GPS bicycle tracker

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AndrewBrown

New Member
I am looking to start up a new project to make a very small GPS tracking device for a bicycle. After my last bike was stolen I thought it could be an interesting project. The idea is to make a system which the user could send a text message (to wake up) and then receive a text message back from the device to their mobile phone containing the GPS co-ordinates. Similar to the spylamp

It will be my first proper picaxe project for a while and I know that although it would probably be cheaper to just buy the spylamp, I think I'd like to give it a go myself.

I Imagine I will need;

GPS module
GSM module
Antennae
Picaxe chip
Battery (lithium)

I had imagined that I would embed all of the electronics into a plastic tube type thing which I could slide down the seat pole and easily take out to charge the battery etc. So size is probably the most important part of this project. Does anyone know of any projects similar to this posted here? Or recommend some GPS/GSM modules, which picaxe chip would be the best for the job?

Thanks
 
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papaof2

Senior Member
If the bike frame is metal, sliding the assembly inside the seat pole won't work - your GPS and GSM module will be totally shielded and thus unusable. You'll have better results if the frame is carbon fiber or similar material.

If the bike frame s non-metallic, you still need to verify the following:

1. You can get modules that will fit inside the seat pole. Most GPS receivers are about 1" square.

2. You can get batteries with adequate capacity that will fit inside the seat pole.

3. You will actually remember to charge the batteries when needed.

A 14M2, 18M2, or 20X2 PICAXE should work. An 08M2 might work.

Look at Sparkfun for GPS and GSM http://www.sparkfun.com http;//www.globalsat.com also has a variety of GPS units.

John
 
hippy

hippy

Technical Support
Staff member
On the principle that you likely won't have a full specification when you start, and may want to add capabilities as it develops or after you have built it, it seems sensible to pick the most powerful and capable PICAXE you can. The key thing to note is communications with both the GPS and GSM module are likely to be serially based.

For high speed ( when needed ) , serial comms ( with background receive ), large memory, that would be the 28X2 IMO. The slightly higher cost of a 28X2 is probably going to end up as insignificant in the cost of the entire project.
 
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srnet

Senior Member
I have seen plenty of reports in the RC model world of Carbon fuselages blocking reception, routing the antenna outside of the fuse normally cures the problem.
 
1968neil

1968neil

Senior Member
just an idea but how about mounting the gps antenna in a light or a reflector ?

from experience, having fitted a considerable amount of gps antennas for trackers in cars, the owners where concerned that the antenna would give away the fact it had a tracker fitted. (very expensive cars etc)
GPS antennas do work thru metal if the antenna is a good quality (hence expensive) version.
that aside, the fact the antenna would be shielded by the metal frame and also taking into account the framework in the seat and the body mass of the rider, rf/gps would be poor at best.

You'll have to be clever with the cables, the plastic covers that are used for gear and brake cables make a great shield for the cables and is almost impossible to cut through with hand tools.

the better the signal path for the antenna the more chance you'll have of getting your bike back !

As far as power goes you could switch the whole thing on and off with a tilt switch so once triggred it can stay that way until told differently by a reset of if you plan to use sms you could text the device to switch it off.
A dynamo device could be fitted to the bike to charge the battery as its ridden ?
Just a few ideas to stir the creative juices !

Regards
Neil
 
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eclectic

Moderator
Assuming the tops of the antennae are
above the seat-pole tube,
then the Gel/plastic of the saddle shouldn't be a problem.

Or will it?
(Don't own a bike anymore. :-(


e
 
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srnet

Senior Member
I dont think I would be too concerned about the physical part of the mounting (where/how) someone already appears to have shrunk the bits enough to fit in one of those small rear lights.

A greatwer challange is where do you get hold of GPS units so small. The smallest I have come across, is the Mediatek MTK3329, and that not what I would call tiny. Uses around 50 -70ma too.

There must be smaller GPS units around, they are found in mobile phones thses days after all.
 
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MFB

Senior Member
I did some work on racing car telemetry and can assure you that carbon does act as a pretty good rf screen and antenna ground plane. You would have to mount the antennas outside of the seat tube.
 
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manuka

Senior Member
Mmm- few people ever invert the bike & look UNDER the seat,so this may suit antenna placement. The seat material will usually allow RF thru' as well. Pressure & tilt switches could have design weaknesses however, as stolen bikes may get impromptu rides & be then tossed in nearby wasteland. Perhaps use pressure switch activation when the bike was being ridden- kept on few a few hours afterwards?

Your biggest problem will probably be ensuring the power supply lasts long enough to allow decent tracking. Given the GPS, CPU, & cell phone drain I'd say only a few days battery life may result. If the bike is stashed away indoors you'll loose signals too. (Car tracking is usually not so concerned with this power restriction, as the vehicle battery has far greater capacity & the car will usually be outdoors for significant periods.)
 
