Off-Grid Solar Internet

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Maybe a cheaper option
Dan Maloney • 06/14/2019 at 01:13 • 0 comments

Saw an ad on YouTube this morning that lead me to this. Apparently Digi-Key has partnered with cellular providers to offer SIM cards for IoT applications. They're available in much smaller data increments, and are as cheap as $3/mo for 300 KB and $0.05 per SMS message. Even at $30/mo for 1GB it's cheaper than what Verizon offers directly.
I'll need to explore this further once I know more about my data usage. We got the pole delivered today, so we're getting closer to a finished system.
Moar Power
Dan Maloney • 05/27/2019 at 19:02 • 0 comments
In order to size the solar array needed to run this thing, I have to know how much power it draws. Should be simple - put an ammeter in line with the POE connection and see how much current it draws. Right?

Maybe not. Maybe the router pulls a lot of power intermittently, like when it's first making a connection to the LTE tower. Or maybe it changes over time for other reasons. I'd rather see the average over time, and to do that I need to capture data over long periods. But that's not something I'm set up to do.

I thought maybe I could use my oscilloscope as a sort of trace recorder and look at voltage drop across a shunt resistor. But then I thought, "I've got a bin full of Arduinos. Surely there must be something that can capture current readings in real time." And there is - the INA219 Current Sensor Breakout. Picked one up off Amazon for a couple of bucks, wired it up to a Nano, and came up with this janky test setup:

The Nano and the INA219 are in the middle, just in front of the 12V power supply. I'm sending 12V up the Cat5 cable using a cheap POE injector. That required a little modification of the router - had to cut the power conductors (pins 4 and 5 and pins 7 and 8) off the RJ45 and jump them over to the coax connector for 9-24V power. I wanted to put a right-angle coax plug on, but there's not enough room inside the enclosure. So, I soldered right to the coax jack.

This of course means I can't use the 48V POE wall wart that came with the router, because 48V might damage the lower voltage connection. I need to put that thing away and make sure it never gets used again.

Back to testing. I modified the example program for the INA219 board and uploaded it to the Nano.
```
#include <Wire.h>
#include <Adafruit_INA219.h>

Adafruit_INA219 ina219;


void setup(void) 
{
  Serial.println("Start PuTTY - 30 seconds...");
  delay(30000);
  Serial.begin(115200);
  while (!Serial) {
      // will pause Zero, Leonardo, etc until serial console opens
      delay(1);
  }

  uint32_t currentFrequency;
    
  // Initialize the INA219.
  // By default the initialization will use the largest range (32V, 2A).  However
  // you can call a setCalibration function to change this range (see comments).
  ina219.begin();
  // To use a slightly lower 32V, 1A range (higher precision on amps):
  //ina219.setCalibration_32V_1A();
  // Or to use a lower 16V, 400mA range (higher precision on volts and amps):
  ina219.setCalibration_16V_400mA();

  Serial.println("Bus Voltage (V),Shunt Voltage (mV),Load Voltage (mV),Current (mA),Power (mW)");
  //Serial.println("-------------------------------------------------------------------------------------");
}

void loop(void) 
{
  float shuntvoltage = 0;
  float busvoltage = 0;
  float current_mA = 0;
  float loadvoltage = 0;
  float power_mW = 0;

  shuntvoltage = ina219.getShuntVoltage_mV();
  busvoltage = ina219.getBusVoltage_V();
  current_mA = ina219.getCurrent_mA();
  power_mW = ina219.getPower_mW();
  loadvoltage = busvoltage + (shuntvoltage / 1000);


  
  Serial.print(busvoltage);Serial.print(",");
  Serial.print(shuntvoltage);Serial.print(",");
  Serial.print(loadvoltage);Serial.print(",");
  Serial.print(current_mA);Serial.print(",");
  Serial.println(power_mW);
  

  delay(2000);
}
```
It creates a CSV output that will be easy to import to Excel or something for charting. I used PuTTY to monitor the serial output and log it to a file. Been running for about an hour and the overall trend is somewhere around 1.8 to 2.4 watts(ended up averaging to 2.2 watts over a four-hour test), with occasional excursions past 5 watts. None of those spikes seem to last more than two seconds, though, so they're probably the radio(s) doing some housekeeping. It'll be interesting to see it it happens regularly or randomly.

