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IMPLEMENTATION OF AN ENERGY EFFICIENT WIRELESS SMART SENSOR Sebastian Bicelli, University of BresciaEUROSENSORS XIX - Barcelona - 13/09/2005 1 University.

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Presentation on theme: "IMPLEMENTATION OF AN ENERGY EFFICIENT WIRELESS SMART SENSOR Sebastian Bicelli, University of BresciaEUROSENSORS XIX - Barcelona - 13/09/2005 1 University."— Presentation transcript:

1 IMPLEMENTATION OF AN ENERGY EFFICIENT WIRELESS SMART SENSOR Sebastian Bicelli, University of BresciaEUROSENSORS XIX - Barcelona - 13/09/2005 1 University of Brescia, Dept. of Electronics for Automation and INFM Via Branze 38 - 25123 Brescia (Italy), Tel: +39-030-3715897 Fax: +39-030-380014 E-mail: sebastian.bicelli@ing.unibs.it, Web: http://www.ing.unibs.it/~wsnlab/ S. Bicelli, A. Flammini, D. Marioli, E. Sisinni, A. Taroni OUTLINE Block diagram of a battery-powered wireless sensor Sensor life estimation method Experimental characterization of several prototypes

2 IMPLEMENTATION OF AN ENERGY EFFICIENT WIRELESS SMART SENSOR Sebastian Bicelli, University of BresciaEUROSENSORS XIX - Barcelona - 13/09/2005 2 Low Power Wireless Sensor SensorADC Storage Tx/Rx Power Unit Battery/Batteries DESIGN GUIDELINES How to design an efficient power supply? How to estimate sensor life? Which sensor to estimate a physical quantity? It exists the “best microcontroller”? Processor SW

3 IMPLEMENTATION OF AN ENERGY EFFICIENT WIRELESS SMART SENSOR Sebastian Bicelli, University of BresciaEUROSENSORS XIX - Barcelona - 13/09/2005 3 Batteries 34mm  26mm  (14,5mm  )(10.5mm  ) (26.2 x 17.5 mm) 61mm 50 mm 45 mm44.5 mm ‘D’ ‘C’ ‘AA’ ‘AAA’ ‘9V’ Zinc Carbon AlkalineLithium Nickel - Cadmium Nickel Metal Hydride (NiMH) Lithium Ion Nominal Voltage [V]1,5 31,2 3,6 Internal resistanceMediumLow Very low Capacity (AA) [mAh]60-180022002100600-11001300-2300800-1000 Rechargeable?No(No)NoYes Natural dischargeSlow Very slowQuick Quick (30%/month) Quick (20%/month) Cost (AA, $)113223 NoteOldDiffuseToxicOldDiffuseLight, toxic

4 IMPLEMENTATION OF AN ENERGY EFFICIENT WIRELESS SMART SENSOR Sebastian Bicelli, University of BresciaEUROSENSORS XIX - Barcelona - 13/09/2005 4 Power supply systems LDO: Low Drop Out - Voltage regulators Few components (only bypass capacitors) High ouput current, low noise Low cost Low efficiency V in > V out Charge pump Few components (inductorless) Medium efficiency, Medium cost V in > V out or V out < V in Medium/high noise V out multiple of V in Low output current Step up / Step down converter (Buck boost) High efficiency, high cost Medium/high output current V in > V out or V out < V in Inductor Layout ad-hoc High noise Systems to increase battery usage Important parameters: quiescent current, efficiency, transient response

5 IMPLEMENTATION OF AN ENERGY EFFICIENT WIRELESS SMART SENSOR Sebastian Bicelli, University of BresciaEUROSENSORS XIX - Barcelona - 13/09/2005 5 Battery life L (Time to reach the cutoff voltage, ~ 70% V bat ) C (Ah): battery capacity η: power supply efficiency K v : power supply output voltage gain I cc,mean (A): mean current consumption of the wireless sensor Isleep Tsleep IaTaIaTa I RF T RF T>1s Low data rate (T>1s)

6 IMPLEMENTATION OF AN ENERGY EFFICIENT WIRELESS SMART SENSOR Sebastian Bicelli, University of BresciaEUROSENSORS XIX - Barcelona - 13/09/2005 6 Sensor conditioning Low bias current Ultra low power rail to rail Shutdown pin Processing Unit Peripherals prescaler UART Timers ADC CPU prescaler CPU Main clock Sleep Active Time Current Secondary clock Sensor low power fast transient response SLEEP mode and WAKE UP mechanisms Mixed signal microcontroller Typical consumptions Sleep: 1uA Run: 1mA High performance: 10mA

7 IMPLEMENTATION OF AN ENERGY EFFICIENT WIRELESS SMART SENSOR Sebastian Bicelli, University of BresciaEUROSENSORS XIX - Barcelona - 13/09/2005 7 Radio subsystem Impact of the noise Ease of communication with other devices Consumption (10 - 100mA) Start-up time and available bandwidth TRANSCEIVER ANTENNA Chip antenna PCB antenna External antenna

