The BoosterBox has been designed, to separate the Signal Ground potential of the LOCONET-Net from the Power Ground potential of the rails.
The BoosterBox has been designed as a Pre-device for the Digitrax Command Station (DCS100). It enables the Booster part of the DCS100 to be used in an opto-coupled (input and output have no common potential) mode.
One BoosterBox is required for each DCS100 to be operated in opto-coupled mode.
The Components of the BoosterBox cost about 18 EUR (without power supply connector ) to 20 EUR, the LED-option is about 4 EUR (with blue LED's) or 1 EUR (with green LED's), the printed circuit board (PCB), depending on quality, is 8 to 10 EUR.
The term "LOCONET" is used ambiguously. Therefore I have tried to define the items clearly.
LOCONET:
The Loconet comprises the Peer-Net and the Railsync_Net.
The Loconet is distributed under the whole model railroad (MRR) layout and has connector
outlets (nodes of the net, which are LN-Boxes at FREMO), wherever a throttle or
a booster has to be connected. There are even more devices (not listed here),
which can be connected to the LOCONET.
Peer_Net:
The terminals 3 and 4 of the six pin USOC RJ12 style TELCO connector (also called "western" connector, together with "signal ground" at the terminals 2 and 5.
These terminals carry the messages between the throttles and the Command station.
Railsync_Net:
The terminals 1 and 6 of the six pin USOC RJ12 style TELCO connector, together
with "signal ground" at the terminals 2 and 5.
The voltages at these terminals are a low power copy, i.e. a copy with lower power of the Rail signal ( the current is much smaller, 100 mAmpere compared to 5 Ampere of the Rail signal. From the logical point of view, the Rail signal is the high power copy of the Railsync signal. It is mainly a 10KHz square wave signal. Only this signal does interest the boosters. Both terminals are of opposite phase.
Both terminals are also used for the power supply of the throttles, whichever is positive with respect to "signal ground". The rail-signal is not identical with the Railsync signal in every operation mode, e.g., if the DCS100 is set to "sleep" (in this case one Railsync terminal is at 12 V, the other one at 0V, whereas both rail terminals have 0 V).
Diagonal Current Pickup:
The front bogie of an engine or car is connected to the left rail, whereas the rear bogie is connected to the right rail.
Power (current) consumption of a MRR layout
The total power consumption of all engines and (lighted) cars is higher than the capability of a single Command station and booster with bigger MRR (model railroad) layouts. Take an example with 20 engines with a current consumption of 0.5 Amps each and 100 cars with 0.05 Amps each. The required current would be 15 Amps. In the case of a short circuit , You can have at least some hot spots on the engines' wheels or even worse, burn the thin wires inside an engine. Also, the whole layout is shut off, in the case of an short circuit.
Division of the MRR layout into booster districts
Therefore the MRR layout is divided into booster districts. Each district is powered by its own booster. These boosters supply currents, which can be easily generated and handled. The lower value is given by the consumption of one high power engine, the upper value of current is given by the maximally allowed short circuit current. The values are between 2 Amps ("Spaxbooster" of FREMO) and 8 Amps (Zimo, DCS200). The value of 4 .. 5 Amps seems to be a good compromise, at least in my opinion.
Chief set at home and use in a convention
Some model railroaders bought a Chief set with a DCS100 as Command station & booster for their own use. They use it for mostly small layouts at home with, say 4 to 5 engines, for which the booster section of the DCS100 is sufficient. For the use in a convention the high total power and therefore the division into booster districts is required. So it is advantageous, if these DCS100 could be used as boosters in a convention. One DCS100, of course, acts as Command station and booster. So it is not necessary to buy extra boosters, but one BoosterBox per Booster_DCS100 (my abbreviation for a DCS100 to be operated in booster mode) is required.
It might be possible to use also an Intellibox as a master, but it can never be used as a booster. I did not use an Intellibox as a master yet. (Stefan Bormann gives a hint to a bug in the protocol between Intellibox and DCS100).
But there is one attribute of the circuitry, which arises an issue in the use for booster purposes:
The power ground ( the ground of the rail signal) is connected to the signal ground of the controlling net (LOCONET).
