Radio Control and Battery Power for Model Railroads

S-CAB works with Blunami

12/22/2022

SoundTraxx has added Bluetooth (BT) radio communication to their TSU-2200 decoder. My initial reaction was to tell SoundTraxx I had no reason to buy or promote Blunami. S-CAB already added radio communication to SoundTraxx decoders and an S-CAB hand-held throttle was a more convenient way to operate model trains than using an Apple iPhone.

Then, I received an inquiry from an S-CAB user (I'll call him Bill) who had purchased Blunami and was impressed with the capability added by Bluetooth communication, particularly reading and writing decoder CVs (configuration variables); something that has always been a frustrating aspect of DCC. Bill wanted to operate his loco with S-CAB throttle but use his iPhone with Bluetooth for decoder programming and for demos in large railroading venues where radio interference can be a problem. He sent me his decoder and I decided to learn what I could about Blunami.

Background

I'll digress here with some background information that may help later in this blog.
Bluetooth: Bluetooth (BT) is a radio communication standard first proposed in 1996 by Intel, Ericsson, and Nokia to support short-range wireless connectivity and facilitate collaboration between different products and industries. The standard has evolved as technology improved and today, Bluetooth support is included in all popular mobile phones and most personal computers (PCs).
BlueRail Trains: My first contact from BlueRail Trains was January 2016 when they were working on FCC certification of their first Bluetooth product. I've been watching their progress for 7 years. Their collaboration with SoundTraxx and release of the Blunami product is a significant accomplishment.
U-Blox: U-Blox is a global provider of positioning and wireless communication technologies that
acquired Rigado’s Bluetooth modules business in July 2019. Since BlueRail's early development used Rigado's Bluetooth radio module, their firmware obviously carried over to the U-Blox chip that we find in Blunami.
SoundTraxx: Sophisticated radio communication has been added to the TSU-2200 decoder while retaining the option of standard DCC control. The magic is embedded in firmware within the U-Blox radio module.

Blunami

First step, remove the wrapper and void the warranty. Sorry Bill.

Blunami circuit board looks like a TSU-2000 except for the addition of a small radio receiver produced by a company called U-Blox.
As SoundTraxx explains, if no Bluetooth radio signal is detected, Blunami can be controlled by track DCC. If BT radio is detected, track DCC is replaced by BT communication.

Adding S-CAB Radio

Why not replace track DCC with S-CAB radio input?
Similar to TSU-2200, Blunami should treat S-CAB radio input as if it is track DCC. The two radios work at different frequencies, so radio interference is not a problem and BT should prevail if both are detected, just as it does for track DCC.

Testing

Rather than risk Bill's decoder, I decided to make peace with SoundTraxx and purchase my own Blunami. I checked with George Bogatiuk, who agreed, adding S-CAB radio to Blunami was feasible. Instead of using an Apple iPhone, I bought a refurbished 4th generation iPad for $60 on eBay. It's awkward to hold and definitely not a practical choice for hand-held operation, but the larger screen is nice for desktop tasks such as decoder configuration management.

While waiting for iPad delivery, I went ahead with an S-CAB radio mod. exactly as done for a TSU-2200. This disables track DCC and replaces it with DCC signal from the S-CAB radio receiver. No functionality is lost because battery power disconnects decoder's rail inputs (red and black wires) and uses these connections for battery power supply. This eliminates any possibility of DCC communication from the track.

Conversion was successful. The S-CAB throttle operated Blunami. If S-CAB worked, Bill had agreed to buy a new throttle operating at 918.12 MHz, which avoids interference with NCE wireless throttles (the most common source of interference at train shows). 918.12 MHz is also compatible with CVP Products T-5000 throttle.

Starting the refurbished iPad required an Apple account and the usual new computer setup tasks. That done, downloading and installing BlueRail's Blunami train control app from Apple store was trouble-free. However, the app will not run on old versions of Apple's iOS operating system. It will run on iPhones and iPads with iOS version 9 and later. It cannot be installed on Android devices.

To avoid confusion, "Blunami" will be used as decoder name. I'll refer to the Blunami app as "iPad app".

To begin tests, S-CAB throttle was turned off. Would iPad app find and connect to battery powered Blunami that had been modified for S-CAB radio?

