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PICList Thread
'[EE] Speedometer for the model railroad - RF or IR'
2006\02\14@033810 by Enrico Schuerrer

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I am planning to build a speedometer for the model railroad. It should
measure the actual speed of a train via a sensor on the axle of a wagon (via
a white spot on the black axle and an IR fork lite barrier). The impulses
should be transmitted via ?? to a local base station, max. distance around
30m (90 ft). The power for the barrier and the ?? transmitter will be
delivered from the rails via a LT1073 (Micropower DC/DC converter) working
as a regulator for 5V and a 1F Gold Cap.

In the local station should be the ?? receiver, a PIC for counting and
calculating the "real world speed" (conversion from actual speed in scale
1:160 to speed in 1:1) and presentation on a LCD.

The PIC part is clear - counting the received pulses for a specified time,
calculating the speed and multiply with the scale factor for real world
speed and show the calculation on the LCD. An indication if the link is OK
should even be included and shown on the LCD.

I am thinking about a good method to transmit the pulses to the local
station - either via RF or IR. The advantage of RF is that there has to be
no line of sight between transmitter and receiver, the disadvantage that a
RF transmitter is a bulky element that is maybe not fitting in the space of
a 1:160 wagon. In addition I have no idea if there are small, simple and
cheap integrated building blocks at the market. IR looks much easier but
there has to be a line of sight between transmitter and receiver, in minimum
the reflections from walls or ceiling has to be strong enough to decode the
pulses safely.

So I have a few questions - what do you think is the better method for
transmitting the pulses, is there integrated RF equipment on the market
which is simple to use, cheap and small enough, does somebody have
experience with transmitting simple pules via around 30m max...

Last but not least - the maximum number of speedometers is very small (one
for me, one or two for collegues in our model railroad club).

I really would appreciate your thoughts and help.

Regards
Enrico




2006\02\14@044428 by Jinx

face picon face
> In the local station should be the ?? receiver, a PIC for counting
> and calculating the "real world speed" (conversion from actual
> speed in scale 1:160 to speed in 1:1) and presentation on a LCD

How much room have you got in a 1:160 wagon ? I guessed about
50-60mm x 20mm ?? I'd heard 2mm = 1ft. There are UHF data
modules that are small and cheap. For example the TX434A (14mm
square) and RX434A about half-way down this page

http://www.oatleyelectronics.com/whatsnew.html

I'm using the 433MHz version for a data link, great with a decent
antenna



2006\02\14@060347 by Enrico Schuerrer

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----- Original Message -----
From: "Jinx" <spam_OUTjoecolquittTakeThisOuTspamclear.net.nz>
To: "Microcontroller discussion list - Public." <.....piclistKILLspamspam@spam@mit.edu>
Sent: Tuesday, February 14, 2006 10:44 AM
Subject: Re: [EE] Speedometer for the model railroad - RF or IR?


{Quote hidden}

The room in this wagon is 86 x 23 x 32 mm (length x width x height) (1 inch
= 25.4mm) ~3 1/3 x  ~ 1 x 1 1/4 in inches, but if necessary I can change to
a 6 axle wagon with 125 x 23 x 32 mm ( ~ 5 inches long).

Thank you for the link.

regards

Enrico

2006\02\14@060747 by Jason

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face
How easy are those modules to use?  If reliability is an issue, do you need
to use an error detecting code?

Also, do you know of a north american supplier for a part like that?  All
I've been able to find is something similar at qkits.com  for twice the
price.

Thanks,
 Jason

{Original Message removed}

2006\02\14@062452 by Jinx

face picon face

> How easy are those modules to use?  If reliability is an issue, do you
> need to use an error detecting code?

As the modules are tranceivers, you can use any two-way protocol
you like to check data integrity. So far I've not tested the limits as the
range is presently well within their capabilities

> Also, do you know of a north american supplier for a part like that?  All
> I've been able to find is something similar at qkits.com  for twice the
> price.

