Why is the RepRap Powered Differently than the Cupcake?

I recently ordered the full generation 3 electronics from the makerbot store to use in building a mendel. Reading through the documentation for the motherboard I noticed that the RepRap doesn't use the RJ45 connectors to communicate with the extruder controller, nor does it use the ATX power supply header - instead it says to to desolder he RJ45s and replace them with 2 pin connectors and to remove the power supply header and put in a capacitor and transistor.

Is there an advantage to doing this? Can I just wire up my reprap the way the cupcake is? (powering the motherboard from the PS and using the RJ485 jacks)

It says that the motherboard is powered via the usb-ttl cable on the RepRap setup, if I was to use the atx power supply connection in the cupcake configuration does that change anything with the way I interface with the computer? Would I still just plug the TTL cable in like normal?

Thanks in advance!

I was just going to ask the same thing. What advantage is there to desoldering everything and reworking it for Reprap? I ordered the same stuff and just realized what was suggested for these components.

Hi

I think the modifications to the G3 electronics are only so that the machine runs on any 12volt DC supply. This was part of the original idea so that Repraps could be built anywhere in the world even using solar power. The Makerbot scheme was to make it plug and play which is fine but moves away from the original concept. Mendel is just bringing it back to basics but using the Makerbot supplied electronics.
I cant see any reason why Mendel could not use either configuration without any side effects as the modifications only deal with the 12volts distribution as far as I can make out.

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Regards

Ian

> Reading through the documentation for the motherboard I noticed that the RepRap doesn't use the RJ45 connectors to communicate with the extruder controller, nor does it use the ATX power supply header - instead it says to to desolder he RJ45s and replace them with 2 pin connectors and to remove the power supply header and put in a capacitor and transistor.

Making your own RJ45 leads is quite dificult if not praticed in making them.
I think there have been quite a few problems with this hence. by removing them and using simple connections there is less to go wrong.

I have the RJ45 crimp tool and have made my own cables by taking a std network cable cutting one end off to get the required length and crimping a new connector on.

Problems with RJ45 connections are that there are two main connection standards which can be confusing.
When making a lead you must cut the wires to the exact length for crimping and order the wires correctly in the crimp tool. This can go wrong and you end up with an incorrect lead.
I had to remake two cables due to crimping mistakes. You must buz out each lead before use. Thus simple 3 wire conections are easier/better for the limit switches .



>Is there an advantage to doing this?

hmm if RJ45 sockets alredy solderd on.. I think its quite a task to remove them! If not fitted use the 3pin header as its has less to go wrong.


As for removing an ATX connector from a made PCB again I would avoid doing this altogether! Any ATX PC power supply can just be pludded into it why change it.

If you want to use a diffrent supply cut a cable off an old ATX PSU and use the wires to connect to your other Power source.


>Can I just wire up my reprap the way the cupcake is? (powering the motherboard from the PS and using the RJ485 jacks)

Mine is powerd via the ATX lead for the CPU and seperate disk drive leades for the seperate stepper boards.

>It says that the motherboard is powered via the usb-ttl cable on the RepRap setup, if I was to use the atx power supply connection in the cupcake configuration does that change anything with the way I interface with the computer? Would I still just plug the TTL cable in like normal?

The first Sanguino had its own power reglator with the ability to be powerd by usb or by its power regulator to do this a link was set.

The mother board with the ATX conection has not got this ability and is powerd by the ATX connection.

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Bodge It [reprap.org]
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BIQ Sanguinololu SD LCD board	BIQ Stepcon	BIQ Opto Endstop
BIQ Heater Block PCB	BIQ Extruder Peek clamp replacement	BIQ Huxley Seedling
BIQ Sanguinololu mounting	BIQ standalone Sanguinololu or Ramps mounting	Print It Stick It Cut it

My rep strap: [repstrapbertha.blogspot.com]

Buy the bits from B&Q pipestrap [diyrepstrap.blogspot.com]
How to Build a Darwin without any Rep Rap Parts [repstrapdarwin.blogspot.com]
Web Site [www.takeaway3dtech.com]

Thanks a lot!

Is there any danger in putting enough power through cat5 wire to power the extruder board? Does it depend on the quality of the connectors/wire used?

Quote
wesjanik
Is there any danger in putting enough power through cat5 wire to power the extruder board?

see this thread

Sorry if these are stupid questions; I just began working on the electronics part of the Reprap.

1. What is the difference between RJ45 and RS485? The connection between the motherboard and other generation 3 components use RS485, so I am a little confused about why the documentation for the Motherboard mention both FJ45 and RS485?

2. Bodgeit mentioned that
"The first Sanguino had its own power reglator with the ability to be powerd by usb or by its power regulator to do this a link was set.

The mother board with the ATX conection has not got this ability and is powerd by the ATX connection."