Connection of the power ground terminals of all boosters, the
Pigtail-Wire
The power ground terminals of all boosters should be connected to system power ground. This prevents the development of a DCC rail signal with double voltage, and helps engines with diagonal pickups to cross boundaries of booster districts without hesitation.(see details in the publications of Allan Gartner or Don Crano, you find them in the internet on the digitrax link pages.)
If now an engine crosses the boundary between two booster districts, there are currents across this connection. Therefore this connection has to cope with the full booster current (recommendation: use 2.5 mm2 wire (ca. AWG 12)).
Without this wire, the currents flow across the thin LOCONET wires. The signals in the LOCONET may be disturbed.
The power ground of the DCS100 is connected to its case, and to one terminal in the seven-terminal block. A short piece of wire runs from the case to a lug. Digitrax calls this piece of wire "Pigtail", in German: "Schweineschwanz".
In order to give the wire, which connects the pigtails of all boosters, an impressive name, I call it "Schweineschwanzleitung" (English "Pigtail Wire")
This wire should be a green, flexible wire with at least 2,5 mm2
cross section (AWG12). Preferred lengths are 2m, 5m, 10m, 20m.
The ends should be fitted with isolated push on connectors for flat connector
blades, 6.3 mm. The according flat connector blade is sold as multiple
connector or with lugs for screwing. The connector blades should be fixed at a
massive part of the MRR layout ( if someone stumbles over the wire, he simply
removes the push on connector from its blade, but does not tear away any
DCS100). A short wire with an isolated push on connector at its end connects the
case of the DCS100 (or the ground terminal of the terminal block) with the flat
connector fixed at the massive part.
All flat connector parts (push on and blade) and wire are available in local car replacement parts' shops.
Rules of German electricians do not allow to connect the Pigtail wire to
the protective earth terminal of the mains in Germany.
Why are both signals, Railsync A and Railsync B transmitted?
During the development of the BoosterBox, I sometimes got the proposal, to prepare only one Railsync signal, and to keep the other one fixed at half the voltage.
There is an important reason against that: I do not know, to which direction the development of DCC at Digitrax will go to. Therefore I designed the BoosterBox to be "transparent", that means that the output signal is an exact copy of the input signal. The output signal of a DCS100 indeed consists of both opposite phased Railsync signals. The BoosterBox does not change anything with the signal.
Furthermore there is no DC present at the output, if the input connection is removed.
Parts of circuitry
The Circuitry comprises the following parts:
Power supply, displayed in an circuit of its own, but on the same PCB
Opto-input,
Opto-output,
Schmitt_Trigger,
Output amplifier,
LED-Additional,
Peer-Net Connector.
In order to keep the circuitry simple to understand and not to draw too many ground wires, I marked the grounds for input side and output side with different ground symbols.
Power
supply:
The BoosterBox is powered by the same secondary terminals of the transformer as the booster_DCS100, to which the BoosterBox is assigned.
The circuitry of the stabilizer follows a common circuitry proposal. and provides Us = 12V. Two items have been added.
Opto-input:
The 2.2 k resistor defines the current for the LED of the optocoupler to 5 mAmp. In the normal use there is only one LED triggered at a time, so the total current amount from the LOCONET is 5 mAmp.
.The fast diode BA159 protects the LED of the optocoupler against reverse voltages.
Both ground terminals of the input are connected.
Opto-Output:
The 4.7 k resistor works as a Collector resistor for the output transistor of the optocoupler.
Schmitt-Trigger:
The Schmitt Trigger is a CMOS circuit of the CD 4093 type. Four similar circuits are in one IC. Unused inputs have been set to "Us" to reduce current consumption and to define the potential uniquely.
Output
Amplifier:
The
output Amplifier has been designed:
to switch to ground potential for input voltages under Us/2 - 0,6 V
to switch to Us potential for input voltages over Us/2 + 0,6
The 220 Ohm resistors are protection resistors, which limit the current between the BoosterBox and the Railsync-terminals of the DCS100, if the DCS100 is not yet in the booster mode and its Railsync terminals may supply currents.
