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Do-it-Yourself Camera Detects Land Mines

Posted March 23, 2017 12:00 AM by Engineering360 eNewsletter

The DOLPi is an affordable Raspberry Pi-based polarization camera that can be used to see polarized light. Users gain the ability to detect unseen objects like pollutants and hidden explosive devices such as mines.


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#1

Re: Do-it-Yourself Camera Detects Land Mines

03/23/2017 9:08 AM

This looks like a fascinating project. Here is a document with detailed instructions on how to build one.

You might try to do manually what this camera does automatically using a camera mounted on a tripod with a polarizing filter. Aligning the filter at 0, 45, and 90 degrees, you can take three shots and load them into GIMP (or Photoshop), decolorize, and assign them to RGB color channels.

From his document: http://www.diyphysics.com/wp-content/uploads/2015/10/DOLPi_Polarimetric_Camera_D_Prutchi_2015_v5.pdf

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#2
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Re: Do-it-Yourself Camera Detects Land Mines

03/23/2017 2:08 PM

I read something about a new liquid crystal flat lens: For circular polarized light, applied potential results in a focus with a positive focal length (real image), but for opposite polarity, it results in a negative focal length (imaginary image). This can be a real advance in the study of polarization effects....

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#3
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Re: Do-it-Yourself Camera Detects Land Mines

03/23/2017 8:24 PM

I ordered one of the self-darkening welding filters which they use as a voltage controlled polarization analyzer (VCPA) and drive it with a 555 timer circuit. It will swap polarizations at about a 3 Hz rate. I have a quarter-wave filter that I can orient at 45 degrees to the VCPA axis so that it will blink circularly polarized light.

http://www.diyphysics.com/wp-content/uploads/2015/09/DOLPi_Polarimetric_Camera_D_Prutchi_2015_v2.pdf

For a few bucks outlay, it ought to be fun to experiment with.

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#4
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Re: Do-it-Yourself Camera Detects Land Mines

03/24/2017 9:30 AM

Maybe something along those lines might fit in with diagnostics on a system I am engaged in engineering for personal use.

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#5
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Re: Do-it-Yourself Camera Detects Land Mines

03/24/2017 9:55 AM

You still finding land mines down there from that little skirmish with Mexico 180 years ago?

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#6
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Re: Do-it-Yourself Camera Detects Land Mines

03/24/2017 10:12 AM

Only some undiscovered tequila bottles strewn along the route of the Army of Santa Ana.

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#7
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Re: Do-it-Yourself Camera Detects Land Mines

03/24/2017 10:36 AM

Don't know if that camera is going to work for that, but I do know what a "booze" bottle from that era is worth these days. My Father was a serious digger/collector and had bottles like that worth thousands of dollars. Good luck finding them.

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#8
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Re: Do-it-Yourself Camera Detects Land Mines

03/24/2017 11:42 AM

First step: Find good accounts from Gen. Cos, or someone else involved as to the movements of the Mexican Army. (also correlated with movements of Sam Houston's Army)

Second step: Get permission (legal waivers) to retrace the steps over public and private lands (not an easy one there).

Third step: Get out there and go to it!

Fourth step: Bring your snake bite kit next time, and an extra one or three. Bring extra beer and something to cook. Have fun!!

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#9
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Re: Do-it-Yourself Camera Detects Land Mines

03/24/2017 12:44 PM

I think I will change the driver circuit. You're not supposed to drive LCDs with DC as it shortens their lives. I can drive a Johnson counter with a 555 and subtract two 90 out-of-phase square-waves with a pair of opamps. (Driving either polarity causes the LCD to rotate the polarization).

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#12
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Re: Do-it-Yourself Camera Detects Land Mines

03/24/2017 11:18 PM

Rixter, have you considered using an Arduino Nano? Get your frequency and duty-cycle exactly the way want it without external components. Sum digital outputs with resistors to get that waveshape shown, and without op-amps. $6.95 and you don't have to build anything on a perfboard. If you want potentiometer control of freq/duty cycle, etc., it has six 10-bit analogue-input pins to use however you like. I would seriously consider using it over a 555. Much more flexible.

