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Author Topic: Voltage sensor. Isolated  (Read 1776 times)
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Hi Now have a voltage sensor using voltage divider , I'm measuring a solar battery bank .
This bank has a lot of amps 1000, and a lot of high amps devices inverters etc
When the inverter push by the battery arduino some times get strange USB results on the pc side  ...
So going direct I want to measure voltage without having common grounds..
At first I was thinking in 2 arduinos that communicate wireless
One measuring voltage other connected to pc ..
Then one arduino wireless connected but...
Must be a way to this cheaper and easy ..

Please give me advices ..
Regards
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Brunsbüttel, SH, F.Rep.GERM
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i had the idea to do it with a mechanical relay that connects both ends of a capacitor first to the battery and then to the arduino... but i dont know if the relay likes it... smiley-wink

the other idea is: 1 ATtiny13 for each battery (powered by that battery) and communication with the "central" via opto-couplers...   smiley-roll
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-Arne

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For now I dont want to measure. Individual cells, just all bank total  range from 23v to 30v...
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Brunsbüttel, SH, F.Rep.GERM
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ok
u could still use that relay idea with a voltage divider and a 35V capacitor:

http://www.falstad.com/circuit/#%24+1+5.0E-6+81.92041607667615+50+5.0+43%0A178+208+112+288+112+0+2+0.2+0.02563182296591928+0.05+1000000.0+0.02+178.0%0Ag+208+160+208+176+0%0Aw+208+144+176+144+0%0AR+176+144+80+144+0+2+100.0+2.5+2.5+0.0+0.5%0Ac+128+64+128+112+0+9.999999999999999E-5+29.999998525073813%0Aw+128+112+208+112+0%0Aw+128+64+208+64+0%0Av+288+128+352+128+0+0+40.0+30.0+0.0+0.0+0.5%0Ag+384+96+384+112+0%0Ar+288+48+384+48+0+33000.0%0Ar+384+48+384+96+0+1000.0%0Ap+480+48+480+96+0%0A167+480+48+576+48+0+4%0Ax+500+189+551+195+0+24+ADC%0Aw+384+48+432+48+0%0Aw+432+48+480+48+0%0Aw+384+96+432+96+0%0Aw+432+96+480+96+0%0AR+480+144+448+144+0+0+40.0+1.1+0.0+0.0+0.5%0Aw+288+96+384+96+0%0Ac+432+48+432+96+0+1.0E-7+0.01474927170325975%0Aw+288+80+352+80+0%0Aw+352+80+352+128+0%0Ad+208+160+176+160+1+0.805904783%0Aw+176+160+176+144+0%0Ao+11+8+0+34+1.25+9.765625E-5+0+-1%0A
« Last Edit: September 05, 2012, 12:35:07 pm by RIDDICK » Logged

-Arne

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Thanks but I'm bit lost with your diagram I will try to understand this better on the conputer.
But how does a relay and a capacitor isolate grounds ?

Rhanks
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Brunsbüttel, SH, F.Rep.GERM
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maybe my drawing is a little bit too weird...  smiley

the isolation works as follows:
1. when the capacitor is connected to the battery pack, it is not connected to arduino ground (not even via a voltage divider... air is a good isolator...)...
2. when the capacitor is connected to the voltage divider, it is isolated from the battery (again by air)...
 smiley-cool

does the URL work for u?
it doesnt work for me...

PS: i took the idea from the LTC1043 datasheet...  smiley-razz

PPS: the relays might need external fly back diodes...

PPPS: i changed the picture a little bit... it might be easier to read now...
« Last Edit: September 05, 2012, 12:34:37 pm by RIDDICK » Logged

-Arne

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Hi no the link dont work and now no picture on the post
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Brunsbüttel, SH, F.Rep.GERM
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then u can use the File-Import method with this (it is animated):  smiley
Code:
#$ 1 5.0E-6 81.92041607667615 50 5.0 43
178 208 112 288 112 0 2 0.2 0.02563182296591928 0.05 1000000.0 0.02 178.0
g 208 160 208 176 0
w 208 144 176 144 0
R 176 144 80 144 0 2 100.0 2.5 2.5 0.0 0.5
c 128 64 128 112 0 9.999999999999999E-5 29.999998525073813
w 128 112 208 112 0
w 128 64 208 64 0
v 288 128 352 128 0 0 40.0 30.0 0.0 0.0 0.5
g 384 96 384 112 0
r 288 48 384 48 0 33000.0
r 384 48 384 96 0 1000.0
p 480 48 480 96 0
167 480 48 576 48 0 4
x 500 189 551 195 0 24 ADC
w 384 48 432 48 0
w 432 48 480 48 0
w 384 96 432 96 0
w 432 96 480 96 0
R 480 144 448 144 0 0 40.0 1.1 0.0 0.0 0.5
w 288 96 384 96 0
c 432 48 432 96 0 1.0E-7 0.01474927170325975
w 288 80 352 80 0
w 352 80 352 128 0
d 208 160 176 160 1 0.805904783
w 176 160 176 144 0
o 11 8 0 34 1.25 9.765625E-5 0 -1

is the picture back?
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-Arne

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Have you considered to use analog optocouplers? Like this one:

http://www.conrad.ch/ce/de/product/140035/OPTOKOPPLER-HCNR201-000E
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