If it's any help, the chip on the ones I have here is a Nordic nRF401

http://www.nvlsi.no/index.cfm?obj=product&act=display&pro=56

2006\02\14@063645 by Jinx

face picon face


> How easy are those modules to use?  If reliability is an issue, do
> you need to use an error detecting code?

Just to clarify - I said "my" modules are transceivers. They came
from Oatley too but are not the TX434/RX434 (which are not
bi-directional) and were slightly more expensive at NZ$9 each

Although I've not looked into in depth yet, I would imagine error
checking would be simpler with a bi-directional link, as you can
send checksum/data verification from either/both ends

2006\02\14@065456 by Jinx

face picon face

> Thank you for the link.

I haven't played around with FM bugs for a long time, but that
might be a possibility if you can't find a UHF one at the right
price. Although personally I'd rather just pay for a built one

Some links to crystal-controlled FM (broadcast band) bugs

http://members.tripod.com/~transmitters/links.htm

Don't annoy the neighbours ! ;-)

2006\02\14@100604 by Paul James E.

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Enrico,

Why don't you build a small transmitter operating at say 200Khz or so and
capacitively couple the modulated signal to the rails.   You can then pick
it off from anywhere on the rails.   You're already transmitting power
through the rails.  You could have your modulated signal riding on the
rails too.  No pun intended.

                                            Regards,

                                              Jim


{Quote hidden}

> --

2006\02\14@101615 by Juan Cubillo

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face
Check out the RF transmitters and antennas from Linx (IIRC...).
Specialy the plannar antenas and the KH modules.
VERY small and VERY useful

Juan Cubillo

{Original Message removed}

2006\02\14@140702 by Jinx

face picon face
>  Why don't you build a small transmitter operating at say 200Khz
> or so and capacitively couple the modulated signal to the rails

That thought occured to me initially but I wondered about the amount
of electrical noise from the motor(s) going back on to the track

2006\02\14@161005 by Paul James E.

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Thats the neat thing about modulating a signal.  You can modulate it so
that noise cannot immitate it, therefore, the receiver won't be confused.
And there are filters.  It's worth a shot in my opinion.  And besides,
whats to say that the same noise, if any, wouldn't interfere with RF too.
Just a thought.  I had planned to use this method with my brother-in-laws
HO trains, but he moved and I didn't get a chance to get it all together
before he moved.

                                              Regards,

                                                Jim


>>  Why don't you build a small transmitter operating at say 200Khz
>> or so and capacitively couple the modulated signal to the rails
>
> That thought occured to me initially but I wondered about the amount of
> electrical noise from the motor(s) going back on to the track
>
> --

2006\02\14@164740 by Enrico Schuerrer

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-----Ursprüngliche Nachricht-----
Von: "Paul James E." <jamespspamKILLspamintertex.net>
An: <.....piclistKILLspamspam.....mit.edu>
Gesendet: Dienstag, 14. Februar 2006 04:05
Betreff: Re: [EE] Speedometer for the model railroad - RF or IR?


{Quote hidden}

Hi Jim,

thanks for the idea. I think the problem for this solution is the construction. We have different modules and different supply areas, the rails are often isolated between the modules, depending on the supply area. The modules will be arranged in different configurations depending were we build up an exhibition and which area is available.

Regards

Enrico

2006\02\14@171405 by Jinx

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Enrico (and anyone else), I'd forgotten about an article in the
Dec 05 Silicon Chip (http://www.siliconchip.com.au) about cheap
433MHz wireless

The article isn't available on-line, but here are some names
mentioned

Jaycar ZW-3100/ZW3102

Computronics (Western Australia) TX433/RX433

Rentron/Laipac TWS/TLP RWS/RLP 433

Google for "433 ISM" -> Superior Ming, Chipcon

Keymark RXB1/TXC1 (http://www.keymark.com.tw)

