Chances are pretty good that at some time in your life, you’ve crossed paths with a norovirus. And chances are that you remember the encounter vividly, or at least its aftermath. I recall a run-in with the bug one Christmas, when my parents brought over more than just toys for the kids when they visited. Within a day, everyone in the house was sharing the joy. Twas the season; they don’t call it the winter vomiting bug for nothing.
Most of the 685 million norovirus infections each year resolve after a few miserable days, but some require hospitalization and 200,000 of them result in death, mainly from dehydration and mainly children. An easy to use, cheap, and accurate means of detecting the virus in the field would be quite a boon to public health. And soon, smartphones may be able to do just that.
Continue reading “Norovirus Smartphone: Using Megapixels And Microfluidics To Fight The Other Kind Of Virus Infection” →
Having a motorized gate on your driveway is great, but only if there’s an easy way to trigger it. [Andrew] says the gate at his parent’s place could only be controlled by manually pushing a button on the panel or with a dinky remote that didn’t have nearly the range they wanted. So he decided to build his own magnetometer allowing the gate to automatically open when a car was trying to leave.
Naturally, there are commercial offerings that would solve this problem. But with a sticker price of more than $150 USD, [Andrew] was more than happy to spend a bit of time tinkering to get the job done for less than 1/10th the cost with an ESP8266 and a QMC5883X series magneto-resistive sensor. Of course, this is one of those projects that seems simple enough in your head, but ends up taking a bit of finesse to pull off in the real-world.
For one, [Andrew] had to figure out how to prevent false positives. Pretty much any object brought close enough to the sensor, including his hand, would cause it to react. He ended up coming up with a way to use a rolling average to prevent the gate from firing off just because a squirrel ran past. The built-in safeties are designed to ensure that the gate only opens when an actual car is sitting in the appropriate spot for long enough.
Speaking of, we love how [Andrew] deployed the QMC5883X sensor for this project. The small sensor board and a few moisture-absorbing packets were placed in a Sonoff IP66 waterproof enclosure, and buried under the rocks of the driveway. A standard CAT5 cable is used to tether it to the ESP8266, relay, and assorted other goodies that now live in the gate’s control box. In the future he says the cable will likely have to go into a conduit, but for now the system is working more or less how he expected.
If your estate isn’t quite palatial enough to have a motorized gate out front, we’ve seen plenty of projects that add some much-needed intelligence to the humble garage door opener which might be more your speed.
If you’ve heard of core rope memory, it will probably be in the context of vintage computing equipment such as Apollo-era NASA hardware. A string of magnetic cores and sense wires form a simple ROM arrangement, which though long-ago-superceded by semiconductor memory remains possible to recreate by the experimenter. It’s a path [Nicola Cimmino] has trodden, as he’s not only made a few nibbles of core rope memory, but incorporated it with an Arduino as part of one of the most unusual LED flashers we’ve ever seen. The memory holds a known sequence of bits which is retrieved in sequence by the Arduino, and the LED is kept flashing as long as the read values conform to those expected.
The memory itself is simple enough (and not to be confused with magnetic core memory). The cores are ferrite rings that form a sequence of small transformers that become the bits of the memory. Individual bits are set high or low by either passing a sense wire through a core to create a primary, or bypassing it. Multiple sense wires can be used for separate nibbles in the same cores, so for example his four nibbles all share the same four cores. Pulses are sent down the wires, either passing through a core or not, and equivalently picked up or not on sense lines.
In this case the sense wire is driven directly to ground by Arduino pins which means that the circuit is relying upon the current limiting of the ATmega328 to avoid destroying itself, it’s possible we’d add a driver transistor. The bits are read meanwhile from the secondary windings through a diode rectifier and capacitor to an Arduino analogue pin.
Core memory has been paired with an Arduino before on these pages, though of the RAM variety.