I am looking to design a wearable tracking device for participants in a research study. Participants location will be tracked and the device will need to make a sound/ send an alert to the research team and participants when an established geofence is crossed (we have the software sorted out). Location accuracy does not need to be any greater than a few meters, and location only needs to be sent ~ every 10-15 minutes. The device will be worn as a patch on the participants torso, so it needs to be small and not too heavy. It would be ideal if the deivce could run for ~30days on a single charge, but concessions can be made here for a smaller/ lighter device. For the network, we have looked into using either cellular or gps. GPS would likely be advantageous as this study will be international and likely to include rural area but, if it reduces size and battery consumption, than cellular may be the way to go. The easy part in all of this is that budget is not a problem!
What components would I need to make this device work building off of these breakouts? Since the deivce itself will need to be alerted when the geofence is crossed, is an antenna or an additional chip/ module required? What would be the smallest battery we could use to power the device for ~30 days, or 2 weeks at a minimum.
Any guidance here is appreciated as I know next to nothing in the world of device design.
That is VERY difficult, especially if GPS is involved, as the receivers are power hungry. Take a look at commercial tracking options, e.g. SPOT Trace and animal trackers, to see what sort of battery life that professionals, with decades of experience, can come up with.
Cellular connections are also very power hungry. This is not a project for beginners to design and build.
Thanks for the feedback. I do understand the battery life with this is a challenge. If we put the battery issue aside for now, could you recommend some Sparkfun products to make this device compact?
This makes me think that you should be looking into writing an mobile app for your participants to install on their phones that they already âwearâ and monitor charging. The requirements of a standalone wearable device, as described, are not realistic, if even possible.
It is a great idea, and one that has already been proposed. But I am just an assistant on this project so that is not my decision to make, and they are going with a wearable deivce. The battery problem will eventually fall to someone else, but what I am looking for is just a list of components to make this device work. For example, what components would I need if I use the SparkFun GPS Breakout - ZOE-M8Q (Qwiic)?
In addition to the GPS, you need a microcontroller and a means of communication with the outside world. If shopping Sparkfun, perhaps the RockBlock MK2 and an Arduino compatible MCU board with at least two UART serial ports.
Itâs a fun thing to wish for but, as said, not realistic. You can remind the powers-that-be of the limitations of roughly comparable devices like game & wildlife tracking @jremington suggested or amateur radio APRS systems that donât rely on network infrastructure to get their cargo delivered. Vehicle tracking systems, both covert and fleet management, rely on local cellular networks and are either extremely short lived/charge or wired into the vehicles electrical system. Even the Enterprise sometimes canât reach/locate the away team.
Take airline âblack boxâ underwater transponders. When they get wet, they sound an acoustic tone to help in their location. They arenât wearable or lightweight, they donât know their own position, they donât connect to any particular receiver or do anything but make noise, they play an undeniably important role and need all the battery life they can get and those barely last 30 days.
It is a fun project, and straightforward to implement with the off the shelf parts I mentioned, but the âsmall, wearable and 30 day battery lifeâ aspect is sheer fantasy, as you will discover.