Hi Guys,

I'm in the process of implementing some simple control nodes (just
switches) and looking for the simplest (cheapest) network protocol to
use.  To date, LIN bus seems to be the best candidate.  I need very
low speed, high reliability and low off-board distance (a few up to
10s of feet).

Ideally, something that could be two wire with power and data combined
would be ideal, so that the power could be distributed to power the
slave nodes.  LIN is good, but it requires a 4 wire (or 3 I suppose)
interface.

I looked at ASI (Acuator Sensor Interface), but not sure how practical
it is.

Anything else on the radar screen?

Paul

Paul W. wrote:
> Hi Guys,
> 
> I'm in the process of implementing some simple control nodes (just
> switches) and looking for the simplest (cheapest) network protocol to
> use.  To date, LIN bus seems to be the best candidate.  I need very
> low speed, high reliability and low off-board distance (a few up to
> 10s of feet).
> 
> Ideally, something that could be two wire with power and data combined
> would be ideal, so that the power could be distributed to power the
> slave nodes.  LIN is good, but it requires a 4 wire (or 3 I suppose)
> interface.
> 
> I looked at ASI (Acuator Sensor Interface), but not sure how practical
> it is.
> 
> Anything else on the radar screen?

There just may be:
http://www.interfacebus.com/Design_Connector_Field_Buses.html

In article <7...@posting.google.com>,
Paul W. <b...@hotmail.com> wrote:
>Hi Guys,
>
>I'm in the process of implementing some simple control nodes (just
>switches) and looking for the simplest (cheapest) network protocol to

You want cheap:


               L1
DC source ----))))))))----------------------- To others
or load               !               !
                      \ R1           --- C1
                      /              ---
                      \               !
                      !    R4         / R2
                      !   -/\/\/---   \
!--------------!      !  !         !  / R3
! Micro     TXD!---!!-   !    /+!------/\/\/-- Vcc/2
!              !   C2    !   /  !
!           RXD!------------    ! U1
!--------------!             \  !
                              \-!---- Vcc/2


C2, R1 and L1 turn the RS232 output of the micro into positive and 
negitive going glitches.

L1 blocks the AC from going into the supply or load.  It is in parallel 
with all the others.  The total inductance interacts with C2 to define the 
width of the glitches.

R1 damps the L1 C2 combination to make the responce not overshoot.

C1 picks the glitches off the power line and applies them to U1.  U1 is 
configured to have enough positive feedback that it doesn't chatter.

Now all you need is software.

This method has been done over 1000 foot cables.




-- 
--
k...@rahul.net   forging knowledge

Just my opinion, but AS-i works great and is easy to set up. I just
have one node, my first trial. 12 valves, solenoid operated with open
and close proximity switches, one repeater.

On 19 Jun 2004 07:04:41 -0700, b...@hotmail.com (Paul W.) wrote:

>Hi Guys,
>
>I'm in the process of implementing some simple control nodes (just
>switches) and looking for the simplest (cheapest) network protocol to
>use.  To date, LIN bus seems to be the best candidate.  I need very
>low speed, high reliability and low off-board distance (a few up to
>10s of feet).
>
>Ideally, something that could be two wire with power and data combined
>would be ideal, so that the power could be distributed to power the
>slave nodes.  LIN is good, but it requires a 4 wire (or 3 I suppose)
>interface.
>
>I looked at ASI (Acuator Sensor Interface), but not sure how practical
>it is.
>
>Anything else on the radar screen?
>
>Paul

In sci.electronics.design Paul W. <b...@hotmail.com> wrote:
> Hi Guys,
> 
> I'm in the process of implementing some simple control nodes (just
> switches) and looking for the simplest (cheapest) network protocol to
> use.  To date, LIN bus seems to be the best candidate.  I need very
> low speed, high reliability and low off-board distance (a few up to
> 10s of feet).

You could always go analog.
Each switch has a series LC network, and the control circuit 
just imposes a small AC frequency over the network, and looks at
the impedance.
The plusses of this are of course you only need one real circuit,
the others can practically be built onto a chocolate block.

In article <4...@nospam.com>,
   Fred Bloggs <n...@nospam.com> wrote:

> There just may be:
> http://www.interfacebus.com/Design_Connector_Field_Buses.html

 I looked there, but couldn't see anything related
 to multi-channel control over the DC supply wires.

 I have a pal who (in later life) is resurrecting
 his interest in model railways. Apparently there
 is now some reasonably standardised method of
 multi-device control via the DC supply through
 the rails.  Trains, points and signals can all be
 controlled via one DC supply.  It is supposed to
 be popular in the US model engineering market,
 but he hasn't been able to find out any technical 
 details yet.

-- 
Tony Williams.

