Open Ground Penetrating Radar

Driving across the state of Michigan on a sunny afternoon, I fell in love with the idea of a solar powered rover. Much like my love of Audrey Tautou, it's not terribly practical.

If I was being practical, I'd use a 160cc Honda GX engine and a 24 volt, 110 amp alternator. But, I don't like handling gasoline and I don't like the noise of engines. Besides, Home Depot is having a great sale on Grape Solar GS-Star-100W solar panels. They are less than the UPS Large Package Surcharge dimensions when shipped separately and will fit on a "standard" (40" x 48") pallet when assembled on a rover. Both of these are design goals.

Most importantly, I'm doing what I love.

I could talk about solar's "acoustical advantage over fossil fuel generators." But, I do try to be a bit more genuine than a government system report.

When I was in grade school, I went on a field trip to see a HERO 1 demonstration in the high school auditorium. I've wanted my own robot ever since. But, I wanted it to do something more interesting than roll back and forth across a stage.

What I love about the idea of putting a solar panel on my rover is that it could then "survive" somewhat independently of me. Without a solar panel, I would have to keep it's battery charged and it would probably spend much it's time in the garage. With a solar panel, it could "live" outside and at least tell the world what the local weather is like.

Maker Faire Detroit was amazing!

Thanks to the Intelligent Systems Club - University of Michigan Dearborn for confirming my theory that electric motors are either powerful or inexpensive and for introducing me to the really nice Talon SRX motor controller. (Also used by FIRST robotics competitors.)

Thanks to Jim Summers from Human Electric Hybrids for taking time to talk with me about the batteries they are using. The "LiFePO4 Lithium 24V 20AH Clydesdale Edition Battery for Electric Bikes" from ElectricRider look very promising.

LiFePO4 battery technology is very interesting: "LiFePO4 batteries have somewhat lower energy density than the more common LiCoO2 design found in consumer electronics, but offers longer lifetimes, better power density (the rate that energy can be drawn from them) and are inherently safer. LiFePO4 is finding a number of roles in vehicle use and backup power." --Wikipedia (emphasis added)

And what's not to love about a 3D printer with a nine feet by four feet build area?

The current design performs acceptably on pavement. It moves at about walking speed, which is the targeted 1 m/s.

It works in fields, but I find the performance to be qualitatively unacceptable.

I am trying to build the least expensive system that will work.

I'm currently using the "Wondermotor 12V DC Reversible Electric Gear Motor 50 RPM" which performs just below that line.

I am planning on upgrading to AmpFlow 12.5-inch WheelMotors with E30-150 Motors for $298 each.

This is about three times the cost of the current motor/wheel setup which includes:

$69 motor
$9 wheel
$8 pillow block bearing
$6 axle
$14 Lovejoy couplings

But, the AmpFlow WheelMotor negates the need for a custom manufactured mounting assembly, which was fun to make. But, access to CNC mills and plasma cutters is limited and it was a time consuming process.

"[AmpFlow] motors and controllers are used in diverse applications including robots, industrial motion control, factory automation, semiconductor manufacturing, educational projects, and motorized scooters, go karts, and electric bicycles."

So, they would appear to be exactly what I need. But, AmpFlow Electronic Motor Controllers are $500!

After a bit of consideration, I realized that I could use Hall Effect DC Current Sensors (~$8x2), IBT-3 motor drivers (~$10x2), thermocouples (~$1x2), (plus shipping,) and modified APM:Rover firmware to achieve my performance targets for about 1/10th the cost of the AmpFlows EMC! APM:Rover firmware could also be modified to allow a "Battleshort." Because sometimes you just need more power!

I've published my modified version of JoyBorg at GitHub:
https://github.com/voidmapper/JoyBorg

I've added support for dual IBT-2/3 (Infineon BTS7960/BTN7971) H-bridge motor drivers. (IBT-3 support is untested.)

I'm using this for testing while I modify APM:Rover to work with the IBT-2/3 motor drivers.

I just found this in the box with my free Hackaday T-Shirt. Nice!

To legally operate the oGPR in the United States (for non-commercial use), you will need a Technician Class (or better) amateur radio license. The 35 question exam is not difficult if you study. All 426 possible questions are published. Ron Hashiro has a good study guide. The ARRL has more information.

Choosing a domain name is never easy. I settled on voidmapper.com, as it has meaning on several levels. It's running the Odoo suite of business applications, which has the very true slogan: "Integration has never been so smooth." It's in the Amazon Elastic Compute Cloud.

I did some soul searching before adding Google Analytics. But, I decided to add it. Users can opt-out using the Google Analytics Opt-out Browser Add-on.

The fact that the great AI known as Google rummaged through my tablet, made a cool animation with my photos and then chirped at me to let me know about my new "Auto Awesome" photo kinda warmed heart. Here it is:

I've been struggling for the past few weeks to find an easy-to-use EDA with a comprehensive parts library. DigiKey has really knocked it out of the park with Scheme-It! It's free, but not open source.

Here's a link to the oGPR power and trigger control:
http://www.digikey.com/schemeit/#1rwh

July 25-26, 2015, The Henry Ford in Dearborn, Michigan

http://www.makerfairedetroit.com/