The answer was yes. The iPad app connected when decoder battery power was turned on.
Decoder data was displayed and there was an opportunity to enter loco name and define a few loco characteristics.
Control commands worked.
Decoder CVs could be viewed and edited.
The iPad app saved decoder data.

Inter-operability tests were performed, beginning with iPad in control of the decoder.

When S-CAB throttle was turned on, nothing happened. S-CAB commands were ignored and iPad commands continued to work without problem, as specified.
When iPad was turned off, S-CAB did not automatically take control of the decoder.
However, S-CAB throttle did gain control when the Blunami was rebooted (power off, then on).
When Blunami app. was turned on, it eventually connected and took control away from S-CAB.

At this point, convinced that S-CAB worked with Blunami and did not interfere with Bluetooth capability, I converted Bill's decoder and investigated CV programming, which took me deeper into the iPad Blunami app.

Working with iPad App

SoundTraxx website has decoder documentation but virtually no documentation for the Bluetooth app. That's expected, since BlueRail Trains, not SoundTraxx, is responsible for iPad app. BlueRail's website has good information for older products, some of which is applicable to Blunami, but lacks up-to-date documentation. BlueRail's user interface is reasonably intuitive and help customizing the user interface was quick and easy.

SoundTraxx decoders support flexible assignment of decoder functions to throttle buttons (physical keys). On iPhone or iPad, buttons are screen images, which BlueRail depicts as tabs with labels corresponding to SoundTraxx default assignments. For backward compatibility and consistency of different decoders, S-CAB uses button 5 for battery-off command. For SoundTraxx decoders, this requires that button 5 be mapped to decoder function FX4. For decoders with diesel sounds, SoundTraxx uses button 5 for a command to increase prime mover speed sound and BlueRail displays the tab with "RPM+" as its label. When asked the question, David Rees at BlueRail explained the simple method used for editing function tab labels.

Function tabs are accessed as a slide-out menu from left side of the loco control home page. An additional swipe right drags a duplicate set of editable tabs into view.

Bill was not concerned by loss of RPM+ and RPM-. These tabs alter sound to simulate prime mover speed changes, but do not affect loco motion.

All CV programming to change function mapping was done with the Blunami app.

Conclusion

Contrary to my initial response, I will support Blunami decoders and offer them bundled with S-CAB radio. BlueRail's app solves the problem of reading CVs while operating on battery power. It is an excellent tool for managing decoder configuration and tuning performance. By adding S-CAB radio, users can combine the best features of both technologies. Bluetooth for configuring the decoder; a hand-held throttle for operating trains.

21MTC Connector

8/8/2021

21MTC Interface

The 21MTC interface allows a decoder with appropriate socket to plug directly onto a compatible header within the model. This eliminates the traditional cable connection, which is convenient for both decoder manufacturer and user, but is not so friendly when installing battery power and radio control. It is reasonable to expect decoders using 21MTC to be less expensive than decoders with wire harnesses. It also requires more headroom than decoders with JST 9-pin connectors, which will be helpful if manufacturers increase clearance above motor mechanism.

S-CAB Radio Receivers with 21MTC Header

S-CAB's MB-GP-NEM motherboards (both long and short versions) support 21MTC decoders, but are intended for use in HO scale diesel locos. Adding a 21MTC connector to an S-CAB radio receiver provides an option to choose less expensive and/or interchangeable decoders as well as installing battery power in a broader range of models.

Interface Description

NMRA standard S-9.1.1.3 lists pin assignments on page 6, Dec 1, 2020 version. Although it is best if a user skips the details, 3 pins are used to implement a direct radio connection (DRC) to the decoder.

Pin 16 is decoder positive (positive common)
Pin 20 is decoder ground
Pin 12, which is not mandatory and unlikely to be used by decoder manufacturers, is used for S-CAB radio data connection.

Interchangeable Decoders

Connecting radio data through the NEM socket improves modularity by allowing decoders with DRC to be removed, replaced, or changed without involving the receiver. The following decoders are available with DRC:

NCE D16MTC
SoundTraxx ECO-21PNEM
SoundTraxx TSU-21PNEM

External Connections

The 9-pin JST socket is consistent with NMRA standard. Additional wired connections are provided for speaker, and functions F5 and F6.

