IR Distance Test
A month ago, I had the rather belated realization that merely sticking a bog-standard infrared LED on a short mast on top of my tank was not going to work very well. Most LEDs are intended to be directional. I needed an LED that would point not up but in 360 degrees, so that the opposing tank could detect it, no matter where the tanks were in relation to each other.
So I ordered a few different lenses and infrared LEDs from Digikey. Though the number of choices on that site seem overwhelming at first, once I narrowed-down the options based upon my needs, there were only a few options left for each.
Also, since I finally had a working camera PCB, I used one of the boards plus an OLED display to build a "detector box", a gadget that displays detected IR blobs on the screen. This made testing much easier, since I didn't have to sit next to a computer reading serial debugging information.
[Before I even received the LEDs in the mail I experimented with using sandpaper to scuff some of the LEDs that I had laying around, to see if I could make the light diffuse in a circular, right-angle way. But this was fairly unsuccessful.]
For the limited number of lenses and LEDs that I had, there was a pretty clearly winning combo early on. The LED has a flat top, instead of a dome, which means that there latitude in where it can be placed under a lens.
I tried to film myself testing the detection distance:
In the beginning of the video, the flickering of the white blob means that the LED is at the edge of the detection distance. This video, though, is with the lens just resting on top of the LED. There is a "sweet spot", though, with the lens raised slightly higher, that focuses the light into a pretty bright, side-viewable beam. This was easiest to adjust for by focussing a camera on the lens and making small adjustments. I was able to get an estimated ten feet of detection distance with this setup. It's less distance than I wanted but still workable.
I designed a mount in FreeCAD for the LED and the lens. I gave some tolerance to where the LED can be placed vertically, since I had a really hard time measuring the optimal placement. I figure I can adjust the position with this prototype and then make, in the final version, the bottom of the LED body will rest against a lip in the mount. With the technical drawings for the lens available, I didn't need to do much measuring, and the whole thing came together in a few hours (most of that time was spent remembering how to use FreeCAD).
Here's the 3-D rendering from Shapeways:
So, I'm waiting on a 3-D printed part and on a PCB. While I'm waiting I can work on the software and I can do some wiring to prepare tanks for conversion to robots. But I'm really running out of motivation, based upon my somewhat pessimistic forecast for the success of the motor drivers.
So I ordered a few different lenses and infrared LEDs from Digikey. Though the number of choices on that site seem overwhelming at first, once I narrowed-down the options based upon my needs, there were only a few options left for each.
Also, since I finally had a working camera PCB, I used one of the boards plus an OLED display to build a "detector box", a gadget that displays detected IR blobs on the screen. This made testing much easier, since I didn't have to sit next to a computer reading serial debugging information.
[Before I even received the LEDs in the mail I experimented with using sandpaper to scuff some of the LEDs that I had laying around, to see if I could make the light diffuse in a circular, right-angle way. But this was fairly unsuccessful.]
For the limited number of lenses and LEDs that I had, there was a pretty clearly winning combo early on. The LED has a flat top, instead of a dome, which means that there latitude in where it can be placed under a lens.
I tried to film myself testing the detection distance:
In the beginning of the video, the flickering of the white blob means that the LED is at the edge of the detection distance. This video, though, is with the lens just resting on top of the LED. There is a "sweet spot", though, with the lens raised slightly higher, that focuses the light into a pretty bright, side-viewable beam. This was easiest to adjust for by focussing a camera on the lens and making small adjustments. I was able to get an estimated ten feet of detection distance with this setup. It's less distance than I wanted but still workable.
I designed a mount in FreeCAD for the LED and the lens. I gave some tolerance to where the LED can be placed vertically, since I had a really hard time measuring the optimal placement. I figure I can adjust the position with this prototype and then make, in the final version, the bottom of the LED body will rest against a lip in the mount. With the technical drawings for the lens available, I didn't need to do much measuring, and the whole thing came together in a few hours (most of that time was spent remembering how to use FreeCAD).
Here's the 3-D rendering from Shapeways:
The bottom cylinder bit is designed to slip into an existing hole on top of the tank, which was originally intended to mount a plastic machine-gun. One thing I forgot to account for was that I had wanted a sort-of shroud, to shield the IR beacon from the IR receiver (though I haven't done enough testing to definitively prove that this actually helped with IR reception). So I may end up raising this beacon arrangement a bit higher, on a sort-of mast.
So, I'm waiting on a 3-D printed part and on a PCB. While I'm waiting I can work on the software and I can do some wiring to prepare tanks for conversion to robots. But I'm really running out of motivation, based upon my somewhat pessimistic forecast for the success of the motor drivers.
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