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Open Ground Penetrating Radar

Make the invisible visible for about $500.

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Commercial ground penetrating radar systems cost tens of thousands of dollars. This project aims to create an open hardware alternative for about $500.

This project has three components: the Open Ground Penetrating Radar (oGPR) system, the rover and software to process the data and plot in on OpenStreetMap. This Hackaday project focuses on the first two.

The oGPR is designed to locate underground "voids," such as abandoned mines, were hazards may exist.

Before these hazards can be mitigated, they must be located.

Project Home Page: https://voidmapper.com/

Rover Wiki: http://voidrover.com/

A Baofeng VHF/UHF radio is used a signal generator, which transmits via a Transmit/Recieve switch through an antenna. A RF detector is also connected to the T/R switch, which is connected to the MSO-19.

The radio controller is a 4N25 opto-isolator.

The T/R switch controller is a SN74HC04N (or similar) hex inverter.

Any Pi-compatible GPS and WiFi dongle will do.

The Raspberry Pi triggers the radio, T/R switch and MSO-19 via a buffered GPIO port once per second using a very simple python script.

In the United States, this project falls under FCC Part 97 Sec. 1 (b):
"Continuation and extension of the amateur's proven ability to contribute to the advancement of the radio art."

  • 1 × Link Instruments MSO-19 ($249) 2 GSa/s Mixed Signal Oscilloscope
  • 1 × Baofeng VHF/UHF HT Radio (Amazon, $30) Signal Generator
  • 1 × HMC784MS8GE (DigiKey, $140 eval board) Anetenna T/R Switch
  • 1 × AD8314ARMZ-ND (Digikey, $10) RF Detector
  • 1 × Raspberry Pi (Amazon, $30) Controller, Data Collector, Web Interface

View all 11 components

  • Intro Video

    Glenn Powers08/25/2015 at 07:36 0 comments

    Made with Ardour and OpenShot.

  • $80 Lenovo Tab 2's are great!

    Glenn Powers08/17/2015 at 04:21 0 comments

    I have a Lenovo A1000 tablet that I got about a year ago for ~$80. It works fine for ebooks and 480p/720p videos, but is really too slow for web browsing. The Tab 2's are a great buy for the money. Given the recent coverage of "The realities of a $50 smartphone," the reality of a $80 tablet is that the display isn't nearly as good as a Samsung Tab 4, but it's about half the price and runs Tower and FireFox just fine.

  • My New Robotic Friends

    Glenn Powers08/13/2015 at 01:27 0 comments

    Rovers are a lot like PHP libraries. Developers start by scratching a personal itch. But, in the end, they are all broken in their own unique way. So, I've decided to use rover platforms from SuperDroid Robots, who employs a dozen professional engineers and has been building robots for 25 years. I'll focus my efforts on putting my new friends to work.

  • They're Here!

    Glenn Powers08/13/2015 at 00:30 0 comments

  • BUD Industries Makes Great Boxes

    Glenn Powers08/11/2015 at 16:14 0 comments

    Or, "enclosures." Good design, well made, inexpensive.

    Just search Amazon for "BUD Industries Aluminum Econobox"

  • SV1AFN's $30 RF Switch

    Glenn Powers08/11/2015 at 02:50 0 comments

    HMC784 - 10W RF SPDT Switch, LF to 4000 MHZ (4 GHZ), 30 dB Isolation, 15-40 nSec switching times, Very Low DC current - Good IMD3 (+60 dBm)

    https://www.sv1afn.com/hmc784_trswitch.html

    This uses the same chip as the eval board from DigiKey for $138.75 and includes a hex inverter for single wire control!

    Plus, the DC blocking capacitors are unpopulated. So, you can select the best values for the frequency you are using. Here is a brief discussion on picking the best values for the caps.

  • Stopping Pollution Before It Starts

    Glenn Powers08/06/2015 at 04:41 0 comments

    An anonymous visitor to my table at the Detroit Maker Faire mentioned that he worked for an undisclosed company that was using proprietary methods for locating valves in underground oil pipelines. These valves were then removed before they sprung a leak.

    He said the company considered using ground penetrating radar, but decided against it because of the cost ("$50,000 to $100,000 per system").

    I wonder how many potential problems could be located and mitigated with an unmanned ground penetrating radar system that costs 20% of current manned systems?

