# Making a 110 channel input, Voltage sniffer, from scratch. Advice appericiated!

#### NooBinProgress12

Joined Jan 23, 2021
12
Hello Everyone, my name is Fredrik.
I am new to this forum, and I want to ask you guys about a project I am working on atm.
I plan on making a test tool (or voltage sniffer) for monitoring voltage on multiple signals at once. The ECU I will be monitoring has up to 110 different inputs. My first idea is to build a device with 55 separate analouge volt-meters, and then be able to split the 110x inputs into two switchable channels. Then I can switch between the two channes and view all the inputs, without having to use 110x volt-meters..
The voltage I will be working with is between 0v and 30v. This to allow for some flex to monitor both 12 and 24v systems, as well as 0-5v poti inputs.
How can I make these two channels or groups of inputs switch to the volt-meters?
I have been thinking about several relays and one switch, but this really strikes me as a very spaceous setup.
I have thought about two inputs and one switch on each volt-meter. This probably is the most managable thing to do atm.
I have also looked into the posibillity of using a digital IO somehow, but I do not know quite enough about this yet.

I am not set on the idea of using so many separate meters, so if any of you know a way for me to monitor all the inputs on fex a single screen, this is very welcome!
Best regards
Fredrik

#### KeithWalker

Joined Jul 10, 2017
2,624
What you are planning on doing can be done with a multiplexer and a single D/A converter with a microcontroller and display. How it is done will depend on the following:
Is 110 inputs a necessary requirement or just "would be nice to have"?
What minimum accuracy and resolution is required?
Do the voltages share a common negative or are they all floating at different voltages?
How quickly are the voltages changing?
How often do you need to read the data?
How remote are the voltage sources from the measuring device?
What power sources are available?

#### crutschow

Joined Mar 14, 2008
31,156
So someone is going to be sitting and looking at 110 analog meter readings of all the voltages?
Why analog?

#### NooBinProgress12

Joined Jan 23, 2021
12
So someone is going to be sitting and looking at 110 analog meter readings of all the voltages?
Why analog?
thank you for the response
It doesnt have to be analog. And it wouldnt be 110 meters, but 55 as I explained. I am open for other, easier and more user friendly ways of making this. So if the best way is to go digital, then well do that.
I would still need help with a way to do this Though.
a 110 switchable input, digital voltmeter is not the easiest to come by. And at the same time I would like to be able to monitor several inputs at once, in case I need it.
BR

#### crutschow

Joined Mar 14, 2008
31,156
All digital is likely the best way to go.

So what is to be done with the 110 readings?

You also need to answer all of Keith's questions.

#### NooBinProgress12

Joined Jan 23, 2021
12
What you are planning on doing can be done with a multiplexer and a single D/A converter with a microcontroller and display. How it is done will depend on the following:
Is 110 inputs a necessary requirement or just "would be nice to have"?
What minimum accuracy and resolution is required?
Do the voltages share a common negative or are they all floating at different voltages?
How quickly are the voltages changing?
How often do you need to read the data?
How remote are the voltage sources from the measuring device?
What power sources are available?
I drew a quick sketch of the overall layout of this thing.

110 inputs will be the MAX I will need for this.
Not all of the inputs share a negative. Most of them run separate. so yeah, flowing at different voltages.
My hope is to be able to use this as a tool, with sveral different wire looms which will allow testing on more than 1x type of ECU. I work with many different types of connectors, and this would be a handy tool If I need to sniff the voltages fex while the cirquit is active and loaded.
I need a accuracy of 0.01v if possible
The voltages will be changing all the time. So a quick update rate is to prefer, but not crucial.
The voltage source will be as close or as far away as I choose. Looking at my sketch, you will see that I have two wire looms that I will make myself, this to allow for multiple different ECUs and I can adjust the length of these. I would say 30cm to 1m in remoteness from the source.

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#### NooBinProgress12

Joined Jan 23, 2021
12
All digital is likely the best way to go.

So what is to be done with the 110 readings?

You also need to answer all of Keith's questions.
The 110 readings will be monitored. and this device used as a tool to troubleshoot all the ECU inputs and outputs more or less at once.

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#### NooBinProgress12

Joined Jan 23, 2021
12
Using voltage divider for each input voltage to get the voltage 0~5V from 0~30V, expending the input number to what you want from the circuit below.

A detector of 40 pins connector, for 89C2051,89C2041,8951,8952, pic, arduino, etc...

You can also choose CD4067, 74HCT4067 to reduce the IC numbers -- CMOS single 16-channel analog multiplexer
Concidering space here. How much space would you suppose this setup would require? Given that I will need more than double the amount of inputs than currently in your diagram.

Do I understand this right?
The 5 multiplexers, transmitt the signal from tot 40 inputs. and the 6th multiplex recieve these signals and transmitt this to a IO? Will I be able to simultaniously monitor 5 inputs from the same multiplex, on my screen? Will this work, as all 110 of the inputs I will monitor, is constantly powered, and constantly changing.
BR
Fredrik

#### Deleted member 115935

Joined Dec 31, 1969
0
Have I missed it, but what is a ECU your looking at monitoring ?
Engine Control Unit ?

