Old Gas Meter Gets Smart With The ESP8266

January 31, 2021 by 34 Comments

Measuring the usage of domestic utilities such as water, gas or electricity usually boils down to measuring a repetitive pulse signal with respect to time. To make things easy, most modern utility meters have a pulsed LED output, which can be used to monitor the consumption by using an external optical sensor. But what do you do if your meter isn’t so cooperative?

That’s exactly what [Francesco] had to figure out while developing the non-invasive gas tracking system he calls ESPmeter. His meter might not have an LED, but it did have a magnet attached to the counter disk which activated an internal hall sensor. With some hacking, he was able to attach an external Hall-effect sensor to pick up this magnet and use the signal to monitor his daily gas consumption.


A big stumbling block in such projects is the issue of powering the device for an extended period, and remembering when it’s time to change the batteries. With the clever use of commonly available parts, he was able to reduce power consumption allowing three AA batteries to last about a year between changes. For one thing, he uses an ATtiny13 to actually read the sensor values. The chip doesn’t run continuously, its watchdog is set at 1 Hz, ensuring that the device is woken up often enough so that it has time to power up the sensor and detect the presence of the magnet. Battery voltage is also measured via a voltage divider connected to the chip’s ADC pin.

At regular intervals throughout the day, the ESP8266 polls the ATtiny13 to pull the stored sensor pulses and voltage measurement. Then at midnight, the ESP transmits all the collected data to a remote server. Overall, this whole scheme allows [Francesco] to reliably gather his gas consumption data while not having to worry about batteries until he gets the low voltage notification. Since the data visualization requirements are pretty basic, he is keeping things simple by using Plotly to display his time series data.

If you are unfortunate enough to have an even older meter which doesn’t use optical or magnetic rotation sensing, you can use a disassembled mouse to keep track of the Gas Meter.

This Hot Air Gun Is Either A Work Of Genius Or Lethal, We Can’t Decide

January 31, 2021 by 31 Comments

One of the essentials on the bench is some form of hot air gun. Whether it’s a precision tool intended for reworking PCBs or the broad-stroke item used for paint stripping, we’ve all got one somewhere. The paint-stripping variety are pretty cheap, but not as cheap as [Porcas Pregos e Parafusos]’s home made hot air gun. This slightly hair-raising device is made from a variety of junk parts and delivers hot air, though we suspect the possibility for burning the operator remains high.

At its heart is one of those mains powered water boiler elements designed to be lowered into a cup or similar, and since such devices would burn out if not cooled in some way, there is a fan from a microwave oven passing air over it. The whole thing sits inside an aluminium cone cut from a circular cake tin, and is held together on a wooden chassis to which the handle and power switch from a defunct electric drill provide the operator with something to hold on to.

As you can see from the video below the break it makes for an effective hot air gun, but one that we’re guessing you’d soon learn to avoid touching on the metal cone. Still, as a community we’re used to this with our soldering irons, as the RevSpace T-shirt puts it: “If it smells like chicken, you’re holding it wrong“.

Strangely, this isn’t the first DIY heat gun we’ve seen.

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Mystery Box Gives Up Its Patented Secrets

January 31, 2021 by 21 Comments

[CuriousMarc] likes to go to surplus stores even though there are fewer of them around. On a recent trip, he found a box that had some parts he thought would work for a temperature controller project. It was marked Dial-A-Level and proudly proclaimed that it had a patent pending. The box was from the 1970s and [Marc] was wondering what the device was meant to do.

The device was a bit of a puzzle since it had three oddly-marked probe inputs. A search through the patent database revealed the device was a “capacitance probe for detecting moisture with very long cables.” The idea was to create a capacitor at the end of the cable and use the liquid as a dielectric. The sensor creates a 10 kHz sine wave it uses to excite the probe and an op amp measures the relative capacitive reactance of the probe versus a reference capacitor. The rest of the circuit is a comparator that reacts when the level is at a threshold.

We love seeing the old hand-drawn boards from that era. Component designations are in copper and there’s no solder mask visible. There was a clever application of a silicon controlled rectifiers and a relay to create a type of flip flop, that [Marc] explains.

Interestingly, the company that made the device, Expo Instruments, is still around and [Marc] contacted them. The actual patent holder replied and was amazed that [Marc] had possession of this antique. You can only wonder if anything you build today will wind up on whatever passes for YouTube three or four decades from now.

Capacitive sensing is quite versatile. Of course, there are many other ways to sense liquid level, too.

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3D Printing A Full Scale Fiberglass Speedboat

January 30, 2021 by 15 Comments

It’s an age-old problem. You draw up a nice 6.5-meter long motorboat and then discover the shape won’t allow for a fiberglass mold. What do you do? If you’re [Moi], you grab a few Kuka robots and 3D print it using thermoplastic with embedded glass fibers. A UV light cures the plastic and you wind up with printed fiberglass. That’s the story behind the MAMBO, a 3D printed powerboat.

