Thought experiment- analogue (FM) multi-train control?

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Thought experiment- analogue (FM) multi-train control?

Postby pete12345 » Fri Oct 06, 2017 1:53 pm

DCC has established itself as the standard control system with all its features. But theoretically, could something based on analogue frequencies have worked? Much like an analogue TV signal carried several channels' information down the same cable as FM signals.

I'd envisage each loco working on a particular carrier frequency which contains a speed signal as well as maybe lighting etc. Each controller modulates this onto a channel and the loco demodulates it. Any reason for it nit to work?
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Re: Thought experiment- analogue (FM) multi-train control?

Postby End2end » Fri Oct 06, 2017 2:09 pm

This sounds quite like the way MIDI works (Musical instrument digitial interface).
You have one midi cable connected to your pc which connects to your first synth. The follwing synths are daisy chained using other MIDI cables.
So synth 1 out into synth 2 in, synth 2 out into synth 3 in etc.

There are 16 MIDI channels and each synth is setup to use/respond to ONE midi channel so lets say...
Synth 1 = MIDI channel 1
Synth 2 = MIDI channel 2
Synth 16 = MIDI channel 16

Within each of these 16 MIDI channels they have 128 parameters with 128 "steps" that can be manipulated.
So converting that back to the original idea that's 16 loco's with 128 functions with 128 steps.

NOTE: The above is the old way to do it.

Nowadays it's preferred to use multi-midi out boxes with a direct single cable for EACH synth as you can use upto 16 sounds PER synth at the same time giving you upto 256 sounds all at the same time from 16 synths if the mutli-midi box used has 16 physical midi outputs.

This direct technique using a multi-midi out box helps eliminate latency as the daisy chained technique has to go through all 15 synths before reaching the 16th daisy chained synth to make it make a sound.
There is also now wireless MIDI.

The difference being, yours using frequencies, MIDI, like DCC (I'm assuming) is a protocol / programming language
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Re: Thought experiment- analogue (FM) multi-train control?

Postby Bigmet » Fri Oct 06, 2017 3:34 pm

Theoretically yes, BUT. And it is a big 'but' as you can see. The rail to wheel interface is horribly noisy and the DC motor not a lot better. Digital is very good at noise rejection, analogue extremely poor; so reception could be expected to be very unreliable.

Better if using multichannel analogue to send the control signal by radio, much as aircraft and boat modellers once did. That wasn't terribly reliable either.

With all the world moving to digital signal protocols various, better to piggyback on the progress there with miniaturised components and low power consumption as standard, with all the advantages that brings for small model applications.

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Re: Thought experiment- analogue (FM) multi-train control?

Postby Bufferstop » Fri Oct 06, 2017 4:43 pm

Early attempts at multi train control were attempted that way. R/C model aircraft had nothing better to use for years, but most of their control mechanisms were rather slam-bang operations. Grabs flying helmet and dives beneath baseboard.
One "sophisticated" system offered channels transmitted by audio frequencies and detected by reeds tuned to vibrate and make contact when the tones were transmitted. It was much lighter than the valves and their batteries which would otherwise have been required.
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Re: Thought experiment- analogue (FM) multi-train control?

Postby Bigmet » Fri Oct 06, 2017 9:21 pm

Bufferstop wrote:...Grabs flying helmet and dives beneath baseboard.....

Good place to be. A friend of mine is short most of one finger due to not getting under the baseboard when his R/C aircraft became R/U(ncontrolled).

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Re: Thought experiment- analogue (FM) multi-train control?

Postby GWR_fan » Fri Oct 06, 2017 10:46 pm

This is a method that I considered in largescale many years ago. A U.S. manufacturer produced a wireless control system called "Train Engineer". It was primarily intended as a trackside power supply regulated by wireless signals to control a train's speed. However, if the casing was removed then the power supply could be fitted to an individual locomotive directly controlling the motor input on that loco and collecting full track power. Later versions of the transmitter had ten channels each with ten frequencies, giving control of up to 100 locomotives.

The individual power supplies basically took the place of a decoder with full voltage power supplied to the rails. The system was a little cumbersome in that selecting a new channel/frequency was time consuming and not as simple as selecting a loco address on a DCC handset. Early versions of the "Train Engineer" had only two channels each with just five frequencies and these were more manageable.

A "h.o." scale version was released and from memory a loco was "selected" by way of placing a magnet momentarily on the cab roof which closed a circuit in the loco thus activating it to respond to the Train Engineer signal. This did not progress very far and the range was dropped from production not long after release.

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