All small signal transistors can be used, if the can do more than 20V Emitter-Collector voltage, more than 200 mAmp Collector current, and more than 1 MHz transmission frequency.
Replacement types for BC337 : BC182, BC183, BC237 ...
Replacement types for BC327 : BC212, BC213, BC253 ...
Additional
circuit with four LED's
Two LED's (a red one and a blue(green) one) show, whether the associated Railsync output is at ground potential or at Us-Potential. Normally, you cannot see the 10 KHz square wave transitions, all four diodes are lit. The LED's and their current limiting resistors are not on the PCB, but are set up on a grid-style PC board. They are connected at the 4 terminals, arranged as a cross, between the output amplifiers via IC-socket connectors.
Peer-Net-Connector
One needs to connect the Peer_Net of the input net to the Peer_Net of the output for a short moment at the beginning of a session (I will explain this later on). This is done by a DPDT-Switch, which connects the Input Ground to the Output Ground and the Peer_Net terminal 3 or 4 of the input to the Peer_Net terminals 3 and 4 of the output (of the BoosterBox).
Drill
holes
All holes are drilled with 0.8 mm diameter.
The holes for the Zener diodes and for the Power supply wires have 1.2 mm diameter.
The holes for mounting and for the western sockets have 3.0 mm diameter.
Insertion
of Parts
The parts marked with an "X" on the PCB, are placeholders for further parts. These are e.g. resistors, to match the circuitry more exactly to the trigger voltages of the opto-couplers.
The double bridge from the Peer_Net terminals of the input to the push button terminal gives the following choices:
Zero Ohm resistor located towards the border of the PCB: Conversion to booster mode without connected DT100 possible.
Zero Ohm resistor located towards the center of the PCB: Conversion to booster mode only with connected DT100 possible.
The insertion and soldering of the components will be done from the thin components to the thick components. At first one inserts the zero Ohm resistors (bridges, 3 pieces, 7.62 mm (3/10 '') length, 1 piece 10.16 mm (4/10 ").
The fifth bridge is inserted after the test of the power supply. You also can insert there two fork shaped connectors and connect them later on
Then all resistors and diodes are inserted and soldered.
Nearly all have a length of 10.16 mm (4/10 ''), except for:
R1 and R2 of the power supply have 15,24 mm (6/10 ''),
ZD01 and ZD02 of the power supply have 12,7 mm (5/10'')
R11 and R31 of the output amplifiers have 12,7 mm (5/10'').
The next items are the semiconductors, and the sockets of the ICs. The capacitors will be inserted finally.
I have seen a lot of hair like interruptions on PCB's up to now, if the outlets had been soldered directly onto the PCB. Therefore I also provided the possibility to use outlets with pre-connected leads (You have a lead from each of the pin receptacles, the other end of the lead is soldered to the PCB).
I used pre-connected outlets for the input and directly soldered ones for the output, because the output connection is not changed so often.
Differences
between Rev02 and Rev03
The Layout with revision No 03 has been designed on a PCB with "Europa format" (160 mm x 100 mm, approx. 6.3 '' x 4.0 ''). The connectors are at one 100 mm side.
Power
supply
Apply an AC between 12 V and 22 V or a DC between 14 V and 28 V to the power supply connectors ( the big soldering pads near the diodes 1N4004).
Measure the output voltage of the power supply part. It should read 12.0 V (+_ 0.2 V).
Insert and solder the fifth bridge.
Opto
coupler
Insert the opto-couplers into their sockets.
Apply power to the power supply circuit of the BoosterBox.
Take a variable power supply and connect its terminals to one of the railsync inputs ("+" either to pin 1 or pin 6 of the input western outlet, "-" to pin 2 or pin 5).
The output voltage of the opto-couplers is measured at the socket of the Schmitt trigger IC.
Raise the voltage of the variable power supply from 0 V to 12 V.
At input voltages below 3 V, you should read "Us" (12 V) at the output.
At input voltages between 5 and 6 V the output voltage should start to decrease.
At input voltages over 6 V the output voltage should be below 4 V.
