Testing the TMCC/Legacy Track Output Signal

The 455 KHz signal coming out of the “Track” or “U” thumbscrew on a TMCC/Legacy Base is too high a frequency for most handheld digital voltmeters to read.  I just “invented” a very simple test to see if signal is coming out the Track terminal if you have a common digital voltmeter.

1.  Disconnect the Base from the track and the Serial output 9-pin.

2.  Set your digital voltmeter to the 2V (2000 mV) scale.  Turn on the meter!

3.  Connect a resistor of almost any value (I tested 100 ohms to 47,000 ohms) from pin 5 on the 9-pin plug (lower right corner for Legacy Base; upper left for TMCC Base) to the Track thumbscrew.

4.  Connect a diode – 1N400x or 1N914/4148 – from the Track thumbscrew to one lead of your digital voltmeter.

5.  Connect the other lead of your digital voltmeter to pin 5/resistor.

6.  Apply AC power to the Base.

7.  Read 1.5-2.0VDC on the meter.  The polarity of the reading will depend upon which way you install the diode, but both orientations of the diode will work.

For my testing I saw about 2.0VDC with the 1N914/1N4148 fast small-signal diode, and about 1.5VDC with a 1N4004 slower power diode.

The diode halfwave rectifies the 455 KHz track signal so that your low-cost digital meter will read a DC voltage.  This way the meter doesn’t need to have any high-performance AC specs to detect the track signal.

The resistor is absolutely necessary because of the output capacitor in series with the thumbscrew inside the Base!!  Without the resistor, this internal capacitor “absorbs” the DC offset created by the diode before the DC offset reaches the thumbscrew terminal.

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My Big Kludge power supply for G-gauge

The supply was originally a fixed 28V 8 amp regulated DC supply that I built in graduate school in 1970.  Since I didn’t have the proper transformer originally – only one with a 24V output – I had added a second smaller transformer in series.

For the G-gauge application I wanted 0-24V adjustable.  The original setup could be made adjustable, but the output transistors couldn’t handle the power drop required for low voltage outputs.  The output transistors must “burn off” the excess power that is being dumped when the output voltage is reduced.  In this case, I might have up to 6 amps with a drop across the regulator transistors of 30+ volts – close to 200 watts!

My first step was to cut down the output voltage by removing that extra transformer from the circuit.  This meant I had a lower starting voltage, and hence less drop.

My regulator (a uA723) driving the output transistors wasn’t very sophisticated – a marginal overcurrent protection without any

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temperature sensing.  I decided to take an easy way out by adding a couple of high-power regulator chips to form a cascade of two regulators.  The original regulator would provide a constant voltage source to the second regulator so that I didn’t need to worry about things like voltage ripple.  The new variable regulator would control the output voltage and burn off the power drop from 26V down to the final variable voltage.  The power dissipation would be shared between the two stages of the cascade.

The regulator chips are a pair of very nice Maxim LT1083 adjustable regulators with internal overcurrent and temperature sensing.  I tied two of these in parallel, mounting each on its own finned heatsink.  These chips will shut down if they overheat, as they might if the output is shorted due to a derailment.

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For the variable control device I chose one of the linear faders that I sell as the exclusive distributor for Penny & Giles.  This gives me a smooth control with a stroke of three inches.

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I wanted to include a current meter on the output, but I didn’t have anything with a 10 amp range.  I did have a nice 100 mA meter in an enclosure, and I was able to add a shunt to the terminals to recalibrate it to 10 amps.  The shunt is just a short piece of bus wire.  I determined the appropriate value by using my volt/ohm meter to read the output current to a fixed load while I adjusted the shunt to give the same reading on my power supply’s meter.

I added a double pole, double throw center off switch for reversing polarity and killing the track voltage in the center position.  I also included an incandescent pilot lamp across the output as a simple output voltage indicator.

When I got done, I had a kludge, but it did what I needed.  I can run my four locomotives without the supply ever cracking a sweat.  Sure, I could have bought something smaller and fancier, but what’s the fun in that?  Is it overkill?  You bet!  But it’s mine, and I love it dearly….

