LED chaser effects to follow fast-moving indoor objects around a course? - Page 1
Forum section: electronics / projects

author: victorhooi
author_rank: Regular Contributor
timestamp: June 05, 2025, 02:10:58 pm
content: Hi,I'm trying to design a fun project using addressable (i.e. digital) LED strips, with "chaser" style effects that follow objects in real-time around a fixed course (e.g. go-carts going around an indoor track, or skaters/runners around the edge of a indoor skate rink etc.)Firstly - is this sort of feasible, for the home geek/engineer who doesn't have a PhD in RTLS?Secondly - what sort of sensor technology would you use for the indoor positioning, with low-enough latency for the LED effects to track it accurately?My first thought was some kind of crossing sensor - e.g. magnetic strips on the carts, or IR beam-sensors etc, to track the carts as they crossed specific lines - but you'd likely need a lot of them to get accurate positioning. (I checked, and apparently F1 cars do something like this, using magnetic loops and transponders -discussion on F1 track positioning,more detailed technical post). However, go-carts (or people) are much smaller, and the track is much smaller - and I don't know if it's feasible to have that many sensors for it to work. (I assume the sensors are OK for things like lap timings etc., but not real-time positioning - although let me know if this assumption is false).Alternatively, I read about some places using RF - e.g. UWB transmitters and trilateration to get accurate indoor positioning (e.g.Sewio,this one- although they offer no details on how it works). But would that be responsive enough, to get real-time location, and have the LED patterns follow the object without noticeable latency?I know there used to be a Decawave DW1000 UWB module that was quite low-cost - but they got acquired by Qorvo. I think there are their newer DW3000 range now:https://www.mikroe.com/click/wireless-connectivity/uwbOr MakerFabs has their ones?https://www.makerfabs.com/mauwb-esp32s3-uwb-module.html(uses a ESP32 plus a STM32 to handle some of the positioning?)https://www.makerfabs.com/blog/post/new-features-of-mauwb-data-transmissionOr would ceiling mounted 24Ghz mmWave sensors work here? I guess you'd need a few of them, pointed at the track, and also need a way to fuse several sensors together, to get a overall picture of the track? And I don't think the FOV of them is that great - so you'd need a lot of them spread out over the ceiling.Or would cameras, with ML object detection work? (I think I'd probably just use an existing model pre-trained on cars/vehicles etc.)Or LiDAR?I do know there's a bunch of really cool interactive multimedia exhibits done using theTouchDesignersoftware - I believe they use various depth sensing cameras (e.g. Kinect, Oak etc.) And I assume they can do it all in realtime, with acceptable latency.Thanks,Victor

author: tom66
author_rank: Super Contributor
timestamp: June 05, 2025, 02:33:37 pm
content: Related question - How quickly do you need the LEDs to update? I found that the WS2812B LEDs have inherent jitter in their update time as whilst they will frequency-sync with each other, they do not phase-sync, so if you want a fast moving LED (one per frame on a high speed camera for instance) then they won't work well for that application since you can't predict when the LED will illuminate.If you just need it to work at "human visible speeds" this isn't an issue.

author: ledtester
author_rank: Super Contributor
timestamp: June 05, 2025, 02:39:05 pm
content: Quote from: victorhooi on June 05, 2025, 02:10:58 pmI would see how well YOLO works:Master YOLO Object Tracking in Minutes: Beginner-Friendly Setup for Any Device in 2025https://youtu.be/mfNq5YREPbEand the video has a link to a "drone-view" detection model (straight overhead/forward-looking views).

author: ajb
author_rank: Super Contributor
timestamp: June 05, 2025, 04:08:11 pm
content: There are a few commercial systems designed to do this for live performance applications (like automatically tracking a performer with a spotlight) using different technologies:https://cast-soft.com/blacktrax/https://follow-me.com/trackit-system/https://www.zactrack.com/product-comparisonAll of those require some sort of beacon on the thing being tracked, which is generally going to be more reliable/accurate than machine vision, especially if you can't rely on a strictly controlled environment or object lighting. BlackTrax uses infrared LEDs and cameras, which is probably the easiest option to DIY. The IR beacons blink some sort of ID code so that the cameras can distinguish them from each other and other IR sources in the environment.Some VR headsets use scanned IR and photosensors on the headset to get very precise position and orientation: a fixed device sends a bright IR sync pulse, then scans two lines of IR across the scene, one vertically and one horizontally, at a fixed speed. Each IR sensor records the time from when it sees the sync pulse to when it sees each scan pulse to get angular horizontal and vertical position relative to the fixed beacon. You'd use two or more of those fixed devices to get XYZ position and multiple photosensors to get orientation if you need it.