Pin Cross-reference

The following table lists MTC connections used by LXR-NEM. "NMRA Name" corresponds with NMRA standard but manufacturers use their own terminology. Most NCE decoders provide four function outputs; front and rear light, F1 and F2. SoundTraxx NEM decoders have six function outputs; front and rear lights, FX3, FX4, FX5, FX6.

Application

The LXR-NEM radio receiver replaces factory-installed circuit boards and provides radio control for models with on-board battery power. Track power must be disconnected from decoder's rail inputs (red and black leads) before connecting battery power. Although there is no benefit, radio control can be used with track power (DC or DCC), in which case, decoder rail inputs remain connected to track pickups.

If 21MTC becomes popular, models with factory-installed circuit boards and 21-pin headers can be anticipated; with or without a decoder. If included, a factory-installed decoder is connected to operate with track DCC power. A decoder using direct radio connect (DRC) will not respond to DCC from the rails. Consequently, a factory-installed circuit board with 21-pin header is not helpful and best if replaced with either LXR-NEM receiver or MB-GP-NEM motherboard when using a decoder with MTC socket.

What happens if a decoder with S-CAB DRC is plugged into a factory-installed 21-pin header?
Short answer: Nothing. The decoder will have power from wheel pickups, but no control.
Will it be damaged? No.

Will it Fit?

S-9.1.1.3 defines maximum dimension of MTC decoders:
Length: 30 mm (1.18"), Width: 15.5 mm (0.61"), Height: 6.5 mm (0.26")
LXR-NEM is 2.4 mm (0.1") thick.
If mounted horizontally, allow 8.9 mm (0.35") vertical clearance.

Will MTC Decoders be Useful?

Pro

Plug compatible and interchangeable.
Maximum dimension is defined by standard.
Potentially less expensive decoder.
Decoder works well with S-CAB motherboard.

Con

Vertical clearance may be a problem.
LXR-NEM offers no benefit if model has factory-installed MTC header.

Battery Power and Radio Control in a Plymouth industrial switcher

12/11/2020

The Model

Walther’s HO model of a Plymouth industrial switcher is small. It was initially offered as a DC version and later as DCC-only. A circuit board mounted in loco cab roof includes motor control and lights. The DCC version is an ESU non-sound decoder, which makes an easy conversion to S-CAB battery power and radio control.
We have examples by two S-CAB users. Steve likes sound, Stan prefers non-sound decoders. After some initial confusion, Steve realized he had started with a DC version and, too late, we realized Stan began with a DCC-only version.

Steve’s Installation

This model has a neat decoder installed in roof of drivers cab but, for battery power, it needs a trailing vehicle to carry a battery. As Steve points out the following "battery car" can be any box car, passenger coach, covered hopper, loaded gondola, or loaded flat of any choice. He selected a historical prototype totally in character with his layout.

As Steve explains:

for this Installation I choose to model the last passenger excursion train on the Hetch Hetchy Railroad. It took place on May 25th, 1947 when members of the Railroad & Locomotive Historical Society road in Sierra Railroad passenger car # 6 behind HHRR Plymouth locomotive #1171 from Groveland to Mather CA and return. This 64+ mile round trip took place over rails that had been all but abandoned for several years and proceeded into some of the most wild and dangerous landscapes in the country. If anything had happened to the equipment the participants would have had to walk out from the wilderness of Yosemite National Park without benefit of phone lines or paved roads.

Since Steve was converting a DC version of the model and planned to install a sound decoder, the factory-installed circuit board initially appeared of little use except as a convenient way to make connections.

A BPS-v4 battery power supply, battery, sound decoder, speaker and S-CAB radio receiver would all be installed in the passenger car.
Steve continues,

Once the cab shell is removed, the front edge of the cab circuit board shows four terminals labeled TRKL (Track Left), TRKR (Track Right), M+ (Motor +) and M- (Motor -). Six wires from the loco end up in a bird’s nest just under the board. To unravel this mess, remove one screw holding the circuit board and loosen the other so that the board can be twisted counterclockwise. Four wires are rail power pickup, two from each wheel set, and two are motor connections. Since battery power will be substituted for track power, the 4 wires between wheels and circuit board can be removed. Rail power is used for battery charging but I chose to use passenger car trucks for power pick-up and avoid having extra wires from loco to the following car. Two wires from the decoder must be connected to the loco's motor. Connect decoder orange wire to the wire going to motor from M+ and decoder gray to wire going to motor from M-. (Hint: If loco runs backwards in response to a forward command, reverse the connections.)

