Best wireless GSM/GPRS + GPS module(s) <25mm in size

[Ryner]

I'm trying to make a GSM/GPRS/GPS tracker for my bike for fitness monitoring and location tracking, in the event of a theft. I would like to fit this device inside my bike's seat tube which is 25.5mm in diameter. Looking around the internet I came across this Kickstarter :https://www.kickstarter.com/projects/385904042/shyspy-gps-gsm-tracker-for-bicycles, sadly the goal wasn't reached. But I want more than what they offered.

What I need (in order of priority):
0. Module has to be <25mm.
1. GSM/GPRS capability for retrieving location data and sending it through SMS.
2. GPS capability for retrieving location data (more accurate) and tracking speed/distance for fitness.
3. Bluetooth capability for wireless transmission of fitness data to smartphone/laptop and for finer localization by tracing signal strength on smartphone (<10m distance).
4. GSM Microphone capability for listening on the surroundings of the bike.

I've found some modules from SIMCOM that fit most of my needs, such as the SIM968 but the size is an issue. There is also the SIM800 series that are small enough to fit inside a bike tube but they don't offer both GPS and GPRS.

Question: What modules are available that are less than 25mm in size and offer at least GSM/GPRS functionality?

At the moment I'm leaning towards the SIM800 and being satisfied with just having the GPRS tracking alone. I've also thought about having two separate modules for both GPS and GSM but I'm not too knowledged in that area to say for certain, and I fear that I might be stuck with compatibility issues.

Question 2: What microcontroller would be a good choice for this project?


As a side note: I recently finished my first year at uni; therefore, I'm still an amateur here. And this is my first time on the forum, please be gentle.

[CaptainObvious]

Welcome to the forums! 

I'll start off by saying I can't offer much insight on the modules.. but just a couple things from a glance over

In regards to compatibility, that's why you use a Microcontroller, to provide compatibility! So two modules may be your best solution in the end. Bear in mind, the GPS and GPRS devices may NOT be AT+ compatible. (Serial commands) Keep this in mind while researching hardware! You'll likely want to keep AT+ as an option, mainly for ease of use on microcontrollers. (Or you may find yourself writing your own code:) and potentially some custom hardware connections)

I don't think the hardware will be much of an issue, minus the normal troubleshooting phases of a new circuit board. Mainly just find the two devices that will fit your size and microcontroller requirements, and should be fairly smooth sailing from there. (Keep in mind, soldering some of those devices by hand may be darn near impossible, so be prepared to deal with this, or prepared to pay somebody to deal with this! This can be expensive if you're going through multiple revisions)

Couple things that come up while thinking about it:

• How do you plan on powering the device, as well as recharging the batteries? Curious if you've got some batteries in mind or maybe another solution? Potentially an Dynamo type system to recharge the system?
• How long are you expecting to have the battery last in the case of a "stolen" bicycle? For example.. if your average battery lasts 7 days, and the bike gets stolen 5 days into your "discharge", you've got 2 days to collect data, is that sufficient?

I'm really curious to see how this comes along, I've got a few nerdy buddies who enjoy biking as much as anyone else who would be interested in something like this.

[LabSpokane]

I'm assuming this is a carbon seat tube?

You just need a micro controller that will periodically store and forward NMEA 0183 data grams. A good GPS will generally let you choose which sentences to send to keep the payload down. I hope you find a small module because I need one too.

[Ryner]

Couple things that come up while thinking about it:

• How do you plan on powering the device, as well as recharging the batteries? Curious if you've got some batteries in mind or maybe another solution? Potentially an Dynamo type system to recharge the system?
• How long are you expecting to have the battery last in the case of a "stolen" bicycle? For example.. if your average battery lasts 7 days, and the bike gets stolen 5 days into your "discharge", you've got 2 days to collect data, is that sufficient?

I'm really curious to see how this comes along, I've got a few nerdy buddies who enjoy biking as much as anyone else who would be interested in something like this.