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Limited quantity – Enhanced MANCO Legacy Base Booster

 

Signal Booster for Lionel Legacy Serial Port – Now with “Earth-Ground” terminal!

The chip Lionel chose for the RS-232 output on the Legacy Base will not power more than a very few hard-wired controllers  with optocoupler data inputs (Z-Stuff Data Wire Driver and Lionel TPC.)  The MANCO Booster corrects this problem by amplifying the normal Legacy output current by a factor of ten times, providing adequate drive for many wired controllers.

The Lionel hard-wired controllers require a drive that nominally swings between zero volts and 5 volts. This was the swing provided by the TMCC Command Base, but a 0-5V swing IS NOT a true RS-232 port.  When Lionel designed the Legacy Base, they “corrected” this problem by adopting a chip that swings from –8V to +8V as required by true RS-232, but in the process they lost the higher output current drive capability that the TMCC Base had provided.   An output current of only 7 milliamps will cause the Legacy serial output to sag to 3.5 volts – the lower limit for proper operation of optocoupled devices.

Controller devices such as the TPC (Track Power Controller) and Z-Stuff’s Data wire driver use an optocoupler to electrically isolate the serial digital commands from the circuits being controlled.  The TPC optocouplers require approximately 1.5 milliamps each, and the Z-Stuff driver requires about 3 milliamps.   As a result, layouts with more than a few of these optocoupled hard-wired controllers will load down the serial data line to a point at which the controllers no longer see adequate signal swing, and they quit working.

(Other Lionel accessory controllers such as the BPC, ASC and OTC utilize a different form of input circuit that does not require as much drive current.)

The Booster provides a 9-pin female connector with a boosted serial-output signal capable of providing more than 5 times the output current of the bare Legacy Base.  A second 9-pin connector provides a direct link from the Legacy Base RS-232 output, retaining the +/-8V swing for RS-232 compatibility.  This RS-232 compatible port can be used to conveniently connect an external computer for running the Legacy System Utility (LSU) for Legacy backup/restore and configuration functions.  This port can also be used for other input/output controller, or future Lionel products using RS-232 protocol.

The latest version also includes an external terminal on the box that is connected directly to Pin 5, the ground reference for the TMCC/Legacy Track Signal.  Connect a wire from this terminal to a terminal strip that serves as the star origination point for all of your earth-ground signal enhancement wires.  (See additional documents at www.trainfacts.com regarding measuring the Track signal and steps to enhance this signal.)

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Installation:  Plug the 9-pin male connector on the cable into the Legacy Base 9-pin female socket.  Plug a 9-pin male connector into the “Accessories” port (Pin 2 is the boosted output to accessories, Pin 3 is input from ARC, Pin 5 is ground/common.)  Plug the wall wart into an AC outlet.

The “Computer” port is a pin-for-pin pass-through of the 9-pin Base connector.  It can be used for connecting a computer or a DCS TIU.

 

Price – $60.00 plus $6.00 for Priority Mail shipping.

Contact:

Dale Manquen at MANCO

(805) 529-2496

1694 Calle Zocalo

Thousand Oaks, CA 91360

Visa, Mastercard and PayPal accepted

dmanquen@msn.com

www.trainfacts.com

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Magnetraction Zapper

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Lionel 71-4002-250 Add-On Meter for Postwar ZW Transformers

The Lionel 71-4002-250 Add-On Meter for Postwar ZW transformers provides digital readouts of voltages and currents for all four ZW channels. The unit attaches to the back of the ZW and utilizes the four “U” terminal posts as electrical returns.

This metering unit has a serious flaw related to the current measurement technique. (There is no mention of this problem in the Operator’s Manual.) Instead of reading the individual currents flowing out of the A,B,C and D terminals, the Add-On reads the currents returning through the four “U” terminals. This would be just fine if all of the outputs fed totally independent and isolated loops, but that is not the case for most layouts. The Common or outer rails of all of the layout areas are generally tied together into one massive Common point, and that mixes up all of the currents from the various outputs. We normally do not have separate returns, and that means that there is really only one point to hook up to the “U” terminals. If only one “U” terminal is used, all of the current for all four outputs of the transformer will be read on just the ammeter for the selected “U” terminal.

