[Apexys] is performing some experiments with switched-mode power supplies and needed to compare the inductance of the coils he was using. His multimeter doesn’t have an inductance testing function, but he does have a 555 timer on hand. He put the 555 and some other parts together to create his own L meter. The writeup includes the theory behind this meter, with an incoming AC source converted to a voltage by an RC network.
Once he’d worked out the design it was time to build the circuit. Instead of printing a circuit board he created what he calls a DCB; Drawn Circuit Board. We’ve got to admit that this was way faster than using toner transfer or soldering point-to-point. We also like his use of an Erlenmeyer flask and a torch to heat the etchant. We don’t make PCBs in the winter because our Cupric Chloride is too cold to use outside but that may change now. The final piece in the puzzle is an analog meter which he pulled from an extra microamp meter he had on hand. Check out the demo after the break.
Continue reading “555 inductance meter”
This is the Edison clock, designed by [David Krawczyk]. It shows time in the same way as the multimeter clock, regulating power to two analog needle meters. The feature that makes this one a bit different is the alarm. You can see the series of holes on the front of the base. These have a small light bulb socked in each, and correspond to hours and 5-minute increments. Insert two bulbs to set the alarm time, and make sure that the alarm knob points to ‘on’. As you can see above, the alarm has been set to 8:15. Hidden on the last image of the article above is a PDF with just a bit more explanation. Still, much has been left out so if you replicate this clock we want to hear about it.
[via Gizmodo and Walyou]
As a biomedical equipment technician [Adam Outler] equipment needs to be in top working condition. The emergency room staff were complaining about erroneous noise on the electrocardiogram and it’s his job to fix it. He suspected EMF interference so as a quick first step he decided to throw together an EMF detector using an Arduino. It uses a bank of LEDs as an indicator bar to reflect the EMF picked up by the red antenna. In the video after the break [Adam] checks a room for possible sources of interference, treating the recharging circuit from the emergency lights as the most likely culprit. Since the ECG is many times more sensitive to EMF than the Arduino, this turns out to be a quick and easy way to make sure he’s not barking up the wrong tree.
Continue reading “Arduino EMF sensor”
[AndyO] embraced his inner geek by building this meter clock. It exhibits a lot of features that you’d want to see in a home-built timepiece, include over-complexity, abundant features, and RGB LEDs. We’re fascinated by the design he put into this. For instance, the two indicator LEDs on the clock face are not poking through the surface, but use brass tubes as light pipes. Also, the three buttons on the top are almost indistinguishable, and have an RGB back light that places a halo around each. The case itself was built by first making a form, then laminating thin sheets of wood (a difficult task due to the tight curves). The needles themselves are not actually meters, like the clock the inspired the build, but are attached to servo motors. This all comes together into a fascinating build, and a great writeup.
Here’s an analog bandwidth meter made to look like an old pressure gauge. It’s actually new, but the paper showing the graduated scale was stained in a bath of black tea, then dried in an oven to give it an aged appearance. We think it’s quite effective.
The dial itself is a volt meter driven by an Arduino in much the same way as the multimeter clock. Bandwidth data is pulled from a Linux router, filtered down to the target data using ‘grep’, and sent over the serial connection by a Perl script. Since the meter itself is just waiting for serial data, alterations to the router’s scripting make it easy to represent a count of unread emails, tweets, or whatever data your code can scrape.
How much water do you use when showering, or washing your hands, or washing the dishes? Not how much does the average person use, but how much to you use? That’s what the team over at Teague Labs set out to find with this water usage feedback system. The sensor used is a Koolance flow meter which is intended to measure coolant flow in PC liquid cooling systems. At $20, it makes a nice low-cost sensor which was paired with a WiFi enabled Arduino. In the image above they’re using an iPad as a screen so that you can see how much water you’re using (or wasting) as you wash your hands. This resulted in saving 1/2 gallon of water every time someone washed their hands.
The project code, schematic, and board files are all available for download. Along with the hardware build there’s some nice server-side software that gathers and graphs the data over time. We’ve seen a lot of power-meter hacks, but it’s nice to have the option to track water usage, even if this is tailored to just one tap at a time.
Here’s an analog meter clock using an MSP430G2211 microcontroller. [Doug Paradis] chose this processor because it is the lesser of the two that come with the TI Launchpad. The parts count is fairly low too; a clock crystal, two analog meters, a few buttons, and a voltage regulator.
He’s done a nice job putting this together. We challenge you to give this a try yourself and build on [Doug’s] features. We really liked the calibration subroutine in [Alan’s] multi meter clock. It would be fun to implement that functionality and store the calibration code in the MSP’s flash memory. You can use our ported garage door opener code if you need an example of how to store data in flash.