I have a AC Current Sensor like this SCT013-030 (30A/1V) for energy monitoring.
And this is connected to my Particle Core like this:
Do you know it is safe for the Core if the (5V) power supply is down? (no more voltage (3,3v) in the divider circuit from the core, but potential current in the sensor)
From my point of view, the analogue input (A3) of the Core will be exposed to negative voltage… right? (because we loose the mid point)
Do you see any solution or is it safe for the Core to keep it like this?
Based on the datasheet, I think you are wrong about that sensor, but let’s go with it for now.
You seem to be asking if leaving the AC sensor connected when the Particle device is not powered is safe or not, right? The datasheet for the sensor shows a TVS (transient voltage suppressor) but this is not likely to help at 0-3.3V. The Core and Photon both have protection diodes on the inputs but it would be less than ideal to completely depend on them in the long term–for testing it will be OK. The simplest thing would be to add back-to-back 3.3 zener diodes across the input and ground for added protection.
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