relay

180 Articles

An ESP32 Home Automation Swiss Army Knife

May 14, 2020 by 37 Comments

Thanks to the ESP8266 and the ESP32, we’ve seen an explosion in DIY home automation projects recently. When it only takes $3 and a few lines of code to bring your gadgets onto the network, that’s hardly a surprise. But hacking bare ESP modules onto devices will only get you so far. Eventually you’ll probably want to put together a slightly more mature home automation system, and that’s where things can get a little tricky.

Which is why [Alfredo] created the Maisken Homelay. This device is a one-stop-shop for your home automation needs that leverages the power of the ESP32. With the microcontroller slotted into this compact PCB, you’ll be able to trigger four relays for your high current or AC loads, and still have 8 GPIOs and the I2C bus for expansion. All while retaining compatibility with existing open source projects like Home Assistant and ESPHome.

What really sets this project apart is the attention to detail. [Alfredo] has included a HLK-PM01 power supply on the board which takes mains voltage and brings it down to 5 VDC for the ESP32, so won’t need a separate power cable. He’s also taken the time to add isolation slots to separate the potential high-voltage connected to the relays from the rest of the board, added current and thermal fuses for protection, and peppered the board with screw terminals so you can easily connect everything up.

Sure you could get a simple relay board shipped to your door for a few bucks from the usual suspects. But it’s not going to offer the kind of quality of life and safety features that the Maisken Homelay has. There’s even a 3D printed enclosure available to help tidy things up.

With some of the blatantly anti-consumer decisions big-name home automation companies have been making recently, there’s more reason than ever to roll your own smart home using open source hardware and software. It still takes more effort than buying a bunch of modules from the Big Box retailer, but projects like this one are certainly starting to blur the line between consumer and DIY.

Espresso Machine Now Powers Plants

February 22, 2020 by 6 Comments

This thing has what plants crave! No, not electrolytes exactly — just water, light, and moisture polling every 30 minutes. We think it’s fitting to take something that once manufactured liquid liveliness for humans and turn it into a smart garden that does the same thing for plants.

So let’s just get this out of the way: the espresso machine was abandoned because it was leaking water from a gasket. [The Plant Bot] cleaned it up, replaced the gasket, and got it brewing, and then it started leaking hot water again from the same gasket. We might have gone Office Space on this beautiful machine at that point, but not [The Plant Bot].

Down in the dirt, there’s a soil moisture sensor that’s polling every 30 minutes. If the moisture level falls below the threshold set appropriately at a life-sustaining 42%, the Arduino is triggered to water the plant through a relay board using the espresso machine’s original pump. If the plant is dry, the machine will pump water for two seconds every minute until the threshold is met. [The Plant Bot] tied it all together with a nice web interface that shows plant data and allows for changes over Bluetooth.

[The Plant Bot] started by disconnecting the heating element, because plants don’t tend to like hot steam. But if the cup warming tray along the top has a separate heating element, it might be neat to reuse it for something like growing mushrooms, or maintaining a sourdough starter if the temperature is right.

Via r/duino

Finally, A Rotary Cell Phone With Speed Dial

September 24, 2019 by 10 Comments

If you’re reading this, chances are good that you’re the family IT department. We do what we can to help them, but there’s just no changing the fact that smartphones are difficult to operate with aging eyes and hands. When [sideburn’s] dad started complaining, he took a different approach. Instead of helping his dad adapt, [sideburn] stuffed modern cell phone guts into a 1970s rotary phone — if all you want to use it for is phone calls, why not reach for a battle-tested handset?

[sideburn] figured out the most important part first, which is getting the thing to ring. The bells in those old phones are driven by a huge relay that requires a lot of voltage, so he boosted a 3.2V rechargeable to 34V. Then it was just a matter of getting the GSM module to play nice with the microcontroller, and programming a MOSFET to trigger the boost module that makes the beast jingle.

The worst thing about rotary phones is that they were never meant to be dialed in a hurry. But [sideburn] took care of that. Once Rotocell was up and working, he added an SMS interface that makes the phone a lot more useful. Dad can add contacts to Rotocell by texting the name and number to it from a modern phone. Once it’s in there, he can dial by name, speeding up the process a tiny bit.

The SMS interface can also report back the signal strength and battery level, and will send battery low alerts when it’s under 20%. You can see Rotocell in action after the break.

Got an old rotary or two lying about? If modernizing the internals to make calls doesn’t light up your circuits, try turning it into a voice-controlled assistant instead.

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[Mr. Carlson] Fixes A Fridge

September 21, 2019 by 28 Comments

A dead refrigerator is an occurrence determined to frustrate any homeowner. First there’s the discovery of hundreds of dollars in spoiled food, and then the cost of a repair call and the delay of the inevitable wait for parts. It’s clear to see why a hacker like [Mr. Carlson] would seek another way.

