Memfault State of IoT Report

Project feasibility - Police Speed Gun

Started by IloveGraceKelly 12 months ago5 replieslatest reply 12 months ago139 views

Hi everyone,

I am currently a rising senior majoring in computer engineering. I wasn't able to secure an internship this summer so I wanted to come up with ideas for projects.

One of my project ideas is creating a police speed gun that uses LIDAR to measure the speed at which a vehicle is moving. I was thinking of buying a LIDAR sensor to measure the vehicles speed and using a microcontroller to perform the logic of calculating the speed and displaying it onto an LCD screen. I know I could also use a doppler radar sensor to also to measure speed, but I want to know if this is possible with LIDAR sensors.

These are some of the LIDAR sensors I was thinking of using:

TF03 Long-Distance LiDAR Module (100m)


LIDAR-Lite v3

I know the range and accuracy of the gun is going to be significantly worse than an actual police speed gun due to the LIDAR sensor. Despite this, would this project be possible to implement with the given sensors to some degree? I appreciate all the responses.

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Reply by beningjwJune 2, 2023

Great question, but I'm going to turn it around on you. Does it matter if it is feasible or not? 

Outside of school, we are always building systems that we aren't 100% sure will work or meet cost and schedule constraints. There is an inherent risk of failure in all endeavors. (In school we are taught that we must always succeed, which kills innovation). 

Your ultimate goal is to gain experience in computer engineering by working on a project. What you've described sounds interesting and I think you'll learn and gain valuable experience whether you succeed or fail. 

My advice would be to try it and see if it is feasible. Get the different sensors, do your research, build some mock-ups, do some testing. I've learned the most in my career when I've failed (although my preference is succeed but nearly fail so that I'm stretching myself). 

If you run up against technical questions, hurdles, add a post here, and at some point, let us know if you've succeeded or failed and a bullet list of what you learned. 

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Reply by IloveGraceKellyJune 2, 2023

I really appreciate this response thanks.

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Reply by remcyclesJune 2, 2023

That seems like a feasible project to me.  I've never used a LIDAR sensor myself, but from the datasheets and this video it seems like it should work:

The question is how well does it work?  I would turn it into an experiment and compare against another speed measurement technique (like two beam break sensors across a road at a known separation, a video of the cars traveling between known points, or a speedometer) so you can measure the accuracy.  If you have the budget, compare two of the LIDAR sensors against each other and the reference measurement as well.  Mount the LIDARs on a tripod during those tests.  I'd also recommend experimenting with signal processing on the LIDAR measurements to see how low-pass filtering (or simple averaging) can help clean up the raw sensor readings (numeric derivatives between two samples can be noisy).  How does changing the filter cutoff frequency (or number of samples in the average) help or hurt?  Does configuring the LIDAR sensor for slower or faster sample rates help?

I think it would be a good learning experience and I'm curious how it goes.  I've often thought about doing a similar practice project with RADAR.

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Reply by lmitchamJune 2, 2023

The two things that you will want to consider is firing rate of the laser and accuracy.  Modern LIDAR speed measuring devices fire at rep-rates of 180 to 1000 Hz and have a range accuracy of +\- 6 inches.  This produces a speed accuracy of +1\-2 MPH at 1 sigma.  

Good luck and have fun!

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Reply by AstroJerryJune 2, 2023

That is a very feasible project. I have used LIDAR sensors for a number of robotics projects. I really like the Lightware products like this:


It is pricey but very good. Something like this and a small ESP32 board with a LCD Display and it would be easy. Good luck!

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