Counting help

Hi evry one
I attempted to create a counting system to install on several machine for monitoring.
I have 20 machine with 4 output each.
Each machines have 3 lights (24v) for 3 type of errors.
And 1 pulsation detectors that give 1 signal each cycles (200 to 280 cycle/min)
I need to get the cumulative of each of this information on excel table for start and on a small interface next.
Please advise if any ideas?
One arduino cart for the 80 channels or 20 cars for 4 channels each?

20 Arduinos with just 4 inputs each seems wasteful. An Arduino Mega has over 50 I/O pins so the simplest thing might be to use two Megas and treat one of them as Master which collects data from the other one and sends all the data to the PC.

I presume you are aware that any voltage connected to an Arduino I/O pin must be in the range 0v to +5v

...R

You may be better sourcing the count pulses from earlier in the chain - the driver rather than at the actual 24V light.
If you can’t get in to the control circuit, consider photo sensors to ‘see’ the lights.
Not elegant, but the same number of wires and safer for everyone.

As it's 20 independent machines it makes sense to me to use a WeMOS D1 Mini for each - so you can transfer the counts over WiFi to a server, and collate the data in your spreadsheet.

One controller per machine for far less complexity per unit, and easier building/maintenance (assuming they're all identical).

you could go buy a variety pack of resistors and hook different values to each output on your machine. then the analog voltage could be read to determine which signals where sent. this approach could pry reduce you down to one input per machine.

also look into multiplexers as an option. they are small cheap modules that reduce many inputs down into a small amount of pins for reading.