    I'll probably need to increase the frequency to be able to see the target signature of valves in a 3" pipe at "backhoe depth." But, it's on my growing list of targets.

    First, I'm going after the elephant in the room.

  • NAVIO+ is neat, but expensive

    Glenn Powers08/05/2015 at 15:55 0 comments

    "Navio+ is an improved version of Navio autopilot shield for Raspberry Pi A+/B+. It was designed both for your own custom robotic projects and as a platform for Linux version of APM (ArduPilot). Navio+ eliminates the need in multiple controllers onboard making development easier and increasing robustness."

    But, at $168 the NAVIO+, $12 for the GPS antenna and $24 for the power module, it's three times the cost of a APM 2.6.

  • mechanical speed reduction

    Glenn Powers07/31/2015 at 23:50 0 comments

    "choosing the best [mechanical] reduction ratio is the single most important factor in determining how well the motor will work in a particular application."

    "Do not rely on electronic speed reduction to do the job of a mechanical speed reducer."

    AmpFlow whitepaper:

    http://www.ampflow.com/Using mechanical speed reduction.doc



  • Choosing a Vendor, Letting Go

    Glenn Powers07/30/2015 at 18:18 0 comments

    Jim Summers recommended two battery suppliers: EM3EV and ElectricRider.

    I discounted EM3EV because they don't have exactly what I need. They have a "Request a quote" option, but are located in Hong Kong and don't list a phone number on their web site. When developing a product, it's often important to be able to talk with someone on the phone.

    ElectricRider has what I need. But, when I called the good people down in Texas and asked about a solar charge controller, they said their controller works on 120 volts and if my "solar panel puts out 120 volts, it'll work fine." *facepalm*

    I consulted the great AI known as Google and found Bioenno Power whose "products are trusted and employed internationally and domestically by a wide customer base ranging from amateur model makers using our batteries for RC applications to professional aviators trusting our batteries to power critical avionics and Ham Radio operators." And, they sell solar charge controllers for their LiFePO4 batteries. Wow! Sounds like a perfect fit.

    So, I called them. They were very pleasant and helpful, but insisted that 24 volt batteries need 24 volts of solar power. Inexpensive, small form factor, 100 watt (C/5-ish for 24 volt, 20 amp-hour batteries) pretty much don't exist.

    Not to be deterred in my quest, I consulted Google a few more times and found a vendor in California that sells a device that does what I want. But, it's manual is in poorly translated Chinese, which doesn't inspire confidence.

    So, I've decided to let go of my desire for a solar panel on my rover. This will allow for a smaller, lighter rover that isn't top heavy. I can charge the batteries from a pair of ground mounted 12 volt panels. I could use a DC/DC converter to step up the 12 volt solar panel to 24 volts for the charge controller. But, this is going past the design goal of "keeping it simple."

    Moral of the story: follow your heart. It may not lead you to what you see in your dreams, but it may lead you to a better vendor of LiFePO4 batteries.

View all 32 project logs

  • 1
    Step 1

    Here is the schematic for the power and trigger control board. You can view it in Scheme-It. Q1 is a N-Channel MOSFET to protect against an inverted polarity power supply. I used a LM7806 and a LM7808 instead of a single LM7505 to give a faster switching time. U1..U4 is a 7 channel hex inverter. J6 is a BNC connector. J3 should be a female header, others are male.

View all instructions

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Discussions

Juan Carlos Rodriguez wrote 06/06/2015 at 15:09 point

I'm following your project, because I had an idea for improvement on your design. What I will like to do is make it smaller and instead of using it for GPR, use it for determining the density of rocks; since I like rock hunting.  I live in Puerto Rico, and is very dificult to find gemstones here. But I ran across an interesting stone. I found a corundum  stone embeded in volcanic rock. When I try to see whats in the rock, its so hard that it breaks and turn to powder. To avoid breaking whats inside, I need a density detector, that I can use to see whats inside the rock, to select the rocks and bake them to eliminate impurities in the crystals before I attempt to separate the find. 

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John Leeman wrote 05/24/2015 at 13:39 point

Hi! Super great project! You might take a look at Seismic Unix (SU). In the geophysical community we often use it to process seismic and radar data. Having using commercial units in teaching, I'm really excited to see an open implementation being built!

