Actual and Potential Use of Drones in Precision Agriculture

Ed.: This is a guest blog by Alex Danovich of San Francisco Circuits.

Unmanned Aerial Vehicles (UAV), Unmanned Aerial Systems (UAS), Remotely Piloted Aircraft (RPA) or more commonly referred by mass media as drones are gaining popularity and often discussed for many new approaches to old applications. In the last couple years drones are rapidly gaining attention not only due to the traditional military applications but also civilian uses. This transition brings the drone industry closer into new commercial applications that literally pop up every day.

There are many directions of potential use but according to this economic report provided by the Association for Unmanned Vehicle Systems International (AUVSI) in 2013 more than 80% of civilian drone applications will be connected with precision agriculture (PA), creating many new jobs and billions in market value.

San Francisco Circuits took a look at the growing precision agriculture industry with a supplier and expert in this field, Michal Ruš of e-DRON. “We believe that a low-cost drone can be effective tool for precision agriculture. Our Skyhunter fixed wing configuration (under 2000 EUR) is able to map an area of 150 hectares in less than 30 minutes.”

A few hours after the drone’s flight and scan, an accurate orthophoto map and 3D surface model with RGB and NDVI imagery is created. Such models/images can be exported directly into farm management programs and variable rate prescription maps.

By providing a service-based operation instead of drone ownership, e-DRON believes it is able to remove the burden of operation, maintenance and certification of such drones by farmers. Farmers rely on timely and accurate data to make better decisions. They are focused on their crops and if drones are not bulletproof or easy to maneuver for anyone without proper training, it makes sense to leave its operation to service providers.

e-DRON is currently building such a bulletproof drone with the help of some consultation on custom PCB fabrication and PCB assembly from San Francisco Circuits.

Skyhunter fixed wing with RGB and NIR camera dual configuration

Drone hardware and software. But what is the drone made of? The difference between a drone and a model aircraft/copter is the flight controller with autonomous features. In this case, the heart of the Skyhunter model consists of a Pixhawk autopilot developed jointly by the PX4 open hardware project and 3D Robotics.

The autopilot contains a six-layer PCB with isolated power nets for the main and safety processor. It’s a 1.6mm FR-4 board with 0402 standard components, minimum pitch of 0.2mm and 0.15mm spacing. Copper thickness and stackup are standard with 0.35um copper. The challenge in autopilot electronics is not the base technology, but to ensure highest quality throughout the complete production process from PCB manufacturing to assembly.

Pixhawk - advanced 32bit autopilot by 3D Robotics

Pixhawk – advanced 32bit autopilot by 3D Robotics

The payload itself consists of 2 consumer grade point-and-shoot cameras; one is the original RGB camera and the second is converted to NIR (near infrared).

The processing chain to obtain orthophoto/3D imaging of a desired piece of land has a pretty simple workflow. The mission starts with a drawing a polygon around the desired area in Mission Planner software. Once the mission is complete, the images are transferred to a powerful PC to process the remaining steps.

Depending on customer requirements, ground control points (GCPs) are measured with RTK GNSS (2cm accuracy) before the mission start. These points are then manually assigned together with images from the cameras on the software to produce an accurate geo-referenced orthophoto and 3D model. The NIR-produced orthophoto is then the most useful product for the farmers to spot the crop health immediately. Although more advanced sensors exist that would outrun the performance and accuracy of such a converted NIR camera, this is the lowest cost solution.

Applications in precision agriculture. Drone use in PA is all about saving inputs to farmers. Whether it’s an indication to use fewer pesticides, fertilizers or water for irrigation, PA will make billions of cost savings and greener food products.

The drones are good at monitoring crops for a very low relative price. When compared with satellites or manned planes/helicopters, low cost drones are cheaper and can be deployed every day, even in a cloudy day. The farmers have no other cost effective way to scout their large fields than by drones. Other than the RS detection of the crop health, drones are already able to effectively manage fields by crop dusting with variable rate technology.

