gicolas wrote:Thank you Mahjongg and Mastermushi.
Here is my revised schematic following some advices on a different forum
Thank you in advance
You have some errors.
In this kind of schematics please mind the transistor as the simple switch. Therefore you can write simple equivalent lines to detect those errors. For example: Your input transistor buffer equivalent is actually looks like:
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Ground --- [ 10 K ] --- Transistor (Switch) - [ 470 ] - |LED| --- VCC
And here you can see tht from Ground to LED you have total resistance of 10.470K
Therefore LED wont work.
What to do? Add +1 Transistor to each line. So 2n2222 with 10K will be the high impedance buffer and the second transistor is going to be the LED driver. The better practice is to spend three pins of the processor board to light those LEDs so you always know that software reacts on inputs.
And just for protocol: I have burned two RPIs with 36V inputs. The reason was simple: I have tried to use transistors, ignoring the best practice of optocoupler use. Do not take the risk!