Edit:23 juil. 2018, Cre:28 juin 2009

RCS train control in 2.4GHz

In search of a radio control for garden railway, I got interested by the first Australian RCS control system in 27 MHz, which I thought was well designed and was also compliant with European radio regulation (which was not the case of US systems). I got to the point to make schematics and explanations for this 27 MHz system.

Then appeared 2.4 GHz system which very quickly dominated the R/C market due to their more reliable transmission.
In the garden train use, while distances are short, 27 MHz had some difficulties with the tunnels and also with steel locomotive (live steam), so all 27 MHz train systems soon loose most of its market to 2.4 GHz standard R/C systems.

After contemplating the idea to abandon the garden train control market, RCS finally cames in 2013 with a new system in 2.4 GHz using Deltang modules, with sufficient flexibility to accept either a standard 2.4 GHz transmitter or their own transmitter which have an ergonomy better adapted to garden trains control. This new system reuse the philosophy of the former system and keep the relatively raw external design.
However, in the process, the system to radio control network accessories (switches, lights, decoupler, etc.) was abandoned.

It shall be noted that all 2.4 GHz systems uses complex transmission protocol to check the transmission packets and jump from one frequency to another. Unfortunately, as the first company to issue 2.4 GHz R/C radios (Spektrum) have protected their protocols, this have driven their competitors to develop other non compatible protocols. The Spektrum protocol have itself evolved for data reporting. This means that both transmitter and receiver are not compatible within these different systems (while it exists multi-protocol receivers).

The RCS system use the Spektrum DMS2 protocol.

Tx : Radio transmitter
Rx : Radio receiver: signal output RC servo type
Esc : Electronic speed controller: specific for trains
Snd : Sound card generator

The general philosophy of the RCS system is to have one lightweight (150g) and compact transmitter per running loco. Low cost of transmitters will maintain overall cost way below the cost any DCC rail controlled system.

One RCS transmitter can bind with as many receivers as needed. Binding is done with a cable or automatically at startup depending from the Receiver model.

RCS no longer propose radio system for accessories (switches/points, fixed lighting and sound systems)

What is a train ESC (Electronic Speed Controller) ?

There are two kinds of RC devices, thoses with main motor which goes only forward, like airplane or helicopter and those which could go in both directions, like boats or trains.
Hence RC radio with sticks are adjusted with the 0 power at the stick bottom position or 0 power at the stickcenter position.
For trains, if there is any spring(s) to return the stick to 0, it shall be removed.

For trains, there are two ESC types :

  • The models with 'center off' where only one channel is used for both directions. With stick radios, the 0 power will be adjusted in the center, going forward is done with stick on top and reverse with stick on bottom.
  • The other models, which are driven similarly to most live steam locomotive controllers (where the reversing valve is separated from the power valve), have different channels for the power and direction.
This is used to have a more realistic operation. However, this means that power operating need two radio channels instead of one, and also need two commands devices (sticks, knob, selector, etc.). In some ESC, switching direction may need to have the power near 0 to effectively change direction, as quick reverse may drive to derailment on long trains (as can do quick stop).

Rotating knobs train transmitters works similarly with both solutions.
Some train ESC are equipped with auxiliary outputs to handle accessories signals (typically bell and whistle, couplers or car lights). The RC signals are proportionals and they may need to be relayed for use in sound cards.

RCS site :

Other systems

Deltang proposes integrated Receiver and ESC. Accessories transmitters and receivers available. Web site have large margin for improvement (no menu !).
RCTrains Also use Deltang modules

(c) Pierre ROUZEAU
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