I'm using this handy guide to planning an off-grid solar system for my sizing calculations. Not 100% applicable - it's geared to inverter-based systems - but...
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Up a Pole
Dan Maloney • 05/23/2019 at 17:27 • 0 comments

Most people would find getting a pole a daunting task. But this is Idaho, and there's literally a pole store just up the road from me. You can buy anything from fence posts to Class 5 utility poles, the latter of which are expensive - a 25' pole is about $500. But I don't need a gigantic pole, just something to hold the router, a solar panel, and a few antennas. I called the pole company and they have lathed lodgepole pine poles, 7" diameter and 24 feet long, treated for ground contact, for $141. That might be a little on the skinny side in terms of leaning a ladder up against it, but it should do.

Edit: stopped by the place and looked at a few poles they had stuck in the ground. Decided to go with a 20' pole. Burying 4' still leaves me with 16' AGL, and I think that'll be enough - half again as far up as that test pole, and about as far up as I'm willing to ladder. The pole is actually doweled, which means they jam a tree trunk through a 7" die to whittle the pole down to an even size. Larger diameters are turned on an enormous lathe and cost a lot more.
Delivery costs more than the pole, actually, but less than buying a ladder rack for my truck, which is how they'll delivery it. And they'll be able to drop it from the truck right into the hole, so no gin poles needed. They recommend a layer of gravel at the bottom of a 10" hole, then tamped gravel up to about the last foot. From there a concrete collar to lock it in place. Easy stuff, just have to get it plumbed up nicely.
Onto the next task: sizing the solar panel and battery. I order an INA219 I2C current sensor, so I'll whip up a little Arduino data logger and see how much current the hotspot draws on the bench over 12 hours or so. hat should give me an idea of idle current and in-use current.
Success!
Dan Maloney • 05/23/2019 at 03:48 • 7 comments

I don't usually have much luck out of the gates with any project, but this one was a breeze.

My first test was as simple as possible - parked at the remote site, I threw the hotspot on the roof of the car and plugged the POE injector into the inverter. The WiFi list on my phone was completely empty until one lonely AP showed up. I was able to connect without any issues and make calls, text, and surf the web. Not exactly blazing fast, but it worked with zero optimization. Badda-bing!

The second test was slightly more involved. I put the hotspot on the end of an extensible pole - a roof rake for snow removal - and lofted the unit up about 3 meters AGL.

I wanted to test if height made any difference in connection speed, and to test the range of the WiFi around the property. Speed was definitely better, at least according to my Speedtest app - 2.59-Mbps downloads while up on the pole versus 1.66-Mbps on the roof. I suspect I can improve that considerably by replacing the stock omnidirectional LTE antennas with log-periodic dipole array (LDPA) diversity antennas, but more on that later.

As for WiFi coverage, I was pleasantly surprised. We walked east from the hotspot for quite a way, over 230 meters, before dipping down below the local horizon and losing the signal in the weeds. To the north we were able to range almost to the property line, about 140 meters, and to the west over 100 meters and just about to the gate on the county road. That's a big bubble of WiFi, much better than a typical consumer-grade router can do. Assuming an elliptical pattern, it covers about 62% of the property - again, with almost no optimization. Mounted on a permanent pole with better omnidirectional MIMO WiFi antennas, and this thing would be able to supply WiFi to the neighbors. If there were any.

Next step - measuring the power required by the hotspot and designing a solar array to power it.
Power Problems
Dan Maloney • 05/22/2019 at 05:13 • 0 comments

Getting ready for a field test tomorrow, so I decided to see if I can power it with 12 VDC. That would be the easiest solar system to build - one small panel and an AGM or LiFePO4 battery with charge controller - and I can also just jumper it off the batteries in my car or RV. I modified a little POE injector to take 12 volts from my big 30A ham radio supply, and tried to power it up.

