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.

Continue reading “Switching: From Relays To Bipolar Junction Transistors”

Have Alexa Open Your Garage Door

[yoyotechKnows] built an Alexa-controlled garage door opener after his Liftmaster stopped working. Now all he has to do is holler at his mobile phone and he can raise and lower his garage doors at will.

His project is based around a Photon WiFi kit, with a pair of LCC 120 digital relays triggering the two doors, reed switches, and a serial-equipped LCD to display door status, with Alexa, IFTTT, and OpenHab to process the commands. You can find his code in the project writeup.

Currently he has a LCD display informing him of the status of each door, hot glued a reed switch to keep track of whether each one is closed. This might seem a little bit extraneous since he can also just look at the doors from within the garage. However, he’s thinking about putting the display inside his house. But couldn’t he just ask Alexa?

We love us our home automation here at Hackaday, with everything from swimming pools to chicken coops rigged for app control and datalogging.

Continue reading “Have Alexa Open Your Garage Door”

Fight Mold And Mildew With An IoT Bathroom Fan

Delicious sheets of wallboard coated with yummy latex paints, all kept warm and moist by a daily deluge of showers and habitually forgetting to turn on the bathroom exhaust fan. You want mildew? Because that’s how you get mildew.

Fed up with the fuzzy little black spots on the ceiling, [Innovative Tom] decided to make bathroom ventilation a bit easier with this humidity-sensing IoT control for his bathroom exhaust fan. Truthfully, his build accomplishes little more than a $15 timer switch for the fan would, with one critical difference — it turns the fan on automatically when the DHT11 sensor tells the WeMos board that the relative humidity has gone over 60%. A relay shield kicks the fan on until the humidity falls below a set point. A Blynk app lets him monitor conditions in the bathroom and override the automatic fan, which is handy for when you need it for white noise generation more than exhaust. The best part of the project is the ample documentation and complete BOM in the description of the video below, making this an excellent beginner’s project.

No bathroom fan? Not a problem — this standalone humidity-sensing fan can help. Or perhaps you have other bathroom ventilation needs that this methane-sensing fan could help with?

Continue reading “Fight Mold And Mildew With An IoT Bathroom Fan”

Spoiler Alert! Repairing A Race Car Can Get Complicated, Fast.

[Big Fish Motorsports] has a vehicle with an adjustable rear spoiler system that broke in the lead up to a big race. The original builder had since gone AWOL so the considerable talents of [Quinn Dunki] were brought to bear in getting it working again.

Cracking open the black control box of mystery revealed an Arduino, a ProtoShield and the first major road block: the Arduino remained stubbornly incommunicado despite several different methods of trying to read the source code. Turns out the Arduino’s ATMega324 was configured to be unreadable or simply fried, but an ATMega128 [Quinn] had proved to be a capable replacement. However, without knowing how the ten relays for this spoiler system were configured — and the race day deadline looming ever larger — [Quinn] opted to scrap the original and hack together something of her own design with what she had on hand.

Continue reading “Spoiler Alert! Repairing A Race Car Can Get Complicated, Fast.”

Keep Pedaling To Keep Playing

It’s been said that the best way to tackle the issue of childhood obesity would be to hook those children’s video game consoles up to a pedal-powered generator. Of course, this was said by [Alex], the creator of Cykill. Cykill interfaces an Xbox to an exercise bike, so to keep the video game going you’ll have to keep pedaling the bike.

While there is no generator involved in this project, it does mimic the effect of powering electronics from a one. The exercise bike has a set of communications wires, which are connected to a relay on the Xbox’s power plug. When the relay notices that the bike isn’t being pedaled enough, it automatically cuts power to the console. Of course, the risk of corrupting a hard drive is high with this method, but that only serves to increase the motivation to continue pedaling.

The project goes even further in order to eliminate temptation to bypass the bike. [Alex] super-glued the plug of the Xbox to the relay, making it extremely difficult to get around the exercise requirement. If you’re after usable energy instead of a daily workout, though, there are bikes out there that can power just about any piece of machinery you can imagine.

IPad, Not Flux Capacitor, Brings DeLorean Back To The Future

Add a flux capacitor and a Mr. Fusion to a DeLorean and it becomes a time machine. But without those, a DeLorean is just a car. A 35-year old car at that, and thus lacking even the most basic modern amenities. No GPS, no Bluetooth — not even remote locks for the gullwing doors!

To fix that, [TheKingofDub] decided to deck his DeLorean out with an iPad dash computer that upgrades the cockpit experience, and we have to say we’re impressed by the results. Luckily, the space occupied by the original stereo and dash vents in the center console is the perfect size for an iPad mini, even with the Lightning cable and audio extension cable attached. A Bluetooth relay module is used to interface to the doors, windows, trunk, garage door remote, and outdoor temperature sensor. A WiFi backup camera frames the rear license plate. Custom software ties everything together with OEM-looking icons and a big GPS speedometer. The build looks great, adds functionality, and should make road trips a little easier.

When [TheKingofDub] finally gets sick of people complaining about where the BTTF guts are, maybe he can add a flux capacitor and time circuits.

[via r/electronics]

Vintage Telegraph Sounder Clicks Again

It’s sad, when you think about it: a retired railroad telegraph operator, who probably once pounded out code at 40 words per minute, with a collection of vintage sounders silently gathering dust on a shelf. [kthrace] decided to do something about that, and built this Morse sender to bring those old sounders back to life.

As archaic as Morse might seem, it’s a life skill, one the 92-year old former brass-pounder for whom this was built was eager to practice again. There are code practice oscillators, of course, but dits and dahs are no substitutes for the electromagnetic clicks and clacks that once filled this old fellow’s days. There’s not much information on the circuit, but it looks like [kthrace] chose a RedBoard to read Morse from an SD card and drive some relays to support up to four sounders; that’ll make a racket! The case is custom made and nicely complements the wood and brass of the J.H. Bunnell and Co. sounder, which still sounds great after all these years.

Test your Morse skills in the video below – copying code is a lot harder from a sounder than from an oscillator. Find yourself in need of practice? We’ve got you covered.

Continue reading “Vintage Telegraph Sounder Clicks Again”