Circuit Reviews (I need some advice feed back)

I`m currently making some proto circuits and I would love some feed back/Ideas etc.
All these circuits will connect to Arduino or Arduino compatible devices.

anyone have time to help out with some reviews?

First circuit is a 4-20ma board

Hello there!

I would be glad to help. Why don't you post some schematics and we can go over them.

S1buell:
First circuit is a 4-20ma board

Good idea. That is going to be useful in many future projects.

One way to work out the design is to think about what might go wrong. What happens if it is hooked into the supply power backwards? What current flows into or out of the Arduino input-protection diodes in that case? Think about where it will be used: if everything is 12V then you only need to choose components rated at 16V. If there are some 24V wires nearby that might accidentally contact your circuit then use higher rated components. If it is inside the same box as mains wiring then your circuit probably won't survive an accident but it must fail in a way that won't start a fire or allow people to come into contact with live wires.

Search out the datasheet for the MAX14626 and consider incorporating that chip or similar protection circuits in your drsign.