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Boris van Galvin wrote 05/05/2015 at 22:21 point

I wonder if you could phase and attenuate the RX/TX instead of switching it? 

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byourself wrote 04/30/2015 at 00:57 point

Awesome project. Cavers will love this.

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Pure Engineering wrote 04/29/2015 at 22:17 point

How about your replace the PI+gps with a low cost cell phone.  you could potentially use the audio jack to do the triggering R+L audio. Or a bluetooth or usb expansion.  Also you can plot the data while running to make sure you cover the whole area. may reduce costs overall

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Glenn Powers wrote 04/30/2015 at 03:40 point

Interesting. But the software for the MSO-19 will only run on a desktop/laptop or Pi.

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Pure Engineering wrote 04/30/2015 at 05:23 point

I didn't look at all the specs, but what about something like this https://www.lab-nation.com/

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Warren Bailey wrote 04/29/2015 at 13:20 point

You could also mount a large metal detector on the same frame, and possibly run them at the same time? Or you could switch between them.

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Glenn Powers wrote 04/29/2015 at 17:47 point

This is an interesting idea. A big unknown right now is the minimum detection depth of the oGPR. I designed it detect at the maximum depth with reasonably priced T/R switch.

You could certainly mount an off-the-shelf metal detector to it. oGPR works with VHF or UHF. Metal detectors are usually VLF or LF devices. They may work at the same time, it depends on the quality of the metal detector. The oGPR should not be affected by the metal detector.

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Kiltjim wrote 04/29/2015 at 12:01 point

This is very interesting as I'd always wanted to do something like this, but never really knew how to get started.  Knowing just enough about radio to realize I'm out of my depth, I get the reason for the radio, simply a signal generator (and power amp).  Correct me if I'm wrong, but the antenna switch simply switches from transmit to receive modes, and the antenna switch controller is just the signal buffering between the Pi and the switch?

So after reviewing the AD8314 datasheet, it is used for power measurement of the return signal, correct?  I am then assuming that the oscilloscope is used to measure the signal coming off of this, but I'm having difficulty understanding why an o-scope, and not something more direct (cheaper) such as an ADC?

Again, great project.  I will be watching this with great interest.  I already had a UGV planned for this Summer's project, and this would make an awesome addition.

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Glenn Powers wrote 04/29/2015 at 18:03 point

You are right about the antenna switch and controller. Additionally, the AD8314 requires TWO input changes to switch. Minimum detection depth is dependent on switching speed. So, just using two Pi outputs is not ideal. I'm also running the hex inverter at 6V to save a few nanoseconds.

I'm using an o-scope instead of a cheap ADC, because it can do 1 billion samples per second at 60 MHz bandwidth. (An undocumented feature may allow 120 MHz bandwidth.) It comes ready-to-use for $249, with software.

If anyone has a better option, I'd love to hear about it.

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mbelopedro wrote 11/23/2015 at 19:03 point

Can i buy it ready to use? Thankyou

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Paul wrote 06/12/2016 at 07:10 point
The LimeSDR board looks like a good candidate

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cmduarte wrote 03/22/2015 at 04:16 point

Ah, I see. Details are only in person, my bad.

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cmduarte wrote 03/22/2015 at 04:15 point

Not seeing anything at all on  Pumping Station One site.  Where is the progress really being recorded?

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Glenn Powers wrote 02/28/2015 at 09:24 point

 I'm hoping for a 1-2 meter resolution.

I looked into loops/coils, but Yagis have better gain.

Depth is dependent on RF power. Relatively low cost, high speed T/R switches limit that to 10 watts. Higher power T/R switches are available, but cost more and are harder to get.

Before I found PiMSO, I was considering a laptop. But, I think a Raspberry Pi and tablet or smart phone is a better option. Link Instruments also makes a Windows based interface that can be used on laptops. Post-processing will be done on a laptop, desktop or "in the cloud."

I'm planning on mounting the Yagi "on wheels" of a UGV (unmanned ground vehicle) that I'm also developing.

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B0SC0 wrote 02/27/2015 at 01:55 point

Hi.What kind of depth and resolution will this have?

Are you considering using a coil instead of an antenna?

Maybe something along the lines of a tablet or laptop harness with a large coil on wheels.

B0SC0

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