pmurdock
Paul Murdock
join:2001-09-13
Riverton, UT
| hub or switch at solar powered POP?
I want to add a battery voltage monitoring device to a solar POP that I have, and I will be creating a microcontroller based circuit board with an Ethernet connection on it so I can query the device every hour to see the voltage of the battery and graph it in cacti.
HOWEVER..  my question is - I currently have the access point and the backhaul radio directly plugged into each other. So there are no RJ-45 ports for me to connect this battery monitor to.
Question is : Would a simple 2 port ethernet hub (ie just a splitter and no power usage) work sufficiently or should I put a low power consumption ethernet switch in there. I don't want to add too much of a current load just for the battery monitor. The ethernet physical layer should know how to deal with shared ethernet with automatic backoff and whatnot during a time when the battery monitor and radios want to communicate on the line - I would imagine right? 
cheers,
Paul |
|
Semaphore
Premium
join:2003-11-18
Arnprior On.
| I've used splitters before for customers that were to cheap to install another Ethernet drop, or even a hub. From an electrical isolation point of view I'm sure they suck. But they work... and even a small hub draws a ridiculous amount of power.
BTW... Got pics? I'd love some pointers |
|
BigCreek
God Is Good.
Premium
join:2002-06-25
Heber Springs, AR
| reply to pmurdock
Unless I'm missing something, I don't think a splitter is going to do what you want. They're good for stuffing two Ethernet devices onto one cat5 cable but you still need the ports at the other end.
You need some type of Ethernet hub or switch to connect three devices together.
Perhaps Google for "low power ethernet switch" and see what turns up.
--
SBC Pro Static DSL; Linux. Terrific wife & kids; live on a farm by Big Creek. Software & network consultant. |
|
pmurdock
Paul Murdock
join:2001-09-13
Riverton, UT
| Basically this is what I have setup. The backhaul radio comes into a PVC box and has a female RJ-45 connector on it - which currently connects directly to 1 access point. I want in essence to "split" off that 1 female port into two female ports - (1) one for the AP, and (2) two for the battery voltage monitor. Don't really think there is a need for a powered hub is there? The cable distances are all less than 10 feet.
the pics - of the solar pop or the battery voltage monitor?
cheers,
Paul |
|
pmurdock
Paul Murdock
join:2001-09-13
Riverton, UT
| If I do go with an Ethernet switch what about this one?
»www.controlsysteminnovators.com/itm00045.htm
It shows a power draw of 52 mA with all 5 ports linked up worst case scenario. I will have 3 of those ports so perhaps the current draw will be ~30 mA of constant draw. That's gonna drain the battery BIG time! All just to add a device to allow me to watch the battery because drainage is already an issue!
I've found a number of ethernet splitters, any suggestions on a good approach or should I just manually wire the connectors together.
cheers,
Paul |
|
BigCreek
God Is Good.
Premium
join:2002-06-25
Heber Springs, AR
| said by pmurdock  :I've found a number of ethernet splitters, any suggestions on a good approach or should I just manually wire the connectors together. Could you post links for some of them so we could see what exactly they are.
--
SBC Pro Static DSL; Linux. Terrific wife & kids; live on a farm by Big Creek. Software & network consultant. |
|
pmurdock
Paul Murdock
join:2001-09-13
Riverton, UT
| I was thinking of something like this..
»cgi.ebay.com/ws/eBayISAPI.dll?Vi···ame=WDVW
and then just wire up the ports to all be the same wires.. should work.. ?
cheers,
Paul |
|
BigCreek
God Is Good.
Premium
join:2002-06-25
Heber Springs, AR
| I believe that's just a patch panel. Note the first description line:
quote:
Use in Conjunction with an Active 10/100 Base-T Switching Hub
Here's the manu's page:
»www.hometech.com/techwire/vanco.html
--
SBC Pro Static DSL; Linux. Terrific wife & kids; live on a farm by Big Creek. Software & network consultant. |
|
public
join:2002-01-19
Santa Clara, CA
 ·DSL EXTREME
| reply to pmurdock
said by pmurdock :If I do go with an Ethernet switch what about this one? » www.controlsysteminnovators.com/itm00045.htmIt shows a power draw of 52 mA with all 5 ports linked up worst case scenario. I will have 3 of those ports so perhaps the current draw will be ~30 mA of constant draw. That's gonna drain the battery BIG time! All just to add a device to allow me to watch the battery because drainage is already an issue! You need either a hub or a switch. Both draw power. There is no such thing as a passive ethernet splitter.
