To avoid public transport and the car, I decided to go to work on foot everyday but I have to pass a small, but dark (in the evening) and scaring wood.

Even if I use flashlights, I'd like to have a kind a "life scanner", like the one used by Predator vs Alien to detect alive (hot/moving) creatures.

Beside the sci fiction side of the question, I was wondering if PIR can be used while moving, so that I can mount on my backpack and control it with an arduino while I'm walking.

If it's not possible, do you have any other ideas?

What I need it's just a way to know if there are alive, enough big to be scaring, creatures in the wilderness around me (for not alive creatures we will discuss later).


Has pointed out, a good alternative can be an Infrared camera, there are some good tutorial and Howtos in the Net.

I don't need a detailed image, but just to know if and (more or less) where there are alive creatures (hot blood animals?), as an image sometime is better then 1000 words:

Alien Radar

Edit 2

As it has been pointed out, is this feasible or it's just sci-fiction?

Thermographic cameras exists and are widely used: http://en.wikipedia.org/wiki/Thermographic_camera

I found a solution here http://www.embedds.com/interactive-diy-infrared-and-ultrasonic-scanner/ , but the range is really small (21 inches = 0.5 meters)

Edit 3

This is another way to create a "radar" starting from a home made thermographic camera.


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    \$\begingroup\$ This is a great question! Although I don't think a PIR sensor would work, as I believe it relies on differences between the average level of infrared light from when there is 'nothing' there, to when there is 'something' there. If your walking, then the average level will be continually changing, and so won't be able to get a point of reference for comparison. \$\endgroup\$ – BG100 Jan 10 '11 at 13:53
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    \$\begingroup\$ I think this will help a little en.wikipedia.org/wiki/Infrared_camera \$\endgroup\$ – jsolarski Jan 10 '11 at 14:25
  • \$\begingroup\$ Good! I didn't considered to use Infrared cameras. I'll update the question. Thanks! \$\endgroup\$ – tmow Jan 10 '11 at 15:54
  • \$\begingroup\$ True infrared cameras, actually called bolometers, are very expensive, companies like RedShift and FLIR build modules. The only even moderately cheap ($x00) modules are also quite low resolution, 80x60 ish. All the cheap consumer cameras that are sold are just CMOS cameras which are sensitive to near-IR which isn't really heat and needs illumination from IR diodes to see very far/well. Just take a marshal arts class and buy some pepper spray. \$\endgroup\$ – Mark Jan 11 '11 at 23:58

PIR sensors usually have 2-4 pixels. That, coupled with the intended optics that appear to be designed with "blind spots" (so something moving in/out of them will cause a change) wouldn't really be that helpful.

As tyblu suggests, an IR camera—the cheap ones are NIR, not LWIR (thermal)—may be more helpful, and may even be able to couple it with some FPV (first-person view) goggles for R/C aircraft to make your own hack NVGs.

That said, some FPV goggles and IR cameras can be kinda spendy, so paying just a little more for the convenience (batteries, mechanical package, etc) of some commercial NVGs (or just a scope) might be worth it.

  • \$\begingroup\$ I don't need a detailed view, but just to know if there are big (as a big dog) animals around. But I see the advantages of cameras. I found some howtos explain how to modify cameras to don't filter if. Do you think I can have acceptable results? \$\endgroup\$ – tmow Jan 10 '11 at 21:12

You may want an infrared camera and display module. This cheap security camera apparently works well up to 5 meters. It has its own IR LED cluster, requires a 12V (500mA) DC source, and outputs via RCA cables. One could connect a small screen like this one, with RCA inputs (also req's 12V DC source).

I'm not sure what type of animals you're worried about, but it's generally true that they want to keep away! Make some noise -- this is where "bear bells" came from.

  • \$\begingroup\$ Really good point, also for the above comments! \$\endgroup\$ – tmow Jan 10 '11 at 15:55

If you really want to detect body heat, I don't thing anything short of a thermal imager will work, which will cost a few $000. PIR won't give you the absolute measurement or resolution to be useful. It might be feasible to use something like a thermopile sensor with a PIR lens to get enough coverage angle, but all that will tell you is there is something warm somewhere in th efield of vide, which may end up giving too many false alarme


I just wonder - if something like this was remotely feasible, wouldn't it have been made by someone and commercialized already? I'm in the opinion that (with the level of technology available today) this is sadly still science fiction stuff, or else requires a disproportionate amount of money.

Added: From the comments, the idea about am IR thermometer might be worth looking into. If you could get one that can provide realtime measurements (I suppose 4 per second might be needed for a fair operation), you could then attach some optics to get a bigger FoV and get a sort of "measuring gun" that you could point to suspicions places. I think...

Getting such a thermometer might be expensive if at all possible, but maybe you could dismantle some cheap ones and hack them... I don't know. :P

  • \$\begingroup\$ Thermographic cameras exists and are widely used: en.wikipedia.org/wiki/Thermographic_camera . I found a solution here embedds.com/interactive-diy-infrared-and-ultrasonic-scanner , but the range is really little (21 inches = 0.5 meters) \$\endgroup\$ – tmow Jan 11 '11 at 13:57
  • \$\begingroup\$ @tmow - yes, but that's a camera, not a radar. \$\endgroup\$ – Vilx- Jan 11 '11 at 14:19
  • \$\begingroup\$ @Vilx the second it's a radar/sonar and it's not a camera. Here there is another potentially good idea hackaday.com/2009/07/01/poor-mans-thermographic-camera , but I cannot find much details about it. \$\endgroup\$ – tmow Jan 11 '11 at 15:14
  • \$\begingroup\$ @tmow - OK then. :) I just thought that you wanted something with a 360 degree view, and realistically mountable on your backpack or something. :P As for the second idea - looks like it just measures lots of points for temperature by moving the thermometer around, so it's not a real-time solution. \$\endgroup\$ – Vilx- Jan 11 '11 at 15:22
  • \$\begingroup\$ @Vilx you are right, I'm agree, but indeed I'm looking for a real and realistic solution if any :-) to re-invent the wheel there is time... In fact it's why I came here to post the question. \$\endgroup\$ – tmow Jan 11 '11 at 15:30

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