Future of drones in PA. Multi-sensor drones with more advanced micro-sensors (like hyperspectral, thermal, LiDAR, etc.) and smart zonal auto-classification analytics are in development.

Swarm operations (multiple drones) with continuous remote sensing (day passive sensors and night active sensors) for larger fields and applications are all viable for scaling.

Powering the drones using solar energy with hydrogen fuel cell technology (unlimited endurance, 24/7 operation), making instant real-time cloud processing of acquired data streamed via high-bandwidth telemetry (no need for many SSD/HDDs onboard of multi-sensor drones) is also a very real application. Drones may eventually be programmed to automatically take actions of the whole lifecycle – from RS detection to immediate application of inputs. Harvest or seeding may be the next drone activity.

The future is in the sky!

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Peter Biocca, RIP

Peter Biocca, the longtime face of Kester Solder in the southern US and Mexico, passed away Monday from cancer.

I knew Peter for more than 15 years, dating back to his time with Multicore, when he was one of the regulars at the J-STD-004 and J-STD-005 meetings. Besides contributing to the standards, Peter could always be counted on to prepare papers at all the various technical conferences, participate in road shows, and fill whatever role was needed whenever anyone asked. More than that, he was simply a super nice guy, with nothing but good things to say about other people.

I knew Peter was really ill when he starting missing conferences over the past year. I filled in for him with his old friend Ray Chartrand on a session on alloy selection at SMTAI in 2013.  It didn’t occur to me at the time that I wouldn’t see him again. Knowing that now makes me very sad.

Condolences may be sent to Peter’s wife, Sandy, at:

Sandy Biocca
203 Fairfax Drive
Allen, TX 76013

RIP, Peter.

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Freescale KL03 and PCB123 at 0.4mm Pitch

Small component packages seem to be a recurring theme with me. It’s understandable, I guess. Super tiny packages are becoming more and more common and we build a lot of product with them.

The smallest we’ve built is 0.3mm pitch. Those aren’t common enough to be considered standard — they’re still an experimental assembly — but not many chips use them yet. 0.4mm, on the other hand, is something we see on a pretty regular basis.

What’s so tough about that? The biggest challenge with these form-factors seems to be footprint design and escape routing. I can see why. There really isn’t room to follow any of the standard BGA practices. You can’t fit escape vias between the pads and you can’t put vias in the pads, unless they are filled and plated over at the board house. Filled and plated vias are the easiest way to go, but it can make for an expensive board fab.

KL03 WLCSP20 on a US Lincoln penny. One of my side projects involves trying to make the smallest possible motor driver. For this project, I’ve chosen the Allegro A3903 driver. It’s a 3 x 3mm DFN (dual flatpack no leads) with 0.5mm pitch pads and a thermal pad in the middle. The microcontroller will be the new Freescale KL03 32-bit ARM in a 1.6 x 2.0mm WLCSP (wafer level chip scale) package. It also comes in a 3 x 3 x 0.5mm pitch 16 pin QFN. Without an expensive PCB, that may be my only option.

Pick your CAD package. I’m using the newest version (5.1) of Sunstone Circuit’s CAD package, PCB123, but the principles here will apply to any CAD software. If you don’t already have a copy, download PCB123 V5.1 here.

If you’ve got fast Internet, you’re done now, so go ahead and install it. You’ll need the manual too, which you can get here.

I need to eat now, so stay tuned for Part 2.

Duane Benson
Nerfvana – It’s like Nerdvana, but with more foam darts.

http://blog.screamingcircuits.com/

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Wilk the Winner

Congratulations to Edward Wilk of Facts Engineering, who won the incentive prize for filling out a recent survey of PCB West 2014 technical conference attendees.

Edward, a $50 AMEX gift card is headed your way. Thanks for your support, and thanks to everyone who took the time to respond!