"Tony Williams" <t...@ledelec.demon.co.uk> wrote in message
news:4cc263dcd8t...@ledelec.demon.co.uk...
> In article <4...@nospam.com>,
>    Fred Bloggs <n...@nospam.com> wrote:
>
> > There just may be:
> > http://www.interfacebus.com/Design_Connector_Field_Buses.html
>
>  I looked there, but couldn't see anything related
>  to multi-channel control over the DC supply wires.
>
>  I have a pal who (in later life) is resurrecting
>  his interest in model railways. Apparently there
>  is now some reasonably standardised method of
>  multi-device control via the DC supply through
>  the rails.  Trains, points and signals can all be
>  controlled via one DC supply.  It is supposed to
>  be popular in the US model engineering market,
>  but he hasn't been able to find out any technical
>  details yet.
>
> --
> Tony Williams.

I thought someone would mention this eventually. It's called
Digital Command Control (DCC) and is maintained by the
National Model Railroad Association. The NMRA standards are at
http://www.nmra.org/standards/consist.html#standards-DCC.
There are a lot of manufacturers world-wide that make the
various mobile and staionary decoders, booster/command stations,
hand-held throttles, computer interfaces, etc. Note that the
standard only applies to the booster to decoder side, while the
booster / throttle / computer network tends to be proprietary
to each manufacturer. Most of the modelers I know use Digitrax
http://www.digitrax.com/.

Mike

In article
<I_BBc.12390$O...@bgtnsc05-news.ops.worldnet.att.net>,
   Mike Lamond <N...@NOTworldnet.att.net> wrote:

> I thought someone would mention this eventually. It's called
> Digital Command Control (DCC) and is maintained by the
> National Model Railroad Association. The NMRA standards are at
> http://www.nmra.org/standards/consist.html#standards-DCC.
> There are a lot of manufacturers world-wide that make the
> various mobile and staionary decoders, booster/command stations,
> hand-held throttles, computer interfaces, etc. Note that the
> standard only applies to the booster to decoder side, while the
> booster / throttle / computer network tends to be proprietary
> to each manufacturer. Most of the modelers I know use Digitrax
> http://www.digitrax.com/.

 Thanks for the information.  I've bounced your reply
 to my pal.

-- 
Tony Williams.

"Ken Smith" <k...@violet.rahul.net> wrote in message
news:cb2gfr$at0$1...@blue.rahul.net...

> You want cheap:
>
>
>                L1
> DC source ----))))))))----------------------- To others
> or load               !               !
>                       \ R1           --- C1
>                       /              ---
>                       \               !
>                       !    R4         / R2
>                       !   -/\/\/---   \
> !--------------!      !  !         !  / R3
> ! Micro     TXD!---!!-   !    /+!------/\/\/-- Vcc/2
> !              !   C2    !   /  !
> !           RXD!------------    ! U1
> !--------------!             \  !
>                               \-!---- Vcc/2
>

what would be the disadvantage of removing U1 and all connected parts on
receiving side and connecting C1 directly to RXD grounded through input
impedance resistor ? Now that's inexpensive :)

As for the protection of RXD from spikes, I would consider the built-in
clamp diodes (some microcontrollers have them) together with R2.

Roman

Tony Williams wrote:
> In article <4...@nospam.com>,
>    Fred Bloggs <n...@nospam.com> wrote:
> 
> 
>>There just may be:
>>http://www.interfacebus.com/Design_Connector_Field_Buses.html
> 
> 
>  I looked there, but couldn't see anything related
>  to multi-channel control over the DC supply wires.
> 
>  I have a pal who (in later life) is resurrecting
>  his interest in model railways. Apparently there
>  is now some reasonably standardised method of
>  multi-device control via the DC supply through
>  the rails.  Trains, points and signals can all be
>  controlled via one DC supply.  It is supposed to
>  be popular in the US model engineering market,
>  but he hasn't been able to find out any technical 
>  details yet.
> 

I don't think that DCC is suitable because it looks they reverse the 
polarity on the rails or some crazy thing. The Siemens ASI seems to be 
it. It uses a simple unshielded two wire data+power cable and the 
network can be up to 64 slaves each of which can be multiple I/O. Noise 
immunity is achieved by superimposing a narrowband sinewave that is 
modulated by something called APM= Alternate Pulse Modulation- of just 
exactly what-phase, amplitude, or something else-I don't know, but the 
slave receivers require crystal timebases. The ASI has been around for 
10 years now so that it is well-developed and supported- you can tie it 
into almost any other industrial control bus, or PCI, or VME, or 
whatever- and there are plenty of chipsets available for building a 
product from scratch too. It has quite a bit of protocol overhead so 
that custom development would not make sense unless you're building a 
compatible product for market- an in-house actuator control bus should 
use readily available off-the-shelf modules from any one of dozens of 
manufacturers.