Panel Meter-To-Bluetooth Hack Hijacks The Display Segments

There are a proliferation of cheap digital meter modules available online for pocket money prices. Current, voltage, frequency, or combinations thereof can all be yours for just a few dollars and a wait for shipping. Unfortunately though these meters are all self-contained units. They do not have a serial port or other interface through which you can log their readings.

This failing was not an obstacle for [Scott Harden], though. He simply added a Bluetooth interface to his combined voltage and current meter module by using an ATmega328 microcontroller to capture the signals sent to the module’s display LEDs and interpret them into readings for his Bluetooth module. He details the process of reverse engineering the meter, and his build. The result is an intriguing mess of wires with a DIP ATmega hanging on their ends. But it performs the task requested of it admirably and when mounted in a project box you would not know what lurks within.

He has made his code for the project available in his GitHub repository, we can see that this could be a valuable technique for use with other similar displays. In the video below the break he gives us a full run-down, as if his comprehensive write-up was not enough.

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How to Weigh an Eyelash

So you’re a boxer, and you’re weighing in just 80 micrograms too much for your usual weight class. How many eyelashes do you need to pluck out to get back in the ring? Or maybe you’re following the newest diet fad, “microcooking”, and a recipe calls for 750 micrograms of sugar, and you need to know how many grains that is. You need a microgram scale.

OK, we can’t really come up with a good reason to weigh an eyelash, except to say that you did. Anyway, not one but two separate YouTube videos show you how to build a microgram balance out of the mechanism in a panel meter. You know, the kind with the swinging pointer that they used to use before digital?

Panel meters are essentially an electromagnet on a spring in the field of a permanent magnet (a galvanometer). When no current flows through the electromagnet, the spring pulls the needle far left. As you push current through the electromagnet, it is attracted to the fixed permanent magnet, fighting the spring, and tugs the pointer over to the right. More current equals more pull.

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Monitoring the world’s DNS status using a display straight out of WarGames

Nothing says Cold War like a map of the work with LEDs embedded in it. Throw in some analog dials for good measure and you’ve got a piece that would be comfortable mounted next the WOPR in everyone’s favorite ’80s-computers-run-amok movie. We think [Dima] really hit the mark when building this status panel for OpenDNS datacenter monitoring.

[Dima] works for OpenDNS and wanted to make something special for its upcoming 5 year anniversary. He’d already been toying with making boxes from laser-cut wooden pieces. This was just a matter of choosing a size that would fit the dials and leave a suitable area for a laser-etched map. Each of the twelve panel meters gets a PWM signal from the Arduino Mega that he used to bring the device to life. It shows a comparative server load for each data center based on the previous day’s numbers. There is an LED in the map for each of these centers. Right now they’re all red, but he used RGB LEDs and plans to upgrade the capability soon. He should have no problem doing this as he sourced some TLC5940 drivers to extend his I/O capabilities.

Don’t forget the check out the clip embedded after the break. Continue reading “Monitoring the world’s DNS status using a display straight out of WarGames”