Apply the measurement to the other channel (the other one of the pins 1 & 6, together with pin 2 or pin 5)
Schmitt
Trigger
The Schmitt triggers will be tested after the tests of the output amplifiers.
Output
amplifiers
Measure the transmission characteristics of the output amplifiers
Apply the "+" terminal of the variable power supply to one of those terminals in the IC-socket, which are linked to the used outputs, when the IC is at its place, the "-" terminal is connected to the ground of the output side.
Connect a DC-volt-meter to the output of the corresponding channel. ( "+" terminal to either pin 1 or pin 6, "-" terminal to pin 2 or pin 5 of the output western socket).
Later on repeat the measurement with the other channel.
The output voltages should show the values in the following list.
Uinput [V] Uoutput [V] (Us = 12,00V)
0,0 0,011,0 0,01..
5,0 0,025,2 0,035,4 5,5..
6,4 5,56,6 6,16,8 11,987,0 11,99..
11,0 11,9912,0 11,99
Schmitt
Trigger
Insert the Schmitt trigger IC into its socket.
Connect the variable power supply to one of the Railsync inputs of the BoosterBox as described above (testing the opto-coupler).
Measure the output voltage of the BoosterBox at the output resistor of the corresponding channel.
The output voltage should flip from the low level (approx. 0 V) to the high level (approx. Us (12 V)), if the input voltage is raised beyond approx. 6V
Each Booster_DCS100 has its own BoosterBox.
The power supply terminals of the BoosterBox are connected to the same secondary windings (low voltage windings) of the power supply transformer as the DCS100 itself.
Each DCS100, regardless whether being master or booster, has its own transformer (so called "direct home wiring") with a current capability, matched to the DCS100's needs.
No
welding transformer for all boosters together, please. The short circuit
currents of "welding" transformers may cause fire.
The input part of the BoosterBox is equipped with two Western sockets, connected in parallel (those sockets located closer together). One can daisy chain the LOCONET through the BoosterBox and does not need a separate LN-Box ( similar device as an UP3 of Digitrax). The signal for the BoosterBox and with it for the DCS100 is taken simultaneously.
The output of the BoosterBox is connected by means of a short LN-cable to one of the inputs of the DCS100. All LN-cables are fully implemented, no special design as interrupted ground etc.
The connections between the BoosterBoxes and their DCS100 are no full LOCONET connections. It makes no sense, to insert there some LN-Boxes.
Figure "BoosterBox_Use_G" shows the used devices.
Figure "BoosterBox_Use_V" shows the links between the devices.
At the beginning of the development of the BoosterBox, I got information from Digitrax that the OP switch #2 would set the DCS100 to booster mode. I also got the hint from Don Crano to set OP switch #5 to "thrown" in that case
Booster operation:
Set OPSW#2 to "closed"
Set OPSW#5 to "thrown"
Unfortunately I could not verify that the DCS100 would work as a booster with these settings.
But I found out a workaround:
One connects two DCS100 via LOCONET, the first DCS100 set to "run", the second set to "sleep". If the second is switched from "sleep" to "run", it goes to real booster mode and announces this with 6 beeps, just, as it is described in the manual.
The Railsync terminals go in a state of high resistance, because they should receive only. So they cannot supply power to any other LOCONET components. In this case the Master DCS100 has to supply all attached throttles:
The Railsync output has an inner resistance of ca. 50 Ohms in normal operation. A throttle requires ca. 15 milliamp. If more than 4 ..5 throttles are connected to a DCS100, the Railsync output will no longer supply sufficient voltage. ( Use Railsync Boosters. I cannot recommend to get the throttle power from the rails).
The Peer_Net terminals of the Booster_DCS100 go also in a state of high resistance. After the 6 beeps, the Booster_DCS100 listens solely to the Railsync terminals and produces at its Rail terminals an exact copy of the voltages at the Rail terminals of the Master_DCS100.
Now the BoosterBox comes into the theater.
If one inserts the BoosterBox between the two DCS100's, the link of the master to the booster becomes unidirectional, because optocouplers have no "backward" possibility. The master only can tell something to the boosters, it is not possible in reverse direction. For our purpose it is o.k., if the Booster_DCS100 were already in booster state.
