I want to connect 15 devices/slaves and one server/master together. There is not much power or space (or money). How about Ethernet shields or Ethernet chips. Power over Ethernet would be plus. Ethernet cable is made of twisted line. What if I just make 15 branches to the cable? We won't need high speeds or long cable.
By the way, with Ethernet, it is probably 15 servers and one client.
You say:
I want to connect 15 devices/slaves and one server/master together
Then you say:
By the way, with Ethernet, it is probably 15 servers and one client.
With the word 'probably' indicates you are not very sure about your needs.
What ever the situation, you will need an Ethernet hub/router/switch to connect all those devices into, as you can not simply connect all the wires up together.
Yes, you will need to use at least CAT5 spec cable, not just any sort of other cable.
It sounds like you may be up against some challenges in terms of space, available power and money, all of which you will need sufficient of to do the job properly.
Paul
Would this work
I would make PWB of this, so connections would be more reliable.
But that is only one split. Schema of the Ethernet shield is not very clear, I wonder can I just make more splits.
You need to read carefully what is written in that article and get a better understanding of Ethernet communications.
I will quote from the article:
Unfortunately, Ethernet splitters cannot resolve the network collision issues that may occur if the computers connected to the splitter are using the same network resources simultaneously.
Hence why I say you will need an Ethernet hub/router/switch device to handle this situation.
What the heck is PWB, please avoid using acronyms unless you qualify them with the meaning.
Maybe you might be better with using an EIA-485 multi-drop network topology.
Paul
I forgot to answer this. Your answers are not helping, I am afraid. I cannot use a box called router, switch or a hub. I need schema of a switch or how to connect the Ethernet PHYS to divide a net in two.
A PWB is a politically correct or silly name for a PCB.
It is not possible to do what you want to do then I believe, not with 16 devices.
Again, I will suggest you consider using EIA-485 to have a multidrop network without needing additional equipment.
Provide more details, or we have no idea how else to offer advice to you.
What is the distances between each node ?
How is each node being powered ?
What is the requirement of data throughput, and is it real time ?
Why can you not use I2C if the distances are within I2C specifications ?
EIA-485 (RS485) is good for long distances and has good noise immunity ?
Paul
I forgot to answer this. Your answers are not helping, I am afraid. I cannot use a box called router, switch or a hub. I need schema of a switch or how to connect the Ethernet PHYS to divide a net in two.
A little bit of tech mumbo-jumbo in there. Can you explain the "connect the Ethernet PHYS to divide a net in two"? If your constructing a miniature 16 port ethernet hub for the connections is out of the question, then you have yourself an involved project to tackle.
I have a 15m or yards long bus, RS485, ethernet or what ever. Every 2 yards/meters there is a small box, where one branch goes to the box and second branch continues further.
A CAN or RS485 bus would work but their termination takes too much current. I was thinking if Ethernet would use less.
But currently, I am thinking about plain serial bus, there is room for a bit thicker cable. A bit slower speed is not a problem and I can handle the TXDs with open collector outputs and SW.
LMI, you are not explaining things very clearly for me.
Are you saying you have a single network bus of around 33 metres long, (I say 33 as you say you have 16 devices, 15 slaves and 1 master) ?
And with this single network cable, are there any stubs that extend out from the 'small box' at each 2 metre spot ?
How do you know CAN or EIA-485 takes too much current, what info have you on that ?
What is your expected power budget per node ?
How are you powering this, I can only assume solar, (man, I hate assuming) ?
If solar, you will have batteries, yes ?
If batteries, what sort are you using ?
What sort of Arduino are you using ?
Either take the time to write a detailed explanation or I'm out of here, sorry.
Paul
But currently, I am thinking about plain serial bus, there is room for a bit thicker cable. A bit slower speed is not a problem and I can handle the TXDs with open collector outputs and SW.
Thin cat3 four conductor telephone wire probably could be used to carry tx, rx, gnd, and power.
zoomkat:
Thin cat3 four conductor telephone wire probably could be used to carry tx, rx, gnd, and power.
Exactly. That is what I was last thinking. Actually, we have 6 wires in our (special)cable. So 2 grounds, tx, rx, interrupt and power is what I will use.
For rockwallaby: I have about 5 watts for whole system. But that is not all there is, sorry. I will not reveal all the details. CAN and 485 interface chips take quite a lot of current when active. I checked their datasheets. The buses have small termination resistors which are probably taking the power.
Because we have a relatively short bus, I think it would work with larger termination resistors.
Probably I will build prototype with both buses and check the power consumption. And of course, do they work reliably.
LMI:
I will not reveal all the details.
I will leave this thread and your secrets.