Parallel Bank Monitor

Started by Barry Fields, October 16, 2023, 09:04:21 PM

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Barry Fields

#45
November 01, 2023, 08:22:20 PM
Well you guys have not had a good laugh in a while.

Attached are my attempt at a BANK COMPARE CIRCUIT (the old fashion way).

Any comments or suggestions would be appreciated.

20 years experience in Field Service and Engineering Support in life support equipment and the computer Industry.
I pride myself in diagnostic skills and NOT knowing everything. I do know how to ask the right questions of those who should know the answers. I can do this politely.

boB

#46
November 01, 2023, 09:47:10 PM
WhoA !   A lot going on there.

Top schematic, I would swap the inputs to the diff amps or reverse the input polarity so that you can then use OA5 as a true summing amplifier on its negative input.

Of course the LED circuit's top blinky LED enable amp will need to be one that can pull up the LED anodes.

Are you using Qspice simulator ?  Or, which one ?

boB
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Barry Fields

#47
November 01, 2023, 09:58:29 PM
I did this all on "circuit lab" https://www.circuitlab.com

Quote from: boB on November 01, 2023, 09:47:10 PMTop schematic, I would swap the inputs to the diff amps or reverse the input polarity so that you can then use OA5 as a true summing amplifier on its negative input.

I would then have to rearrange the compare circuitry for negative inputs.

I did not realize what I did was not a "true summing amp". I'll have to learn the difference.

Thanks for the input.

I did try to make it WB compatible.
20 years experience in Field Service and Engineering Support in life support equipment and the computer Industry.
I pride myself in diagnostic skills and NOT knowing everything. I do know how to ask the right questions of those who should know the answers. I can do this politely.

Barry Fields

#48
November 01, 2023, 10:03:21 PM
Found it, point well taken.

So what's the advantage of the non-inverting configuration compared to the inverting summing amplifier configuration. Besides the most obvious fact that the op-amps output voltage VOUT is in phase with its input, and the output voltage is the weighted sum of all its inputs which themselves are determined by their resistance ratios, the biggest advantage of the non-inverting summing amplifier is that because there is no virtual earth condition across the input terminals, its input impedance is much higher than that of the standard inverting amplifier configuration.
20 years experience in Field Service and Engineering Support in life support equipment and the computer Industry.
I pride myself in diagnostic skills and NOT knowing everything. I do know how to ask the right questions of those who should know the answers. I can do this politely.

boB

#49
November 02, 2023, 01:50:58 PM

The advantage of a true summing amplifier (mixer) is that the summing junction, (the negative input) is at ground level and keeps those inputs from interfering with each other.

You will see no voltage at the negative input when doing that.   What you will see with the passive summing amplifier is that the negative input will follow the positive input node.

In a summing amplifier, you will see whatever reference you apply to the positive input node.
i.e.  If you ground the positive input node and use the negative summing input, you will see ground voltage at the negative summing input.

This is how they make audio mix-buses

boB
K7IQ 🌛  He/She/Me

Barry Fields

#50
November 03, 2023, 12:43:57 PM
A little off topic but on my way to the end here.

Are there any advantages or disadvantages to the two different gain circuits attached?
They both simulate the same (within a couple mv).
20 years experience in Field Service and Engineering Support in life support equipment and the computer Industry.
I pride myself in diagnostic skills and NOT knowing everything. I do know how to ask the right questions of those who should know the answers. I can do this politely.

boB

#51
November 03, 2023, 06:02:04 PM Last Edit: November 03, 2023, 06:04:15 PM by boB
The circuit with 27K feedback and 202 Ohms input "should" be lower noise than the 135K Ohm and 1K input is about all.  Just because of the lower resistance making less noise.

You may not find any difference though as long as the op-amps don't mind having that amount of gain at the frequencies you want to amplify is my guess.


From some web page...

erms = √4kTRB

" 4*k*T*R*(BW). In this expression "k" is Boltzman's constant, "T" is temperature in degrees Kelvin, "R" is resistance in ohms, and "BW" is bandwidth, in Hz "

boB

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Barry Fields

#52
November 05, 2023, 11:41:09 AM
Quote from: boB on November 01, 2023, 09:47:10 PMOf course the LED circuit's top blinky LED enable amp will need to be one that can pull up the LED anodes.

You are correct. I have done an improper job transitioning from analog to digital.

