M0LTE’s Arduino APRS tracker boards

Boards

You need one of these:

Contact me to buy one.

Parts

These are the parts to buy.

Modules
2x Arduino Pro Mini                       eBay 182630720464 £2.15 each
1x GPS (pin order VCC RX TX GND)          eBay 152939655666 £10.75

Semiconductors
Q1  BC547/8                                                          PTT - not optional :)
Q2  BC547/8                                                          only if you want the relay
D1  1N4001                                RS 628-8931                only if you want the relay
DS1 DS18b20 temp sensor                   eBay 161879382812 £1.25    only if you want temp sensor
1x  L7808CV regulator                     eBay 172377863651 £0.23    wide range -> 7V
3x  LED (green, red, or yellow)                                      all optional

Capacitors
C1 10nF (103)                             eBay 231179599601          RX audio DC blocking cap
C2 100nF (104)                            eBay 231179599601          TX audio DC blocking cap
Cout1 470nF electrolytic                  RS 711-1677                power smoothing
Cin1 220nF electrolytic                   RS 167-1538 / eBay 221321519025 power smoothing

Resistors
R1 1k                                                                PTT current limiting resistor
R2 10k                                                               RX audio offset pot divider
R3 100k preset                            eBay 130894545879 £0.184   TX audio level set
R4 10k                                                               RX audio offset pot divider
R5 4.7k                                                              Onewire bus vcc-d
                                                                     only if want temp sensor
R6 10k beacon button pull-down                                       only if want beacon button
R7 18k battery voltage sense PD (VCC to A1)                          only if want volt sense circuit
R8 6.8k battery voltage sense PD (A1 to GND)                         only if want volt sense circuit
R9 150R fix LED current limiting resistor *                          only if want LED D13
R10 150R TX LED current limiting resistor *                          only if want LED D9
R11 4.7k relay current limiting resistor *                           only if want the relay
R12 150R spare LED current limiting resistor                         only if want LED D10

* select appropriate values for the LEDs you use

Other
U1 G5Q 5v relay                           RS 841-1420                optional, e.g. drive a fan
Screw terminal 3.5mm pitch                RS 897-1332                or just solder the wires
2x 12 way female pcb socket               eBay 131921173215 £0.21    optional, for the arduinos

Instructions

The left hand Arduino needs to have the Mobilinkd TNC firmware blown on to it. Like this:

avrdude -c arduino -p m328p -P COM3 -b 57600 -U mobilinkd-473-arduino.hex

Download firmware file from here or here

WinAVR from here or here

The right hand Arduino needs to have this Arduino sketch blown on it – but remember to modify it for your own callsign, at the very least! That sketch is rough and ready, built in a hurry, and doesn’t have extras (temp sensor, battery voltage sampling, relay control) implemented. It also depends on MicroNMEA library which you should be able to find fairly easily.

The PWR port is good for 13.8V- the regulator and capacitor circuit is taken from a battery eliminator designed for a vehicle.

Set TX audio level carefully. It’s touchy. You can do this using the Mobilinkd Windows desktop software, plugged into the left hand Arduino, to activate test tones. That desktop utility isn’t very good, fiddle with it until it works.