voltage at pins

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Archived from groups: comp.dcom.lans.ethernet (More info?)

Hi all,

I wanted to check traffic between two pc's. I have 100 megabit ethernet.
I cut a original cable (cross over) and reconnected
tx+ and rx+
tx- and rx-
rx+ and tx+
rx- and tx-

The cable works fine. Between the open pins of the cable I put a LED incl. a
resistor to "see" the bits.
But there is no light during traffic.
I used a LED where I can see the light from 1 milliampere. So I thougt the
load is low enought.
I expected a voltage between the pins lower than 12 volt. Thats why the led
got a 4 kiloohm resistor.
The traffic is not disturbed by the LED.

Any suggestions?

Helge
 
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Archived from groups: comp.dcom.lans.ethernet (More info?)

H. Brüggemann wrote:
> Hi all,
>
> I wanted to check traffic between two pc's. I have 100 megabit ethernet.
> I cut a original cable (cross over) and reconnected
> tx+ and rx+
> tx- and rx-
> rx+ and tx+
> rx- and tx-
>
> The cable works fine. Between the open pins of the cable I put a LED incl. a
> resistor to "see" the bits.
> But there is no light during traffic.
> I used a LED where I can see the light from 1 milliampere. So I thougt the
> load is low enought.
> I expected a voltage between the pins lower than 12 volt. Thats why the led
> got a 4 kiloohm resistor.
> The traffic is not disturbed by the LED.
>
> Any suggestions?
>
> Helge
>
>

LOL. MUCH lower voltage than 12V. Less than the voltage needed to drive
most LEDS. Spec is I belive between 2.2V and 2.8V. Your gonna need to
use an op-amp or sumpthin in there to drive your LED.
 
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Archived from groups: comp.dcom.lans.ethernet (More info?)

In article <10pn232mlasv8c9@news.supernews.com>,
"T. Sean Weintz" <strap@hanh-ct.org> writes:
>H. Brüggemann wrote:
>> Hi all,
>>
>> I wanted to check traffic between two pc's. I have 100 megabit ethernet.
>> I cut a original cable (cross over) and reconnected
>> tx+ and rx+
>> tx- and rx-
>> rx+ and tx+
>> rx- and tx-
>>
>> The cable works fine. Between the open pins of the cable I put a LED incl. a
>> resistor to "see" the bits.
>> But there is no light during traffic.
>> I used a LED where I can see the light from 1 milliampere. So I thougt the
>> load is low enought.
>> I expected a voltage between the pins lower than 12 volt. Thats why the led
>> got a 4 kiloohm resistor.
>> The traffic is not disturbed by the LED.
>>
>> Any suggestions?
>>
>> Helge
>>
>>
>
>LOL. MUCH lower voltage than 12V. Less than the voltage needed to drive
>most LEDS. Spec is I belive between 2.2V and 2.8V. Your gonna need to
>use an op-amp or sumpthin in there to drive your LED.

Even better. If he succeeded to drive his LED it would shine all the
time as there is a constant flow of symbols and I doubt the LED
will interpret an IDLE. :)

--
Manfred Kwiatkowski kwiatkowski@zrz.tu-berlin.de
 
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Archived from groups: comp.dcom.lans.ethernet (More info?)

Manfred Kwiatkowski wrote:

>
> Even better. If he succeeded to drive his LED it would shine all the
> time as there is a constant flow of symbols and I doubt the LED
> will interpret an IDLE. :)
>


HEHEHEHE...

He didn't specify he wanted the LED to be off when there was no traffic,
only that he wanted it ON when there was traffic....

Easiest solution of coruse would be to stick a cheap switch or hub
inline on the cable.