CHEAP Serial bus, control 200 devices, 50 meters

[Brook Stevens]

I'm asking on this group because you folks seem to be more aware of the
lower cost options. I wouldn't mind some outside-the-box ideas.


I need PC control/automation of:
200 machines
Each machine needs 16 logic inputs and 16 outputs
Line lengths may be 50 meters

I want a serial bus to connect the i/o devices at each machine with the PC.
This is to reduce the wires needed, lower costs and simplify design.

It is not a noisy environment. No welding, for example.
I don't need more than 100kHz speed, and might get by with even less.
I don't need environment protection. The devices can be just a circuit
board. It's indoors, not a washdown area.
I don't need super high reliability. It's not a life support system.
Cost is a major concern.

I've been looking at some industrial bus options. Either they cannot handle
200 devices, cannot handle 50 meters, or are very expensive (x200). But,
there are so many, I don't know them all, and maybe some can be modified to
do what I need that I'm not aware of.

Can anyone offer a suggestion or alternative?

[Wayne C. Gramlich]

Brook:

The RS-422/RS-485 stuff is probably what you are looking for.
RS-422 is point-to-point and RS-485 is multi-drop. The interface
chips are readily available.

-Wayne

Brook Stevens wrote:
> I'm asking on this group because you folks seem to be more aware of the
> lower cost options. I wouldn't mind some outside-the-box ideas.
>
>
> I need PC control/automation of:
> 200 machines
> Each machine needs 16 logic inputs and 16 outputs
> Line lengths may be 50 meters
>
> I want a serial bus to connect the i/o devices at each machine with the PC.
> This is to reduce the wires needed, lower costs and simplify design.
>
> It is not a noisy environment. No welding, for example.
> I don't need more than 100kHz speed, and might get by with even less.
> I don't need environment protection. The devices can be just a circuit
> board. It's indoors, not a washdown area.
> I don't need super high reliability. It's not a life support system.
> Cost is a major concern.
>
> I've been looking at some industrial bus options. Either they cannot handle
> 200 devices, cannot handle 50 meters, or are very expensive (x200). But,
> there are so many, I don't know them all, and maybe some can be modified to
> do what I need that I'm not aware of.
>
> Can anyone offer a suggestion or alternative?
>
>

[wkearney99]

> I've been looking at some industrial bus options. Either they cannot
handle
> 200 devices, cannot handle 50 meters, or are very expensive (x200). But,
> there are so many, I don't know them all, and maybe some can be modified
to
> do what I need that I'm not aware of.
>
> Can anyone offer a suggestion or alternative?

Bear in mind that using a PC as the host controller can allow for more than
just one interface BUS. While each technology (485, 1-wire, etc) might have
device, speed or distance limits that doesn't mean you can't use more than
one.

[RedX]

Except not every RS485 transceiver can handle 201 nodes. They can handle 32
Unit Loads (UL), most are 1UL/transceiver or 1/3UL/transceiver, but some
have a lower UL. The LTC1487 can handle 256 devices.

Patrik

"Wayne C. Gramlich" <Gramlich@PacBell.Net> schreef in bericht
news:0WBLd.9676$8Z1.4594@newssvr14.news.prodigy.co m...
> Brook:
>
> The RS-422/RS-485 stuff is probably what you are looking for.
> RS-422 is point-to-point and RS-485 is multi-drop. The interface
> chips are readily available.
>
> -Wayne
>
> Brook Stevens wrote:
> > I'm asking on this group because you folks seem to be more aware of the
> > lower cost options. I wouldn't mind some outside-the-box ideas.
> >
> >
> > I need PC control/automation of:
> > 200 machines
> > Each machine needs 16 logic inputs and 16 outputs
> > Line lengths may be 50 meters
> >
> > I want a serial bus to connect the i/o devices at each machine with the
PC.
> > This is to reduce the wires needed, lower costs and simplify design.
> >
> > It is not a noisy environment. No welding, for example.
> > I don't need more than 100kHz speed, and might get by with even less.
> > I don't need environment protection. The devices can be just a circuit
> > board. It's indoors, not a washdown area.
> > I don't need super high reliability. It's not a life support system.
> > Cost is a major concern.
> >
> > I've been looking at some industrial bus options. Either they cannot
handle
> > 200 devices, cannot handle 50 meters, or are very expensive (x200). But,
> > there are so many, I don't know them all, and maybe some can be modified
to
> > do what I need that I'm not aware of.
> >
> > Can anyone offer a suggestion or alternative?
> >
> >

[Brook Stevens]

> The RS-422/RS-485 stuff is probably what you are looking for.
> RS-422 is point-to-point and RS-485 is multi-drop. The interface
> chips are readily available.
>
> -Wayne

RS-485 sounds great. But, then what protocol should the devices use to
communicate with the PC? The PC needs to address one out of 200 devices and
tell it to set it's inputs, or to send it's outputs. I find lots of
industrial bus options out there that have their own a protocol.

[William Richardson]

How cheap did you have in mind?

100KHz? do you mean Kbit? KBaud?