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#13
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Re: Do-it-Yourself Camera Detects Land Mines

03/25/2017 12:00 AM

Correction: eight, not six, 10-bit analogue inputs.

Also, Arduino direct is out-of-stock, but Amazon carries it.

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#15
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Re: Do-it-Yourself Camera Detects Land Mines

03/25/2017 7:24 PM

Now you have my attention. I'm still designing in the 20th century.

I'll look into it. Thanks!

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#16
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Re: Do-it-Yourself Camera Detects Land Mines

03/25/2017 7:43 PM

They're really a lot of fun as well and useful for all kinds of projects. My daughter and son-in-law gave me an Arduino kit several years ago for my birthday; complete with RC-style servos, steppers, LED dot-matrix & 7-segment displays, 2 x 32 LCD display, various sensors - the whole monty. Loads of fun and the IDE is very easy-to-use (do you know C++? It's a somewhat abbreviated version sans the STL, Boost libraries, etc., but complete enough to get a lot done).

I ordered three Nanos yesterday (the ones with headers you solder-in yourself) from that Amazon page I linked to. $20 with shipping.

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#20
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Re: Do-it-Yourself Camera Detects Land Mines

03/27/2017 4:03 PM

Just remember that a negative voltage will kill an Arduino faster than you say "licketty".

Do not apply supply power higher than about 9 volts, although some will say they get away with 12 V supply (at least for a short time).

5 volt telephone chargers work just fine. If you need op amp circuits, divide that 5 by 2, and that sets up the op amp baseline. Etc. Also be careful about addition of digital numbers on an output, it just means you find a high state longer, voltages will not be additive.

Convert them to analog values, and yes, that waveform can exist as a stepped wave, etc. Then you can send that to a transformer, but you should use an amplifier to step up the signal power.

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#10

Re: Do-it-Yourself Camera Detects Land Mines

03/24/2017 1:33 PM

Oh, really? I have land mines that detect camera then, no kidding James Stewart on this!

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#11
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Re: Do-it-Yourself Camera Detects Land Mines

03/24/2017 2:11 PM

You silly wonk!

Yes if not careful, I am sure the land mine will detect and blow-up the nice fellow walking through there with this special camera. Better idea, suppose we take out all the land mines on your island in one swell foop! I hear tactical nukes are just the ticket for that? Do you still want to play war games?

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#14
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Re: Do-it-Yourself Camera Detects Land Mines

03/25/2017 4:59 AM

Which war, buddy?

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#21
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Re: Do-it-Yourself Camera Detects Land Mines

03/27/2017 4:09 PM

You said war, I said war games. You are trying to draw to an inside straight. You will still lose.

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#17
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Re: Do-it-Yourself Camera Detects Land Mines

03/26/2017 6:52 AM

Tactical nukes are great for detonating land mines, IED's, trolls, etc...

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#18
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Re: Do-it-Yourself Camera Detects Land Mines

03/26/2017 10:08 AM

Too much collateral damage. With any luck, the troll's laptop battery will overcharge and burn out.

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#22
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Re: Do-it-Yourself Camera Detects Land Mines

03/27/2017 4:10 PM

LOL!

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#19

Re: Do-it-Yourself Camera Detects Land Mines

03/27/2017 1:40 PM

Seems like the better thing to do is to figure out how to remotely detonate the IED while it's being ''planted''...

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#23
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Re: Do-it-Yourself Camera Detects Land Mines

03/27/2017 4:10 PM

...says the experienced failure at roadside incidents?

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#24
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Re: Do-it-Yourself Camera Detects Land Mines

04/14/2017 9:07 PM

Every roadside accident one survives, in basic working order, is a success...

...and so far, I have...

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