I used a TCS two wire mini connector with leads of sufficient length that the actual connection was made well within the space in the following car. This allows simplifies connect or disconnect of the loco. Previously on other models I had attempted to connect in the space between loco and following car as that is where the brake line would be connected. That turns out to be difficult. Not only is space severely restricted but when attempted the cars tend to tip over or uncouple.

Lastly, the simplest way to recharge the battery is to install one or two trucks on the following car that have power pick up from the rails. The leads from these trucks are then connected to the gray wires on the Battery Power Supply.

Another reason for not discarding the model’s circuit board is two tiny LED’s on the cab roof that function as forward and reverse lights. These somehow continue to work even without attaching any wires from the decoder. And that’s it. Simple, fast, clean and runs like a top.

Stan's First Installation

As mentioned earlier, Stan was too far into his first installation before he and I realized he had started with a DCC version and could have used the factory-installed decoder. He actually used an NCE D13J decoder bundled with an S-CAB radio receiver together with a BPS battery power supply all installed in a trailing coal car. He describes his installation in the following video.
https://youtu.be/ryinlRLmx9A.

Stan's Second Installation

For illustration to right, the decoder board has been temporarily mounted upside down. Wires from loco wheels (track power pick-up) have been disconnected from the loco decoder board and will be replaced with DCC connections from the S-CAB radio receiver. No change is required for motor connections.

This installation uses the factory-installed decoder by adding a DCC booster to the S-CAB radio receiver. As far as the decoder is concerned, the DCC booster output is no different to DCC received from the track.

The loco's rail power connections can be removed or rerouted to the battery car. As Steve observed, this requires 4 wires between battery car and loco, but it eliminates the need for battery car trucks with power pick-up.

Video: https://youtu.be/nNyWBvL73D0

Installation using S-CAB motherboard

2/24/2019

Introduction

The motherboard concept has been discussed elsewhere. It is intended to simplify installation of an S-CAB battery powered, radio-controlled system in small-scale locos. The purpose of this document is to report its application in a HO-scale Atlas-Kato GP-7. For brevity, we’ll skip the details and go directly to the result.

Ready to roll

This loco is ready to roll. All it needs is a body shell, which slides over the installation onto the chassis without much effort. It’s shown naked and annotated as an introduction to use of an S-CAB motherboard.

For this installation, all components are mounted on the motherboard, including loco’s lights. This arrangement is a convenient characteristic of a GP-7 and other high-nose diesels. Consequently, no wiring connects to the body shell.

The motherboard assembly is completed and tested on the workbench. It is then mounted on the loco chassis and permanent connections made to motor and truck wheel wipers. Additional tests are completed before replacing the body shell. For example, does the forward direction command cause forward motion and operate the headlight.

Testing

No need to replace the body shell for a work-bench test-run. No need for track or power. Just turn on BPS battery power using a magnet wand and the loco (with or without shell) is ready to roll but be careful it does not end up on the floor.

Aside from running off bench-top, this is a low-risk test. The motherboard was tested before making chassis connections and there is no external power source to cause trouble.

A track test is higher risk. First, try it with no track power, which is not much different from a bench test, except the loco can be operated more thoroughly if its battery has enough charge. To test battery charging, turn on track power. This is the step where serious trouble can occur, which is a good reason to do it without the body shell. Common mistakes are forgetting to isolate motor terminals from loco frame, bad choice of power supply, shorted truck wipers, etc.

A green LED on BPS-v4 indicates if battery is charging. It's not obvious because the green LED is on the underside when BPS is mounted on the motherboard. The BPS is oriented so that reed switches are topside where they can be activated by a magnet wand. Another good test is turn off battery power (blue LED off) before turning on track power. BPS starts automatically when track power turns on.

Replacing body

This is a critical step in any installation. Will the lid close? The motherboard helps by enabling test fitting more easily throughout the project. Wiring clutter is eliminated, components don’t rearrange themselves by accident, and tight spots inside body shell can often be trimmed. The most difficult issue is headroom. Is there enough clearance above the loco’s mechanism for the motherboard assembly? This question must be addressed when planning an installation.