But the DCS100's communicate via Peer_Net, which one is master and which one is booster (the first one in "run" state remains master) and do not watch the Railsync signal on the Railsync_Net.
A Peer_Net connection is required for that purpose.
There is a difficult and a simple solution for this connection.
The difficult solution is the bi-directional opto-coupling of the Peer_Net.
The simple solution is a push button, which connects the Peer_Net of the BoosterBox input to the Peer_Net of the BoosterBox output, as long as the Booster_DCS100 is switched from "sleep" to "run". As stated above, it is necessary that information can be transmitted in both ways (from the Master_DCS100 to the Booster_DCS100 and vice versa). This kind of transmission is necessary only at the beginning. There is no motion of any train at that time, so one also has no power currents between the booster districts. At that moment the ground potentials of both DCS100 are allowed to be connected.
After the 6 beeps the connection is not longer required. The push button returns to its normal position and separates the Peer_Nets of input and output (and also the ground potentials!).
Preparation
of the Master_DCS100
The Master_DCS100 does not need any preparation.
Preparation
of the Booster_DCS100
All DCS100, which are intended to become a booster, are prepared as follows:
Switching
on
The items 5 to 8 are repeated with each Booster_DCS100 and its corresponding BoosterBox.
Test:
The DT100 at the Master_DCS100 (keys (RUN/Stop) and (+) res. (-)) must be able to switch on and off the track power of the Master DCS100 and of all attached Booster_DCS100. Also, each DT100 at the LOCONET must be able to switch on and off the rail power of the whole layout.
The track status LED's at all DCS100 and other power indicators must show the transition.
Test
for matching polarities
If the Master_DCS100 is involved in the power supply of the MRR Layout, one starts at its power district and any neighbor district. The rails of the districts are double gapped at their ends, but connected indirectly via the "Pigtail wire".
Check the voltage between the rails of the same side (north or south) of both booster districts with a power indicator showing also low voltages (e.g. Steinel Voltcheck 3) And check diagonally.
(Full voltage means voltage across the rail terminals of one DCS100 (one booster district))
Case
a)
Same side => low voltage
Diagonally => full voltage
The
polarity matches.
Case
b)
Same side => full voltage
Diagonally => low voltage
Swap
the Rail connectors from the booster to MRR Layout ( Connect the terminal, which
lead to the south-rail, to the north rail and connect the terminal, which lead
to the north rail, to the south rail)
Check again. Now You should have case a). If not, something is seriously wrong, but, of course, I cannot tell you from here.
Do the polarity test now with the next booster district. Swap the rail connectors, if necessary, always of the added booster district.
Interrupt
the operation
Switch off track power (keys (RUN/Stop) and (-)).
Resume
the operation
Switch on track power (keys (RUN/Stop) and (+)).
Switch
off totally
Switch off the power for all the Boosters.
Switch off the power for the Master_DCS100.
If the layout is not under surveillance, one should switch of all transformers for safety reasons.
Switch
on from scratch
Repeat the items 3 to 6 with each Booster_DCS100 and its corresponding BoosterBox.
AMENDMENTS
TO THE CURRENT STATE (MAY 2001)
At the moment I build the "Europa" format PCB version of the BoosterBox. If this version is ready and tested, I will publish a picture of the layout.
The layout pictures are not well suited for zooming and making PCB's. If someone wants to build this circuitry, I ask him kindly to get in touch with me (Thomas Müller). Tell me, whether You want a transparent (positive)(ca. 5.-DM, 2.55 EUR), a PCB (ca 15.- to 20.-DM, 7.65 EUR to 10 EUR) or a use-ready device. I will see, what I can do, I will make a proposal and publish it either here as a file of its own or at FREMODCC.
So, please do not put money in an envelope for sending it.
Because I did not develop this device under commercial aspects , I regret to disclose any warranty for any damages caused by the use of this device.
But I am keen on information about issues with this device and will fix them as soon as possible.
Inhalt
von Dr. Thomas Müller.
HTML-Version von Stefan Bormann.