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### Topic: Voltage sensor. Isolated (Read 3784 times)previous topic - next topic

#### fca

##### Sep 04, 2012, 12:38 pm
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 ..

Regards

#### RIDDICK

#1
##### Sep 04, 2012, 03:19 pm
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...

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

#### fca

#2
##### Sep 04, 2012, 03:28 pm
For now I dont want to measure. Individual cells, just all bank total  range from 23v to 30v...

#### fca

#4
##### Sep 04, 2012, 08:20 pm
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

#### RIDDICK

#5
##### Sep 04, 2012, 08:25 pmLast Edit: Sep 05, 2012, 07:34 pm by RIDDICK Reason: 1
maybe my drawing is a little bit too weird...

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)...

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

PS: i took the idea from the LTC1043 datasheet...

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

PPPS: i changed the picture a little bit... it might be easier to read now...

#### fca

#6
##### Sep 05, 2012, 11:23 pm
Hi no the link dont work and now no picture on the post

#### RIDDICK

#7
##### Sep 06, 2012, 07:45 am
then u can use the File-Import method with this (it is animated):
Code: [Select]
`#\$ 1 5.0E-6 81.92041607667615 50 5.0 43178 208 112 288 112 0 2 0.2 0.02563182296591928 0.05 1000000.0 0.02 178.0g 208 160 208 176 0w 208 144 176 144 0R 176 144 80 144 0 2 100.0 2.5 2.5 0.0 0.5c 128 64 128 112 0 9.999999999999999E-5 29.999998525073813w 128 112 208 112 0w 128 64 208 64 0v 288 128 352 128 0 0 40.0 30.0 0.0 0.0 0.5g 384 96 384 112 0r 288 48 384 48 0 33000.0r 384 48 384 96 0 1000.0p 480 48 480 96 0167 480 48 576 48 0 4x 500 189 551 195 0 24 ADCw 384 48 432 48 0w 432 48 480 48 0w 384 96 432 96 0w 432 96 480 96 0R 480 144 448 144 0 0 40.0 1.1 0.0 0.0 0.5w 288 96 384 96 0c 432 48 432 96 0 1.0E-7 0.01474927170325975w 288 80 352 80 0w 352 80 352 128 0d 208 160 176 160 1 0.805904783w 176 160 176 144 0o 11 8 0 34 1.25 9.765625E-5 0 -1`

is the picture back?

#### pylon

#8
##### Sep 06, 2012, 04:11 pm
Have you considered to use analog optocouplers? Like this one: