ORD-3 Universal Spaxbooster / DDXBooster / DCC232 Booster 3Amp stabilized

The final result

The three RJ12 connectors at the front of the ORD3 are LocoNet only.
Spax booster configuration
RailSync driven via LocoNet connectors
RS232 driven Direct USB driven
USB serial adapter in the connector

The Spaxbooster is a well known booster, very easy to use , with a nice stabilised power output.
Without a regulated power supply in the booster, the output voltage to the trains will fluctuate with the amount of running trains.
Also different transformers give different voltages.
Therefore , the original Spaxbooster is already equipped with a regulated power supply for 15 Volt.
But that voltage can not be changed, meaning that Spaxbooster is made for HO-scale.
Also the type of power supply is generating much heat, specially when used transformer is giving more voltage output as expected.
The ORD-3 does have a far more efficient switching power supply, and the output can be adapted to the different voltages, dependable on the used scale.
Voltages of different scales according to the NMRA DCC standard are:

Large scale 18V
0/S/H0/TT scale 15V
N scale 12V

The selection of output of the ORD-3 is done by dip-switch or switch mountable in front panel.
Due to the use of the A/D converter in the processor, the maximum current output is also pretty accurate selectable.
ORD-3_V2 connects to a Central unit by means of standard LocoNet connector, using only two wires.
ORD-3_V2 is also useable for a direct connection to Serial port, USB<>RS232 cable. or even Raspberry Pi, where the connected computer is set to run DCC232 in Rocrail.

See description on this page.

The ORD-3_V2 is already used many times in praxis, to proof its functionality.
Three standard LocoNet connectors are available in front.
The signal input of ORD-3_V2 is galvanic isolated by means of ultra fast opto-coupler.


ORD-3 V2 has a few nice features:

  • Most connections and signal-leds are on one side of the unit, making it easier to fix it to a front panel.
  • On board supply is stabilised for the chosen voltage output.
  • On-board dip switch to select N-HO-G output.
  • On-board dip switch for selection of 1 Amp or 3 Amp maximum output.
  • Wide power input range : 16-20V ac / 19-30V dc, due to the use of switching power supply.
  • Power output shut-off 30 mSecs after no pulses received (according NMRA spefications). Your precious N-Lok will not run away on power off.
  • Perfect suitable as DCC232 booster. Optionable also for USB.
  • Automatic stop at short circuit (selectable >1A or >3A) and automatic try to restart after 5 secs.
  • Fully compatible with CAN-GC3 command station.
  • Can be driven with any DCC and/or Motorola command station
  • High speed opto-coupler signal input, for safe interconnection between multiple ORD-3 units.
  • Ready designed for use with Railcom (Firmware not available yet.)

Pulse comparison

//These are measurements taken by hobbyists. See disclaimer for more information on content. All units were connected with Ohms load to draw 1,2 Amp.

pulse-ord2.jpg pulse-dcs200.jpg pulse-intellibox.jpg
ORD-3 Digitrax DCS200 Intelllibox 1

Mounting instructions

First start with all small resistors and IC sockets.
Then small capacitors and small elco's.
Then all connectors, leds, fuse and dip-switch(or 3 pin header).
Before mounting VR1,VR2,U1 and GR1, first fix the cooling block with two screws.
After that place VR1,VR2,U1 and GR1 in the pcboard and fix them with the clips.
Be sure that all parts are flat to the surface of the cooling and then solder them.
After that, cut the wires at the bottom at 1 mm outside the pcboard surface, and solder the wires.
Then fix resistors R5 and R10.
Be sure to leave some space between pcboard and resistors.
The best way to do that is using little pieces of 2mm tubing. (See picture).
In parts package (available from www.phgiling.net), these tubes are included.
At last fix C9,C11.
Before inserting U2, test power 5V on pins 1 and 8.
FB1 connector could be used for feeding back a short circuit situation to S88, LocoNet, CanBus etc.
For connection a PC(Serial port) to ORD-3_V2 use RS232 connector.