Done

Good news. The lid fits.

Motherboard Assembly

The following components are mounted on the motherboard:

BPS-v4: Provides 11 volt power supply from 3.7 volt LiPo battery. Includes battery charging from track or other external power
Battery: A 1P-420 LiPo cell with integrated 6 amp fuse
Sound Decoder: A SoundTraxx TSU-1100 sound decoder
Radio receiver: An S-CAB radio receiver integrated with decoder
Speaker: A 1 watt mini-cube
Head and rear lights: Surface mount LEDs with 4700 ohm resistor

With no components attached to the body shell, there is no wiring to prevent its removal. Easy preparation for painting this model is an immediate benefit.

Maintenance

Battery replacement: The battery is best secured to the motherboard by a removable method that does not leave a mess to clean up. Kapton tape is good and leaves no residue. Double sided adhesive tape is not recommended. When freed, lift the battery and lever its plug from BPS socket with tweezers or needle nose pliers. Since the battery leads are deliberately short (about ¾”) and the plug is tight, pulling by the battery may remove the battery and leave its plug stuck in BPS socket.

If the loco’s mechanism needs maintenance, unsolder motor and truck pickup connections from the motherboard. If glued in place, there are 2 locations to pry loose and the assembly lifts off as a unit. If held in place by Kapton tape (author’s preference), cut and/or peel off the tape to remove the assembly.

Conclusion

This installation was performed by John Lloyd in four identical models for a Canadian customer. The motherboard was designed to fit the GP-7 as well as a popular selection of North American diesel-electric locomotives. EMD GP, F and E class locos are good candidates. As we gain experience, the motherboard may be provided as basic, partial and fully assembled versions.

S-CAB Motherboard

2/22/2019

What is a Motherboard?

A motherboard is a circuit board onto which various sub-units ("modules") are mounted. Connectors and circuit traces on the motherboard facilitate modularity and eliminate wiring between modules.

MB-GP-v2: S-CAB installation motherboard

MB-GP-v2 fits a broad selection of HO scale, US style diesel-electric locos; EMD GP series, for example, often called "Geeps". It measures 0.67” wide, 5.75” long (17 x 146 mm), which is small enough for a GP-7 installation, yet large enough to accommodate a complete battery powered, radio controlled, ready-to-run system using commercially available DCC sound or non-sound decoders.

In addition to mounting BPS battery power supply, battery, radio receiver and decoder, the board includes terminals for external connections; track power pick-up, motor, LED lights and speaker. Depending on loco, lights and speaker can be mounted on the motherboard, which eliminates wiring connected to loco’s body shell and requires only 4 connections (power pick-up and motor) to loco chassis/frame.

Assembly

A 9-pin JST connector is provided for decoders with NMRA-compliant socket. No wiring harness is required. Decoders without a compliant JST socket require soldered connections and careful reference to decoder documentation. The BPS-v4 battery power supply can be mounted directly on motherboard (as in photo) or with a wired connection.

Add a decoder: This motherboard version requires either a SoundTraxx or NCE decoder with integrated S-CAB receiver. As shown in photo, no wiring is required for a SoundTraxx TSU-2200 decoder; just plug it in.

Plug in a battery: Depending on loco's space, 420, 800 or 1000 mAh batteries fit on the motherboard. If clearance between top of motor and roof interior permits, a 2P battery may be possible. However, 1P and 2P-420 are the only choices for HO scale, narrow-hooded GPs. The following photo includes a 1P-420 battery. Note the 3/4” battery leads, which will be default choice for batteries included with a motherboard installation.

Application

For HO models, application depends on the model’s prototype and its manufacturer. S-scale modelers should find the motherboard an easy fit. Fully assembled with a 1P-420 battery, the motherboard requires 0.44” (11.2 mm) headroom. Allow 12 mm (approx 0.5") clearance if using a 2P-420 battery.

Models with limited headroom, motor mounted high on the chassis, for example, are not good candidates for this motherboard. Small yard switchers (SW series) in HO scale can also be eliminated as candidates. This still leaves a large selection of diesel prototypes for which this motherboard is applicable. However, creating unobstructed space can be a challenge. Factory installed circuit boards, over-sized metal castings, light-pipes, existing wiring and other clutter may have to be removed.

