Resolved - 18650 battery powered temperature sensors

[rozpruwacz]

what are your resistor devider values ? your "Volts per bit" value sugests that the max voltage you can measure is 3.78V so I guess you have wrong division ratio. I would go for 1M and 1k ohms, then you can measure up to 12V.

[rozpruwacz]

and also this may help :) https://en.wikipedia.org/wiki/Voltage_divider

[gohan]

Look at my post about solar powered node, I explained how to measure higher input voltage

[pihome]

after changing r2 to 1k ohms and volts per bit to 1.076344086 i m getting first reading is 34.44v and then 2.15, this is even more messed up.... :(

float batteryV  = battSensorValue * 1.076344086;

0 MCO:BGN:INIT NODE,CP=RNNNA--,VER=2.1.1
4 MCO:BGN:BFR
65 TSM:INIT
65 TSF:WUR:MS=0
73 TSM:INIT:TSP OK
75 TSM:INIT:STATID=25
77 TSF:SID:OK,ID=25
79 TSM:FPAR
116 TSF:MSG:SEND,25-25-255-255,s=255,c=3,t=7,pt=0,l=0,sg=0,ft=0,st=OK:
438 TSF:MSG:READ,0-0-25,s=255,c=3,t=8,pt=1,l=1,sg=0:0
444 TSF:MSG:FPAR OK,ID=0,D=1
2125 TSM:FPAR:OK
2125 TSM:ID
2127 TSM:ID:OK
2129 TSM:UPL
2164 TSF:MSG:SEND,25-25-0-0,s=255,c=3,t=24,pt=1,l=1,sg=0,ft=0,st=OK:1
2355 TSF:MSG:READ,0-0-25,s=255,c=3,t=25,pt=1,l=1,sg=0:1
2361 TSF:MSG:PONG RECV,HP=1
2365 TSM:UPL:OK
2365 TSM:READY:ID=25,PAR=0,DIS=1
2371 TSF:MSG:SEND,25-25-0-0,s=255,c=3,t=15,pt=6,l=2,sg=0,ft=0,st=OK:0100
2506 TSF:MSG:READ,0-0-25,s=255,c=3,t=15,pt=6,l=2,sg=0:0100
2514 TSF:MSG:SEND,25-25-0-0,s=255,c=0,t=17,pt=0,l=5,sg=0,ft=0,st=OK:2.1.1
2525 TSF:MSG:SEND,25-25-0-0,s=255,c=3,t=6,pt=1,l=1,sg=0,ft=0,st=OK:0
4534 TSF:MSG:SEND,25-25-0-0,s=255,c=3,t=11,pt=0,l=18,sg=0,ft=0,st=OK:Temperature Sensor
4544 TSF:MSG:SEND,25-25-0-0,s=255,c=3,t=12,pt=0,l=4,sg=0,ft=0,st=OK:1.34
4554 TSF:MSG:SEND,25-25-0-0,s=0,c=0,t=6,pt=0,l=0,sg=0,ft=0,st=OK:
4562 MCO:REG:REQ
4564 TSF:MSG:SEND,25-25-0-0,s=255,c=3,t=26,pt=1,l=1,sg=0,ft=0,st=OK:2
4841 TSF:MSG:READ,0-0-25,s=255,c=3,t=27,pt=1,l=1,sg=0:1
4847 MCO:PIM:NODE REG=1
4849 MCO:BGN:STP
4851 MCO:BGN:INIT OK,TSP=1
Pin Reading: 32
Battery Voltage: 34.44 v
Battery percent: 3 %
4859 TSF:MSG:SEND,25-25-0-0,s=1,c=1,t=38,pt=7,l=5,sg=0,ft=0,st=OK:34.44
4870 TSF:MSG:SEND,25-25-0-0,s=255,c=3,t=0,pt=1,l=1,sg=0,ft=0,st=OK:3
4878 MCO:SLP:MS=750,SMS=0,I1=255,M1=255,I2=255,M2=255
4884 MCO:SLP:TPD
4886 MCO:SLP:WUP=-1
4919 TSF:MSG:SEND,25-25-0-0,s=0,c=1,t=0,pt=7,l=5,sg=0,ft=0,st=OK:19.7
4927 MCO:SLP:MS=56000,SMS=0,I1=255,M1=255,I2=255,M2=255
4933 MCO:SLP:TPD
4935 MCO:SLP:WUP=-1
Pin Reading: 2
Battery Voltage: 2.15 v
Battery percent: 0 %
4941 TSF:MSG:SEND,25-25-0-0,s=1,c=1,t=38,pt=7,l=5,sg=0,ft=0,st=OK:2.15
4952 TSF:MSG:SEND,25-25-0-0,s=255,c=3,t=0,pt=1,l=1,sg=0,ft=0,st=OK:0
4960 MCO:SLP:MS=750,SMS=0,I1=255,M1=255,I2=255,M2=255
4966 MCO:SLP:TPD
4968 MCO:SLP:WUP=-1
5001 TSF:MSG:SEND,25-25-0-0,s=0,c=1,t=0,pt=7,l=5,sg=0,ft=0,st=OK:19.5
5009 MCO:SLP:MS=56000,SMS=0,I1=255,M1=255,I2=255,M2=255
5015 MCO:SLP:TPD

[gohan]

I used R1 1.22M (1M + 220K) and R2 300K in order to read a maximum of 5.57v

((1e6+220e3+300e3)/300e3)*1.1 = Vmax = 5.57 Volts
5.57/1023 = Volts per bit = 0.005448028

[pihome]

Do you have 1m and 220k in series?

[gohan]

Yes of course. Use the following link to find the most suitable divider for the resistor you have, just remember to keep output voltage to 1.1 http://www.ohmslawcalculator.com/voltage-divider-calculator

[rozpruwacz]

@pihome sorry, I meant 100kOhm. I would suggest You to understand the theory behind the voltage divider, then you would know what you are doing and be able to solve your problem by yourself. This is just one simple formula, not magic.

[gohan]

I started to punch in resistor values more or less randomly of various combinations of the resistors I had until I got close enough to the maximum input voltage I wanted to have

[pihome]

thank you guys for help, really appreciate this. for 18650 battery with 4.2volt in following combination would do the job for you, i m adding here so in future if some one wants reference and save some time on trial and error. @rozpruwacz i m using your idea with 1m and 100k thank you for help.

620k
220k
1.1v out

470k
170k
1.116v out

1m
355k
1.1v out

220k
80k
1.12v out

680k
270k
1.194v out

390k
150k
1.167v out

330k
120k
1.12v out

270k
100k
1.135v out

[gohan]

Try to use the highest total resistance in order to lower the battery drain as much as possible

[pihome]

@gohan i m using 1m with 100k but second best combination would be then 620k with 220k ?

[gohan]

Yes, but there could be also other combinations that will allow you to detect higher voltage but with an higher total resistance