Switching: from Relays to Bipolar Junction Transistors

How many remote controls do you have in your home? Don’t you wish all these things were better integrated somehow, or that you could add remote control functionality to a random device? It’s a common starting point for a project, and a good learning experience for beginners.

A common solution we’ve seen applied is to connect a relay in parallel to all the buttons we want to press. When the relay is triggered, for example by your choice of microcontroller, it gets treated as a button press. While it does work, relays are not really the ideal solution for the very low current loads that we’re dealing with in these situations.

As it turns out, there are a few simple ways to solve this problem. In this article, we’re going to focus on using common bipolar junction transistors instead of relays to replace physical switches. In short, how to add transistors to existing electronics to control them in new ways.

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Whole House HiFi Tamed Without Fuss

One of the problems that has accompanied the advent of ever more complex home entertainment systems is the complexity of the burgeoning stack of remote controls that manifest themselves alongside your system. It doesn’t matter if you have a fancy does-the-lot universal remote, you are still left with a slew of functions to perform before you can sit down to enjoy the music.

[Robert Cowan] had this problem with his whole-house audio system. Playing music required a fiddle with the remote, and the moment was gone. What was needed was an automatic system that simply issued the relevant commands to the stereo without all the fuss.

His solution was to have everything happen when an audio output was detected from his Sonos Connect streaming media player. He tried rectifying its line output to detect music but hit problems, so instead used a SparkFun audio detector module. This in turn speaks to an Arduino, which then talks via a level shifter to the stereo’s RS232 port. [Robert] included all the relevant parts, schematic, and software is links in the video description. It’s a project that should almost be a feature built into a decent stereo, yet the manufacturers prefer the awful interfaces of their remote controls.

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Hacklet 118 – Infrared and Universal Remote Controls

The first remote control for a TV was the Zenith Space Command back in the 1950’s. Space Command used sounds at ultrasonic frequencies to control the set. It wasn’t until the 1980’s and the Viewstar cable box that infrared entered the picture. Remote controls spread like wildfire. It wasn’t long before every piece of consumer electronics had one. Coffee tables were littered with the devices. It didn’t take long for universal remotes to hit the scene. [Woz] himself worked on the CL9 Core device, back in 1987. Even in today’s world of smart TV’s and the internet of things, universal remotes are still a big item. Hackers, makers, and engineers are always trying to build a device that works better for them. This week’s Hacklet is about some of the best universal and IR remote projects on Hackaday.io!

smoteWe start with [Harikrishna] and zmote. Zmote is an open source WiFi enabled, infrared,  360° remote control. That’s a mouthful. It might be easier to say it’s an ESP8266 and some IR LEDs. An ESP-01 module connects the device to WiFi and provides the 32-bit processor which runs the show. Learning functionality comes courtesy of a TSOP1738 modulated infrared receiver. The beauty of the Zmote is in the software. REST and MQTT connectivity are available. Everything is MIT licensed, and all the code is available on Github.

 

easton

Next up is [Benjamin Kenobi] with TV Remote Control, Limited. Not everyone can operate the tiny buttons on a modern remote. [Benjamin] built this device for Easton, a special kid with a disability that impairs his motor skills. The 3D printed case holds two buttons – one for power, and one to change the channel. An Arduino Nano running [Ken Shirriff’s] IR library is the brains of the operation. The IR signal timing is hard coded for simplicity. One problem [Ben] ran into was the Nano’s high current draw, even in sleep mode. Batteries wouldn’t last a week. A simple diode circuit with a reed relay keeps the Nano shut down until Easton presses a button.

 

openirNext we have [Nevyn] with OpenIR – Infrared Remote Control. A dead DSLR remote shutter release was all the motivation [Nevyn] needed to start work on his own universal remote control. OpenIR can be connected to (and controlled by) just about anything with a UART – a PC via an FTDI cable, a Bluetooth module, even an ESP8266. The module can be programmed by entering pulse length data through a custom Windows application. The Windows app even allows the user to view the pulses graphically, like a scope. The data is stored on an EEPROM on OpenIR’s PCB. Once programmed, the OpenIR board is ready to control the world.

onebuttonFinally, we have [facelessloser] with One button TV remote. This project may be the simplest open source remote control this side of TV-B-GONE. He wanted to build a simple remote control for his young daughter to scan between the various kids channels. A simple toggle switch turns the device on, and one button performs the rest of the magic. [Facelessloser] wanted to “move up” from an Arduino to an ATtiny85. This project became part of his ATtiny education. A custom PCB from OSH Park ties things together. A simple black project box keeps the electronics safe from tiny fingers – at least until she’s old enough to use a screwdriver.