#### NooBinProgress12

Joined Jan 23, 2021
12
Have I missed it, but what is a ECU your looking at monitoring ?
Engine Control Unit ?
The ECU sends and revieves values from/to both sensors and actuators mounted on the engine. In a troubleshooting scenario, I would like to have this monitoring tool for easy reading of raw values, to find problems before parts break, etc.
BR

#### eetech00

Joined Jun 8, 2013
3,418
Might be able to use a PLC with the appropriate number of analog inputs.

#### NooBinProgress12

Joined Jan 23, 2021
12
Might be able to use a PLC with the appropriate number of analog inputs.
Thank you for the suggestion!
Sounds a bit overkill Im sure I could use one, if I were to do more, like bring all the info wireless out to a laptop in my car. But it sounds like this is perfect as more like a permanent sollution for monitoring stationary equipment. Not a mobile handheld tool, which I am after

#### eetech00

Joined Jun 8, 2013
3,418
Thank you for the suggestion!
Sounds a bit overkill Im sure I could use one, if I were to do more, like bring all the info wireless out to a laptop in my car. But it sounds like this is perfect as more like a permanent sollution for monitoring stationary equipment. Not a mobile handheld tool, which I am after
Not really. It can be small and mobile. Its basically similar to that mentioned in post #2.

#### KeithWalker

Joined Jul 10, 2017
2,624
The only way you can display 110 different voltages at exactly the same time is by using 110 different voltmeters. That is why I asked you how quickly the voltages are changing and how often you need to read the data?
You can not possibly read 110 displayed values at the same time and make sense of them. You need a system that allows you to select a small group of inputs that you can view simultaneously.
What you need is a multichannel data acquisition system, a 10 bit D/A, a microcontroller and a display. You will also need some kind of input device to select the channels to be viewed, maybe touch-screen? The inputs do not all share a common reference so the multiplexer will need double pole switching. The overall speed of the system will depend on the maximum time that can be permitted between subsequent readings. The faster the system, the more it will cost!
I very much doubt whether you can get all of that into a hand-held meter.

#### NooBinProgress12

Joined Jan 23, 2021
12
The only way you can display 110 different voltages at exactly the same time is by using 110 different voltmeters. That is why I asked you how quickly the voltages are changing and how often you need to read the data?
You can not possibly read 110 displayed values at the same time and make sense of them. You need a system that allows you to select a small group of inputs that you can view simultaneously.
What you need is a multichannel data acquisition system, a 10 bit D/A, a microcontroller and a display. You will also need some kind of input device to select the channels to be viewed, maybe touch-screen? The inputs do not all share a common reference so the multiplexer will need double pole switching. The overall speed of the system will depend on the maximum time that can be permitted between subsequent readings. The faster the system, the more it will cost!
I very much doubt whether you can get all of that into a hand-held meter.
As you say, I cannot read and make sense of over 100 values at once. obviously. I think 2 or 3 inputs at once would be good enough. But I cannot find a mux that is actually rated for this high voltage.. most is down at the 3-6v range, as far as I can see. Am I missing something here?
Im actually starting to belive that 55 mini DC voltmeters 10x23mm, and one 2pos switch for each meter, is the simplest way to go with this XD

#### NooBinProgress12

Joined Jan 23, 2021
12
Not really. It can be small and mobile. Its basically similar to that mentioned in post #2.
I like you optimism! Does anyone sell PLC`s with this many inputs though?

#### NooBinProgress12

Joined Jan 23, 2021
12
Not really. It can be small and mobile. Its basically similar to that mentioned in post #2.
I understand the logic. We have to convert the analouge signals to digital, in order to transfer and view them on the digital display. This I guess cuts down the need for inputs in the PLC. meaning the PLC dont have to be huge
I really dont have a budget for this, as the planing phase has just started, but looking at PLCs and DACs I realize the price is on the steep side if I go all digital first off

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#### Deleted member 115935

Joined Dec 31, 1969
0
Are there not off the shelf engine monitors ?
I thought all this information was on a bus system now days ?

Are you looking for of the shelf solution, modules you can use like the volt meters, or are you up to doing a bit of circuit building,

Looking at the inputs,
"all" you have to do if they are over the range your equipment can measure is to attenuate the signal, a bunch of resistors would do that.

There are many ADC's with mux's on the inputs,
examples would include MCP3208 through to chips such as ADS8588S

Alternative could be an arduino
https://www.pjrc.com/teensy/
with an analog mux on the inputs,

More than anythign I would say it depends upon your level of expertise, and expectations

#### MisterBill2

Joined Jan 23, 2018
13,849
The problem is that what the application requires, really, is 110 DIFFERENTIAL inputs and then a selector to feed the selected input to one of three amplifiers feeding three or more A/D converters, one optimized for each voltage input range.
But there is already a product made that gets most of the way there. That is a 110 input front-end made for ultrasound scanners. That has been a product for a couple of years, at least. And it already presents the digital voltage reading and the channel ID to a computer input.