multiple current sensors advice needed

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virtualdave

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Hi all,
Need some advice from people much smarter than me in the ways of the electricity.
Quick overview: a Teensy 4.1 is at the center of a new prototype I'm working on, essentially a networked lighting fixture. The fixture has 8 outputs powered by an external 48V power source. I wanted to be able to detect when a functional device was connected into one of these outputs (not just plugged in, but plugged in and drawing power/doing its thing). Since I have a few extra analog inputs on the t4.1 thought I'd use them in conjunction with a current sensor (specifically the INA169, but probably not important for this question) and sense the current output on *each* of the outputs independently. The assumption: if current on an output >= threshold, something is attached and drawing power. However as I was building the circuit I had a a big duh moment: all the outputs share the same 48V power supply so when I plug in one device, in theory all the current sensors will register a change in the current. At least I think that is what will happen!

So question: Even though all the outputs are supplied by a singular 48V power supply, is there a way to "isolate" the 48V for each of the 8 outputs? A combination of schottky diodes or similar? I figure once I can get each output isolated I can get back to figuring out how best to sense the current draw on that output.

Here's a quick screen grab showing what I have so far pertaining this question (half the current sensing circuits, at least). Note that the outputs all share the same "48V" and "GND_IN", which I believe is what is where my issue will be.

I'm sure more info is needed...please let me know. Thanks in advance for any pointers.

David

current-sense-schematic.jpg
 
Are your lights connected in parallel? If so I'm not sure I see the issue. Can you put a current sensor to the supply for each light? I'm not familiar with that current sensor, I use ACS758's but as you say, that should not matter.
 
Your shunts are all wired in parallel to 48V and GND. Shunts go in series with the load. I'm not familiar with the chips, but your schematic shows 4 shunt resistors shorting out 48V to GND.
 
@KrisKasprzak: yes, parallel.
@boxxofrobots: well yes, that it is a problem, isn't it! That's a bit embarrassing.

Let me fix my mistakes and come back. I'll also look into the ACS758.

Thanks for the input!
David
 
OK. Now that I know how to wire the current sensor, the question above is easily answered. I saw VIN+ and VIN- in the docs and immediately associated VIN- with ground. Nope! Also switched to the ACS70331 sensor.
Thanks for the help and apologies for the noise.

Cheers,
David
 
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