For the time being I think I'll just stick with GSM/GPRS for the first prototype and get it working as best as I can. Now as for the battery, according to the datasheet of the SIM800 the power consumption in sleep mode is .88mA. With a polymer lithium ion battery/cell with 1000mAh or more should get me to the end of the month. My plan with the usage (GSM verson) is that I only turn it on when I lock the bike in a public location and I'll have it send me updates of its location based on a set time interval; time interval would be set by SMS or set to a default if none is stated. The charging system would have two chargers, one primary and one secondary (passive). The primary one would be a direct link to the battery charging circuit through a port under my bike seat. I wanted to do wireless charging but my bike frame is steel, but I can keep that as an option for a carbon frame. As for the secondary passive charger I want to add a kinetic charger. Kinetic chargers such as a magnet in a coil tube and/or a small motor with a weight on it (similar to a self winding analog watch). These are still just ideas I don't know the efficiency of them, but I do have a lot of cobblestone roads where I live which might increase the benefit of them. On the other hand I can also strap the kinetic chargers on my thigh or calves and have a wire running into my bike seat. Since I cycle about 10km to school and back it could be a very effective way of charging the device.

As for building the device I have a lot of experience with soldering especially with SMD's. The biggest obstacle I'll have will be the software.

I'm assuming this is a carbon seat tube?

You just need a micro controller that will periodically store and forward NMEA 0183 data grams. A good GPS will generally let you choose which sentences to send to keep the payload down. I hope you find a small module because I need one too.

My bike has a steel frame. I've found a GPS module, the SIM68 series, from SIMCOM that comes in a very small package. But I don't know how difficult it's going to be making it work with the GSM module, as I have next to no experience working with something like this.

[LabSpokane]

Consider using the uC to power down the GSM module when not in use. Even a AVR can sleep at 45uA without much effort. The GPS draws 75mA by itself, so you will have a fairly steep power draw during TX.

The SIMCOM modems are AT command based.  If you do some googling, you'll find a tutorial on how to handle all of the commands needed. 

I'm trying to find a US site where I can get a datasheet.  From what I can gather, the modem and GPS are on the same module, but powered separately, so you're likely going to need to interface the GPS serial output lines to the uC, then parse and forward what you want through the modem. 

Anyone know of a good US distributor for SIMCOM? 

[Marco]

Where do you want to hide the antenna? You could use a nylon fibre seatpost (ie. non conductive, carbon might block reception). Put the module on the bottom of the post and the antenna inside at the top to get it above the frame.

[8086]

GPS: SIM28M
GSM/GPRS/BT: SIM800C (or H)
MCU: LPC11U35

These are what I am using for a tracking project I'm currently working on. I got my SIMCOM modules from Aliexpress.

[Ryner]

Where do you want to hide the antenna? You could use a nylon fibre seatpost (ie. non conductive, carbon might block reception). Put the module on the bottom of the post and the antenna inside at the top to get it above the frame.

I'll be putting the module inside the seatpost and have the antennas and the charging wires run up the tube to the opening at the top. The space between the saddle and the opening is roughly a 50 x 30 x 20mm box. I'll have to 3D print a special case to house the bluetooth, GPS, and GSM antennas inside along with a charging jack, everything waterproofed of course.

From what I can gather, the modem and GPS are on the same module, but powered separately, so you're likely going to need to interface the GPS serial output lines to the uC, then parse and forward what you want through the modem. 

I've found those modules too but their package size is too big to fit inside a bike's seat tube, <25mm. My only option at the moment seems to be using two separate modules for GSM and GPS.

[splin]

Probably not a big issue for you but bear in mind that 2G and 3G networks are coming to their end of life - in the USA and Australia they are already being shutdown.

In the UK it has suggested that they could be turned off by 2020 but some think that 3G will be retired first and 2G kept going longer - the smart meter rollout will get even more expensive if they all have to be upgraded to 4G in a few years time.

[Wilksey]

Adafruit have started stocking the SIM808, have you looked at that?
http://www.adafruit.com/products/2637

24 * 24 in size.

Some of the bike trackers i've seen use the UBLOX Leon G1/G100 and a GlobalTop (MTK 3389 chipset) receiver with ceramic patch.

The newer Quectel M66 is quite small so is the 800C from SIMCOM

[Ryner]

Adafruit have started stocking the SIM808, have you looked at that?
http://www.adafruit.com/products/2637

24 * 24 in size.

Some of the bike trackers i've seen use the UBLOX Leon G1/G100 and a GlobalTop (MTK 3389 chipset) receiver with ceramic patch.

The newer Quectel M66 is quite small so is the 800C from SIMCOM

The module size of the SIM808 would be a real pain to design a PCB for when I have a less than 1mm to work with. I've already ordered the SIM800H so I can run some tests and start building a prototype.