Example - Atlas-Kato GP-7 Installation

This example used version 1 of the motherboard. No modification of loco chassis was required. The shell required some work. Light pipes were removed and interior of body shell decluttered. Lights and speaker were mounted on motherboard.

The lens portion of light pipes was retained and glued into body shell.

Components used: TSU-1100 decoder, S-CAB radio receiver, 1P-420 battery, BPS battery power supply, mini-cube speaker, LED headlight and rear light.

NCE and SoundTraxx manufacture decoders referenced in this blog. Their proprietary rights, including product names, is acknowledged.

New Battery Sizes

10/7/2018

Effective October 31, 2018, we introduce two new battery sizes and phase out BPS-300 and BPS-500 batteries.

New Batteries

BPS-420
This is the battery of choice for HO-scale narrow-hooded diesels (GP series, for example). It replaces BPS-300 and BPS-500 batteries which will be discontinued.

BPS-1000
This adds a larger cell to the BPS battery range. It is intended for use in steam loco tenders and in S-scale diesel locos.

BPS-850
There is no change here. This is the most popular BPS battery used for HO-scale full-width diesels (E and F series, for example) most steam loco tenders and all larger scales (On30, On3, S). The new BPS-1000 is expected to replace it in some of these applications.

Discontinued

The 300 mAh cell is no longer available from manufacturer and is replaced by higher capacity 420 mAh cell which is same width and half an inch longer. The BPS-500 cell, which has been sourced from a different supplier, is replaced by the 420 so that all LiPo cells can be purchased from the same manufacturer.

Standard Configurations

Each cell size will be available as 1P and 2P back-to-back assemblies. Integrated fuse protection is standardized at 6 amps to be compatible with latest version of Battery Power Supply (BPS-v4) which requires up to 4 amps battery current at full output.
"P" indicates cells are connected in parallel. Voltage is same as single cell (nominally 3.7 volts) and capacity adds so a 2P-420 battery provides 840 mAh.
25C indicates cell is rated for high discharge; specifically, 25 times cell capacity. That is, 25 x 420 mA equals 10.5 amps from one cell and 21 amps from 2 cells in parallel. This should remove any doubts regarding the importance of embedded fuse protection.

Custom Configurations

When a back-to-back arrangement is too thick for some applications, cells can be wired with an arbitrary length of wire between them. With the arrangement illustrated (right) cells share one fuse as is done with a back-to-back assembly. However, this leaves one cell with external wiring and no internal protection. Although the risk is low, this practice will be discontinued.

In future, separated 2P arrangements will use two 1P batteries (each with fuse) connected in parallel. One precaution with this arrangement is make sure cell voltages are approximately equal before connecting. The equalizing current surge created by a large voltage difference may be sufficient to blow one or both fuses. Be sure to connect positive to positive.

BPS v4: A new addition to the BPS family

9/24/2017

This fourth generation BPS power supply is intended for on-board battery power installations requiring up to 1 amp from a package small enough for installation in HO, On3, On30 models. It's also a good choice for S scale models with efficient can-type motors.

BPS v4 Top View

Energy is provided by one or more lithium polymer (LiPo) cells connected in parallel and higher voltage output is produced electronically using a step-up converter. Battery charging, protection and switching are also included in one, small double-sided circuit board assembly.

BPS v4 Side View

Improvements

Size: 1.4”x0.7”x0.4” (35 x 17 x 10 mm)
20% size reduction
11 volt output with overload protection
1 amp output. Double previous capability
Battery power On, Off switches included.
Battery On/Off indication (blue LED

Plug in a battery for a complete on-board power supply

Battery switches are on the circuit board

Battery Charging

Battery charging power can be from track or a connector.

To use track power, connect gray wires to rail pick-up. For a plug-in supply, install a 2-pin connector on a loco and connect gray leads.

Power source can be DC, DCC or AC

DC Voltage can be from 6.5 to 16 volts.
Keep AC voltage below 12 volts (RMS).
Peak voltage must not exceed 30 volts.

Warning: Many hobby-type DC train controllers do not produce filtered DC output and peak voltage can be as high as 3 times a DC measurement.

6 amp Battery Fuse

Batteries for previous versions of BPS included a 3.5 amp fuse and used insulation displacement battery plugs.
At 1 amp load, BPS v4 consumes up to 4 amps from the battery, which requires a 6 amp battery fuse, heavier leads and a crimp-style plug.

