TOF

17 Articles

Measuring Air Flow With Ultrasonic Sensors

July 26, 2017 by 23 Comments

Measuring air flow in an HVAC duct can be a tricky business. Paddle wheel and turbine flow meters introduce not only resistance but maintenance issue due to accumulated dust and debris. 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.

The principle behind the sensor [ItMightBeWorse] is working on is nothing new. 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. It’s another one of those “Why didn’t I think of that?” things that makes perfect sense in theory, but takes some engineering to turn into a functional sensor. [ItMightBeWorse] is using readily available HC-SR04 sensor boards and has already done a proof-of-concept build. He’s getting real numbers back and getting close to a sensor that will go into an HVAC automation project. The video below shows his progress to date and hints at a follow-up video with more results soon.

Here’s wishing [ItMightBeWorse] the best of luck with his build. But if things go sideways, he might look to our post-mortem of a failed magnetic flow meter for inspiration.

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Digitize Your Room With LIDAR

May 15, 2017 by 20 Comments

What’s the best way to image a room? A picture? Hah — don’t be so old-fashioned! You want a LIDAR rig to scan the space and reconstruct it as a 3D point map in your computer.

Hot on the heels of [Saulius Lukse]’s scanning thermometer, he’s replaced the thermal camera on their pan/tilt setup with a time-of-flight (TOF) camera — a Garmin LIDAR — capable of 500 samples per second and end up scanning their room in a mere fifteen minutes. Position data is combined with the ranging information to produce a point cloud using Python. Open that file in a 3D manipulation program and you’ll be treated to a sight like this:

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Ball Balancing Robot Uses New TOF Sensor

February 14, 2015 by 24 Comments

By now, you’ve most likely have seen or even played with an ultrasonic distance sensor. They work by emitting a sound, and then listening for the “ping” to return. The sensor can then tell how far an object is away by calculating the time in between. With sound waves traveling at 343.2 meters per second (768 mph), it’s no small task to measure the short time it takes for the sound to be emitted, then hit something a few feet away, and return. Now, imagine trying to do that with light.

Light in comparison moves at a whopping 299,792,458 meters per second (or about 671 million miles per hour). You’re going to have to have a pretty fast finger on a stopwatch to measure the time it takes for light to bounce back from an object a few inches away.

[Paul Bristow] is doing just that with the use of a new Time of Flight (ToF) sensor called the TeraRanger One. Developed in cooperation with CERN, this sensor uses a very narrow beam of light (listed as +/- 2 degrees) to accurately measure the position of an object to a resolution of 5mm, with distances up to 14 meters away. It boasts an impressive update rate of >1000 samples a second, and is very micro-controller friendly with UART, I2C, SPI, and PWM output.

[Paul] and his fellow hackers at the Post Tenebras Lab Hackerspace in Geneva got their hands on this sensor, and in a short time had a ball balancing robot up and running. The crude program is not running a PID controller, so the results seen in the video after the break aren’t that impressive. Also, the sensor isn’t exactly cheap at about $180 USD. Despite that, it will be interesting to see what applications these sensors will be used for. If you have any ideas, leave them in the comments below.

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