My question is what would happen if I power the motherboard in the Cupcake configuration (directly from computer power supply) and just hook up motherboard to my computer with a USB to TTL cable? If this works, isn't the Mendel USB and power connector (http://objects.reprap.org/wiki/Mendel_USB_and_power_connector#The_RepRap_USB_Connection) unnecessary?

3. In http://objects.reprap.org/wiki/Electronic_wiring, the big diagram shows that many of the connections are RS485. However, http://objects.reprap.org/mediawiki/images/1/1f/Mendel.jpg shows no RS485 connectors coming from the motherboard. I am wondering if the RS485 connections will do the job?

Any help will be greatly appreciated.

wesjanik Wrote:
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> Is there any danger in putting enough power
> through cat5 wire to power the extruder board?
> Does it depend on the quality of the
> connectors/wire used?

Nope, no problem as I can see, just noise cross talk to adjacent data lines.

mochen72 Wrote:
-------------------------------------------------------
> Sorry if these are stupid questions; I just began
> working on the electronics part of the Reprap.
>
> 1. What is the difference between RJ45 and RS485?
> The connection between the motherboard and other
> generation 3 components use RS485, so I am a
> little confused about why the documentation for
> the Motherboard mention both FJ45 and RS485?
>

Well, I can answer that one... RJ45 is a connector, RS485 is a comunication protocol.
So in the makerbot config of the Gen3 electronics: you are comunicating (sometimes with RS485, sometimes not) over a piece of Cat5 cable with RJ45 connectors at each end.
It was done that way because RJ45 connectors are very cheap, as is Cat5 cable.

Potentially confusing


>3. In [objects.reprap.org], the big diagram shows >that many of the connections are RS485. However, [objects.reprap.org]
>/mediawiki/images/1/1f/Mendel.jpg shows no RS485 connectors coming from the >motherboard. I am wondering if the RS485 connections will do the job?

And on that one... There is no such thing as an RS485 connector (at least not in the way you seem to mean). Again, its the language being spoken, not the plugs involved. You can use any connector you want really. Cat5 cable is good because its a very clearly defined standard, fairly consistent, and works well with RS485. You could solder the wires directly to the board, but that would probably just cause more trouble later. A cheap easy connector like RJ45 makes a lot of sense. Especially when you can pick up lots of pre-made leads at local computer shops and online!
My normal connector of choice (at work) is an XLR of some type.. and those start at about £4 each for good ones

Edited 2 time(s). Last edit at 11/07/2009 06:03AM by TheRuttmeister.

>2. Bodgeit mentioned that
"The first Sanguino had its own power reglator with the ability to be powerd by usb or by its power regulator to do this a link was set.


2> its a good idea to remove the link completely if you use the first Sanguino boad plugged into the mother board so it is only powerd by the ATX PSU.

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Bodge It [reprap.org]
=======================================

---

BIQ Sanguinololu SD LCD board	BIQ Stepcon	BIQ Opto Endstop
BIQ Heater Block PCB	BIQ Extruder Peek clamp replacement	BIQ Huxley Seedling
BIQ Sanguinololu mounting	BIQ standalone Sanguinololu or Ramps mounting	Print It Stick It Cut it

My rep strap: [repstrapbertha.blogspot.com]

Buy the bits from B&Q pipestrap [diyrepstrap.blogspot.com]
How to Build a Darwin without any Rep Rap Parts [repstrapdarwin.blogspot.com]
Web Site [www.takeaway3dtech.com]

Triffid_Hunter - thanks for the link. I have to say I'm a little confused here. It's been a while since I worked with electronics in school, so you'll have to forgive me if these are silly questions.

Let me start by saying I'm guessing that the three +12V/GND power pairs are basically tied together to form a single +12V/GND pair since I don't see +36V anywhere on the circuit diagram. If the extruder board is running a 12V stepper motor at say 1A, wouldn't that translate to sending 1A divided among three Ethernet cable wires? If the wire is only rated for 350mA, you're just under the rated limit without having even turned on a heater (ignoring the relatively minimal power used by the electronics).

Looking at this in the most basic sense, it seems like the (rated) maximum power you can pass through the 3 pairs is 1.05A @ 12V or around 12.6W. That's a far cry from the "something like 10 amps" stated here, which would mean moving 120W through those cables. It looks like Power over Ethernet achieves its power rating by using higher voltages, but even the highest power rating stated on Wikipedia is still only 51W yielding 4.25A @ 12V.

What am I missing here?

wesjanik:

you're not missing anything - the ethernet cable is carrying power that it can only carry for a short run through free air (and even then it's marginal at best). ensconsed in a wall it would definitely be a fire hazard. I'd personally prefer to run power through a drive molex like all the other boards.

[en.wikipedia.org] lists the maximum current per conductor at just above 0.5A, so that's a mere 1.5A across the 3 pairs.