I was doing a simple logic circuit in proteus when i realised that something was going wrong.
It looks like the NAND gate provides high voltage to its inputs from nowhere. No errors provided, but if i let the simulation running for a while, it always end with an unexpected close.
You can see that in the picture that i'm getting 4 volts from the inputs of a non-connected nand gate, and you can also see that if you connect the terminal to the ground(the ones on the top of the image), it seems to work as expected.
Should the nand gate have +4V on their input terminals when they are not connected? I think that it will only should have high state on the output terminal if the inputs are not connected or connected to the ground.
I'm newbie, its never late to learn. Pls help :D