He discovered a paper from 2015 that describes the method that measures the change in time-of-flight of an ultrasonic pulse across a moving stream of air in a duct.
The principle behind the sensor is working on is nothing new. Being able to measure ducted airflow cheaply and non-intrusively, like with this ultrasonic flow meter, could be a big deal for DIY projects and the trades in general. Paddle wheel and turbine flow meters introduce not only resistance but maintenance issue due to accumulated dust and debris. Measuring air flow in an HVAC duct can be a tricky business. Looking for an outdoor anemometer rather than an HVAC flow meter? We’ve got one made from an old electric motor, or a crazy-accurate ultrasonic unit.Ĭontinue reading “Custom Cut Pinwheel Makes A Useful HVAC Duct Flow Meter” → Posted in Misc Hacks, Slider Tagged air, anemometer, duct, flow meter, hvac, reflective sensor, turbine But for a quick and dirty measurement, it’s not bad. The limitations are obvious: duct turbulence, flimsy construction, and poor bearings. A reflective optosensor counts revolutions as the turbine spins in an HVAC duct, and with a little calibration the rig produces good results. But a simple pinwheel, custom cut from patterns scaled down from a toy, proved to be just the thing. That calls for some kind of turbine producing a signal proportional to air flow, but a first attempt at using a computer fan with brushless DC motor failed when a gentle airflow couldn’t overcome the drag introduced by the rotor magnets. His experiments in air duct flow measurements, which previously delved into ultrasonic flow measurement, led him to try mechanical means. Great in theory, perhaps, but as found out, a homemade pinwheel is far from an ideal anemometer. Pinwheels are pretty optimized from a design standpoint, and are so cheap and easy to build that putting a pinwheel to work as an HVAC duct flow meter seems like a great idea. One of our favorite EDF drone innovations that we saw recently was this thrust-vectored single rotor device, a really unique idea that took some interesting control methods to implement.Ĭontinue reading “A Safe, Ducted Drone With No Visible Blades” → Posted in drone hacks Tagged Carbon Fibre, drone, duct, EDF, safetyĮveryone is familiar with pinwheels, and few of us haven’t crafted one from a square of paper, a stick, and a pin. The power electronics needed are far more serious than we’d usually see on a drone of this size, to compensate for the extra mass of the thrust ducts and the impediment to the air-flow caused by the two 90° bends. Whilst there’s no doubt that the finished drone succeeds at being safe, the design does come at the cost of efficiency.
Some DJI electronics provide the brains, and there’s also a parachute deployment tube on the back. He even went to the trouble of running CFD on the design before manufacture, to ensure that there would be adequate thrust. We’re impressed by the fact that custom moulds were made for every part of the body, allowing to manually create the required shapes out of carbon fibre cloth and epoxy. The creation is described as a bladeless drone, but it’s not: they’re just well hidden inside the carbon fibre. ’s solution was to take some EDFs and place them in the middle of large carbon fibre thrust tubes, making it impossible to get anywhere near the moving parts. Conventional prop-guards like those seen on consumer drones often only protect the side of the propeller, not the top, and the same problem goes for EDFs. We love a good drone build here at Hackaday, but no matter how much care is taken, exposed propellers are always a risk: you don’t have to look far on the web to see videos to prove it.
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