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Question to those who know the landscape of little microcontrollers well: if I wanted to build a small pet tracking chip (gps and cell, probably) that would wor

Question to those who know the landscape of little microcontrollers well: if I wanted to build a small pet tracking chip (gps and cell, probably) that would work way out in the boonies (like middle-of-nowhere-Wyoming), where should I look? Am I right to be thinking gps+cell, or is this something where I could get away with just GPS (and somehow track where that GPS is pinging from)? And would something like a tumble generator provide enough power?

HeyLaughingBoy 11y ago
That's going to be a module, or set of modules, not a single chip. Doubt you'd get cell service in middle of nowhere Wyoming.
anyfoo 11y ago
By "tracking", do you mean being able to check remotely where your pet currently is, or simply record its current location to some kind of storage, and being able to review that once you have physical access to the device? I.e. are you concerned about your pet getting lost, or do you just want to know where it has been? If it's about remotely checking, then you will need some kind of communication, which is most likely going to be cell phone related (i.e. GSM, UMTS, LTS...). A GPS device does not send anything to the satellites, it merely (as a simplified explanation) receives time codes from multiple satellites and triangulates the current position from that. If you only want to record, then GPS alone would be fine, obviously. Though there is "Assisted GPS" that makes use of cell phone technology to increase the accuracy/decreases the triangulation time. However, I do not know whether that can be leveraged from standalone GPS modules.
Gibbon1 11y ago
I think there are dog trackers on the market that use GPS + Cell. At least there are motorcycle trackers. Generally the problem with WiFi is if it's close enough to work the dog can usually hear you. You could use a directional antenna but an extra 10db isn't going to buy you much. And at 2.4GHZ WiFi gets attenuated rapidly when not line of sight. Same is true for anything else in the 900MHz/ 2.4GHZ bands. Cellular gets around this by putting their antennas up high to clear local clutter (buildings, trees, hills, etc). Problem with Cellular is the power drain and the monthly bill. On the other hand, probably will work. Cellular coverage is pretty good everywhere now. If you want to mess about I think there are modules with Cellular and GPS. You also might be able to use a 900MHz solution[1] where you just send a ping of the GPS coordinates every so often. If you up the power to the max allowed (Like 20-30db) and drop the data rate down to a few hundred/thousand bits per second. You could probably go two to three miles. I think your current choices here are some sort of FSK radio or the newer LoRa radio. The reason is FSK radios and LoRa both allow you to turn the bandwidth way way down. The lower the bandwidth the better the signal to noise for the same transmit power. [1] The lower the transmit frequency better it will propagate through clutter on the ground. But lower frequency means a bigger antenna. PS: If you're messing with RF using module or manufactures dev board is the way to go. It's very hard to tune the RF path and antenna without experience and a spectrum analyzer. PSS: I've found the transceivers from SemTech to be pretty bulletproof. They have their own power regulators on board which makes them insensitive to being powered by crappy supplies.
lovelearning 11y ago
Have a look at goTenna (http://www.gotenna.com/ http://www.gotenna.com/). It uses 151-154 MHz radio waves to communicate upto 4 miles. Doesn't require mobile network. It's probably too large for your requirement, but may give you some ideas to DIY or adapt its PCB.

HeyLaughingBoy 11y ago

That's going to be a module, or set of modules, not a single chip. Doubt you'd get cell service in middle of nowhere Wyoming.

anyfoo 11y ago

By "tracking", do you mean being able to check remotely where your pet currently is, or simply record its current location to some kind of storage, and being able to review that once you have physical access to the device? I.e. are you concerned about your pet getting lost, or do you just want to know where it has been? If it's about remotely checking, then you will need some kind of communication, which is most likely going to be cell phone related (i.e. GSM, UMTS, LTS...). A GPS device does not send anything to the satellites, it merely (as a simplified explanation) receives time codes from multiple satellites and triangulates the current position from that. If you only want to record, then GPS alone would be fine, obviously. Though there is "Assisted GPS" that makes use of cell phone technology to increase the accuracy/decreases the triangulation time. However, I do not know whether that can be leveraged from standalone GPS modules.

Gibbon1 11y ago

I think there are dog trackers on the market that use GPS + Cell. At least there are motorcycle trackers. Generally the problem with WiFi is if it's close enough to work the dog can usually hear you. You could use a directional antenna but an extra 10db isn't going to buy you much. And at 2.4GHZ WiFi gets attenuated rapidly when not line of sight. Same is true for anything else in the 900MHz/ 2.4GHZ bands. Cellular gets around this by putting their antennas up high to clear local clutter (buildings, trees, hills, etc). Problem with Cellular is the power drain and the monthly bill. On the other hand, probably will work. Cellular coverage is pretty good everywhere now. If you want to mess about I think there are modules with Cellular and GPS. You also might be able to use a 900MHz solution[1] where you just send a ping of the GPS coordinates every so often. If you up the power to the max allowed (Like 20-30db) and drop the data rate down to a few hundred/thousand bits per second. You could probably go two to three miles. I think your current choices here are some sort of FSK radio or the newer LoRa radio. The reason is FSK radios and LoRa both allow you to turn the bandwidth way way down. The lower the bandwidth the better the signal to noise for the same transmit power. [1] The lower the transmit frequency better it will propagate through clutter on the ground. But lower frequency means a bigger antenna. PS: If you're messing with RF using module or manufactures dev board is the way to go. It's very hard to tune the RF path and antenna without experience and a spectrum analyzer. PSS: I've found the transceivers from SemTech to be pretty bulletproof. They have their own power regulators on board which makes them insensitive to being powered by crappy supplies.

lovelearning 11y ago

Have a look at goTenna (http://www.gotenna.com/ http://www.gotenna.com/). It uses 151-154 MHz radio waves to communicate upto 4 miles. Doesn't require mobile network. It's probably too large for your requirement, but may give you some ideas to DIY or adapt its PCB.