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Designing Energy Harvesting Solar Powered Sensors
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Transcript of Designing Energy Harvesting Solar Powered Sensors
Designing Energy HarvestingSolar Powered Sensors
Dan Wright, Engineering ManagerLeviton Manufacturing Co., Inc.19 November 2014
AgendaWhy Energy Harvest?
Product Landscape
Low Power Wireless Controllers
Solar Cell Landscape
Energy Storage Options
Power Management
Sensor Technologies
Lens for Occupancy Sensors
Design and Product Challenges
Agenda: Energy Harvesting Design
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Our BUILDING Blocks
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Availability of free energy: Light
Reduce energy consumption
Solar cell (Photovoltaic) technology improvements
Low power technology maturity (often wireless)
Easy to install
Images: Microsoft clipart, Plow & Hearth
Why Energy Harvest?
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Many Energy Harvesting products leverage EnOcean wireless module
Product Characteristics:• Very low power, typically passive sensor: PIR, Humidity, CO2, ALS, Temp, Switch
• Solar Powered
• Ability to store charge for extended bridge time
Images: Leviton, KMC Controls, EchoFlex, AdHoc, EnOcean
Product Landscape
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EnOcean: TCM300 (8051 Based): 315, 868, and 902MHz
ZigBee (2.4GHz): TI, Silicon Labs (Ember), Atmel, NXP, etc.• CEL offers MeshConnect based module
Sigma Designs Z-Wave: 868, 908, 921MHz frequencies
Bluetooth technology: Various
Others (no standard, Sub GHz): Micrel, Silicon Labs, Microchip, etc.Images: EnOcean, CEL, Sigma Designs
Hardware: Low Power Wireless Controllers
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Least power consumption possible (< 1uA)
Work under a wide range of voltages (1.8 – 5V)
Average current draw (including radio transmit) < 10uA at 3.0V
May want to have black-out “no transmit” periods (1-2 minutes)
Select low leakage capacitors (Ceramic, Tantalum)
Hardware: General Circuitry Requirements
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Amorphous Silicon Solar Cells (Glass Substrate)• Sanyo (Panasonic Eco Solutions) Amorton
• Sinonar Solar
• Trony (Solars-China.com is reseller)
• Wasonlong / Blue Solar
Alternatives• IXYS – Thicker, more efficient, requires boost
• G24i Power – Flexible, requires boost
• AltaDevices – High efficient (24.1%), flexible, new company
• SolarPrint – High power density, glass base, requires boost
Flexible solar panel efficiencies have reached 18.7% which is on par with silicon (ECN Magazine, 5/2014).Images: Blue Solar, IXYS, and G24i Power
Hardware: Solar Cell (Photovoltaic) Landscape
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Sanyo 55x20mm (AM-1805) I-V Data• At 200 Lux will supply 12uA @ 3.0V (minimum), 15.5uA typical.
• At 50 Lux will supply 8-9uA @ 4.5V using two solar cells in parallel.
Source: Sanyo AM-1805 Datasheet addendum
Hardware: Solar Cell (Photovoltaic) Example
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Sanyo 55x20mm (AM-1805) I, V vs. Lux• Working range up to 1k (~5.5V)
• In sunlight will > 6.0V
Source: Sanyo AM-1805 Datasheet graph
Images: Cooper Industries (Direct, Indirect lighting: Corelite, Class A), Synergy Lighting, 7-11 Goes LED
Hardware: Solar Cell (Photovoltaic) Example
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Bridge Time: Length of time the device will continue to work without light
Selecting correct storage device is critical!• The more storage the device has, the long it will take to CHARGE the device.
• Increase Cap = Increase Bridge Time and Charge time
Example: 0.33F SuperCap charge time:
At around 10uA an hour would drain 0.33F cap: 1V per 24hrs
Last somewhere around 36-48hrs at full charge (4.5-5V).
Hardware: Energy Storage Options – Bridge Time
Charge Time (hr) Light Level (Lux)
28 50
14 100
6 200
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Supercapacitors (aka PowerStor, Gold Cap, Dynacap, EDLC)• Cooper Bussmann, Panasonic, Elna, Cap-xx, Kemet
• 0.33F cost: $0.70/1k
• Time (0.33F) = (0.33 * 2V) / 5uA = 132000s = 36.7 hours
Solid State/Flat Battery Alternatives:• Cymbet Enerchip (CBC050): 50uA (> 5000 discharge cycles)
• ST EnFilm (EEL700A39): 3.9V at 0.7mAh
• Rocket Electric Korea (LIP292240): 3.6V, 5mAh, Lithium Ion Polymer Battery
Traditional Rechargeable Battery:
• Coin cell, AA, AAA, etc.
Images: Cap-XX, Panasonic, and Cymbet
Hardware: Energy Storage Options
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Boost: Necessary for low voltage solar cells
Buck: Good for higher voltage solar cells
Specialized Energy Harversting• BQ25504/05/70: Boost, Iq=1.4uA, use with solar cells, battery/supercap storage
• LTC3107: Has internal shunt, works with battery and optional capacitor storage
• LTC3106: Buck-Boost. Works with solar-cell and battery/supercap. Iq=1.5uA
• LTC3129: Buck-Boost DC/DC converter with Iq=1.3
• LTC3330: Nanopower Buck-Boost
• MAX17710: Can be used with solar cells and rechargeable batteries
• MB39C811, MB39C831 (Spansion): Buck (811) and Boost (831) for energy harvesting
• SPV1050 (ST): Buck-Boost converter with built in LDO. Has battery charger
• ADP5090 (AD): Ultra low power boost regulator with charge management
• TPS82740A/40B (TI): Step down micro SiP module, Iq=260nA
Hardware: Power Management Circuits
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Passive Infrared (Motion)• PYD1096, PYQ1098 (Excelitas): Smart DigiPyro, 2/4 element, 15uA
• LHI1128, LHI944 (Excelitas): Analog sensors
• PaPIR (Panasonic): 1, 2, 6uA Digital PIRs with lens
• DigiPyro (Nicera): Similar to Excelitas, 15uA
Humidity / Temperature / CO2
Door/Window• SM351LT/SM353LT (Honeywell): Magnetoresistive Sensor IC, Average current 360nA
Ambient Light Sensor• MAX44009 (Maxim): I2C controlled with 1uA operating current (lowest in industry)
• ISL29020 (Intersil): I2C controlled with 65uA operating current, 0.5uA sleep
• BH1730FVC (Rohm): I2C controlled with 200uA operational and 1.5uA sleep
Images: Panasonic PaPIR, Excelitas
Hardware: Sensor Technologies
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Optics:• Panasonic – Included with sensors
• Fresnel Technologies – www.fresneltech.com
• Carclo Optics – www.carclo-optics.com/pir-sensor-lenses
Images: Carclo optics
Mechanical: Lens Optics for PIR Sensors
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Making product cost effective
Minimizing current usage (< 10uA), Black-out periods
Startup time at a given light level
Bridge time (48 hours with 0.33/0.47F super cap)
Analog versus Digital PIR
Quite Supply
Battery vs. Supercap vs. Rechargeable battery
Operational Voltage / Shunt Voltage
Wireless communication range / Antenna Position
FCC Certification
Leaky capacitors (Electrolytic, Super Cap) @ Temp
Lessons Learned: Design Challenges
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Customer Expectations vs. Energy Harvesting trade-offs
Value Add cost of Energy Harvesting
Lessons Learned: Product Challenges
+ + + + =
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Thanks for Attending
Any Questions?
Contact Information:
[email protected], [email protected]
Questions: 5 Minutes