Sorry. I should not have referred to that rev32 schematic. Too confusing. I only meant that the top section, which I omitted from the schematic posted today, was the same.7circle wrote: I thought at first you where just adding the bits to a spare board as you only need one in the circuit.
But your Pin1 uTxm on IC1 has swapped with Byp on Pin6 and the designators are all different. (R8,9,10,11,15 .. and others)
Thanks for taking an interest. "Cell+" is the cell voltage. "CellV" is perhaps a poor choice of name for the divided voltage to be compared against the 1.5 V reference.Looks like your putting the CellV straight in with out divider.
(Sorry I'm nosey)
We need to use the 1.5 V reference because wqe want everything to work down to a cell voltage of 1.8 V. We should put "1.5 V" on the schematic.
Each ordinary BMU measures the voltage between its cell's negative terminal and the positive terminal of the preceding (more negative) cell. The first (most negative) cell has no preceding cell so there will be nothing connected to its link-in (LI) terminal (JP11) and so the associated analog input can be used for current measurement instead, via a shunt and the differential amplifier.I take it the JP11 is not connected for Current Sense.
It must be for Cell No 1.
The current shunt must be connected to the negative terminal of the cell carrying the diff-amp board, by a short thick power cable, as the common mode range of the opamp only goes 300 mV below GND.
Right.200A is 50mV on Shunt so thats 10x gain for 500mV
So since we are using the 1.5 V reference we have a range of +-300 A.3.0V/2 =1.50V = +200A
2.5V/2 =1.25V = 0A (Ref+)/2
2.0V/2 =1.00V = -200A
1.50V = +300A (max count)
0.75V = 0A
0.00V = -300A (zero count)
-3dB frequency is 1/(2pi*RC)Your Filter is at 1/T=f=1/RC = 1/(150k x 100n) = 66kHz @3dB
Not sure if my calc is right. Need small signal model.
You may need slower filtering for your AD rate.
I thought very slow like 10 samples a second with filter would work.
= 10.6 Hz
Agree not worth adding diodes as it can take +-30 V as it is. For an actual shunt current to produce that would require 120kA. But we must never disconnect the high current cable before disconnecting the sense wires.What happens if their is 2000A in shunt or wild voltages?
The is it worth clamping Op- and Op+ with diodes.
Probably not worth it with 15k R21 and R22 and MCP6001 has +/-2mA on the pins and ESD ratings on all pins.