an203_stm110_battery_powered
Contents
1. APPLICATION NOTE 203 Green Smart Wireless enocean Applications based on STM 100 110 without enough Illumination Alternatively to the use of a standard solar panel e g in applications with no or not enough light the power supply standard input V_SC1 of the STM 110 110C module can be driven by another suitable external energy sources of 2 2 5 0 V like a small Li MnO2 coin cell for example In sleep mode the supply current of the STM 110 module V_SC1 is typically around 100 nA only In operation the module current consumption strongly depends on the frequency of measurements and radio transmissions Please notice that the V_SC1 power supply is buffered by an internal on module capacitor so the average current over time has to be considered for calculation of the module current consumption Estimation of the Module Average Current Consumption Using the following tables from chapter 2 4 of the STM 110 User Manual the supply current of the module can be calculated in dependence of measurements on average Wake up cycle time in s seconds and transmissions on average sending a telegram every m measurement cycles R_C1 6 MQ after 3 V applied for 10 min gt gt 10MQ after 24h R_STM depends on wake up cycle time transmit intervals and supply voltage In the following table R_STM is given at a supply voltage of 3V typical values R_STM kQ is 10s 100s 110s Every wake up 24 240 2400 26002. Every 10 wake up 63 630 6300 6900 Every 100 wake up 7500 8300 The current consumption is almost independent from the supply voltage typical values I_STM pA 10s 100s 110s Every 10 wake up Every 100 wake up Fig 1 Equivalent schematic of V_SC1 input APPLICATION NOTE 203 Green Smart Wireless enocean Typical Calculation Examples a Cyclic measurement every 10 s Transmission every 15 minutes on daily average I STM amp 4 0 uA transmission every 100 wake up on average b Cyclic wake up disabled WAKE inputs operated around 10 times a day I_STM z 0 35 pA transmission every 110 s x 100 Lithium Batteries For low cost applications standard manganese dioxide lithium 3 V coin battery can be used Depending on the energy demand different capacity sizes can be chosen Please note that most of the small coin batteries are not dimensioned for the required short current peaks of up to 30 mA Both V_SC power inputs of the STM 110 110C do have internal block ca pacitors so additional external capacitors are not needed With the upper mentioned sce nario a and a battery capacity of gt 0 220 Ah e g type CR2032 the lifetime is gt 3 years 0 220 Ah 2 4 uA This calculation considers a margin of 50 from the nominal capacity as available in praxis Using the integrated Goldcap for stronger power buffering Generally it is not recommended to use the V_SC2 while using battery because the
3. internal Goldcap draws an inherent additional leakage current However if a stronger power buffer ing is desired that can be easy realized by simply connecting the V_SC2 input in parallel to V_SC1 For more details please consult the user manual R_C2 375 kQ after 3 V applied for 10 min 5MQ after 24h Fig 1 Equivalent schematic of V_SC2 input Power Supply Monitor In general please consider the limited life time behavior of batteries even if the energy balance calculation indicates a multiple year operation time It also could be useful to have a control of the supply voltage to know in time when the battery voltage fails below a cer tain limit to be changed before failure The circuitry described in the Application Note AN309 POWER SUPPLY MONITOR can be used to do this Disclaimer The information provided in this document describes typical features of the EnOcean radio system and should not be misunderstood as specified operating characteristics No liability is assumed for errors and or omissions We reserve the right to make changes without prior notice For the latest documentation visit the EnOcean website at Www enocean com
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an203_stm110_battery_powered