Despite the color, the fiberglass isn’t blue out of the gate — the boat is painted. Still, it looks nice with lines inspired by [Sonny Levi]’s Arcidiavolo design from 1973. MAMBO stands for Motor Additive Manufacturing BOat. It has a dry weight of about 800 kg and is fitted with a cork floor, white leather seats, and an engine. We presume none of those things were 3D printed.

Although it wasn’t fiberglass, we’ve seen a 3D printed boat before. In particular, the University of Maine’s giant 22,000 square foot printer cranked one out. We’ve also seen boats printed in standard PLA filament, which then had fiberglass cloth and resin applied after printing. True that one was only RC, but there’s no reason the concept couldn’t be scaled up if you had the patience.

Master Video Call Control Panel Is Made Of PCBs

January 30, 2021 by 6 Comments

[memestra] is a teacher whose life has become a series of videoconferences over the last year or so. With all the classes and meetings, they spend the whole day switching between either Zoom, Teams, or Meet. If anyone needs a single piece of hardware to control them all, it’s [memestra]. Well, and every other teacher out there.

The hardware — an Arduino Pro Micro and some buttons — should come as no surprise, except for maybe [memstra]’s use of a resistor network for the LEDs. Still, there’s a lot to like about this little box, starting with the enclosure. That’s not milled or laser-cut metal — each side is a PCB, and they’re all soldered together into a box.

We especially like the top panel, which fits down over the PCB that all the components are soldered to. Each of the non-volume buttons has multiple functions that are accessed by pressing, long pressing, or double pressing. But even the volume buttons do double duty: press them together to mute and un-mute. If [memestra] ever forgets which button does what and how, there’s a handy reference table silkscreened on the bottom panel.

In true teacher fashion, [memestra] has written comprehensive instructions for anyone looking to build a similar device. The heavily-commented code should make it a cinch to drop in keyboard shortcuts for Discord or anything else you might be using, though it’s worth noting that this box is optimized for the desktop apps and not the browser-based versions.

Just looking for a fun way to end video calls? Pull chains are pretty fun.

Scrappy: Drag Racing Bush Plane

January 30, 2021 by 19 Comments

We like to feature hacks that are affordable and accessible to the average person, but from time to time it’s fun to dream about the projects we’ll tackle when we’re all grown up and stinking rich. [Mike Patey] appears to fall rather comfortably in the latter category, but thankfully he hasn’t lost his “excited kid with big plans” spirit. A talented and experienced experimental aircraft builder, he’s currently working on Scrappy, a small bush plane built to be a short take-off and landing drag racer.

Scrappy started life as a Carbon Cub, a modernized kit version of the venerable Piper Super Cub. The only thing left of the original plane is a part of the fuselage frame, with almost everything else being custom. The engine is a 780 cubic inch (13 liter) horizontally opposed 8-cylinder, scavenged from one of [Mike]’s racing planes, and fitting it required extensive structural changes to the fuselage. The paddle-like propeller was intended for an airboat, and is designed for high thrust at low speeds. The skin of the aircraft is all carbon fiber, and the suspension almost looks like it’s borrowed from an off-road racing truck. [Mike] also added (and test fired) a ballistic recovery parachute. The cockpit instruments are also over-the-top for an aircraft like this, with seven Garmin multi-function displays.

Scrappy is still missing its wings, which will also be heavily modified. From the oil-cooling system to the door latch and gust-lock for the stick, everything was designed and made by [Mike]. We’re enjoying the in-depth build videos that show how he tackles all the little challenges that pop-up in such an ambitious project.

[Mike] made a name for himself with his previous monster bush plane Draco, which was sadly destroyed during an ill-considered take-off last year. Fortunately nobody was harmed in the incident, and Draco became a part donor for Scrappy. If budget planes are more your style, check out [Peter Sripol]’s latest electric microlight.

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A Heat Reclaimer For Your Woodstove; The One Thing It’s Not Is Cool

January 30, 2021 by 27 Comments

It’s the middle of winter for those of us who live in the Northern Hemisphere, which naturally turns minds towards heating, or sometimes the lack of it. It’s particularly difficult for those who rely on a wood stove to escape the feeling that perhaps most of that hard-won heat may be whistling up the chimney rather than keeping them warm. It’s a problem [Lou] has addressed with his DIY chimney heat reclaimer.

As can be seen from the video below the break, his stove appears to be in a workshop, and has a long single-wall metal stove pipe. Over the outside of this he’s placed a pair of T pieces joined by a longer length of pipe all of a larger bore, and a mains-powered fan forces air through this air jacket. The result is a continuous flow of hot air that he claims delivers a 45% heat reclamation. We’re curious though whether the reduction in flue temperature might cause extra tar condensation and thus the build-up of flammable material further up the chimney. The stove itself is a double barrel affair with access for smoking, and the video describing it is worth a look in itself.

Whatever the stove, be sure to ensure a constant supply of fuel!

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