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measured values in bold - other values from datasheet or calculation
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MeasurementValueUnitsNotes
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voltage regulator efficiency 85.00%assume average battery voltage of 3.9V, regulating down to 3.3V
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lipo battery voltage3.7V
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Max current draw while charging empty batteryFIXMEuAif battery is empty
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Actual battery capacity1,200.00mAh
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Battery capacity derated by lm3480 losses1,020.00mAh
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Battery (derated) power hours3.77Wh
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CPU data
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CPU voltage3.00V
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systemoff, no ram, wake on reset0.40uA
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system off, full ram retension, wake on ISR1.29uA
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system on, wake on any event2uA
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CPU current draw typical, with BLE link2,300uA
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CPU current draw max8,000uAlikely worst case, cpu full on 64Mhz, transmitting bluetooth
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typical CPU power draw with no active power managment4,000uAearly test build on NRF52DK devboard
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expected cpu power consumption awake with BT and not crummy software2,000uAmight be less!
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Typical CPU power draw6,000uW
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CPU power draw while off1uW
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radio supply voltage3V
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sx1262 radio in sleep mode (not receiving at all)3uAper datasheet
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in receive mode (boost on)2,500uAper SX1261 datasheet, 10mA, but measurements on sx1262MB2 board show more like 4mA (when not trying to do clever power managment). with starttReceiveDutyCycleAuto and a 32 bit preamble, this drops to about 2.5mA
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sythesizer mode3,550uAper SX1261 datasheet
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standby mode800uAper SX1261 datasheet
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in transmit mode +22 dBm boost118,000uAper SX1261 datasheet and measurement
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Typical radio power draw8,250.00uWFIXME, currently we assume 100% RX, should make better guess about % time xmitting and do version for router vs normal node
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radio power draw while in sleep mode9.90
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GPS voltage3.30VFIXME - assumes a ublox GPS
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GPS while in "backup mode"7.00uA
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GPS in "standby mode"1,000.00uA
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GPS while in "full on"20,000.00uA25mA for aquisition, 20mA for tracking
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FIXMEuAperiodic mode can be entered _after_ in "full on" state. See 3.4.4 of datasheet, can select any interval of run time and sleep times
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GPS "alwayslocate backup mode"3,000uAor just use 3.4.5 alwayslocate backup mode
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Typical GPS power draw9,900uW
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GPS power draw in backup mode23uW
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GPS power draw in standby mode3,300uW
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GPS duty cycle5%Assume completely powered down when off
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Average GPS power draw including limited duty cycle165uW
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Display voltage3V
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LCD display current5uANo idea - just a guess
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Typical display current draw17uWFIXME, a rough guess and need to add expected on time of backlight (currently no backligh)
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case 1: Expected average current draw (LCD on 100% no backlight, BLE on, GPS on occasionally as needed, radio on in rcv mode)14,431.50uWFIXME need to add duty cycle for BLE xmit and LORA transmit (both will increase current draw a slight amount), and GPS sleep (which will decrease current draw) and better LORA radio sleeping (which will decrease draw)
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battery runtime10.90daysI bet this number is quite conservative and once measurements are in and code is tuned it will go up at least 30%
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case 2: Repeater node (BLE off, GPS on super rarely, radio xmitting often, LCD mostly off)14,432uWFIXME - make this number real, currently just using case 1 #s
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power consumed per day0.35Whsolar panel needs to make this much average power per day (including night and clouds)
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Low power mode duty cycle1515= 1 min out of 15 min awake, 5 1 min out of 5 min awake. It might be possible to shrink the wake time to something more like 30 seconds
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case 3: super low power mode: wake only 1 minute out of every X minutes to exchange messages with mesh, phone, GPS7,211.10uWIf wireless mesh is chatty when we wake, we could agree to keep the mesh alive longer. This could save lots of power and be invisible to the user (other than higher latency for sending a message any time the mesh was in 'low power mode')
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battery runtime21.81days
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Total power draw when "off"34uW
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battery shelf life to hold some charge - if GPS is in backup mode4598days
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Musings on solar panel sizes
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Power produced by a sq m of solar cell ideal195W/m^2Good rules of thumb on solar panel area: https://www.aliexpress.com/item/33019573544.html?spm=a2g0o.productlist.0.0.676c6674bdM3T2&algo_pvid=40822ab4-0d41-44b2-a6b7-40745133898b&algo_expid=40822ab4-0d41-44b2-a6b7-40745133898b-23&btsid=0ab6fa7b15879132356843765e21cf&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_
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Power produced by a m of solar cell, compensating for blank area146W/m^2more solar tips here: https://www.sparkfun.com/news/1131
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typical solar power per year in Michigan for 1m^2 panel280kWhper https://en.wikipedia.org/wiki/Solar_cell_efficiency
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typical solar power per year in England for 1m^2 panel175kWhper https://en.wikipedia.org/wiki/Solar_cell_efficiency
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Typical solar power from 1m^2 panel 479Wh/dayFIXME, for now just using England - better instead to use worst case average for a few days in the norhern USA
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Sunpower C60 cell 125mm x125mm7Wh/day7x Margin for router config?
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80x35mm cell1.34Wh/dayMarginal, too small to guarantee net charging, especially because on a backpack strap angle is far from ideal
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110x60 cell3.16Wh/dayPossibly barely adequate if on a backpack strap? i.e. this assumes a pretty optimal mounting angle
src: https://www.aliexpress.com/item/33024528396.html?spm=2114.12010615.8148356.6.22506c0dIORZhk
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