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papaof2

Senior Member
There are some small (1/2" in largest dimension) GPS modules http://www.wi2wi.com/products/datasheets/W2SG0084_PB rev1.0.pdf Mouser has these for $20US plus shipping http://www.mouser.com/ProductDetail/Wi2Wi/W2SG0084i/?qs=sGAEpiMZZMsyM1rGGtQxrEAXW8JWm9Jn

As mentioned above, power is a concern. This device runs on 3 volts with 50ma peak current.

If you configured the PICAXE with a real time clock (to have accurate time), the PICAXE could be set to run at low speed and power, then come to normal operation at specified times and turn on the GPS, check for GPS lock, turn on the GSM module and send the current location. Alternatively, the PICAXE could turn on the GSM module for perhaps 6 minutes at specified times (i.e., 11 minutes past each even hour). If the phone receives a call in that time period, turn on the GPS. When lock is achieved (or after some timeout period waiting for lock) respond with the current location or a "no GPS data" message.

Some RTC modules can run for a year on a coin cell backup battery. Most have some type of alarm output which could be used to interrupt the PICAXE to bring it out of a minimal power mode.

The RTC option would greatly extend battery life, as the PICAXE would be running at low speed and power and the other devices (GPS, phone) would only be on for short periods of time and on an intermittent basis.

John
 
hippy

hippy

Technical Support
Staff member
papaof2 said:
Alternatively, the PICAXE could turn on the GSM module for perhaps 6 minutes at specified times (i.e., 11 minutes past each even hour). If the phone receives a call in that time period, turn on the GPS.
Click to expand...
The spylamp link in post #1 gives quite a few details on the way it operates which is quite clever in terms of minimising power.

When not knowing it's been stolen it seems to wake up every 6 hours or so and check if it has received an SMS which is quite handy because the phone company should hold on to SMS's until delivered ( at least for a reasonable amount of time ) so you don't have to coordinate timing accurately.

It would be interesting to consider how UK and other country's proposals to throw the kill switch on SMS and messaging in times of civil disturbance would affect these types of alarms and trackers. As long as the battery lasts and it's not been stashed in a Faraday cage it should come back to life once the restrictions are over or moved out of a silenced area. That also overcomes the fact that SMS is not a guaranteed delivery service.

Given the capabilities of spylamp it looks like value for money to me.
 
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klotz

New Member
I've also built a Picaxe-based GPS tracker project using Part 15 "garage door" type transmitters. See http://wa5znu.org/2009/05/marauders-map/
It was difficult using the 08M chip to parse the GPS output. The new M2 series chips and the bigger one with buffering may make it easier.


I've built a few GPS bike trackers using APRS hardware from argentdata.com, either the OpenTracker+ or the Tracker2 VHF data radio combo.
There, the APRS and data takes place on another modem+controller device, which itself is open source but not easily replicated and certainly not a Picaxe.

However, I did build a Picaxe-based motion controller for it, using a Piezo and a solid-state relay. It's about 1ma draw and when the piezo gets triggered, it turns on the radio+modem for 5 minutes, and then turns it back off. Originally I had it stay on when the piezo detected motion, but I had a lot of trouble with the piezo detecting the RF as well, so the Picaxe would confuse radio transmissions with motion. I eliminated the 5v zener protection and put in bypassing, to no avail. It seemed like the piezo itself was picking up the RF and rectifying it, which doesn't seem that unlikely.

In my next design, I'm using the 08M2 and hope to receive messages from the radio+modem; one thread will monitor the piezo and another will monitor the radio+modem serial output. I'm hoping to use the extra 100 bytes of RAM on the 08M2 to buffer messages and output them to a speaker in CW.

BTW here is the GPS I used: https://www.argentdata.com/catalog/product_info.php?cPath=23&products_id=137

Leigh/WA5ZNU
 
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AndrewBrown

New Member
Thanks for the replies.

I had thought that there may be a problem receiving signal if it was all mounted within the frame itself. I can't see there being any problems with running an antennae into the seat itself. And although battery life is important, I only really need it to run for up to 24 hours max, I take the seat off when its not in the most secure location (people in dundee really will steal anything).

I think to begin with I will prototype this project with the 28x2, plenty of those lying around. And i'm sure a few friends will have some other components I could borrow. Then I'll go for making it as small as possible and testing where the best place on the bike to put it would be.

I have also been looking at the telit GM862. It would be one module for GSM, GPS and a sim card slot, I just don't know if it would be small enough.

I'll just have to give it a go, if it doesn't work I'll just buy the spylamp and I'm sure I'll find another project for the components. I'll keep you posted with progress.
 
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Paix

Senior Member
AndrewBrown said:
. . . I only really need it to run for up to 24 hours max . . .
Click to expand...
Wise, I notice that in the midlands, your bike is likely to find itself on the back of a scrap metal collector's wagon tout de suite if left unattended - even in your garden. The number of kiddies bikes that I see on these trucks is quite depressing and makes me think that they haven't all been left on the public pavement overnight, but rather just inside the garden gate where mum & dad imagine it to be safe.

I guess that in Dundee your bike could get spirited away in a sporran . . . :)
 
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