Pico Trackers

Project Pico Trackers
Status	In progress
Contact	User:Costyn_van_Dongen
Last Update	2013-11-13

Intro

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

What it does:

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

Hardware

The hardware consists of a custom PCB, a uBlox6G GPS, an RFM22B transmitter and 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

TODO: which balloon to use (depends on payload weight, desired free lift, desired float altitude, etc.)

Rough weight estimates:

Component	weight	Remark
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	35 g

Schematic

Schematics:

• File:Picofalcon - Power.pdf
• File:Picofalcon - Top Level.pdf

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)
CON4	CON JST BOX 2P	JST				JST 2P
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
U1	GPS	UBlox	MAX-6G
U2	uC	Atmel	ATmega328P of [1]		ATMEGA328P-AU
U3	Tranceiver	HopeRF	RFM22B
U4	Pressure Sensor	Bosch	BMP085
U5	DC/DC Regulator	TI	TPS61200		tps61200drct
XTAL1	4Mhz Crystal	TXC CORPORATION	AT-4.000MAGE-T		HC49/US	4MHz

Parts Pricing

Upu's store

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

Farnell

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