8 IMPLEMENTATION OF AN ENERGY EFFICIENT WIRELESS SMART SENSOR Sebastian Bicelli, University of BresciaEUROSENSORS XIX - Barcelona - 13/09/2005 8 The realized prototypes AA Batteries alkaline and rechargeable LDO, Stepup, Charge pump Low power microcontroller and PSOC RF Transceiver IEEE802.15.4 and Proprietary PCB antenna Hardware Software Wireless USB (proprietary) Zigbee (IEEE802.15.4) Star topology Time division multiplexing Search coord.Tx: 14 bytesWait ACK (11 bytes) Sleep Wake up OK Timeout Timeout x4

9 IMPLEMENTATION OF AN ENERGY EFFICIENT WIRELESS SMART SENSOR Sebastian Bicelli, University of BresciaEUROSENSORS XIX - Barcelona - 13/09/2005 9 Experimental results: batteries characterization Different behaviour: Temperature Discharge mode Battery type Constant resistive load: constant resistive load (R = 40Ω) Pulsating load: 500ms with a constant resistive load (R = 20Ω), 500ms without load (period T = 1 s and duty cycle D = 50%) Constant current mode: load requires always the same current (50,25 mA) Batteries tested Rechargeable 1.2V 2.3Ah NiMH battery NH15 by Energizer (BATR) Alkaline 1.5V 2.85Ah Zn/MnO2 E91 by Energizer (BAT1) Alkaline 1.5V 2.85Ah Zn/MnO2 MN1500 by Duracell (BAT2) Discharge mode

10 IMPLEMENTATION OF AN ENERGY EFFICIENT WIRELESS SMART SENSOR Sebastian Bicelli, University of BresciaEUROSENSORS XIX - Barcelona - 13/09/2005 10 Batteries characterization: voltage discharge curves Temp. = 23°CDuracell alk.Energizer alk.Energizer r. Continuous disch., R=40Ω (V cut-off =0.8V) 96.3 h88.2 h63.9 h Pulsed discharge, R=20Ω (V cut-off =0.8V) 93.2 h90.3 h66.6 h Pulsed discharge, R=20Ω (V cut-off =1.0V) 79.6 h75.7 h65.5 h Continuous disch., I=25mA (V cut-off =0.8V) 125.2 h123.8 h90.2 h Continuous disch., I=50mA (V cut-off =0.8V) 59.2 h58.7 h45.0 h

11 IMPLEMENTATION OF AN ENERGY EFFICIENT WIRELESS SMART SENSOR Sebastian Bicelli, University of BresciaEUROSENSORS XIX - Barcelona - 13/09/2005 11 Power supply systems characterization LDO TPS76633 LDO TPS79433 STEP UP TPS61016 CHARGE P. MCP1252 V I [V]3.6 1.43.0 Measured  90% 98%70% Expected  -- >90%>60% Transient Response TPS76633TPS79433TPS61016MCP1252 40 µs12 µs1.2 µs1.4 µs I 0 =100mA, V 0 =3.3V

12 IMPLEMENTATION OF AN ENERGY EFFICIENT WIRELESS SMART SENSOR Sebastian Bicelli, University of BresciaEUROSENSORS XIX - Barcelona - 13/09/2005 12 Transceiver characterization CYWUSB6934MC13192CC2420 Sleep<10 µA <20 µA Idle3.3 mA880 µA440 µA Transmitting67 mA30 mA18 mA Receiving60 mA30 mA19.2 mA Tx (30mA, 448  s) Rx (30mA, ~650  s) Idle (500μA,7.2+0.5ms) Sleep (2.3μA) Tsleep=10s MC13192 Sleep [52 µA, 9989 ms] 0.052 mA Measure [10 mA, 10 ms] 0.010 mA Tx/Rx [30 mA, 1.1 ms] 0.003 mA Icc,mean 0.065 mA 1 AA alkaline battery (2.2Ah) + STEPUP 98% 1.38 years

13 IMPLEMENTATION OF AN ENERGY EFFICIENT WIRELESS SMART SENSOR Sebastian Bicelli, University of BresciaEUROSENSORS XIX - Barcelona - 13/09/2005 13 Conclusions Subject: how to design an efficient battery powered wireless sensor Future evolutions: Sensors: system on Chip (i.e. microcontroller with transceiver) Power supply systems: low power real time clock and low quiescient current, high efficiency LDO, charge pump and step up. Results: Simple method to estimate sensor life Sleep current is the most important factor in low data rate applications Importance of battery selection and experimental characterization Efficiency/Cost trade off determines the power supply architecture New sensors, conditioning circuits and microcontroller must be considered to limit power consumption


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