Hot Wheels Toy Turned Radar Gun


[Ken] was strolling through a department store one day looking for a gift for his daughter when he stumbled across a Mattel’s Hot Wheels Radar Gun for $30. He purchased it, took it home, and tested it out. Surprisingly, the device had the ability to not only scan toy cars, but also regular size vehicles, spinning bicycle wheels, and joggers as well. As his mind began to churn coming up with new ideas, he purchased another toy and repackaged it creating a more professional grade DIY radar speed detector.

The process was pretty simple. First, he disassembled the device getting to the Doppler radar system inside, which was similar to the professional radar guns that police officers used. This toy was able to transmit a continuous wave at 10.525GHz, measuring the returning frequency of returning waves that bounced off of moving objects. However, the detection range of this toy was severely limited. [Ken] then upgraded the antenna housing unit with a 3″ diameter acrylic document tube, making the quality look a lot better. After that, the system was attached to a tripod allowing for the device to be easily transported and setup near a busy traffic road, quietly watching the speed of cars driving by.

This custom toy radar gun hack is a useful tool that can be transitioned into other areas like baseball. The antenna might need to be upgraded for that use, but this project is a good starting point for creating a nice little radar gun that could be utilized elsewhere.


40 thoughts on “Hot Wheels Toy Turned Radar Gun

  1. Wonder what the accuracy of the unit is ?
    Or for that matter it’s susceptibility to various multipath artifacts (ie. “cosine error”).
    Eh, interesting *toy* ….. but definitely not in the same league as an MPH or
    Kustom Signals law enforcement grade device.

    Agree w/the other poster, unit is an EMITTER !!! not a “detector” !

    1. oh yes you can always assume that a speeding ticket from a “law enforcement grade device” is 100% accurate.

      If it’s just an EMITTER than maybe you can explain to us how it manages to detect the speed!

  2. I don’t see any modifications to the antenna or amplifier to increase the range from the original 40′, just modifications to the housing to make it look prettier. there’s no hack here that I see. Am I mistaken?

    1. you say: ” just modifications to the housing to make it look prettier. ”

      the article says: “the system was attached to a tripod allowing for the device to be easily transported”

      The detector is indicating a lack of reading skills

      1. Funny, my missing the point detector’s needle is pegged…

        Yes, this does qualify as a hack in my book as the functionality is improved by a tripod stand and the aesthetics improved with a new shroud, and wiring changes were required to move the display further from the antenna.

        But as Chris C. points out below – the wording of Hackaday’s writeup implies that the hack would address the limitated detection range, but then veers off into the form factor changes.

        I’d wager that a good portion of the Hackaday audience would be capable of lashing everything inside one of these troys to a tripod with some longer wires. I’d also guess that few of us would know where to begin with upgrading the detection range of a radar based velocity detector. I for one don’t, and I was looking forward to learning from an example of how it could be done. I felt let down by this hack, and I doubt I’m the only one. Likely because Matt wrote “was severely limited” instead of “is still severely limited”. Past tense implies this has changed, when it has not.

  3. This was originally described as a “Radar Speed Detector”. Dropping “speed” entirely changes the meaning. Also:

    “The process was pretty simple. First… However, the detection range of this toy was severely limited. [Ken] then upgraded the antenna…”

    At that point you’re expecting a functional upgrade to the range, which doesn’t follow. And which makes the reader tend to stop, then re-read, to make sure they didn’t misunderstand.

    This is caused not just by the particular wording, but the grouping of statements within the paragraph. The paragraph starts by claiming to describe the modification process, but soon goes on a tangent with details of the function and limitations of the original device, before returning to the process. That would be proper *if* some of these details were immediately relevant to the process, for example because they were changed, affected decisions made, etc. But that’s not the case. So the details of the original device warrant a separate paragraph, or at least to be broken out of the “process, first, then” bracketing.

