Hot Wheels Radar Gun for distance calc.

[meratz]

I found a webpage on hacking the Hot Wheels radar gun. I would like to use it on a robot for distance calculation outside in the sun and wind. I have tried to find info on what kind of distance I could measure with little success. If anyone has had a chance to mess with one and know its capabilities, I would appreciate a little help. I would like to measure a maximum distance of around 30 to 40 feet or 10 to 12m. A circuit implementing the gun for distance checks would be outstanding. Also, could one separate the tranmitter and reciever and make a beacon for use outside? This would be great since IR and ultra sound don't work well in the sun and wind respectively, at least not at a distance.

 

[evandude]

You say you already found info on hacking the radar gun, but you don't say what page it was... In any case, you should read this one:
https://www.edparadis.com/radar/

He goes into how he's trying to hack it for distance measurements, but explains the difficulties involved.

Needless to say, it's not going to be a very simple hack no matter how you go about it. The speed measuring job that it does by default is pretty simple, which is why this inexpensive device exists commercially, but distance measurement is a totally different story.

 

[meratz]

That was the webpage I found. Finding the distance looked a bit over my head. I was hoping someone smarter than me would be able to figure out how to hack the distance out of the gun.

 

[evandude]

That was the webpage I found. Finding the distance looked a bit over my head. I was hoping someone smarter than me would be able to figure out how to hack the distance out of the gun.

It's not a matter of "hacking the distance out of the gun", because such information is not available in the basic radar gun - it's a matter of using the gun as a part of a more complicated system to get a distance measurement.

In short, speed measurement is not very hard, because when you apply the transmitted and reflected 10.5GHz signal to a mixer, what you get out is a low frequency signal that is proportional to the speed of the object you're looking at. Faster movement = higher frequency. Again, this is why they were able to make a radar gun cheap enough to be sold as a toy.

To be able to measure distance, you have to get into the more complicated things that he was talking about - sweeping the frequency of the output, so that the time delay between transmitted and reflected signals due to the distance the signal travels results in a frequency difference, which is then mixed and measured like before - however, as he discovered and pointed out in his article, you do need to sweep the frequency very quickly (nanoseconds) over a large range (tens or hundreds of MHz), and preferably somewhat linearly, in order to be able to make it work - which is not a simple task.

 

[meratz]

Sounds like I should probably think of something else. I want to stay away from complicated. I am in my family years and all I have is quick and easy time. Thanks for the input.

 

[Sceadwian]

A well shielded ultrasonic mic and transducer should work fine outside for short distances.