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The problem is related to the current sensing technique that is employed in the Add-On. Each “U” terminal on the Add-On feeds a .01 ohm current-sensing resistor (the four large black cylindrical components in the photo) that dumps the current onto the “U” bus of the actual transformer. An analog-to-digital converter reads the voltage developed across the current-sensing resistor to calculate the current through the resistor. The “U” bus is attached to the (single) zero-volts end of the transformer’s secondary winding.

Assume for a moment that we are using the A and D handles to feed Train A and Train D, respectively, and Aux handle B is used to supply a group of isolated accessories (not units like the cattle or horse corrals that physically and electrically connect to the track Common.) The currents to Trains A and D pass through separate power blocks to the trains, and the currents return through the outer rails to the central Common point for the layout. The currents are no longer separate, and they cannot be separately fed into the “U” terminals for A and D on the Add-On.  The A and D current meters will each read part of the returning current, but the portion that each reads is not necessarily the portion that went out the respective A and D terminals.  The sum of the two currents will equal the total current from A and D combined.

The solution to this problem is to read the currents on the A-D terminals by inserting small current-sensing transformers on the A-D leads.  I have tested this technique and found that it works well, overcoming the “current distribution” problem.

Other components on the board in the photo above include:

The voltage regulator and connection for the 9V battery on the left,

An LM324 quad opamp for boosting the voltages across the current-sensing resistors,

The LED display driver transistors in the upper right, and

The large PIC microcontroller that includes the A/D converters and outputs the LED display information.

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MANCO Contact Information

Dale Manquen
1694 Calle Zocalo
Thousand Oaks, CA 91360
dmanquen@msn.com
www.manquen.net

Please do not ship to MANCO with “signature required”.

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TMCC Controller Repairs

Introducing a new service – Component-level repair of TMCC Controllers

If any of your customer’s TMCC controllers fail, now you can offer your customer a solution! Lionel won’t fix or exchange out-of-warranty devices, and you certainly don’t want to troubleshoot down to the component level. Now you can recommend that your customer contact MANCO for repairs.

MANCO can repair many of the failures on the following devices:

CAB-1

TMCC Command Base

Powermaster

TPC 300 and TPC 400

SC-1 and SC-2

ASC

BPC

Modern ZW

ZW meter add-on

(Legacy items are still covered by Lionel under an extended warranty program.)

Repairs are limited to internal electronic components that are commonly available. Exclusions include broken plastic parts and Lionel-proprietary programmed logic chips. (MANCO has found that the pre-programmed microprocessor chips are not a common failure item. Usually the failure is in the circuitry around the microprocessor.)

Typical repairs are about $25 plus return shipping.

MANCO does not repair locomotives or the circuit boards internal to the locomotives.

Contact Dale Manquen at MANCO

1694 Calle Zocalo

Thousand Oaks, CA 91360

(805) 529-2496

dmanquen@msn.com

www.trainfacts.com

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Dale Manquen’s Control Panel

My layout is on the floor of an attic that is only 52” high at the peak. You might call it a “rug rat” layout since I must move around on my hands and knees on the carpet that covers the open areas. (The main access path also has carpet padding.)

For this layout, I needed to make the control panel as small as possible so that I don’t interfere with my view of the layout.  (Actually, I am sitting in the center of the layout to operate the panel, with trains all around me.)  My choice was to build a single panel split into 3 sections – accessories, switches and power blocks.

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Control Pedestal left-to-right

TMCC controller for accessories and switches, accessory manual controls, turnout manual control with indicators, block power controls, TPC

The panel is “old school”, using toggle switches and buttons for activation. I do use bicolor LEDs to indicate the status of the track turnouts/switches. The manual buttons and switches for accessories and switches are paralleled with TMCC controllers that I designed with the help of Jon Zahornacky of ERR. In addition, the most important power blocks can be activated from an ASC.

