Pico Trackers

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Project Pico Trackers
Status Abandoned
Contact User:Bertrik_Sikken
Last Update 2019-07-14

Current status:

  • software is basically ready
  • pico tracker boards still have to be populated with actual electronic components


This page is about a so-called tracker for use with small ("pico") balloons, which is light-weight electronics board carried by a balloon and sends telemetry back to earth.


The software of the payload tracker basically does the following:

  • get position data from the GPS receiver
  • get temperature and battery voltage (optionally barometric pressure)
  • broadcast this data using a radio transmitter (RTTY, 70cm band, about 10 mW)
  • repeat until battery is exhausted ...

The source code can be found at https://github.com/bertrik/picoballoon

It is based on the source of the pFalcon balloon by Nick Blommen.

To build it:

  • install platformio
    • sudo apt-get install python-pip
    • sudo pip install platformio
  • use platformio to compile it (libraries are downloaded automatically)
    • pio run

Special features:

  • (runs the GPS in low-power mode for extra battery savings)
  • resets the RFM22 radio every 8 cycles, in case it goes weird because of low temperature


The hardware consists of a custom PCB, a uBlox6G GPS receiver, an RFM22B transmitter, all controlled by an ATMega328.

Power budget

To reduce the power consumption as much as possible, the board runs at a low voltage, 1.8V. The AVR clock frequency needs to be limited to 4 MHz, as this is the fastest the AVR can run at this voltage. See here for more information on running at low-voltage / low-frequency mode.

Current estimates:

Component current Remark
RFM22B 27 mA 27 mA @ +11 dBm transmit
uBlox 6G 12.2 mA 22 mW @ 1.8 V Power Save Mode (1 Hz)
AVR 1.7 active current, 4 MHz, 3V
Total 41 mA current drawn from the 1.8V boosted voltage

Assuming 1.2V average battery voltage and adjusting for step-up ratio (1.8V / 1.2V) and voltage converter efficiency (60%), this means about 103 mA average current draw from the battery. An Energizer 1.5V primary lithium battery has a capacity of about 3000 mAh, so it is expected to last approximately 29 hours (3000 mAh / 103 mA).

Weight budget

Most commonly used for pico balloons seems to be the Qualatex 36 inch foil balloon, see [1]. This balloon weighs about 37g and has a volume of about 100 liter. See here for a graph of reachable height vs payload weight and maximum free lift to reduce the chance of bursting.

A possible alternative balloon is a Qualatex 36 inch latex balloon, weighs about 35 gram and a volume of about 400 liter (fully inflated).

Rough weight estimates:

Component weight Remark
Balloon 37 g assuming Qualatex 36 inch latex
Battery 15 g one 1.5V lithium AA (non-rechargable)
Enclosure 10 g insulation to reduce RFM22B drift, "rope", etc.
PCB + components 5 g rough guess
Miscellaneous 5 g battery holder, wiring, antenna, etc.
Total 72 g 35 g excluding balloon




Andere benodigde onderdelen

Designator Description Manufacturer Manufacturer Part Number Manufacturer series Package Value
ANT1 ANTENNA Johanson Technology Inc 1575AT43A0040 GPS ANTENNA
C1 Capacitor - non polarized 0805 0.1uF
C2 Capacitor - non polarized 0805 0.1uF
C3 Capacitor - non polarized 0805 0.1uF
C4 Capacitor - non polarized 0805 0.1uF
C5 Capacitor - non polarized 0805 18pF
C6 Capacitor - non polarized 0805 18pF
C7 Capacitor - non polarized 0805 0.1uF
C8 Capacitor - non polarized 0805 0.1uF
C9 Capacitor - non polarized 1210 10uF
C10 Capacitor - non polarized 1210 10uF
C11 Capacitor - non polarized 0805 0.1uF
C12 Capacitor - non polarized 0805 1uF
CON2 6 pin 2.54mm Dual Row Pin Header
CON3 SMA Emerson 142-0701-801 SMA (End-Launch)
CON5 3 pin 2.54mm Pin Header
FB1 Ferrite Bead 0805 Murata BLM21BD102SN1D EMIFIL FB1
L1 SMD Shielded Tiny Power Inductor WE-TPC, L=2.5µH Wurth 744031002 WE-TPC 3816 2.5 µH
LED1 Led 0603 2mA - 1.8V
LED2 Led 0603 2mA - 1.8V
R1 resistor 0805 2K2
R2 resistor 0805 2K2
R3 resistor 0805 10K
R4 resistor 0805 10K
R5 resistor 0805 1K6
R6 resistor 0805 1K6
R7 resistor 0805 10K
R8 resistor 0805 475K
R9 resistor 0805 182K
U2 uC Atmel ATmega328P of [2] ATMEGA328P-AU
U3 Tranceiver HopeRF RFM22B
U4 Pressure Sensor Bosch BMP085
U5 DC/DC Regulator TI TPS61200 tps61200drct

Parts Pricing

Upu's store

Pico Trackers GPS Radio parts.png

  • Zo'n €33,- per setje (gps+antenne, 434MHz zender)


Pico Trackers - other bits.png

  • Om van alles één te hebben is het ongeveer 7,87 euro.