Battery Bypass

Power can flow from input to output though battery bypass. It can also flow from battery via battery switch to step-up converter.

The path that delivers higher output voltage supplies most (or all) output power.

No input: battery provides all output.
No battery: input must supply all output.

Since the step-up converter produces 11 volts, output is supplied by the battery when bypass voltage drops below this value.

If track voltage is high enough (12 or more volts), bypass voltage exceeds 11 volts and track power supplies output as well as battery charging. Battery energy is consumed only when needed to substitute for track power.

BPS is the ultimate keep-alive power source.

A small battery can sustain a long operating session with some help from track power.

Over-voltage and short-circuit protection

The protection block in the above diagram protects against three abnormal conditions.

Excessive input voltage: Turns off input when voltage exceeds 20 volts and restarts at 18.5 volts. Since protection is virtually instantaneous, voltage spikes, peaks, as well as sustained conditions are controlled.
Overload: Rectifier output is limited to 1.2 amps, which is comfortably within the 2 amp rating of the rectifier diodes.
Short-circuit: Fast trip (less than 1/4 msec.) occurs at 2 amps.

Wiring

BPS v4 has a 5-pin JST connector or directly soldered leads. Previous wire colors are retained and pin labels on circuit board are SDN (brown), IN1 and IN2 (gray), OUT (red), GND (black).

An installation kit is generally delivered with OUT, GND and SDN leads already connected to a decoder.

Decoder Off command

By default, S-CAB installations with SoundTraxx or NCE decoders are set up to use a decoder ‘F5’ command to shut down battery power. This requires connection of the BPS shut-down wire (brown) to the appropriate decoder function output as shown in the above diagram. For SoundTraxx, this is a brown wire (output FX4); for NCE decoder, the wire color is purple/violet.

BPS as a general source of on-board power

If a locomotive or traction model needs on-board DC power, BPS can do the job so long as demand does not exceed 1 amp. Temporary overloads up to 1.2 amps are okay. Standard output voltage is 11 volts, but can be customized within a range from 9 to 12 volts.

Atlas-Kato GP-7 Installation

8/4/2016

Introduced 1987-89, these models, which were manufactured by Kato and sold by Atlas, have excellent mechanisms and are great candidates for S-CAB battery power and radio control. The cast metal frame is heavy enough for traction, but leaves space above the motor for electronics and battery. With some careful trimming of the body shell, this space can be extended the full length of the loco. The completed installation (photo left) shows no evidence of any modification to the loco.

This description illustrates use of a circuit board (sometimes called a "motherboard") to simplify installation and complete as much work and testing as possible on the workbench. Wiring within the loco is minimized by mounting front and rear lights on the components circuit board. As a result, there are no wires connected to the body shell, which can be removed and replaced without restriction. The project involves modification of the loco body and frame, assembly and test of two subsystems and finally, installation.

Loco Modifications

Subsystems

Assembly

Traces on the loco interface circuit board are used for rail pickup connections to front and rear trucks. If convenient, motor connections can also be to this board, which makes a total of 6 wires (2 to each truck and 2 to the motor) to be disconnected should it ever be necessary to remove motor or trucks.

The component board sits on top of the interface board and is held in place by electrical tape.

Since LED lights are mounted on the components board, there are no connections to the loco body, which simply slips into place to complete the installation.

On3 Climax Battery Power Installation

8/4/2016

I occasionally hear from an S-CAB user (Michael) who models On3. Since he's an innovative guy, as well as a skilled modeler, his feedback is always interesting. His latest effort is an S-CAB radio and BPS battery power supply installation for a Climax loco.

Here are Michael's comments:

Thought you would like to see my latest car (trailing) for the battery and BPS electronics board. The decoder/wireless/speaker are in the Climax but I need a car for the battery etc.

You will note the two pipes (lower left with the chain over the pipes) – these are for power to the loco – there are two small plugs on the loco on the same side, so thin wires will do the connection.

Also, on the top rear of the tank are two small pipes – one higher than the other – these are the recharge points. Just plug in the power supply and the recharge will start. The tank is not firmly secured on the flat car just sort of held in position with the chains. The barrels etc are glued down. The chain (not glued) at the back is part of the chain keeping the tank in position.

