The consequences of a badly wired cat5 cable

[Nixay]

I just plugged some new cat5 cables (home made) into my network chain and powered up my controllers (all DC boards) to check communications - no lights are plugged in at this stage.

I first noticed that none of the red status lights on any of the controllers came on, so I checked the power supplies and found that one of them had gone into overload. So after first killing that power supply for safety, I hunted down the new connections I had made to see what on earth I had done wrong. This is when I found one of my new controllers making a quiet crackling sound and a burning smell - no power was applied to this controller so power must have been coming down the cat5 from the next controller which was powered.

I shut the whole lot down and pulled out the victim controller. IC4 was very hot and seemed to be where the smell had come from. Fortunately on my test machine this controller seems to still be working and responding to the hardware utility, and I've tracked down what seems to be a bad cat5 cable. Isolated between a USB adapter and the single controller, plugging in this particular cable causes the red status light on the controller to go off completely, and presumably if left there could start something bad (although I'm not leaving it there long enough to find out!)

Until now, I thought a bad cat5 cable would just mean things didn't work. What I have just observed was almost catastrophic for one of my controllers. I guess there must be a short between one of the wires in the cat5 cable, but I had no idea it could be so bad for the controller hardware.

Nixay.

[cmoore60]

Pins 4 and 5 are the signal and pin 3 and 6 are voltage.

IT MIGHT be that you have the position of the wires for 3 and 6 reversed in one of your connectors. Make sure that all your cables are wired identical on both ends.

Cat5 cables used in the LOR network are straight thru cables.

Chuck

[-klb-]

If this relates to the question about doing a Y with the phone cable port, remember that the phone cable port is not just half the number of pins, but also rolled. So the cable would likely need to look something like this;

RJ-45 RJ-11 (4 position)

1 NC
2 NC
3 4
4 3
5 2
6 1
7 NC
8 NC

If you ran this the opposite way, you would have the controller power supply hooked to ground on the PC, and the if using the USB-485B, the computer generated 10V connected to controller ground..


Also, on the Y topic, remember that it is not the controllers that cause the echo, it is just the length of cable plugged in as a Y that causes the signal echoes.

[Richard Hamilton]

Nixay, I'm just wondering if you created your own cables and got the pins mixed up? The problem you mentioned shouldn't be happening on a cat5 cable unless it got pinched and caused a couple pins to short out (very unusual).

This comment is not related to your problem, but should serve as a good remember of a problem that can be just as nasty. DON'T USE booted cat5 cables either. Some of them are practically impossible to remove once you insert it in the LOR. There are warnings about this elsewhere on the board. If you buy a booted cat5, cut off the boot before you use it. I haven't bought any LOR units in the last year so I don't know if the cat5 sockets are any newer or better. Units I have from 2005 through 2008 don't use the a "soldered support" socket, so they are easy to break away from the circuit board if you are not careful while removing a cable. Booted cables require you to squeeze very hard to get them out.

[Tim Fischer]

If you make your own cables, you really need to 'invest' in a cable tester. I put 'invest' in quotes because they're really cheap: They can be had for under $10 shipped on eBay. Most of them can break into two pieces so you can put one end at each end of a cable run.

One of my setup procedures every year is to test the cables before hooking them into the boxes. I do this out in the yard, right before plugging them in.

Glad you don't see any damage from your mishap...

[Nixay]

Yes, as I mentioned above, the cat5 cables I had cut and crimped myself so I must have reversed some wires. It was very late at night! It's only when I make these things that I wished I had a tester, but then I never end up getting one..... lesson learned.

Regarding the Y configuration I was experimenting with, I have steered away from that and will just do the long daisy-chain. Next year I might invest in a network repeater.

Nixay.

[Nixay]

Yep, looks like I've wired one end entirely backwards. That'll do it!

[Greg]

I agree with Tim, I test my cables several times before they get hooked up for the season, Can never be too careful. A cat 5 tester is well worth it.

[Denny]

Tester - $2.49 and free shipping. http://www.meritline.com/multifunctional-cable-tester-242---p-35693.aspx?source=dealnews

[Richard Hamilton]

Tim Fischer wrote:

One of my setup procedures every year is to test the cables before hooking them into the boxes. I do this out in the yard, right before plugging them in.

Yup Tim, I think the key statement you make is "right before plugging them in."

I actually route the cat5 right into the inside of the box and plug the cable into my tester at that point. I think this is what you are talking about. I learned this lesson because I used to layout and route the wires, test them, then push the wire into the box and plug them in. A couple years ago, I had an older cable where one of the wires broke internally as I I looped it into the hole in the bottom of the box and connected it.

In my case, nothing was damaged since it became an open circuit, but I sure spent a lot of time trying to figure out why data was not getting to the box as I didn't think it was the cable after having just tested it.

You must have gotten a deal. My tester was $20. but still really worth it.

[Steven]

Denny wrote:

Tester - $2.49 and free shipping. http://www.meritline.com/multifunctional-cable-tester-242---p-35693.aspx?source=dealnews

That sounded like a great deal, so I ordered 2.

[JeffBlan]

DOH!!! I was setting up this year and wish I had read this post when it was first posted!

I was creating some new cables for my LOR network this year and accidently swapped either wires 3 & 4 or 5 & 6 (one of the ends, just not sure which end). This ended up frying my CCR controller (Yes one of my brand new CCR controllers!).

What a bummer! I've emailed support so hopefully I can get a new one before Friday.

I'll be putting an order in for a tester as soon as I'm done with this email. I never realized I could fry a controller with a network cable. Makes sense though since voltage is coming down the cable. I wish they had a fuse in the line somewhere in the box to take care of that.