Creating a USB-C Passthrough with power charging detection

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StealthRT

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Hey all I have a project I am needing to do but I'm unsure as to the best way to go about doing it.

What I am wanting to do is check to see if a tablet or laptop is plugged into the USB-c cable so that I can have a visual representation of confirmation that it is connected correctly.

Most of the tablets I am using do not have any visible feature that showcases that its plugged in or not. But even if it did i would never be able to see it due to the tablets being close together.

This is what my setup I created looks like:


When your placing the tablet/laptop into the slots from the front it's difficult to tell if it made it into the connector or missed it.

So my idea was to create a PCB that has 6 female USB-C inputs and 6 female USB-C outputs. But I am not sure what I need to test on the pins to determine if its connected to something or not? I plan on using an arduino to check the voltage and see if it drops XX amount when something is plugged in but again, there may be a better way of checking it?

My PCB would look similar to this one but without the headers and holes and with more than one set:
 
You need to monitor the current, not a voltage. Put a small-value resistor, like 0.1 ohms, in series with the power. Measure the voltage across the resistor. Since you don't actually need to measure the current, just detect a threshold, you can use a comparator such as LM311. If you did want to measure the current, for example to detect end of charging, use a current sense amplifier such as an INA199 to gain-up the small voltage across the sense resistor to a level your Arduino ADC can easily measure.
 
Note that the LM311 can easily drive an LED so you wouldn't need anything else, like an Arduino. Or, you can buy USB cables that have current/power indication built-in. Search Amazon for "usb c cable with display"
 
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