You can find a lot cheaper one. |
|
pmurdock
Paul Murdock
join:2001-09-13
Riverton, UT | reply to BigCreek
isn't that all I really need though is a way to splice the cables together?
cheers,
Paul |
|
public
join:2002-01-19
Santa Clara, CA
·DSL EXTREME
| said by pmurdock :isn't that all I really need though is a way to splice the cables together? cheers, Paul No. Ethernet twisted pair needs a hub. |
|
pmurdock
Paul Murdock
join:2001-09-13
Riverton, UT
| I'm not so sure about that.. A hub is useful where you need to repeat the signal over larger distances.
However, the ethernet protocol is a CSMA/CD protocol, which implies "C"ollision "D"etection.. this means that a number of transmitters theorectically could be on the EXACT same wires and still be able to communicate as I understand it. When a collision occurs a random backoff period happens and then the two transmit again at different times.. simply by splicing the wires together indeed I will create the opportunities for collisions to occur, but it still should work?
cheers,
Paul |
|
public
join:2002-01-19
Santa Clara, CA
·DSL EXTREME
| said by pmurdock :I'm not so sure about that.. A hub is useful where you need to repeat the signal over larger distances. However, the ethernet protocol is a CSMA/ CD protocol, which implies "C"ollision "D"etection.. this means that a number of transmitters theorectically could be on the EXACT same wires and still be able to communicate as I understand it. When a collision occurs a random backoff period happens and then the two transmit again at different times.. simply by splicing the wires together indeed I will create the opportunities for collisions to occur, but it still should work? cheers, Paul That applies to original thick wire ethernet.
Read up on 10baseT requirements. |
|
cmaenginsb
Premium,MVM
join:2001-03-19
Palmdale, CA | reply to pmurdock
I don't think you can splice 3 connections together. You can try it though and let us know.
It's not a matter of collision detection, it's how you tie the tx and rx pairs together. |
|
wysockib10
join:2004-03-05
93770 | reply to pmurdock
What type of equipment are you using? If you are using 802.11b for your AP you could look into tranzeo wireless they have a radio with two ethernets. |
|
jdmarti1
Jack
join:2004-06-15
Oilton, OK
| reply to pmurdock
My biggest concern would be to create a chance for collisions on my backhaul. That is a very important link. This little unit only takes one watt. I am unsure what voltages you have on your power supply, so you either use the wall wart with this or use the 7.5v.
»www.trendnet.com/products/TE100-S5P.htm
--
»magicwisp.com |
|
Semaphore
Premium
join:2003-11-18
Arnprior On. | reply to pmurdock
The Solar Pop and battery layout please. It's not something we need to do immediately, but it would be beneficial in the future. |
|
pmurdock
Paul Murdock
join:2001-09-13
Riverton, UT
| reply to jdmarti1
looks like it is 7.5 Watts.. maybe I'm better off going with that ethernet switch up at the top that consumes 2 Watts or 52 mA @ 24VDC.
I see what you mean about tying which wires together.. that does present a problem. As it is now, they are a cross over direct connect.
Does anyone have a feel for what a "low power" switch should be.. is 52 mA really the best we can do?
cheers,
Paul |
|
John Galt
What...me panic??
Premium
join:2004-09-30
Happy Camp
| said by pmurdock :Does anyone have a feel for what a "low power" switch should be.. is 52 mA really the best we can do? That's pretty low...!
--
A is A |
|
pmurdock
Paul Murdock
join:2001-09-13
Riverton, UT
| Here's another one I found.. made by Parvus
»www.parvus.com/products/IODataco···itch104/
Says it is a 1.5 Watt, as opposed to the 2 Watt usage by the other one. Though at 5 volts, the P=IV equation says it will draw 300 mA.. how can that be lower than the 52 mA device that draws 2 Watts.?!?
cheers,
Paul |
|
