Post by thread:[EE]:Can you get +5V out of a 10baseT connection?

Well Richard the short answer is No, unless you are intend consuming picoamps of current. A perusal of the IEEE802 will reveal that the receiver connected to the physical media is essentially a device with a high impedance input. Regards Chris Lets say you connect a small box to your small ethernet 10baseT network, can I get power off any of the signals without upsetting the data? Richard. -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email .....listservKILLspam@spam@mitvma.mit.edu with SET PICList DIGEST in the body -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listservKILLspammitvma.mit.edu with SET PICList DIGEST in the body

> Lets say you connect a small box to your small ethernet 10baseT network, > can I get power off any of the signals without upsetting the data? Short answer: NO. Long answer has to do with transformer coupling, etc, blah, blah, but still "no". ***************************************************************** Olin Lathrop, embedded systems consultant in Devens Massachusetts (978) 772-3129, .....olinKILLspam.....embedinc.com, http://www.embedinc.com -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email EraseMElistservspam_OUTTakeThisOuTmitvma.mit.edu with SET PICList DIGEST in the body

Lets say you connect a small box to your small ethernet 10baseT network, can I get power off any of the signals without upsetting the data? No. However, 10baseT only uses 4 of the available 8 wires in an RJ45; I understand that some switches and/or installations are starting to provide power (for small internet appliances like IP phones) on some of the otherwise unused wires. I don't know offhand whether this is standardized or not, though... BillW -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listservspam_OUTmitvma.mit.edu with SET PICList DIGEST in the body

Chris Carr wrote: > > Well Richard the short answer is No, unless you are intend consuming > picoamps of current. A perusal of the IEEE802 will reveal that the receiver > connected to the physical media is essentially a device with a high > impedance input. > >>Lets say you connect a small box to your small ethernet 10baseT network, can >>I get power off any of the signals without upsetting the data? >> >>Richard. Actually it is relatively low impedance- the IEEE 802.3 spec states that the ethernet transciever must be able to drive a 100 ohm load. When I test ethernet, I use a 100 ohm resistor. If the interface is IEEE compliant, a reciever should be able to communicate over a 10 dB loss cable- this is because there is no consistent dB/m rating for unshielded twisted pair- this works roughly to 100m (my tests actually show that a 10dB cable (at 16MHz) is about 130 m of modern CAT5 cable). Nominally at the transmitter the signal should be about +/- 2.5 V. If you are willing to tolerate a decreased distance you can communicate over, you have some margin. On the other hand, the interface is transformer coupled, so you would only be able to draw power when something is actually talking on the interface. On a 10BASE-T signal there should always be link test pulses on an idle line, but they are very short and only come around at a relatively low rate. 10BASE-T does only use 4 of the 8 wires that are in the standard ethernet cable, you *could* try to use some of the other wires in the cable to send power, but be *very* careful, often the unused wires are terminated at the connector (usually with a 75 ohm resistor, but sometimes with a dead short). Any sort of noise on the other wires can get into the ethernet signal, so the power must be *very* clean. People have tried to put telephone/voice over the unused pairs, but they tend to have very poor results. Matt Bennett -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email @spam@listservKILLspammitvma.mit.edu with SET PICList DIGEST in the body

> Chris Carr wrote: > > > > Well Richard the short answer is No, unless you are intend consuming > > picoamps of current. A perusal of the IEEE802 will reveal that the receiver > > connected to the physical media is essentially a device with a high > > impedance input. > > > >>Lets say you connect a small box to your small ethernet 10baseT network, can > >>I get power off any of the signals without upsetting the data? > >> > >>Richard. > Matt Bennet Replied > Actually it is relatively low impedance- the IEEE 802.3 spec states that > the ethernet transciever must be able to drive a 100 ohm load. When I Snip I Concur - I am incorrect, well it was late at night and for some reason I was thinking Coax Cable not twisted pair Chris -- http://www.piclist.com hint: To leave the PICList KILLspampiclist-unsubscribe-requestKILLspammitvma.mit.edu