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I used multipin connectors so that the panel can be removed for modifications.

The panel is flanked on each side by two sets of four circuit breakers. The left breakers protect the four main outputs (A and D) for the two ZW’s. I use the rocker switch style breakers so that the breakers can double as convenient ON/OFF switches. The right breakers (only two are installed) are for my accessory power busses, and for these busses the ON/OFF function is quite useful when making changes.

The device on the left side of the panel is the TMCC controller for my turnouts and accessories. Each layer can control 32 switches or 64 accessories. As shown, there are two tiers for 64 switches, and one tier for 64 accessories.  More tiers can be stacked for up to 128 functions of each type. (Addresses above 99 cannot be accessed from the TMCC or Legacy handheld controller, but the computer can access the full 128 addresses of each type.)

The array for the track switches utilizes flat ribbon wires to help keep things orderly. Each switch also has one bicolor LED, a resistor and two diodes for the status displays. I was fortunate that that I had chosen to use flat ribbon wiring initially because when it was time to tap into all of the switch control leads to add TMCC, I could use IDC taps

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(insulation displacement connectors that clamp onto the flat ribbon wire) to connect to my home-built Massive Switch Controller.

The accessory switches were not wired with flat ribbons, and that required tapping into the accessory circuits at the multipin connectors.

Inside the pedestal I have mounted 1 TPC300, 3 Powermasters, 1 TMCC Bridge, an ASC and my hand-wound toroidal transformer accessory power supply. Needless to say, things are a bit crowded (and a bit messy, I must admit.) I also have provided bypass switches on the TPC and Powermasters so that I can take them out of the circuit for manual operation from the ZW handles.

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Battery Replacements for MTH PS-1 Locomotives

(If you don’t like reading technical information with detailed explanations, I suggest you exit this page now and go to a website where you can buy a ready-made battery replacement.)

I never have liked devices that are powered by rechargeable batteries. Sooner or later (usually sooner for me) the batteries will either lose capacity or short out, leaving me with a device that is useless unless I buy a new battery. Sometimes replacement batteries cost as much as the device did originally! As a result, I avoid battery operated tools, but I am stuck when it comes to cordless phones, cell phones, portable computers, electric shavers and many other devices.

MTH Trains used a Nickel Cadmium or Nickel Metal Hydride 9V (nominal voltage) batteries to provide power to their PS-1 locomotives. Battery failure in these devices can lead to serious problems that can scramble the train’s microcontroller or cause corrosion due to leaking chemicals. In my opinion, these batteries are ticking time bombs.

To avoid these problems, I began in mid-2002 to design my own circuit to replace the battery with a module that contains ultracapacitors. The ultracapacitors have a very long operating life permitting thousands of recharging cycles.

Ultracapacitors are a relatively new form of capacitor that can have vastly more capacitance than conventional electrolytic capacitors. Unlike conventional capacitors which are rated in hundreds or thousands of microFarads, small ultracapacitors are available with ratings of a few Farads.

The Achilles heel of present day ultracapacitors is that the voltage rating is very low, coming in at 3 volts or less. To get the 9 or 10 volts, we will need to connect four ultracapacitors in series. For series connected capacitors we add the voltage ratings of the capacitors, but we must also divide the capacitance value by the number of capacitors. In one example below we use four 3.3 Farad capacitors in series, yielding an effective capacitance of 3.3 divided by 4 or .823 Farad. This is sufficient capacitance to keep a PS-1 engine alive long enough for a complete the 20 second shutdown cycle including the shutdown sounds.

Conventional batteries provide a nearly constant voltage as they discharge, but capacitors begin losing voltage as soon as discharging begins. If the current drain is constant, the voltage will drop linearly with time. For our application, we must be sure that the terminal voltage stays high enough at the end of the shutdown cycle to sustain proper operation.

The UP Turbine that I used for my testing has a 3-stage shutdown that draws 65 mA for the first 10 seconds, then it ramps down to 50 mA for 5 seconds, and finally down to 35 mA for the final 2 seconds. This totals up to just about one Coulomb of discharge. (A Coulomb is the number of electrons that will flow in one second at one ampere.)

