I have a question regarding Single Pair Ethernet, is it possible to carry power with two wires?
For example, controlling and powering a motor 12V 0.5/1A
\$\begingroup\$
\$\endgroup\$
6
-
\$\begingroup\$ @Finbarr, thank you. But this link says, we can do it, right? \$\endgroup\$– FreshmanJun 9 at 10:36
-
\$\begingroup\$ @Finarr, "Single Pair Ethernet (SPE) describes the transmission of Ethernet via only one pair of copper wires. In addition to data transmission via Ethernet, SPE also enables simultaneous power supply to end devices via PoDL - Power over Data Line. " is it right? \$\endgroup\$– FreshmanJun 9 at 10:37
-
\$\begingroup\$ I thought not, but apparently you can using PoDL. See here \$\endgroup\$– FinbarrJun 9 at 10:37
-
2\$\begingroup\$ So you already know the answer? \$\endgroup\$– FinbarrJun 9 at 10:37
-
\$\begingroup\$ @Finbarr, I just saw the link and saw it was like this. Just wanted to know whether it is right \$\endgroup\$– FreshmanJun 9 at 17:00
|
Show 1 more comment
1 Answer
\$\begingroup\$
\$\endgroup\$
Possible, yes. Ethernet is an AC-coupled signaling method, meaning there is spare bandwidth below the signal, where DC could pass.
The basic method to do this is called a bias tee. A balanced type is required, as the data is balanced.
This is different from the transformers used in multi-pair PoE, where the DC is balanced within each pair (currents go the same direction in each wire within a pair); cheaper (or even identical, to non-PoE that is) transformers can be used. (The CMCs must be arranged differently however.) A bias tee requires inductors rated for DC current flow, with enough [inductive] value not to disturb the data.
I would not suggest constructing one yourself from this answer alone, as the DC needs to be well filtered to avoid coupling interference into the data path -- or destructive transients, as the nominal signal level is only a couple volts. Additional common mode chokes will likely be necessary to resolve data and DC path impedances to meet EMC.
Get a copy of the appropriate standards and follow them closely, and/or use components designed specifically for the relevant standards.