Himark RX3400

Silicon Chip Dec 05 references

http://www.picaxe.orcon.net.nz/433txrx.htm


2006\02\14@174303 by Steve Smith

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face
Just a thought
If you position the pic '508 / 202 in the train then the speed and id can be
generated local to the sensor and teh data transmitted in packets with a
checksum a single receiver and display could then display info from many
trains. This does away with complex modulation to transmit simple pulses and
provides data verification in the form of a checksum or couple it to the
track (same difference the checksum is the verification)

Rgds Steve

{Original Message removed}

2006\02\14@201620 by Peter van Hoof

face picon face


--- Enrico Schuerrer <EraseMEenricospam_OUTspamTakeThisOuTgmx.at> wrote:

{Quote hidden}

But this is the ADVANTAGE of this solution
Imagine running multiple trains on the track
rail voltage on a section would give rpm's (speed)
on this section. this way different trains could be
running in different sections each with their own
feedback

furthermore if you did want more than one segment
coupled all you would need is a capacitor between
these sections (the supply for the sections would
go thru a coil and you take the hf off at the rail
side with a capacitor)

Peter van Hoof

2006\02\14@201629 by Peter van Hoof

face picon face


--- Enrico Schuerrer <@spam@enricoKILLspamspamgmx.at> wrote:

{Quote hidden}

But this is the ADVANTAGE of this solution
Imagine running multiple trains on the track
rail voltage on a section would give rpm's (speed)
on this section. this way different trains could be
running in different sections each with their own
feedback

furthermore if you did want more than one segment
coupled all you would need is a capacitor between
these sections (the supply for the sections would
go thru a coil and you take the hf off at the rail
side with a capacitor)

Peter van Hoof

2006\02\15@024100 by Enrico Schuerrer

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-----Ursprüngliche Nachricht-----
Von: "Peter van Hoof" <RemoveMEpvhoofTakeThisOuTspamyahoo.com>
An: "Microcontroller discussion list - Public." <spamBeGonepiclistspamBeGonespammit.edu>
Gesendet: Mittwoch, 15. Februar 2006 02:16
Betreff: Re: [EE] Speedometer for the model railroad - RF or IR?


{Quote hidden}

I need only to know the speed of one train. Unfortunately the rail voltage and the speed are a) not linear and b) not absolute (each locomotive has a different gear).
The wiring between the modules is defined so I can't change it (the modules belong to different people - if I want to change the wiring all other club members would have to do it in the same way). This was the reason why I am looking for an independent solution.

I have looked onto the different RF solutions and now only have to find a source here in Austria where to buy. It makes no sense to buy 2 transmitters/receivers in the USA for $12 and pay $30 for delivery...

Due to the fact that there are only pulses with different frequency (from lets say 0 Hz to 30 Hz) over a RF link it's not clear for me how to code it...

Regards

Enrico  



2006\02\15@025558 by Jinx

face picon face
> Due to the fact that there are only pulses with different frequency
> (from lets say 0 Hz to 30 Hz) over a RF link it's not clear for me
> how to code it...

You could include a small PIC, eg 10F or 12F. What, for example,
happens if the train stops with the pulse high ? With a micro you could
count and send ASCII once per second or something like that

2006\02\15@060401 by Alan B. Pearce

face picon face
>>  Why don't you build a small transmitter operating
>>  at say 200Khz or so and capacitively couple the
>>  modulated signal to the rails
>
>That thought occured to me initially but I wondered
>about the amount of electrical noise from the motor(s)
>going back on to the track

That is essentially how Marklin do their new mfx loco decoders. In their
case they use a Radio Data System chip at the controller end as the
receiver. AFAIK there are patents involved in this, so I suggest you don't
try and make it commercially ;)

2006\02\15@074234 by Enrico Schuerrer

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----- Original Message -----
From: "Alan B. Pearce" <TakeThisOuTA.B.PearceEraseMEspamspam_OUTrl.ac.uk>
To: "Microcontroller discussion list - Public." <RemoveMEpiclistspamTakeThisOuTmit.edu>
Sent: Wednesday, February 15, 2006 12:03 PM
Subject: Re: [EE] Speedometer for the model railroad - RF or IR?


