><\/p>\n

After five years, it\u2019s time we took another look at using infrared remote controls with microcontrollers. We\u2019ll work with some updated libraries and see what we can do to decode those \u201cstubborn\u201d air conditioner remote controls.\u00a0 We\u2019ll also take a closer look at the hardware used to exchange IR signals. And, of course, we\u2019ll build many fun IR remote projects!<\/span><\/p>\n

Introduction<\/span><\/h2>\n

It\u2019s a safe bet that you own at least one infrared remote control. In fact, it\u2019s likely that you own several, perhaps so many that you would have trouble accounting for them all. Once exclusively used for televisions, remote controls are now included with all varieties of electronic gear.<\/span><\/p>\n

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IR Remote controls offer numerous possibilities for experimenters and microcontroller enthusiasts. We can use microcontrollers to emulate remote controls, placing a wide variety of devices under the control of our programs. We can also get our micros to respond to IR remote controls, providing a convenient way to control our projects.<\/span><\/p>\n

Microcontrollers also open up several advanced capabilities, such as converting remote control codes from one manufacturer to another or playing back sequences of remote control codes.<\/span><\/p>\n

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Today, we will see how these little gems work and how we can use them in our projects.<\/span><\/p>\n

IR Remote Controls<\/span><\/p>\n

Televisions, air conditioners, sound systems, electronic blinds, humidifiers – all of these appliances come equipped with infrared remote controls.\u00a0 Usually, they play nice together, although occasionally, we get into a conflict, and turning up the sound on the TV also changes the humidifier settings.<\/span><\/p>\n

Let\u2019s learn more about these devices to see if we can understand how they work, how we can use them in our projects, and why we have so many of these critters on our coffee table!<\/span><\/p>\n

History of Remote Controls<\/span><\/h3>\n

It\u2019s hard to imagine life without remote controls, but believe it or not, there was once a time when you actually had to get out of your chair to change channels or adjust the sound on the TV!<\/span><\/p>\n

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The remote control has a rich history that spans several decades. The first television remote control, named “<\/span>Lazy Bones<\/span><\/i>,” was developed by Zenith Radio Corporation in the late 1940s. However, it was connected to the TV with a wire, and at 30 dollars (387 dollars in 2023), it was an expensive accessory.<\/span><\/p>\n

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In 1955, Zenith’s Eugene Polley developed the first wireless remote control called the “<\/span>Flashmatic<\/span><\/i>.” It worked by directing a visible light beam toward photocells on the television set. As you might suspect, this design was prone to interference from other light sources, so it wasn\u2019t very successful.<\/span><\/p>\n

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Just one year later, Robert Adler, also from Zenith, designed the “<\/span>Zenith Space Command<\/span><\/i>.” This was a true precursor to the modern remote. It was ultrasonic, meaning it emitted high-frequency sounds to control TV functions. When a button was pressed, it would strike a bar and produce a sound, which the television would then interpret as a command. This design eliminated the problems associated with ambient light interference.<\/span><\/p>\n

Ultrasonic remotes were the dominant form of television remote controls for nearly two decades.\u00a0 They were sometimes difficult to use; they emitted \u201cchirping\u201d sounds and were known to bother dogs and cats. But, on the plus side, they didn\u2019t require any batteries!<\/span><\/p>\n

By the late 1970s, the shift from ultrasonic to infrared technology had begun. IR remote controls became the standard, primarily because they were cheaper to produce, had a broader range of functionality, and avoided the audible sounds of ultrasonic remotes.<\/span><\/p>\n

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As consumer electronics proliferated, so did the applications of IR remotes. They started being used for VCRs, DVD players, stereos, and eventually, air conditioners, cameras, and more.\u00a0 These days, they are everywhere.<\/span><\/p>\n

Infrared Remote Control Basics<\/span><\/h3>\n

In its most basic form, an IR remote control sends a pulsed beam of infrared light, which contains the key code for the button you pressed. The receiver extracts the code and performs the desired operation.<\/span><\/p>\n

Infrared Light<\/span><\/h4>\n

The light these devices use is in the \u201cinfrared\u201d range, meaning the range of light below red in the visible spectrum.<\/span><\/p>\n

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Light can be measured by its wavelength, and most infrared remotes operate in wavelengths ranging from 850 to 960 nanometers.\u00a0 By far, <\/span>the most common wavelength is 940nm<\/b>.<\/span><\/p>\n

Carrier Frequency<\/span><\/h4>\n

The pulses of infrared light are also modulated with a carrier wave, just like a radio signal. This technique allows the receiver to distinguish the remote signal from the infrared background noise, which can sometimes be quite high.<\/span><\/p>\n

Carrier frequencies can vary between 30 and 60 kilohertz, but <\/span>the most common carrier frequency is 38 kHz<\/b>.<\/span><\/p>\n

Modulation Techniques<\/span><\/h4>\n

All remote control data is sent in a serial format. The data is encoded using a number of different modulation techniques. These different techniques determine how the zeros and ones are formatted for transmission over the infrared light beam.<\/span><\/p>\n

There are three basic modulation techniques used, along with several variations of them.<\/span><\/p>\n