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Support Forum » Very hot USB cable

July 07, 2012
by Ralphxyz
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Possible this has something to do with Windows 7 losing my Com port.

The Nerdkit USB is HOT!!

Not scorching hot but hot enough that I would not want to leave my hand on it.

This is the section at the start of the cable, the A end.

Not the whole cable though it is probable warm.

I do have a switch on my USB yellow and green wires so I'll be switching that off but any idea if a hot USB cable is a problem and then what to do about it?

Thanks,

Ralph

July 08, 2012
by Rick_S
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I wouldn't think that is a good sign Ralph. Sounds like a short somewhere or too much current draw from something. If nothing is connected to it and is still gets hot, I'd start to think something inside the adapter is heading south. I don't typcially use the USB/Serial dongles, but when I do, I've never felt one even get warm let alone hot.

Rick

July 08, 2012
by Ralphxyz
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Hi Rick, thanks for the reply.

Using the switch on the yellow and green wires , which I had just stopped doing seems to alleviate the problem. I had always used the switch and stopped just to see if I needed to always use the it.

The current load obviously has to be key, I guess it must be loading through the mcu on the yellow or green wire probable the green. I suppose I should hookup my Amp meter.

I could see this happen if I were using the red USB power line but I am not.

I definitely will keep a eye on it, maybe I will get a new dongle just in case, I haven't gotten one for a while.

What do you use in place of the dongle?

Speaking of Amp meters I just picked up a Simpson Model 260 Analog Multi Meter.

I guess this will give me a good excuse to try it out. I really prefer analog over digital.

The Simpson 260 used to cost a couple of hundred bucks 30 - 40 years ago.

Ralph

July 08, 2012
by sask55
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Ralph

Are you able to use USB when you close the switches, ie can you program a chip?

Are you saying that your USB does not get hot or will cool down when you open the switches you have on the yellow and green wires ?

It would seem that In order to produce heat your USB must be drawing or supplying considerable current. This should not be the case espesialy thru either the TXD or the RXD wires. If the heat is only noticeable when your switches are closed the current must be related one of those wires.

You could place ammeter in parallel to each of your switches one at time. When the switch is open you will be measuring the current draw on the RXD green or TXD yellow wires. I have never actually measured those value but both of those value should be very small. Once you have determined where the current draw is you may be able to better notice any problems in the wire connections on your nerd kit board.

It does seem very strange that either RXD or the TXD will have a high current flow.

Darryl

July 08, 2012
by Rick_S
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My pc has a true serial port, and when I bought my nerdkit, it came with the board you see in a lot of their documentation that takes the DB9 connector from a serial port and converts it to the TTL of the chip. That's what I use only with my real port rather than the usb to serial I got with it which was usb on 1 end and DB9 on the other. When I'm not using that, I may use an FT232 based arduino board I modified with a crystal socket so I can use a NK crystal with NK MCU or an arduino crystal and arduino MCU. I don't even own one of the NK current version dongles with loose wires.

Ahh the good ol' days of analog meters. Simpson's were once the creme de la creme of meters and were highly sought. Enjoy the new (old) meter. Analog meters really shine where values are bouncing around a lot, the analog dial can kinda smooth out the reading to give you a good feel of the value you are getting. Sounds like fun... in an old school kind of way. Wink

Rick

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