Hi guys - as requested - I am giving you - cheap DIY GPS tracker for car / motorbike / quadcopter - below 20$. All details here device when called by mobile phone polls info from GPS module of SIM808 chip ( if can fix to sattelites - tries several minutes to fix - now hardcoded 5 min to get fix) or when not available polls cell-id info from nearest 2G cell and using GPRS query Google servers for GPS location of that 2G cell (A-GPS option). Collected location information is send back as text message to your phone as Google Map link. The accuracy is from 1 to 5 meters even on cheapest passive GPS antenna (tested in Europe location) !!!
The code can be modified to send continously GPS data over HTTP to some server or to send text messages with GPS position in specified time intervals. Look on the github for most updated code with new functions...
The part list is (with the cost as in 2019):
a) SIM808 based board (10-12 USD for cheapest BK-SIM808 on Aliexpress ), search for "www.amd-global.com" boards BK-SIM808, BK-808 or equivalent...
b) GPS (passive) antenna with IPEX connector matching BK-SIM808 board - 2 USD
c) GSM antenna with IPEX connector matching BK-SIM808 board - 1 USD
d) ATMEGA 328P (arduino uno) - 2 USD - or "ARDUINO PRO MINI" board (3.3V version if you will use BK-808 board)
e) 3x 1N4007 (1 USD) - to convert 5V from powerbank to 3.3V for ATMEGA328P VCC
f) 2x 1000uF / 16V capacitor ( 0.5 USD) - connect to VCC & GND of SIM808 board (optional) AND to existing 100uF (parallel) on the SIM808 board (must have)
g) 100nF capacitor (0.2 USD) - connect to VCC & GND of SIM808 board - optional
h) universal PCB, pins & connector (2 USD)
i) USB Powerbank 5V to make it work...
To upload program code to the chip use cheapest USBASP programmer (less than 2 USD on eBay/Aliexpress) and several cables to connect programmer to the ATMEGA chip - there is a tutorial here : people do not like to use universal PCB and are having problems with soldering. You may use "Arduino Pro Mini 3.3V" board instead. There are two options for this board - 5V voltage and 3.3V voltage. Pay attention to it when selecting the board so it could match SIM800L board 3.3V TTL logic. To use "Arduino Pro Mini" you will have to connect USBASP programmer from KANDA socket (look here : ) to appropriate pins of this board : SCK (pin 13), MISO (pin 12), MOSI (pin 11), RESET (pin RST), pin VCC, pin GND - look at the board details here :
This GPS tracker solution is not based on ARDUINO FRAMEWORK (it does not use ARDUINO bootloader), it uses pure C code instead so USBASP programmer is still needed.
The BK-808 (BK-SIM808) boards are not perfect - I had to add another huge electrolytic capacitor to the board ( otherwise it was continously restarting itself while 2G network registartion attempts) and get rid of power signalling LED (takes addditional several mA of current).
Even though passive GPS antenna is used (small with only 15mm diameter), field test show from 1 to 5 meters accuracy for positioning (Europe location) because SIM808 GPS receiver is very sensitive.
Depending on your location you may use antoher board like LTE CAT-M : SIM7100a(america)/SIM7100e(europe) or LTE/3G : SIM7000e(europe)/7000a(america) series with GNSS/GPS and 3G/LTE, but these boards are more expensive like ~ 20-40 USD and you would have to adapt a bit of AT commands in the code to get it working...
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