Electronics > Repair
PV inverter - Voltage reading circuit
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Inverted18650:
I would bet its a relay issue. Try to bypass the relays or bridge the connections around them. Based on everything i have read today, that always seem to be the err031 problem. I read a lot about it trying to figure this out, as I am really into Inverter repairs as well.
boB:

--- Quote from: Inverted18650 on January 11, 2019, 05:41:00 am ---I would bet its a relay issue. Try to bypass the relays or bridge the connections around them. Based on everything i have read today, that always seem to be the err031 problem. I read a lot about it trying to figure this out, as I am really into Inverter repairs as well.

--- End quote ---

I thought he had already tried that.  Maybe not ?  That would have been a good first thing to try.
fzabkar:
IIUC, the non-inverting input is biased at a DC level of +1.65V, ie midway between ground and Vcc. This means that the inverting input will also sit at this same DC bias, if the op amp is operating within its linear region. Therefore the op amp configuration is that of an inverting amplifier with a gain of …

Av =  -Rf / Rin = - 75K / (10M + 10M + 10K) = -75 / 20010

Now the AC input is 240Vrms, so the output of the op amp is …

Vsense = 240 x 75 / 20010 = 0.9Vrms = 1.27Vp

This means that the output of the op amp should swing by +/- 1.27V on either side of the DC bias level of 1.65V, ie 0.4V - 2.9V.
webgiorgio:
@Inverted18650 First thing I did was replacing all the relays with new one. One of the old relays had a burned via, which I repaired.


--- Quote ---I wonder if both op-amps share the same GND and 3.3V ?
--- End quote ---
I can't find the datasheet of the 14 pin op-amp to identify the gnd and + pins :(  (the marking looks like "ST 24I EZX 6111")
However I could figure out which is the output thanks to the negative feedback resistor 75 k.
The other 75 k is to the same 1.65V pad of the OPA270.

I am working on the schematic and I will share as soon as is decent.

I would like to measure the output of the op-amps without using my isolated probe 1:50, but using two normal 1:10 probes, so that I can take simultaneous measurements.
What if I float my scope, connect the GND clip to the 1.65V node, and the probes to the output of each op-amp?
So that I can verify the values offered by fzabkar! :)




Inverted18650:

--- Quote from: webgiorgio on January 11, 2019, 06:31:39 pm ---@Inverted18650 First thing I did was replacing all the relays with new one. One of the old relays had a burned via, which I repaired.


--- Quote ---I wonder if both op-amps share the same GND and 3.3V ?
--- End quote ---
I can't find the datasheet of the 14 pin op-amp to identify the gnd and + pins :(  (the marking looks like "ezx 6111")
However I could figure out which is the output thanks to the negative feedback resistor 75 k.
The other 75 k is to the same 1.65V pad of the OPA270.

I am working on the schematic and I will share as soon as is decent.

I would like to measure the output of the op-amps without using my isolated probe 1:50, but using two normal 1:10 probes, so that I can take simultaneous measurements.
What if I float my scope, connect the GND clip to the 1.65V node, and the probes to the output of each op-amp?
So that I can verify the values offered by fzabkar! :)

--- End quote ---

Sorry mate, I did see you already said you replaced them all...I am tryingt o find the datasheet of the ezx6111 part now. Not much luck,TI does make a level shift IC but not in the 14-pin SOIC package that has EZX in the part number....I'll keep looking
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