{Quote hidden}

I would suppose that this is not exactly how mfx works :-) mfx is more or
less a further development of DCC done by the german company Doehler & Haas,
the developers of the model railroad controlling system SX. They added 2way
communication to the controlling system and direct decodeable addresses
(which allows a user to know that he controls the locomotive E103 and not an
address 95). All control is done via the rails - so a simple transmitting
system for pulses is state of the art (or behind :-) ).

regards

Enrico



2006\02\15@080548 by Alan B. Pearce

face picon face
>I would suppose that this is not exactly how mfx works :-)

It is how mfx works, the information is stored in the loco and read back by
the controller when the loco is put on the track.

>mfx is more or less a further development of DCC done by
>the german company Doehler & Haas, the developers of the
>model railroad controlling system SX.

Not familiar with this system, would appreciate a web link if you have one.

2006\02\15@103316 by Enrico Schuerrer

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----- Original Message -----
From: "Alan B. Pearce" <A.B.PearceEraseMEspam.....rl.ac.uk>
To: "Microcontroller discussion list - Public." <EraseMEpiclistspammit.edu>
Sent: Wednesday, February 15, 2006 2:05 PM
Subject: Re: [EE] Speedometer for the model railroad - RF or IR?


> >I would suppose that this is not exactly how mfx works :-)
>
> It is how mfx works, the information is stored in the loco and read back
by
> the controller when the loco is put on the track.

Alan, you wrote: "That is essentially how Marklin do their new mfx loco
decoders. In their
case they use a Radio Data System chip at the controller end as the
receiver. AFAIK there are patents involved in this, so I suggest you don't
try and make it commercially ;)"

There is AFAIK no RDS chip at the controller. The controller is built around
an AVR µC and the naming information for the loco is stored in the eprom.
>From the "mobile station" or "central station" it is possible to change the
name (if you have two times the same loco on the tracks) and other
parameters like acceleration/decelleration curve, extra functions a.s.o. The
loco by itself tells the controller that the loco is on the rails - it's
push information, not pull.


>
> >mfx is more or less a further development of DCC done by
> >the german company Doehler & Haas, the developers of the
> >model railroad controlling system SX.
>
> Not familiar with this system, would appreciate a web link if you have
one.

Doehler & Haas is AFAIK an engineering bureau, I'm afraid I found no
webpage. There is some information about mfx system in the web but I found
only german websites.

Kind regards

Enrico

2006\02\15@111011 by Alan B. Pearce

face picon face
>>Alan, you wrote: "That is essentially how Marklin
>>do their new mfx loco decoders. In their case they
>>use a Radio Data System chip at the controller end
>>as the receiver. AFAIK there are patents involved in
>>this, so I suggest you don't try and make it commercially ;)"
>
Enrico wrote:
>There is AFAIK no RDS chip at the controller.

There is certainly one in the mobile station. It is a Princeton technology
Corporation PT2579 RDS Demodulator chip. It is run with a lower crystal
frequency than normal RDS uses though.

2006\02\15@133409 by Enrico Schuerrer

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-----Ursprüngliche Nachricht-----
Von: "Alan B. Pearce" <RemoveMEA.B.PearceEraseMEspamEraseMErl.ac.uk>
An: "Microcontroller discussion list - Public." <RemoveMEpiclistspam_OUTspamKILLspammit.edu>
Gesendet: Mittwoch, 15. Februar 2006 17:10
Betreff: Re: [EE] Speedometer for the model railroad - RF or IR?


{Quote hidden}

Maybe there is a misunderstanding - I meant there is no RDS chip in the building block "mfx loco decoder" in the loco.

regards

Enrico

2006\02\16@130150 by Bill & Pookie

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Maybe try a voltage to frequency method.  Or a speed to pulse rate method.
The faster the speed the greater the rate of the RF pulse transmitted.

Bill

{Original Message removed}

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