Measure Voltage - galvanically separated

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karl222
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Measure Voltage - galvanically separated

#1 Post by karl222 » 19 Mar 2018, 19:54

Hi,
I have to measure individual voltages in a 14 in series battery pack and - of course - it has to be galvanially separated. Each pack has a voltage range of 2.5V up to 4.3V which adds up to +55V.

With 14 devices in espeasy I will reach its limitations, so I hope that upyeasy will be my solution with an esp32, once I get it up and running.

FIrst approach: use ADS1115 with voltage dividers. Problem here is, that every little failure in calibration adds up badly...

Second approach: use ADS1115 but hook an IL300 linear optocoupler in between. But this is not enough, it needs a complex opamp before and so on, which leads to a quite complex setup.

Third approach: optical isolation of i2c. Problems here:
1. I have no clue of that in a hardware perspective
2. does it work with espeasy
3. every ADS1115 can only measure one channel instead of 4, which limits the whole setup to 4 channels because ADS is limited to 4 addresses...

Does anyone have an Idea for me?

Best regards
Karl

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Re: Measure Voltage - galvanically separated

#2 Post by TD-er » 20 Mar 2018, 19:17

There are galvanic isolators which can handle digital signals up to several MHz.
These have often some kind of transformer like separator. So these can be used for SPI-like speeds.
These are bi-directional.
For example Ti has some: http://www.ti.com/isolation/digital-iso ... rview.html

karl222
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Joined: 23 Aug 2017, 17:18
Location: Vienna

Re: Measure Voltage - galvanically separated

#3 Post by karl222 » 18 Apr 2018, 07:55

sorry, i totally missed your post!

i wonder whether there isn’t a circuit which does exactly that....

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