    I’m sure the “shuddup haters and backseat editors” folks will appear soon enough. But at the time of writing this comment, all four previous comments express confusion or disappointment in the writeup. Figured I’d try to be constructive, and take some time to explain why the writeup isn’t going over so well. Hope it’s taken in the spirit intended.

    One final question. I seem to recall HAD was originally started by a fellow that eventually moved on to run Make. As such, there was sort of a gentleman’s agreement that HAD generally wouldn’t cover material in Make, and vica versa. Is that no longer the case?

    1. +1 for the poor quality of the writeup – Matt Tendrup’s other articles have had me biting my tongue for similar reasons. I mean “then upgraded the antenna housing unit with a 3″ diameter acrylic document tube, making the quality look a lot better” is not even English – worse still, I actually have no idea what the author intended to say. If they can afford to send people to space surely they can afford to pay a copy editor?

    2. I also clicked in haste to see this antenna upgrade and then came here to the comments. Not let down like “Crystal Skull” let down, but I agree the wording could use some alteration. I do love a good toy shelf upgrade/hack so hopefully this guy will keep on keeping on with the tinkering :)

    3. Gentlewomen agreements are only as worth the paper their written on. Probably enforceable but may not worth the effort, how could we know without knowing the agreed to terms beyond a vague recollection the may have been on? Not worth bringing up, and I spent way too much time on this myself.

    1. It’s already trivial to gain access to the 10Ghz band. there are surplus 10ghz Full GUNN Diode transceivers are all over ebay for almost nothing.

      Heck I used to take apart surplus grocery store people detectors for the doors to do this. you can feed it line level audio and send AM audio to the other end full duplex. Hear and talk at the same time, kind of cool to aim at hills and hear your echo.

      Adding gain via a free Dish TV dish is just as trivial.

    2. I actually bought two of these when they first came out to see if this was possible. Unfortunately, I never got around to trying it out. Gave one of them away as a kid’s birthday present. The second is still in my closet waiting for me to overcome inertia and do something with it.

  4. Yup, actually bought one of these guys to check my speedometer after reading the original MAKE article a while back. If I remember correctly, there were a few others who modded theirs to increase the range, though I don’t think I have the links anymore. But, here’s a link that might be more suited to a HAD reader’s tastes. It goes into how you can integrate this $25 wonder into some other project.

  5. This guy paid way too much for that device. I tend to buy mine (I have a few) from Goodwill for about $5.00 USD…

    That said – the real hack for the Hot Wheels Radar Gun (that no one has managed yet – and in fact may be impossible with the device according to everything I have read about it) – is to be able to turn it into a functioning radar system.

    Basically, if it could be mounted, and in some manner rotated or swung about a vertical axis – then “pinged” in the same manner as real radar – it could be used to detect distances and locations of objects around it. It could make for another interesting and useful sensor for robotics, for instance.

    I tend to wonder if this device – perhaps coupled with some info from that DIY MIT radar courseware – could potentially lead to such a sensor hack?

    1. I feel that it will not be possible. You will need some sort of transmitter modulation for ranging radar. These doppler detectors normally have a free running LO that is transmit and also mixed with the received signal so the doppler shift remains. The easiest method with this architecture is sweeping the LO (look up FMCW radar) but these modules typically use a DRO which cannot be electrically detuned very well. Pulse modulation may work in theory with an isolating switch in series with the TX antenna, but due to the short range a very fast pulse rate would need to be used, making the signal extremely broadband, and thus mostly fall outside the receive range.

  6. Improvements for this hack:

    1) interface with a camera (to get a picture of the license plate of drivers exceeding a certaing speed reading) and an RasPi (to email said picture to the local police department). Yes, I know this picture isn’t legally enforcable, but in many communities (like mine) it will result in a form letter asking the car’s owner to drive within the speed limit.

    2) Once people figure out what this thing is, you’ll also want to make this thing a bit more “baseball-bat”-proof.

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