New to electronics. Bare with my question...Scanning for 5V input.

Dear all,

I have 20 inputs of 5V which are either open or closed (0V =Closed ... 5V =Open).
I want to build a circuit to scan those 20 inputs (for now lets suppose 20 cables) and if one is open, write to a .txt or similar file, which one of the 20 inputs is On as well as the time it went ON and the time this input went OFF.

I expect that when a user sets an input to 5V, it will remain at this state for at least 30 min. So On/Off is not a fast process.

Please provide some hints as what equipment should I use and what to do.

I must let you know that I am not an electronics guy so please be as explanatory as possible, without breaking your b....:grin:

Best Regards.

This 90% a software problem, the electronic hardware side is trivial. Its called "data aquisition". You can buy cards to go into an old desk top PC to do this AND they would come with software.
To do it yourself (1), you will need to get a suitable program to run on a PC and use the pins on the parallel printer port as your input terminals. - That will make it difficult!
To do it yourself (2), you will have to programme a microprocessor, this will involve in many modules of software and usually a separate real time clock chip. Professional software writers normally buy these modules in.
To do it yourself (3), you could do it all in hardware, sort of by running a real time clock, and when an input changes putting the real time clock time and the input number into a memory chip. As part of the kit you also make a decoder, so you can go from memory location to memory location and decode the numbers, so as to give you time and input numbers, using , say, 01 for input 1 on, and 11 for input 1 off, 02 for input two coming on, 12 for 2 going off. . .
Frank

Can you be more explanatory on No. 3 choice, because I need to create it myself.

If possible provide some links or schematics / parts that one would need to craft this device.