Teardown: Bug Zapper Bulb

February 9, 2021 by Tom Nardi 17 Comments

Up here in the Northern Hemisphere, mosquitoes and other flying pests are the last thing on anyone’s mind right now. The only bug that’s hindering gatherings at the moment goes by the name of COVID-19, but even if we weren’t social distancing, insects simply aren’t a concern at this time of year. So it’s little surprise that these months are often the best time to find a great deal on gadgets designed to deter or outright obliterate airborne insects.

Case in point, I was able to pick up this “Bug Zapper LED Bulb” at the big-box hardware store for just a few bucks. This one is sold by PIC Corporation, though some press release surfing shows the company merely took over distribution of the device in 2017. Before then it was known as the Zapplight, and was the sort of thing you might see advertised on TV if you were still awake at 3 AM. It appears there are several exceptionally similar products on the market as well, which are likely to be the same internally.

In all fairness, it’s a pretty clever idea. Traditional zappers are fairly large, and need to be hoisted up somewhere next to an electrical outlet. But if you could shrink one down to the size of a light bulb, you could easily dot them around the porch using the existing sockets and wiring. Extra points if you can also figure out a way to make it work as a real bulb when the bugs aren’t out. Obviously the resulting chimera won’t excel at either task, but there’s certainly something to be said for the convenience of it.

Let’s take a look inside one of these electrifying illuminators and see how they’ve managed to squeeze two very different devices into one socket-friendly package.

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An ESP Will Read Your Meter For You

February 7, 2021 by Jenny List 17 Comments

As home automation starts to live up to its glossy sci-fi promise there remains a deficiency when it comes to interfacing between the newer computerised components and legacy items from a previous age. A frequent example that appears in projects on Hackaday is the reading of utility meters, and in that arena [jomjol] has a very neat solution involving an ESP32 camera module and a software neural network to identify meter readings directly.

The ESP and camera sit at the top of a 3D-printed housing that fits over the meter. The clever trick comes as each photo’s orientation is determined, and not only is OCR used to read digits but also figures are derived from small dial meters and other indicators on the meter face. It’s a very well-thought-out system, with a web-based configuration tool that allows full customisation of the readable zones and how they should be treated.

This project makes full use of the ESP32’s capabilities, and the attention to detail that has gone into making it usable is particularly impressive. It certainly raises the bar against previous OCR meter reading projects.

[Thanks for the tip Sascha]

Open-Source Thermostat Won’t Anger Your Landlord

February 6, 2021 by Anool Mahidharia 51 Comments

[Nathan Petersen] built a Hackable Open-Source Thermostat to smooth out temperature fluctuations caused by the large hysteresis of the bimetallic strip thermostat in his apartment. While it may be tempting to adjust the “anticipator” to take care of the problem or even replace the bimetallic thermostat with an electronic version, building your own thermostat from scratch is a good way to add to your project portfolio while making your way through college. Plus, he got to hone his hardware and software design chops.

The hardware is designed around the STM32, using a cheap, minimal variant since the device just needs to sense temperature and control the furnace in on-off mode. The TMP117 high-accuracy, low-power, temperature sensor was selected for temperature measurement since accuracy was an essential feature of the project. Dry-contact output for the furnace is via a normally-open solid state relay (opto-isolator). For the user interface, instead of going the easy-route and using an I²C/SPI OLED or LCD display, [Nathan] used three 7-segment LED displays, each driven by an 8-channel constant current driver. The advantage is that the display can be viewed from across the room, and it’s brightness adjusted via PWM. Temperature set-point adjustment is via a simple slide potentiometer, whose analog voltage is read by the micro-controller ADC. To remind about battery replacement, a second ADC channel on the micro-controller monitors the battery voltage via a voltage divider. The PCB components are mostly surface mount, but the packages selected are easy enough to hand solder.

[Nathan]’s Github repo provides the hardware and firmware source files. The board is designed in Altium, but folks using KiCad can use either the awesome Altium2KiCad converter or the online service for conversion. (The results, with some minor errors that can be easily fixed, are quite usable.) Serendipitously, his PCB layout worked like a charm the first time around, without requiring any rework or bodge wires.

The firmware is a few hundred lines of custom bare-metal C code, consisting of drivers to interface with the hardware peripherals, a UI section to handle the user interface, and the control section with the algorithm for running the furnace. [Nathan] walks us through his code, digging into some control theory and filtering basics. After making a few code tweaks and running the thermostat for some time, [Nathan] concludes that it is able to achieve +0.1°F / -0.5°F temperature regulation with furnace cycles lasting about 10-15 minutes (i.e. 4-6 cycles per hour). Obviously, his well insulated apartment and a decent furnace are also major contributing factors. Moving on, for the next version, [Nathan] wants to add data collection capabilities by adding some memory and SD card storage, and use an RTC to allow seasonal adjustments or time-based set-points.

This is his first attempt at a “functional’ useful project, but he does love to build the occasional toy, such as this POV Top.

Old Gas Meter Gets Smart With The ESP8266

January 31, 2021 by Anool Mahidharia 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.

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

January 30, 2021 by Jenny List 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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Keeping An Eye On The Water Heater Pilot Light

January 21, 2021 by Danie Conradie 44 Comments

[WJCarpenter]’s gas water heater uses a small pilot light that needs to stay burning permanently to ignite the main burners as required. Four or five times a year, the pilot light goes out and needs to be manually lit. This involves an expedition from the upstairs bathroom to the basement, always in the early morning, after having spent a few fruitless minutes waiting for hot water. Having grown tired of this exercise, [WJCarpenter] built Water Watcher, a pilot light monitoring system with some ESPs and a light sensor.

Water Watcher consists of an ESP8266 connected to a light sensor taped to the inspection window of the water heater. It reports the status of the pilot light over MQTT to an ESP32-based M5 Atom Matrix in the main bedroom, which displays it using a 5×5 RGB matrix, as demonstrated after the break. Both ESPs run ESPHome, so programming is as easy as giving it a YAML config file. [WJCarpenter] tested a few different light sensors, until he found the TSL2591, which is sensitive to the right wavelengths and has enough dynamic range for watching a pilot light.

This might not be a complicated hack, but we do not doubt that it reduces frustration a bit on those fateful mornings. Be sure to check out the Water Watcher project page, it’s an entertaining read! Continue reading “Keeping An Eye On The Water Heater Pilot Light” →

Automated Balcony Shade Uses NFC

January 20, 2021 by Bryan Cockfield 3 Comments

[Udi] lives in an apartment with a pleasant balcony. He also has three kids who are home most of the time now, so he finds himself spending a little more time out on the balcony than he used to. To upgrade his experience, he installed a completely custom shade controller to automatically open and close his sunshade as the day progresses.

Automatic motors for blinds and other shades are available for purchase, but [Udi]’s shade is too big for any of these small motors to work. Finding a large servo with a 2:1 gear ration was the first step, as well as creating a custom mount for it to attach to the sunshade. Once the mechanical situation was solved, he programmed an ESP32 to control the servo. The ESP32 originally had control buttons wired to it, but [Udi] eventually transitioned to NFC for limit switch capabilities and also implemented voice control for the build as well.

While not the first shade controller we’ve ever seen, this build does make excellent use of appropriate hardware and its built-in features and although we suppose it’s possible this could have been done with a 555 timer, the project came together very well, especially for [Ubi]’s first Arduino-compatible build. If you decide to replicate this build, though, make sure that your shade controller is rental-friendly if it needs to be.

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