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I have a digital microscope connected to my pi (usb) that you can use in a browser with a java web app that I have written. The microscope is also powered through the usb. There is no on or off switch, whenever you power on the pi, the microscope is turned on as well. I don't like this and I would like a button on my webapp that can turn on/off the microscope. I thought about doing this by cutting off the power to the microscope by using a usb-relay of some sort that I can control with the pi. But I'm not sure how to do this. So normally I just plug in the usb in my pi and whenever you press button x the webapp shows what the microscope 'sees'. But as said the problem is that the microscope is powered on the whole time (which I don't like).

My device looks like this:

https://i5.walmartimages.com/asr/8ee11de0-7de3-45ef-b914-e40a9d3f5159_1.e33288600d53dc421979397897e1a6e5.jpeg

The setup would be something like: Pi connected to a 'usb-relay', then that relay connected to my digital microscope...or something. From my pi I would then send a command to the relay to allow the digital microscope to receive power (turn on) or not (turn off). The Pi still needs to receive images from the digital microscope. I found something online that would pretty much do the trick I guess: https://www.yepkit.com/products/ykush

But I'm wondering if this could be done with a relay? And if so what kind of relay would I need?

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    Is this a solution stackoverflow.com/questions/59772765/… It may depend what else you have plugged in where. I would try via SSH just in case you turn they keyboard off and it does not respond when plugged into another port :-) – user130616 Mar 13 at 15:28
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Most well-behaved USB devices have a sleep mode which is activated when no active communication is taking place. If this is the case, simply unloading the driver will effectively power down the scope.

Otherwise, I would check out uhubctl mentioned by @Andrew. On a Pi4, you can control all 4 ports simultaneously, which will not do if you have other USB devices you need to remain powered. Connecting the microscope through a USB hub might help, but I suppose that depends on the hub.

You could, of course, use a relay to cut the power. I would avoid this solution if possible, as it will take time to implement and will not be strictly USB compliant.

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