Location Network

[lbjstetson]

For LoRa you will have to use a 3rd party library - RadioHead is the popular one, see this page for getting started with that. I am sure there are plenty of examples on the web on how to better utilize that library. I would personally start with a pilot using RFM69HCWs and see how that does.

Gotcha. I didn't know that there was any other difference than the cost and maybe the antenna. I'm pretty new and inexperienced yet on electronics and hardware, I'm a web developer.

The antenna is important especially in mobile applications like yours. RF does not like enclosures, especially metal. Any antenna will love to be elevated as much as possible, with no obstacles in the line of sight, keep as much to that principle as possible to maximize the chance to receive packets.

I plan on using antennas and running the cable through a cable gland into the box. For the GPS/GSM units, I plan on using a magnetic combo antenna similar to THIS. I see the article you posted about PCB antennas. What's a good way to make those weatherproof?

I would not go to 300kbps in real practice except when range requirement is minimal or for short range wireless programming. I think the default 55.5K is good, and perhaps if the question comes, you can lower it to 19.2k or even lower.

To maximize battery life you need to sleep everything inside the mote that might use power, when the mote is not in use. There are various ways to monitor battery life. The simplest is a voltage divider to bring the battery voltage under the 3.3v operation of the Moteino, and read that on an analog pin. Several examples in the RFM69 library (motion mote is one).

I would not focus too much on removing the LDO at the moment, that will save you 2uA and I think your effort is better spent elsewhere.
Make sure to sleep the FLASH MEM chips as well since I see you have that in the photo.

Ok, I'll keep these things in mind when I'm working on my prototype.

For enclosures, look around in the projects forum for inspiration, there have been lots of great examples how people got creative with cases in various projects. I think it's easier to develop your motes around an existing case rather that the reverse. Choose a case that makes sense, there are lots of possibilities. Perhaps choose one with a rubber ring top that mounts with screws. You can mount your 3xAAA or similar power pack on the top with velcro or hot glue, for the RF use coax cable pigtail of 1/4 wavelength to route the signal from the mote to a panel mount SMA (you can find some on ebay precut to length). Then use external mounted antenna with matching SMA mount.

How about pelican cases? I know they're a little bit pricey but I'm tired of ordering them online only to see that the rubber gasket looks cheap. The per unit cost isn't super important to me.

I've been having some issues with condensation in some of my other cases. How do I prevent that from screwing up my units?

[ChemE]

I've been having some issues with condensation in some of my other cases. How do I prevent that from screwing up my units?

There was some very good discussion here on this subject.

[ChemE]

This is a pretty cool project which uses a piezo transducer to detect vibration of a vehicle and send GPS location via GPRS/SMS using the SIM5320e module.

That is a cool project but a sleep current of 3mA seems crazy high.  The piezo produced spikes of 0.5V.  If I understand correctly, the interrupt will trigger at +1.65V right (half of the board voltage)?  Seems like one could just use a transformer to boost that voltage passively and get the sleep current back down to 6uA like it should be.  Maybe is was 3mA because he choose a horrible LDO...

[ChemE]

Not zero but it did occur to me that an accelerometer board I just bought and have yet to play with can generate interrupts.

https://cdn.sparkfun.com/datasheets/BreakoutBoards/ADXL362.pdf

This gets the sleep current down to 270nA and eliminates a good amount of complexity from the project Felix posted.  This would allow an unmodified Moteino to sleep on 2.5uA most of which is the MCP1702!

EDIT: Just hooked everything up and slept the radio and the uC forever.  I'm measuring 1.9uA for a sleeping radio, uC, and ADXL362.  Current jumps to the tens of uA as soon as I tap the ADXL362 so it does appear to be sensing impact within that minuscule power budget.

EDIT2: And 1.7uA when run from a set of 2xAA Energizer Ultimate Lithium batteries currently at 3.37V.

[Felix]

lbjstetson,
Pelican cases (google search) seem too bulky and overkill for what you need. I would keep these as small as possible.
I looked at some GSM units and there are 2 I think could do the job and have GPS and GSM/GPRS bundled in 1 unit: the SIM808 (2G) and SIM5360A (3G) the latter being more expensive. You can find these on various breakouts  - seems like adafruit's variants could be pretty good for what you need.

These will require a GPS antenna and GSM antenna. Then if you have the RFM69/LoRa radio, that has its own antenna. So 3 antennas in total for the gateway. The rest of the units just have the RFM radio, so 1 antenna.
The tricky part with these is the GPS units may have different capability and time to get a location fix, and require different types of antenna (passive for the 808 and active for the 5360 for best performance) seems like the SIM808 can take a while to fix location and 2G being slower GSM/GPRS could also take a while to send data, which impacts your battery life.

For the PCB dipoles I don't think they require water proofing. In fact you would likely want those exposed since soldermask protects the copper and wrapping them in anything starts to attenuate them. They could mount directly ontop the enclosure with a matching SMA connector soldered directly on them. They are probably cheap enough to scrap if they do get damaged over time.

ChemE,
The GPS/GSM project I linked was more for reference, and indeed the 3mA sleep seemed way too much. But I thought it might be of inspiration in some ways.
Cool about the ADXL362, I wonder if the ADXL could sense loud noise/alarms like beeps from a fire alarm

[lbjstetson]

Pelican cases (google search) seem too bulky and overkill for what you need. I would keep these as small as possible.

They make some smaller ones that would be about the right size. Here. They have smaller models also.

I looked at some GSM units and there are 2 I think could do the job and have GPS and GSM/GPRS bundled in 1 unit: the SIM808 (2G) and SIM5360A (3G) the latter being more expensive. You can find these on various breakouts  - seems like adafruit's variants could be pretty good for what you need.

I'm already using 808 for another project and it seems to work pretty well, though the cell network isn't great which is important. I plan on testing a few different GPS modules for the nodes. I was looking at Adafruit's Ultimate GPS Breakout but it looks like it might be overkill.

My budget right now for the first few units is about $120 for each node and $200 for the GSM unit. I think I'm pretty comfortable with those numbers.

These will require a GPS antenna and GSM antenna. Then if you have the RFM69/LoRa radio, that has its own antenna. So 3 antennas in total for the gateway. The rest of the units just have the RFM radio, so 1 antenna.
The tricky part with these is the GPS units may have different capability and time to get a location fix, and require different types of antenna (passive for the 808 and active for the 5360 for best performance) seems like the SIM808 can take a while to fix location and 2G being slower GSM/GPRS could also take a while to send data, which impacts your battery life.

I'm not really concerned about battery life on the gateway. I'm planning on using a battery that'll recharge when the vehicle is on via the cigarette lighter slot. I could also use a solar panel to recharge the battery which might be a better option since I wouldn't have to run wires.

For the PCB dipoles I don't think they require water proofing. In fact you would likely want those exposed since soldermask protects the copper and wrapping them in anything starts to attenuate them. They could mount directly ontop the enclosure with a matching SMA connector soldered directly on them. They are probably cheap enough to scrap if they do get damaged over time.

Ok, excellent.


Thanks for all of the advice, it has been a big help. I'll be sure to post pictures and give updates when I get approval to start testing.