Modifying a switched USB hub for project power distribution

Most of my projects are fairly simple, low powered and run off 5V. Until recently I’ve used a cheap USB hub plugged into an old iPad charger. This actually worked fairly well, other than the hub connections being a bit dodgy. However, I wanted to be able to switch individual items on and off. You may be thinking that the items plugged in should have their own switches in the devices, but I want to have strings of LED lights that don’t.

I found one of these switched hubs on eBay. It was sold as ‘USB 2.0 HUB High Speed Powered AC Adapter Cable 7 Port PC Splitter Extender’ I paid AU$14.28 (US$9.59) which may have been too much, but I bought it from an Australian seller. I’ve seen them for sale for less direct from China.

It is made of fairly thin plastic, exactly what I expected for this price. There are lights on the front that indicate when a socket is turned on. These where extremely dim. The cord is fairly thin, probably ok for running some low current devices, but I had concerns about using it for powering the devices that I was intending to use it for. It does have a small external barrel jack, but it was quite small and I don’t have a plug to fit it.

Inside

Opening it up was easy. There are no screws. The back just clips together and easily opened with a spudger. Immediately there were a few surprises. It was immediately obvious why the LED indicators were dim. It is a single sided PCB with the tracks facing downwards and surface mount LEDs were used, so while they were bright they face the wrong way. I was interested to see that instead of regular power limiting resistors to the LEDs it uses some sort of resistive track on the board that measures around 150 – 200 ohms. I have not seen that before. There is also space for a power LED that was not filled.

The other surprise was the ICs and a few other components on the board. I had expected just switches and LEDs but thinking about it having those parts makes sense. The switches don’t switch both data and power. The ICs have ‘CN6G09 1’ marked underneath. While I couldn’t find out any information about them, I presume they manage both data and power to the sockets.

Testing

I only did a couple of tests with it used as intended with a couple of USB memory sticks. I got mixed results. When I turned the switch on Windows recognised that the drive was there and opened as it would have if plugged directly into one of the computers USB ports. Turning it off removed the drive but it didn’t return when I switched it back on. I had to remove it and plug it back in. Not sure why that is.

Modifying

I have no intention of using it connected to a computer and decided to remove the ICs and capacitors and just leave the switches, sockets, LEDs and their resistors. I also wanted to do something about the LEDs and replace the cable.

I only have 5mm LEDs and while there are holes in the board the LED would not have physically fit behind the opaque windows. 3mm may have worked or if I had been thinking at the time the 5mm ones may have worked if I soldered them downwards and then folded them around the board. I didn’t do that, instead I did it the hard way. I soldered in some wire and then soldered the surface mount LEDs to that. I found it very challenging.

The ICs and other surface mount parts came of very easily with a hot air gun. I also added a red power LED, well, because more LEDs are always better :). Next was replacing the USB cable. I found the perfect replacement. Good quality and pliable. It had a micro USB plug on one end with broken insulation around it. I carefully cut off… the wrong end. Oops. So now I’ve had to use a less than perfect cable. In the future I may remove it and use thicker wire and connect it directly to a 5V power supply.

Here it is finished. Notice the blue LEDs now appear much brighter. A new red LED also shows through at the back right.

Summary

Has it been a worthwhile project? I think so. I’ve been careful to not overload it. It would be easy to overload the plugpack and the hub itself. But, I may have been better just to have bought a 5V supply and connected directly to that.

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