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Pin-in-Paste Aperture Calculations Using Solder Preforms

Folks,

The pin-in-paste (PIP) process is often the best choice when the PCBA is a mixed SMT and through-hole board with a small number of through-hole components. However, ensuring that the correct volume of solder paste is printed to ensure an adequate amount of solder for a reliable thorough-hole solder joint can be a challenge. One tool to help in this regard is the Pin-in-Paste Aperture Calculator. This calculator is now online at http://software.indium.com/. The solder volume equations were developed by good friend Jim McLenaghan of Creyr Innovation.

To estimate the right amount of solder paste, we need to calculate the volume of the plated though-hole, subtract the volume of the component pin, and add the volume of the solder fillet. See Figure 1.

Figure 1. Solder volumes in the pin-in-paste process.

Let’s assume we have the PCB and component pin metrics, as seen in the left hand column of Figure 2, under the header “Input.” Blue cells are inputs, green cells are calculations by StencilCoach. Notice that, if you have a rectangular pin, the software will calculate the equivalent pin diameter for entry into the “Input” cells. The “paste reduction factor” is the fraction of the paste volume that is solder. Most pastes are about 50% by volume flux, so, typically, this metric would be about 50% or 0.50.


Figure 2. PIP metrics.

The “Output” calculations are not really necessary for the task at hand, which is determining the stencil aperture dimensions, but may be of interest. The important stencil dimensions are shown in the “Stencil Metrics” section. Note that in our example, even though we have a 7-mil thick stencil, we would need a square aperture with a side dimension of 93-mils to get enough solder paste. With a circular aperture the radius must be >50-mils, if the pin spacings were 100-mils, there would not be enough spacing between the printed deposits, they would overlap. So we must use square apertures.

As in this case, it is a common problem with the PIP process to deliver adequate solder volume. If the PCB and component metrics are such that obtaining enough solder paste is an issue, it can be helpful to use solder preforms to increase the solder volume. The next post will cover this topic.

Cheers,

Dr. Ron

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Optimal at Optimum

As corporate models go, Optimum Design Associates isn’t unique. Several firms have launched as design shops only to add EMS capability as they matured.

But one thing ODA does that I really like is provide a much greater level of detail about its financials on its website.  See below:

Financial Disclosure

Financials through 12/31/2013

Ownership Private
Annual Revenue $19 million
Credit Access $5 million
Loan Balance $133,000
Principal Payments $3,700
Access to additional financing Yes
Executive changes last 90 days No
Ownership changes last 90 days No
Return on Assets (last quarter) 3.6%
Current Ratio 2.2
Quick Ratio 1.21
Capitalization 23%
Cashflow 5.45
Debt to Equity Ratio .003

 

For a privately held company, that level of public disclosure is unusual. For a small business, it’s unheard of. Certainly any OEM worth its salt would ask for verification of financial stability prior to engaging, but having that data on hand upfront makes determining whether ODA is the right fit a little easier for potential customers (which could also be a time-saver for ODA), and moreover offers a high degree of confidence that ODA will be above board.

Perhaps that’s willingness to break the mold is why ODA is again on the Inc. list of the fastest-growing companies. (It also made the 2007 and 2008 rankings.)

Congratulations to Nick and the gang at ODA.

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VTP: Very Tiny Parts

A while back, I wrote about a new ARM Cortex M0+ chip from Freescale. It’s not the first M0+, but I do believe that it’s the smallest. I’ve been checking stock off and on and finally found the smallest package to be in stock and available to ship. 

I actually bought a couple of different types. First, there’s the WLCSP 20. It’s got 32K Flash, 2K SRAM and an 8K bootloader. The real kicker is that the package is only 1.6 X 2.0 mm. I also got a few in the QFM-16 package, which is a bit more workable at 3 X 3mm.

Finally, I bought a Freedom development board with the 4 X 4mm QFN-24 package. The dev board is hardware compatible with Arduino shields, so that will make for some interesting possibilities.