I have two magnetic reed switches (the ones you supplied) glued up at the top inside both ends of the tank. So I just wipe with the magnetic wand for start and stop.

In the background is another battery car – the tank.

Full S-CAB Installation in On30 Forney

8/3/2016

Project

This is a complete battery power, radio control, sound installation in a Bachmann On30 Forney. The entire system fits under the coal load with the battery barely visible where it protrudes on the floor of the driver's cab.

Preparation

Since this model already has a factory-installed non-sound decoder, the hope is that installation can be simplified by use of existing wiring to motor, headlight and driver wheel rail pick-ups. It's also convenient that the fuel bunker is a separate molding attached to the frame by 4 screws.

Lifting the lid, we find a relatively large circuit board with a standard 8-pin decoder socket, decoder and speaker. None of this is reusable, but the expected 6 wires are nicely accessible, despite non-standard color coding, which fortunately is labeled on the circuit board.

Begin by clearing the clutter and planning efficient use of available space. Laying the battery flat on the loco frame and using space in the cab accommodates a 500 mAh battery. Obviously, the speaker must be mounted elsewhere. Internal space within the fuel bunker is 40 mm long, 40 mm wide and 22 mm high. Since the battery is approx. 6 mm thick, the challenge is to fit a sound decoder, S-CAB radio receiver, BPS battery power supply and speaker in the remaining 16 mm above the battery. Several arrangements are possible, but I eventually decided on a major rework of the BPS circuit board to make it a "middle layer", with radio receiver and speaker mounted at the top of the assembly. This gives good speaker acoustics and keeps the radio antenna clear of metal surfaces and wire tangles.

Modified BPS board

BPS has 2 standard arrangements. The long configuration can be cut in half and the 2 halves mounted back to back to form a short configuration.

BPS-L
This is the standard, one-sided BPS circuit board

Because the Forney space is square, 2 halves of the BPS board are arranged side-by-side, wired with a few extra connections, and glued with epoxy, which was never considered in the original design. I remember something about "necessity being the mother of invention". It's not something I expect a user or even an experienced installer to attempt, but having done it for this project, it could be a special-order item.

Installation

At this point we have an installation plan and a modified BPS circuit board. Let's determine if everything fits.

First, add (using super glue) a styrene plastic frame to hold battery (the slot at bottom) and modified BPS board above between the side tabs.

The trail fit looks good, but there's still a third layer of components and some awkward wiring to fit into the remaining space.

Here's a closeup photo of the completed installation.

And yes, . . .
. . . the lid fits.
The battery is visible though the open cab door, but there is no externally visible change to the model.

Wiring

What to do with a tangle of wires is often considered too late in an installation. For this model, the entire installation must fit a space measuring 1.575" square (40 mm) and 0.79" high (20 mm). The planning process included component placement as well as arranging wires to minimize both quantity and length while still being able to make the required connections. The final arrangement is illustrated below. There are 3 unused decoder function outputs (green, yellow and brown wires) where leads have been shortened, but are still accessible for (unlikely) future use.

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Author

I'm a retired electrical engineer, but still spending more time on engineering than on my layout. These days, it's mostly about applying radio control and battery power on smaller scale layouts (HO, On3, On30)

Background

Blunami

Adding S-CAB Radio

Testing

Working with iPad App

Conclusion

21MTC Interface

S-CAB Radio Receivers with 21MTC Header

Interface Description

Interchangeable Decoders

External Connections

Pin Cross-reference

Application

Will it Fit?

Will MTC Decoders be Useful?

Pro

Con

The Model

​Steve’s Installation

Stan's First Installation

Stan's Second Installation

Introduction

Ready to roll

Testing

Replacing body

Done

Motherboard Assembly

Maintenance

Conclusion

What is a Motherboard?

Assembly

Application

Example - Atlas-Kato GP-7 Installation

New Batteries

Discontinued

Standard Configurations

Custom Configurations

Improvements

​Battery Charging

6 amp Battery Fuse

​Battery Bypass

Over-voltage and short-circuit protection

Wiring

Decoder Off command

BPS as a general source of on-board power

Loco Modifications

Subsystems

Assembly

Project

Preparation

Modified BPS board

Installation

Wiring

Author

Categories

Archives

Steve’s Installation

Battery Charging

Battery Bypass