Still working on it, think I've got it now. I'll get back to you once I am more edumacated.
20 years experience in Field Service and Engineering Support in life support equipment and the computer Industry.
I pride myself in diagnostic skills and NOT knowing everything. I do know how to ask the right questions of those who should know the answers. I can do this politely.

Barry Fields

#53
November 10, 2023, 11:31:15 AM Last Edit: November 10, 2023, 11:36:24 AM by Barry Fields
oh I am getting closer.

A couple of questions on comparators because I do not have ultimate trust in Circuit Lab's simulator.

Is there any differences in the input configurations in the red boxes on the attached schematic.

If the power rails of the lm339 comparator are +12v and -12v (because it is available) should the output be close to +/- 12v.

Would +/- 5v or +5v/ground or +12v/ground be viable options?  ( Vin = +10v to -10v )
20 years experience in Field Service and Engineering Support in life support equipment and the computer Industry.
I pride myself in diagnostic skills and NOT knowing everything. I do know how to ask the right questions of those who should know the answers. I can do this politely.

boB

#54
November 10, 2023, 01:46:30 PM
Barry, 10K pullup is fine to 12V if your LEDs can be seen OK with 700 microamps of current.

I would possibly add MegOhms or 100s of K-Ohms of positive feedback to give some hysteresis to keep the output edges square and not bouncing around.  That is, if your sinewave source is LOW impedance. 

The hysteresis might want to be several milli-volts at the sinewave inputs to the comparators.

Comparators, typically, but definitely LM339 and LM393 types are open-collector so they do not pull up to Vcc.

If this is for just 60 Hz, you could get away with a semi-decent op-amp which will have output pull-up and pull-down.

boB
K7IQ 🌛  He/She/Me

Barry Fields

#55
November 10, 2023, 03:17:33 PM Last Edit: November 10, 2023, 03:20:24 PM by Barry Fields
 The actual input is an amplified input from a Battery bank shunt (slow mover). The sine wave is for simulation only.

A 100a shunt 75mv to -75mv signal is way too small to window +/- 10% of a float current of 500ma.
75mv / 100A = .75mv /amp
500ma(bat current)  = .375mv  +/- 10% window would be +/- .0375mv

I have amplified the 75mv shunt signal to 10 volts/100a.
10volts / 100a = 100mv /amp
500ma(bat current) = 50mv     +/- 10% window is now  500ma = +/- 5mv

 
20 years experience in Field Service and Engineering Support in life support equipment and the computer Industry.
I pride myself in diagnostic skills and NOT knowing everything. I do know how to ask the right questions of those who should know the answers. I can do this politely.

Barry Fields

#56
November 14, 2023, 04:51:47 PM
This Circuit Lab is nice but it doe not know how to properly simulate a Comparator.

The simulator seems not to handle a dual rail comparator or positive feedback.

Pretty sure if my input signals go from -10v to +10v the bottom rail has to be 2v below -10v.

Before I go further I have attached the way I am handling the LM393.

Thanks in advance for any comments/corrections/suggestions
20 years experience in Field Service and Engineering Support in life support equipment and the computer Industry.
I pride myself in diagnostic skills and NOT knowing everything. I do know how to ask the right questions of those who should know the answers. I can do this politely.

boB

#57
November 14, 2023, 05:19:07 PM

I would use LTspice for the simulator.

Will take a bit of learning curve but it is free and works great !

It can also use standard spice models.   LTspice is from Analog Devices now but they bought Linear Technology a few years ago and although they have parts that will work for your simulation, it is sometimes best to just download a real LM393  .ASC file and .LIB file from the wonderful LTspice group.

Try this link...

https://groups.io/g/LTspice/

There is a HUGE repository of circuits and I am sure they also have LM393 ones if you search for it.

boB
K7IQ 🌛  He/She/Me

Barry Fields

#58
December 06, 2023, 11:13:05 AM
Just to let ya know, I am still alive.
Busy actually building a prototype PCB to prove concept. So far so good. Will update soon.
20 years experience in Field Service and Engineering Support in life support equipment and the computer Industry.
I pride myself in diagnostic skills and NOT knowing everything. I do know how to ask the right questions of those who should know the answers. I can do this politely.

Barry Fields

#59
December 24, 2023, 11:57:39 AM
LTspice is nice. Thanks.

I have learned that LTspice does not have a smoke alarm to warn you of an exceptionally high base current.
20 years experience in Field Service and Engineering Support in life support equipment and the computer Industry.
I pride myself in diagnostic skills and NOT knowing everything. I do know how to ask the right questions of those who should know the answers. I can do this politely.
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