X-band radar sensor

Jimmylee

Has anyone used the x-band radar sensor, Parallax item # 32213? That is other then doing the sample demos. It appears to be a very interesting sensor, but I have seen only a very few past threads about it in the forum and not much activity. Would appreciate suggestions or where to go for discussion on it's application and more advance programming on item#32213.
Thanks much.

Ron Czapala

I experimented with it a little.

I was surprised when it detected movement thru the brick walls of my house.
I set up two basic stamps - one with the X-band sensor and an XBEE transceiver, the other with an XBEE and an LCD display.

I pointed the X-band sensor toward an outside wall and went outside with the other unit. As I walked within a couple of feet of the brick wall, it detected the movement.

ElectricAye

I wonder if this gadget could be used to create something like ground-penetrating radar. I know it detects only movement, but if you move the sensor and keep track of where it's pointing and keep track of its other motions and somehow filter through the resulting data and... and... and... any chance it could "see" through a foot or so of dirt?

Jimmylee

Thanks much for sharing your experience Ron Czapala.

Timmoore

I have seen some interesting effects if there is an object very close to the sensor - it reads a moving object even though the object isn't moving nor is there anything behind it that is moving. Soon as I move the object a bit further away it reads no movement correctly.

snotling

In order to build something similar to a speed radar, I've been searching for the right sensor.
I've found specific devices that match my requirements (e.g. Houston Radar products, etc) but they're quite expensive (around $500) for a hobby project !
So I was thinking of using the much cheaper X-Band radar sensor instead. However, the documentation states that:

In contrast to speed guns, which use a wave guide to direct the antenna radiation pattern, the X-Band
Motion Detector’s antenna has a wide radiation pattern to convert velocities from multiple points to
oscillations that notify the microcontroller that movement was detected. This device is designed to detect
motion, not to determine speed of a moving object. However, an application may still use a rearranged
version of the Fd equation to determine speed provided everything else in the detection area stays still.

The "wide radiation pattern" might be problematic in my case. Is there a way I could make it "narrower"?
As for the equation, what kind of "rearrangement" would it require to accurately calculate the speed of a moving object?

Thanks for your help!

Timmoore

There is an equation in the doc. The main problem is it needs the angle to the object which you probably dont know. I just assumed 90deg and left it out. After that the equation is straight forward
V = cyclespersec*30000/2105 gives you mm/sec
V = cyclespersec*30000/53467 gives you in/sec
but what is the accuracy and under what conditions I dont know and I haven't tested the accuracy against a known source.
Also note the supplied driver gives you cycles in the measurement time not cycles/sec

snotling

Thanks for your help Timmoore.

I've finally managed to get my hands on a X-Band.
My initial quick tests showed quite "erratic" readings...
So now the question is indeed how to get an accurate speed measurement out of the sensor.

First, I think I need to narrow the RF beam, following the advice in this thread.

thatguygomer

snotling, did you happen to get any resolution to your questions? I ask because I have been thinking about buying one of these for a project in which I will need to obtain the speed of a target as well.

-g