Anyway, here at Screaming Circuits, I’m most interested in that 1.6 X 2.0mm package to see how easy (or difficult) it is to use – see if there are any particular layout challenges. The other stuff is just for after hours play time.

Duane Benson
I’m not a number. I’m a free development board!
(Free, as in named “Free…”, not free as in “don’t cost nothin”)

http://blog.screamingcircuits.com/

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The HP Split

Those wondering how the HP split might shake out should read this piece in Bloomberg today. In summary, HP’s PC group just lost some of its pricing advantage, as the servers and other business-oriented gear are going with the new Hewlett-Packard Enterprise company. HP is currently Intel’s largest customer, but that will change as the two primary hardware lines are separated. (HP’s server gurus have been working on a competitive line using Applied Micro chipsets, so that ranking might eventually have been in jeopardy either way.)

On the other hand, given HP’s deservedly stodgy reputation in tablets and handheld PCs — despite, or perhaps because of, its acquisition of Palm in 2010 — the shakeup could enable the new HP Inc. to focus on trendier designs for the mobile market.

What’s not clear is whether each group will retain a certain number of chip designers. This is an area of strength for Apple, and HP Inc. will need to ensure it has the internal talent to advance in the hypercompetitive PC space.

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Cost Reduction in Design — More Advice

If you’re looking for the absolute, cheapest possible assembly service, you’ll need to look outside of North America. If you really need a decent price with good quality and good service, you can keep your gaze West of the Atlantic and East of the Pacific.

Like everything else in the modern world, design decisions can have a pretty big impact on your cost. So, lets take a look at some design decisions that can make your manufacturing more affordable.

  • Accept longer lead times

Lead times are one of the biggest factors in electronics manufacturing. Screaming Circuits can turn a kitted assembly job overnight, but it costs a lot of money to do that. Screaming Circuits also has a 20 day turn-around that is much, much more affordable. Accepting longer lead times on PCB fab will drop your cost as well.

  • Avoid leadless packages like QFNs and BGAs

We build tons of QFN and BGA boards – even down to 0.3mm pitch micro-BGAs. That’s great if you need those packages. However, since all of the leads are underneath, we have to x-ray every part. That adds a bit of cost to the process. If you can, stick with TSSOPs and other parts with visible leads.

  • Use reels, or 12″ or longer continuous strips

We will gladly assemble parts on strips of almost any size. But, to save costs, use full or partial reels or continuous strips of at least 12″ long. It costs us less time to work with reels and continuous strips, and we pass those saving on.

  • Stick with surface mount

These days, through-hole components tend to be hand-soldered. That costs more than machine assembly, so use surface mount wherever possible. Surface mount components tend to be less expensive than through-hole too. If you do need a few through-hole parts, this is an opportunity to put in a little sweat equity by soldering the through-hole yourself and save a bit of money.

  • Panelize small boards

We can work with really tiny boards individually, but sticking with a larger size makes the job easier, and, again, we’ll pass those saving on. If your PCB is smaller than 16 square inches, panelize it. We put in less labor and you get a price break.

By following these guidelines, you get a decent price and really good quality and service.

Duane Benson
That would be telling

http://blog.screamingcircuits.com/

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Red Makes Green

The arrival of India’s Mars Orbiter is an achievement on many levels. Much will be made of the fact that it is the first Asian satellite to reach the red planet’s orbit. That they accomplished it on their first try will open some eyes to India’s hardware capability as well, given than the success rate for the rest of the world is just 40%.

What I’d like to focus on is the price: India spent a reported $74 million on the Mars Orbiter Mission. That’s barely 10% of what NASA spent on the Maven mission.

Coincidentally, the F-22 Raptor saw action for the first time this week. But the fighter has been under fire for years for what critics call a bloated price tag and unmet performance objectives. The DoD has spent $67 billion for 188 planes, and no more will be produced.

Wall Street Journal

Should the US government wake up and realize that a huge price tag does not necessarily translate into performance, what will be the impact on the electronics supply chain, especially in the US where so much of it relies on military spending?

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