If you want to see more IR and universal remote projects, check out our new infrared and universal remote projects list. See a project I might have missed? Don’t be shy, just drop me a message on Hackaday.io. That’s it for this week’s Hacklet, As always, see you next week. Same hack time, same hack channel, bringing you the best of Hackaday.io!

Ultimate Remote is Ultimate

[Joedefa] had a Griffin Beacon Universal Remote that was collecting dust, and decided that it needed to stop collecting dust. He had a growing number of wireless devices in his house and found himself in need of a remote to control them all. The Griffin Beacon fit the bill, but most of his lights and outlets were RF controlled. So he did what hackers do best… broke out the screw driver and soldering iron and rewired it!

[Joedefa] is using an Attiny85 as the brains between an infrared LED and a RF transmit module (if anyone can identify the source of this module, please let everyone know in the comments).  A pair of red and green LEDs lets him know if the remote has received commands successfully.

It’s always nice to see a discontinued product made useful once more with a little ingenuity and an Arduino some hacking skill. Hat’s off to [Joedefa] for a righteous hack!

A 7″ Touchscreen TV Remote Control from Scratch

[Jason] always wanted a touchscreen TV remote control. He could have pressed an older Android tablet into service, but he wanted to roll his own system. [Jason] gathered the parts, and is in the process of building his own 7″ touchscreen setup. He started with a 7″ LCD capacitive touchscreen. He ordered his display from buy-display.com, a Far East vendor.

[Jason’s] particular display model comes mounted on a PCB which includes controllers for the display and touchscreen, as well as some memory and glue logic. The LCD controller board has quite a few jumpers to support multiple interfaces and options. While the documentation for the display was decent, [Jason] did find a few errors. After getting in touch with tech support at buy-display, he wrote a simple application which determines which jumpers to set depending on which hardware interfaces are selected from drop down lists.

With the LCD sorted, [Jason] still needed a processor. He selected the venerable Microchip PIC32MX series. This decision allowed him to use a Fubarino for the early prototypes, before switching to his own board as the system matured. [Jason] was able to get a simple GUI up and running, with standard remote buttons to control his TV and cable box. Code is on his Github repository.

[Jason’s] most recent work has centered on cutting the cord. He’s switched over from DC power to a 2600 mAh LiPo battery. Click past the break to see [Jason] test out his fully wireless work in progress.

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Eloquent universal receiver for your home entertainment equipment

home-entertainment-universal-receiver

We’re really starting to enjoy the home entertainment control hacks which use a universal receiver to act on commands from any remote. This one is especially interesting as it uses a single remote to control the system but rolls in lots of extras.

Looking at the receiver itself the white plastic dome of the PIR sensor should raise an eyebrow. Since the cable box takes a while to turn on [Ivan] included the motion sensor to switch that component on when you walk into the room. This way it’ll be ready to go by the time you sit down. It does this by sending IR signals from the PIC32 dev board. Of course the board has its own receiver to listen for the remote control commands. The remote buttons have been mapped a bit differently than originally intended. You can see in the diagram above that the normal VCR/DVD/DVR buttons have been set to control the room’s LED strips. There’s even a power consumption monitor rolled into the project. All of these features are demonstrated in the clip after the break.

This is a nearly perfect base setup. But we’d love to see it with a web interface at some point in the future.

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Real multifunction “Sonic Screwdriver”

dr who sonic screwdriver

“I don’t understand, you don’t have the technology.” OK, so it’s not actually a futuristic tool with the same capabilities as the one off the hit TV series Dr. Who, but this homemade “sonic screwdriver” is a multifunction device that’s pretty cool nonetheless.

Created around an Arduino Pro Mini, [Gunther] really one-upped the last screwdriver we featured. Built in functions include: brown note tone generator, dog whistle, EMF meter, flashlight, IR universal remote, laser pointer, ohm meter, sound level meter, voltage detector, and a voltage meter.  You can also have an electromagnet or output voltage supply if you want. If that wasn’t enough, it can even play the theme song from Star Wars! Whew. That’s a mouthful of functionality.

Although he has posted the Arduino code, you’ll have to keep an eye on his site for more details if you want to create your own. He’s mentioned that he’s working on blue prints and a full parts list… Awesome. Now where’s that lock pick function?

Check out a video showing off some of the features after the break.

[via Make]
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