Pico Trackers
| Project Pico Trackers | |
|---|---|
| Status | In progress |
| Contact | User:Costyn_van_Dongen |
| Last Update | 2013-11-19 |
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 and sends telemetry back to earth.
Software
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.
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
Hardware
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 |
Schematic
Schematics:
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 [2] | 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.