Nothing.

Turns out that POE wants 48 V, and that's what the supplied wall wart injector is rated for. That poses some problems. Building a 48 volt solar system is prohibitively expensive - that would be eight GC2 golf cart batteries, and 48 volt solar inverters are expensive. But the docs for the router clearly state that it runs off of 12 to 24 volts. So I was confused.

Luckily, there's a second DC input on the main router board. The 2.1-mm coax jack is labeled "9-24VDC", and when I jumped 12 volts into the jack, the router powered up. Success! I ordered a right-angle coax plug - tight quarters in there - and I'll wire that up to the POE pairs (4,5 + and 7,8 gnd) from the internal RJ45 plug. Sophie suggested soldering them to the coax connector, and maybe that's a good idea. We'll see.

Looks like everything is ready for a field test tomorrow. If I can get it working on site then I'll start tackling the solar aspect - panel, battery, and charge controller. Plus some kind of mounting pole.
Oh Verizon
Dan Maloney • 05/22/2019 at 05:00 • 0 comments

I suppose Verizon is like any other cell phone store. Wild guess on my part, since I avoid those places like the plague. But needs must, and I packed up the router and headed off to the store, fearing defeat loomed ahead.
It was a close call. The dear, sweet girl who tried to help us was out of her depth. If we had a phone problem, I'm sure she would have been fine, but coming into the store with a cardboard box bearing a Chinese router bristling with antennas just threw her into shock. Luckily, Jamel came along - think he was the store manager - and he figured it out. We bought a SIM card for a JetPack and put it in the router, and it worked! Walked out satisfied after having tested it by making a few calls and texts on my phone over the router.
Lesson learned: stand your ground. We finally got somewhere when I said this would just be like walking in off the street with an old tablet and needing a SIM card. Then they got the concept. Until then it was like a scene from Idiocracy - "What, like from the toilet?"
I spent a good deal of time configuring the router on the bench at home - admin password, stuff like that. I was able to SSH into it, and use the GUI - it's based on OpenWRT. I had trouble getting it set up for remote access, though. I gather that entails getting a domain, registering it, and setting it up DDNS so that the name follows the device. I did that once before for a security camera system, but for some reason I just can't get all the buttons pushed. Not a show stopper, and I'll get it eventually. Just frustrating for now.
Change of Plans
Dan Maloney • 05/18/2019 at 19:05 • 0 comments

So I checked out hotspots with Verizon, and to say the least, I was underwhelmed. The current offering that Verizon has is woefully inadequate for the task. It's battery powered, which is nice, but it's not robust at all. It's built to slip into a backpack or briefcase and be deployed on the dash of a car or a hotel desk, not on a remote, rugged piece of land. And it would have to be hacked to provide power from a solar array, which id the main goal of this project - remember, there's no power on this site.

But the biggest problem is the antennas - they're all built into the device. Yes there are jacks for an external antenna for the LTE radio, but the WiFi antenna is built in and inadequate. The stated specs are 60-70' radius for WiFi, which is woeful. I need to cover a much larger area - the property is over 20 acres, and I want to be able to use my phone over as much of it as possible.

So I did some Googling and found OutdoorRouter.com. They make a range of cellular to WiFi routers, all built in sturdy IP67 enclosures suitable for pole mounting. It's got POE power with Ethernet entering through a weatherproof gland, and external antennas for both LTE and WiFi. Those connectors are robust threaded N-type connectors. The manufacturer claims they have one that works with Verizon, and it doesn't cost a whole lot more than that chintzy JetPack thing.

After a little back and forth with the wonderful Sophie Tang, sales manager for OutdoorRouters.com, I sent in an order for an EZR30. It shipped out of Shenzhen and arrived DHL in five days, even with a hold in LA for customs.
I was greatly impressed by the build quality - sturdy cast aluminum case, gasketed door with captive screw closures, well sealed penetrations. I was apprehensive about getting it online, though, thanks to a few emails back and forth with Sophie that clued me in to the fact that Verizon might give me grief about getting a SIM card.

As it turned out, she was right to warn me...