CorB 64 Posted September 24, 2013 Share Posted September 24, 2013 Would a 3.3V Zener (1W ?) also do the job when you use 3xAA or 3xAAA batteries (I am using NiMH that start at around 1.4V after being charged, so 3x would be 4.2V). Quote Link to post Share on other sites
oPossum 1,083 Posted September 24, 2013 Share Posted September 24, 2013 The useful life of an alkaline cell is about 1.55V (new) to 900 mV (under 10% capacity). At 1.25 volts there is still a lot of capacity left in the cell. So if you want to use the full capacity of two AA cells, then the circuit must operate on 1.8V to 3.1V. Low voltage boost converters that can boost a single AA/AAA/AAAA cell to 3.3V are becoming increasingly popular. Microchip (MCP1623/24/40), TI (TPS61220/21/22), and others make them. spirilis and timotet 2 Quote Link to post Share on other sites
CorB 64 Posted October 1, 2013 Share Posted October 1, 2013 (edited) Additionally: my DS1820 sensor still works perfect at 2.62V (as measured by MSP430). No odd values seen thusfar. regards CorB Edit at 19 december. My setup is still running, current batterylevel is 2534mV according to the MSP430 batteryreadout. Edit 4 july 2014. Still running on 2 AAs, current batterylevel is 2510mV (2 AAs are providing power to an MSP430AnarenAirRFbooster and sends DS1820 data every minute since replacement 1 february 2014). Edited July 4, 2014 by CorB Quote Link to post Share on other sites
Register 3 Posted October 22, 2013 Author Share Posted October 22, 2013 One of my sensors keep rebooting at 2.49 don't know why. Should send me a notice when current drop by a certain value, but i receive notice with always the same value and as i send the battery level at startup... it send it at erratic intervals between 2 hours and 10 minutes... Don't know why Quote Link to post Share on other sites
Register 3 Posted January 27, 2014 Author Share Posted January 27, 2014 Hum, think that there was connection problem between the sensor and the battery. Now the sensor are working fine @~2.47. Quote Link to post Share on other sites
t0mpr1c3 91 Posted January 27, 2014 Share Posted January 27, 2014 Good to know - I have never tried running DS18B20 sensors below 3V. What value are you using for the pullup resistor? Quote Link to post Share on other sites
Register 3 Posted January 27, 2014 Author Share Posted January 27, 2014 It's 4,7Kohm I think. Quote Link to post Share on other sites
t0mpr1c3 91 Posted January 27, 2014 Share Posted January 27, 2014 I wonder if that is also true of DHT22 / AM2303 which contains DS18B20. Datasheets variously list minimum voltage as 3.3 or 3.5V but I have been running them off 2x alkaline AA @ 3V. Lower voltage supply digital thermometers do exist but don't use 1wire communication or TO-92 package. Quote Link to post Share on other sites
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