My first unit was built with a pair of PC5-5 ultracapacitors from Maxwell Technologies in San Diego. These units are flat modules that can be stacked to fit into the recycled shell of a 9V battery. Later on I tried some cylindrical capacitors that were also small enough to fit into a battery shell. Both types work well.

The PC5-5 is actually a module containing two 3.6 Farad capacitors in series to yield a 5V rating at 1.8 Farad. Two of these modules in series ups the rating to 10V, but drops the capacitance in half again to .9 Farad. Discharging a .9 Farad capacitor 1 Coulomb will cause a voltage drop of 1.1 volt. This means that if we start at 10V with a fully charged unit, we will still be at 8.9 V at the end of the shutdown cycle. (MTH trains do not mind a voltage somewhat higher than the original 8.4V NiCad battery because the battery voltage is regulated down to 5V.)

A major problem with series strings of capacitors is that the capacitors don’t necessarily share the charging voltage evenly. To illustrate the point, we will assume a series string of 4 capacitors, with three of them being 1 F and the fourth being a weak unit with only .5 F capacitance. (This is an extreme variation, but it makes the math simple!)

When we pump a charge of 2 coulombs (equal to one ampere for 2 second) through the series string, each capacitor will get a voltage boost of Q/C (capacitance divided by charge.) The three 1 F capacitors will charge up 2 V, but the .5 F capacitor will charge up 4 V! This may overcharge the smaller capacitor, leading to degradation or failure. Real capacitors don’t vary quite that much in value, but their typical tolerance of +/-20% can easily provide a 40% spread.

There are a few methods for trying to maintain equal voltage across a series string of capacitors. Most of these schemes use resistor ladders across the capacitors to force the capacitors to share the voltage, but this doesn’t work very well. We would like to have a high resistance in the ladder to avoid wasting a lot of power in standby mode, but we also want low resistance so that the voltages will balance out quickly. Even a very low resistance ladder with multiple 10 ohms resistors will take 180 seconds to balance out. (Capacitor/resistor circuits take about 5 Time Constants to reach 99% of the final charging value. The Time Constant value for our example circuit is R x C, or 10 ohms x 3.6 F = 36 seconds.)

A better solution for equalizing the voltages is to use Zener diodes across each of the capacitors. If one of the capacitors starts to overcharge, the excess voltage is bypassed around the fully charged capacitor so that the other units in the string can continue charging to full voltage. If the fully charged unit is removed from the charger (as when the power to the PS-1 engine is turned off), the Zener will not bleed off the charge on the capacitors the way shunt resistors would.

I have chosen 1N5223B Zener diodes for my design. These diodes have a voltage drop of 2.7 V at 20 mA, which is about the maximum charging current at 10 volts. (Mouser has these parts for $.05 each.)

The schematic for my second battery replacement unit is shown below. Nichicon JUMT1335MPD capacitors found at http://www.mouser.com/catalog/catalogUSD/644/840.pdf are suitable. If you find less expensive devices elsewhere, please notify me.

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There are a few more pertinent comments that are appropriate.

  1. Ultracapacitors, like most other electronics components, don’t like heat. If the capacitor’s ambient temperature is raised 10 degrees Celsius, the life of the capacitor is cut in half. Mount the unit away from heat sources.
  2. Ultracapacitors should not be used in applications that require rapid charge and/or discharge. The capacitors have more internal resistance than normal capacitors, resulting in internal heating when large currents flow frequently. This isn’t a problem in the PS-1 application.
  3. The internal resistance will cause an abrupt drop in voltage when switching from the charging state to the discharge state. The size of the step depends upon the amount of current being drawn.
  4. Allow time for the capacitor to charge fully when first turning on the track power. I wait 15-20 seconds.
  5. My measurements with the UP Turbine indicate that any track voltage above 6 volts will fully charge the module.
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Passenger Car LED Lighting

This schematic is for driving multiple white LEDs for passenger car illumination. Values for the components have not been determined.

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