Now, normally a fridge repair video would by unlikely fodder for a Hackaday article. After all, there’s generally not much to a fridge, and even with the newer microprocessor-controlled units, diagnosis and repair are usually at the board-level. But [Mr. Carlson] has had this fridge since 2007, and he’s got some history with it. An earlier failure was caused by the incandescent interior lights welding relay contacts closed thanks to huge inrush currents when starting the cold filaments. That left the light on all the time, heating the interior. His fix was a custom solid-state relay using zero-crossing opto-isolators to turn the bulbs on or off only when the AC power was at a minimum.

That repair kept things going for years, but when the latest issue occurred, [Mr. Carlson] took a different tack. He assumed that a board that has been powered 24-7 for the last twelve years is likely to have a bad capacitor or two. He replaced all the caps, threw in a few new relays to be on the safe side, and powered the fridge back up. It whirred back to life, ready for another decade or so of service.

Kudos to [Mr. Carlson] for his great repair tips and his refusal to surrender. The same thing happened when his solder sucker started to give up the ghost and he fixed it by adding a variable-frequency drive.

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Minivac 601 Replica Gets A Custom Motorized Rotary Switch

July 13, 2019 by 2 Comments

One of the joys of electronics as a hobby is how easy it is to get parts. Literally millions of parts are available from thousands of suppliers and hundreds of distributors, and everyone competes with each other to make it as easy as possible to put together an order from a BoM. If you need it, somebody probably has it.

But what do you do when you need a part that doesn’t exist anymore, and even when it did was only produced in small numbers? Easy – you create it yourself. That’s just what [Mike Gardi] did with this unique motorized rotary switch he needed to complete his replica of a 1960s computer trainer. We covered his build of the Minivac 601, a trainer from the early computer age that let experimenters learn the ropes of basic digital logic. It used mostly relays, lamps, and switches connected by jumpers, but it had one critical component – a rotary control that was used for input and, with the help of a motor, as an output indicator.

[Mike]’s version of the switch is as faithful to the original as possible, at least in terms of looks. The parts are mostly 3D-printed, with 16 reed switches embedded in the walls and magnets placed in the rotor. The motor to operate the rotor is a simple gear motor mounted to a hinged bracket; when the rotor needs to move, a solenoid pulls the motor’s friction drive wheel up against the rotor.

The unique control slots right into the Minivac replica and really completes the look and feel. Hats off to [Mike] for a delightful replica of a lost bit of computer history and the dedication to see it through to completion.

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A Faithful Replica Of An Early Computer Trainer

June 17, 2019 by 11 Comments

Turn the clock back six decades or so and imagine you’re in the nascent computer business. You know your product has immense value, but only to a limited customer base with the means to afford such devices and the ability to understand them and put them to use. You know that the market will eventually saturate unless you can create a self-sustaining computer culture. But how does one accomplish such a thing in 1961?

Enter the Minivac 601. The brainchild of no less a computer luminary than Claude Shannon, the father of information theory, the Minivac 601 was ostensibly a toy in the vein of the “100-in-1” electronics kits that would appear later. It used electromechanical circuits to teach basic logic, and now [Mike Gardi] has created a replica of the original Minivac 601.

Both the original and the replica use relays as logic switches, which can be wired in various configurations through jumpers. [Mike]’s version is as faithful to the original as possible with modern parts, and gets an extra authenticity boost through the use of 3D-printed panels and a laser-cut wood frame to recreate the look of the original. Sadly, the unique motorized rotary switch, used for both input and output on the original, has yet to be fully implemented on the replica. But everything else is spot on, and the vintage look is great. Extra points to [Mike] for laboriously recreating the original programming terminals with solder lugs and brass eyelets.

We love seeing this retro replica, and appreciate the chance to reflect on the genius of its inventor. Our profile of Claude Shannon is a great place to start learning about his other contributions to computer science. We’ve also got a deeper dive into information theory for the curious.

Thanks to [Granz] for the tip.

Moped Turn Signals, Now With More Cowbell

June 7, 2019 by 14 Comments

Cue up the [Christopher Walken] memes, it’s time for moped turn signals with more cowbell. Because moped turn signals with less cowbell are clearly the inferior among moped turn signals.

It seems that [Joel Creates] suffers from the same rhythm recognition disorder that we do. The slightest similarity between a rhythmic sound such as turn signals, and any song in our seemingly infinite intracranial playlist cues up that song for the rest of the day. [Joel] heard “(Don’t Fear) The Reaper” in his turn signals, and that naturally led to a need for More Cowbell. So with a car door lock actuator, a relay, an improvised clapper, and a lot of hot glue and cable ties, the front of his scooter is now adorned with a cowbell that’s synchronized to the turn signals. The video below shows that it’s of somewhat limited appeal in traffic, but at least [Joel’s dad] was tickled pink by it.

Kudos to [Joel] for marching to the beat of his own [Gene Frenkle] on this one. It may be a little weird, but not as weird as an Internet of Cowbells.

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