Need a good multimeter? The Fluke 17B is an excellent basic meter that will last your entire career. It’s also $100 USD. Need something cheaper? Allow me to introduce the AIMOmeter MS8217. On the outside, it’s a direct copy of the Fluke 17b, right down to the screen printing but understandably lacking the yellow enclosure. $30 USD will get you an exact copy of a Fluke 17B, it would seem. Right? Not a chance. [electronupdate] did a teardown of the AIMOmeter, and while this meter looks like a Fluke on the outside, it’s probably going to kill somebody.
The teardown begins with a look at the ratings on the back of this off-brand meter. It does have two fuses, but the engraving on the back strangely claims ‘Wrrebt insurance limit’. If anyone has any idea what a ‘wrrebt’ is, please leave a note in the comments. The only references to this word in Google are mis-OCRed blackletter type in a book from the early 1800s.
Opening up the meter reveals – surprisingly – two real fuses in the meter. There were no markings on the bigger fuse, which could be a problem for verifying if the fuse is of the proper value. That’s not really a problem, though: the fuse isn’t even between ground and the amp probe socket. Yes, this fuse is completely useless, and testing the resistance with the fuse out of the circuit confirms this.
After putting the meter back together, [electron] tests the accuracy of the meter. With a 1 mA current source, the mA setting seems to work, but when testing the larger Amp range of this meter, the results display in milliVolts. Don’t worry, there’s an easy fix for that: just press the dial down just right and the correct setting will be displayed. Wow.
You get what you pay for, and if you only ever use an AIMOmeter for measuring Arduinos and batteries, you might – might – be alright. This is not the kind of meter you want to measure line voltage, motors, or anything else with, though.
[Carl] recently upgraded his home with a solar panel system. This system compliments the electricity he gets from the grid by filling up a battery bank using free (as in beer) energy from the sun. The system came with a basic meter which really only shows the total amount of electricity the panels produce. [Carl] wanted to get more data out of his system. He managed to build his own monitor using an Arduino.
The trick of this build has to do with how the system works. The panel includes an LED light that blinks 1000 times for each kWh of electricity. [Carl] realized that if he could monitor the rate at which the LED is flashing, he could determine approximately how much energy is being generated at any given moment. We’ve seen similar projects in the past.
Like most people new to a technology, [Carl] built his project up by cobbling together other examples he found online. He started off by using a sketch that was originally designed to calculate the speed of a vehicle by measuring the time it took for the vehicle to pass between two points. [Carl] took this code and modified it to use a single photo resistor to detect the LED. He also built a sort of VU meter using several LEDs. The meter would increase and decrease proportionally to the reading on the electrical meter.
[Carl] continued improving on his system over time. He added an LCD panel so he could not only see the exact current measurement, but also the top measurement from the day. He put all of the electronics in a plastic tub and used a ribbon cable to move the LCD panel to a more convenient location. He also had his friend [Andy] clean up the Arduino code to make it easier for others to use as desired.
With tiny, Internet-connected computers everywhere these days, home automation is finally hitting it big. [Jelora] was looking for a few more home automation projects and realized his electric meter had a pair of ‘digital information outputs’. With a Raspberry Pi and a few bits of wire, he figured out how to read this digital output and put a log of his electricity consumption up on the web.
The digital output on [Jelora]’s meter is a bit odd; it’s 1200 bps, 7 bits per character, parity, with one stop bit. It’s also a 50 kHz AC signal for a binary ‘0’ and nothing for a binary ‘1’. To read this signal, [Jelora] is using a diode to throw out half the signal, a 6N138 optoisolator so the Pi isn’t connected directly to the meter, and a small cap to smooth out the signal. Simple, and it works.
This cleaned up signal is then connected to serial to USB chip and a PHP script scrapes the data every minute. The data received from the meter is stored in a data base along with a few other bits of information: if the meter is being charged peak or off-peak rates, and the price per kWh. All this is saved on an IDE hard drive (more reliable than the SD card, surprisingly), and a ‘electricity cost per day’ is plotted on a nifty graph and served up by the Raspberry Pi.
If you want to make your home more energy-efficient, chances are you will need a way to monitor your electricity usage over time. There are off-the-shelf solutions for this of course, but hackers like us tend to do things our own way. Take [Karl] for example. He recently built himself a solution with only a few smart components. We’ve seen similar projects in the past, but none quite like this.
[Karl’s] home has a power meter that blinks an LED to indicate the current amount of used electricity in Watt-hours. He knew all he needed was a way to electronically detect the blinking LED and he’d be able to accurately track his usage without modifying the meter.
The primary components used in this project were a CC3200 development kit and a photoresistor module. The dev kit contained a WiFi module built-in, which allows the system to upload data to Google spreadsheets as well as sync the built-in clock with an accurate time source. The photoresistor module is used to actually detect the blinking LED on the power meter. Everything else is done easily with code on the dev kit.
Remote sensing applications that make sense and cents? (sorry, couldn’t help ourselves) That’s what [hackersbench], aka [John Schuch], aka [@JohnS_AZ] is working on as his entry for The Hackaday Prize.
He received a multi-thousand-dollar water bill after having an underground pipe break and leak without knowing it. His idea will help you notice problems like this sooner. But if you actually have a way to capture data about your own water use you also have a tool to help encourage less wasteful water use habits. We wanted to learn more about the hacker who is working on this project. [John’s] answers to our slate of questions are after the break.
Continue reading “THP Hacker Bio: hackersbench”
From the look of this you can tell that [Jasper Sikken] has some pretty interesting stuff going on to monitor the utilities in his home. But it’s important to note that this is a rental home. So adding sensors to the gas, water, and electric meters had to be done without making any type of permanent changes.
The module above is his own base PCB which accepts an mbed board to harvest and report on usage. His electric meter has an LED that will flash for every Watt hour that is used. He monitors that with a light dependent resistor, crafting a clever way to fasten it to the meter using four magnets. The water meter has a disc that makes one revolution for each liter of water that passes through it. Half of the disc is reflective so he uses a photoreflective sensor to keep track of that. And finally the gas meter has a reflective digit on one of the wheels. The sensor tracks each time this digit passes by, signifying 10 liters of gas used. He also monitors temperature which we’re sure comes in handy when trying to make sense of the data.