Are you looking for Relay outputs? optical outputs? What sort of input?
Digital / Analog?

Yes RS485 would appear to be the way to go. Try www.rs485.com


"Brook Stevens" <brook@nospam.com> wrote in message
news:BE242207.21D25%brook@nospam.com...
> I'm asking on this group because you folks seem to be more aware of the
> lower cost options. I wouldn't mind some outside-the-box ideas.
>
>
> I need PC control/automation of:
> 200 machines
> Each machine needs 16 logic inputs and 16 outputs
> Line lengths may be 50 meters
>
> I want a serial bus to connect the i/o devices at each machine with the
PC.
> This is to reduce the wires needed, lower costs and simplify design.
>
> It is not a noisy environment. No welding, for example.
> I don't need more than 100kHz speed, and might get by with even less.
> I don't need environment protection. The devices can be just a circuit
> board. It's indoors, not a washdown area.
> I don't need super high reliability. It's not a life support system.
> Cost is a major concern.
>
> I've been looking at some industrial bus options. Either they cannot
handle
> 200 devices, cannot handle 50 meters, or are very expensive (x200). But,
> there are so many, I don't know them all, and maybe some can be modified
to
> do what I need that I'm not aware of.
>
> Can anyone offer a suggestion or alternative?
>
>

[John Hines]

Brook Stevens <brook@nospam.com> wrote:

>
>
>> The RS-422/RS-485 stuff is probably what you are looking for.
>> RS-422 is point-to-point and RS-485 is multi-drop. The interface
>> chips are readily available.
>>
>> -Wayne
>
>RS-485 sounds great. But, then what protocol should the devices use to
>communicate with the PC? The PC needs to address one out of 200 devices and
>tell it to set it's inputs, or to send it's outputs. I find lots of
>industrial bus options out there that have their own a protocol.

How about a serial port per unit? They have, at least 10 years ago they
did, concentrators that will run 16 ports remote from the CPU.

This was IBM hardware at the time, but I think the same is available for
PC's. Unix has no trouble accessing 250 ports. Otherwise look at
terminal server types of products.

Then a PIC based controller, with a serial connection, depending on your
hardware.

Device independent, in that one unit does not depend on another to
function.

[Brook Stevens]

William Richardson wrote:

> How cheap did you have in mind?
>
> 100KHz? do you mean Kbit? KBaud?

You're right, that was unclear. I meant KBaud, Kbps. I realize the protocols
will have some overhead, and that's fine. I could maybe get by with 9600bps.

> Are you looking for Relay outputs? optical outputs? What sort of input?
> Digital / Analog?

Logic level.

> Yes RS485 would appear to be the way to go. Try www.rs485.com

Thanks for the suggestion! That's very interesting.

[Steve Letkeman]

Have a look at my site www.brightan.com This system is capable
of 5*128 nodes with each node having 128 devices (single input
or output or complex device like a RS232 port). This is all
CAN (Controller Area Network) based. You can even download
new firmware to a node across the network. Although the
main idea is lighting control I have designed the protocol and the
display software to be expandable to whatever you want. I do
not currently offer a 16 input and 16 output module but it would
be trivial to create one.

Steve
--
Steven D. Letkeman BSc.
President - Zanthic Technologies Inc.
403-526-8318
www.zanthic.com Embedded micro-controllers and CAN interfaces
www.brightan.com Automated lighting systems

"Brook Stevens" <brook@nospam.com> wrote in message
news:BE242207.21D25%brook@nospam.com...
> I'm asking on this group because you folks seem to be more aware of the
> lower cost options. I wouldn't mind some outside-the-box ideas.
>
>
> I need PC control/automation of:
> 200 machines
> Each machine needs 16 logic inputs and 16 outputs
> Line lengths may be 50 meters
>
> I want a serial bus to connect the i/o devices at each machine with the
PC.
> This is to reduce the wires needed, lower costs and simplify design.
>
> It is not a noisy environment. No welding, for example.
> I don't need more than 100kHz speed, and might get by with even less.
> I don't need environment protection. The devices can be just a circuit
> board. It's indoors, not a washdown area.
> I don't need super high reliability. It's not a life support system.
> Cost is a major concern.
>
> I've been looking at some industrial bus options. Either they cannot
handle
> 200 devices, cannot handle 50 meters, or are very expensive (x200). But,
> there are so many, I don't know them all, and maybe some can be modified
to
> do what I need that I'm not aware of.
>
> Can anyone offer a suggestion or alternative?
>
>

[rich@gossel.org]

Have a look at this...this stuff has been used for just about
everything you can imagine, and if done right...is bullet-proof...

It's not shrink wrapped...but it extremely flexible and you can do
whatever you need with it. There is also an extremly active user
community...

www.jlcenterprises.net/Products.htm

It was originally developed for the Model RR community, but it's been
used for just about everything...and you can get it in kit form...or
completely assembled...or just buy part...so cost can be
contained...depending on your situation. Also will run on very old &
slow machines...on dos...or...on windows if you like...