Important notes

  • ORD-3_V2, connected via serial Port for Direct drive is only supported for DCC232.
  • ORD-3_V2 can be used for DCC232 OR LocoNet, but not together!!!!!

As with all published units from GCA, the transformer used to supply this booster MUST be dedicated only to this unit.
Any connections from this transfomer to anything else (except of course the 230V supply) is strongly discouraged.
It might result in very strange and sometimes dangerous situations.
Keep it separated !!

LED configuration

LED Colour Indicates (if on)
LED1 green Power on
LED2 red Booster off
LED3 green Booster on

Hardware files ORD-3_V2

The schematic
The pcb and parts positions
The bill of materials
N.B. Self made pc boards are not supported!

Hardware files of previous ORD-3 Version


The PIC12F675 in this unit provides control over the output.
The very simple program, needed for this chip, is writen in PICSimulator IDE Basic from Oshonsoft

Firmware for PIC processor ORD-3_V2

Problems experienced with older type computers.

Using the ORD-3 with DCC232 in older computers, can sometimes show a very short constant flashing of the red led.
Also sometimes the running looks stop for very short moments.
This is caused due to the fact that the computer is not fast enough to constant refresh the data to be sent to the serial port.
ORD-3 switches off after no pulses are received for longer that 30 mSec (= NMRA standard).
The cure for this is making this timing a bit longer.
Using the next firmware curs that problem.
Be aware that the DC option in your locdecoder should be disabled (usually bit 2 of CV29).

ORD-3_V2 Firmware for DCC232 in slow pc

If you are plannning to use this firmware in stead of standard one, be sure to disable the possibility of the decoder in your locs for running on analog signals!
This is usually to be found in CV29 Bit2.

One other issue might be the setting in the serial Port.
If computer is showing a message like “Error on mutex trywait”, it could be a problem in settings of Com port.
In windows goto hardware > ports (com & LPT) > COMx > Port settings > advanced.
Here try to decrease the transmit buffer to maybe 4 or 6.
That useually will fix the problem.

ORD-3 with USB-Serial converters.

Serial ports are getting exotic in personal computers allthough in the professional machine world they are widely available.
But there are very cheap boards available to be used in your PC, adding two or more standard COM-ports to your PC.
But for laptops, all this is no option.
One possibility, not the cheapest one, is the use of a SUB D9 USB-F connector.
It fits straight in the ORD-3 V2 board, (see right-hand picture on top of this page) and the driver is loaded usually automatic when connected to the PC.
The other option is using a USB-RS232 cable.
There is no guarantee that the cable you already have is working, but it is worth trying.
Basicly the ORD-3 input is set for a general minimum of 16 Vpp from a standard serial port.
But the use of more than one ORD-3 V2 together, is no option here.
For 3,3V Raspberry-PI this resistor could be as low as 390 Ohm.
No experience about multiple Fruit-Pies here. LOL
In that case you could opt for a little driver board between USB and ORD-3.

Multiple ORD-3 connection

In both LocoNet or DCC232 situation a second ORD-3 can be connected with standard RJ12 cable to the first.
And the third to the second, etc. The three RJ12 connectors on front of ORD-3 are all the same.

But ALL ORD-3 units with separate Transfomers!!!!!!!!!!!!!!!!!!

Previous ORD-3 board, without Sub-D connector

The first Version of ORD-3 (blue board) did not have a connecor for direct PC connection with DB9.
There fore a cable should be made form DB9 female to RJ12.
Theese are the connections:

ORD-3 RJ12 to DB9 female
1 5
6 3

Alternative cooling

If you do not like to spend money on cooling, it is possible to make it yourself.
Simply look at ORD-2 how this done.
It is not necessary to isolate both chips from the metal, but consider that the alu plate will be connected to 0V of the board.

Dip-switch Settings

The settings a in this table are also printed on the PCB itself.

dip 1 dsip 2 scale dip 3 max output power
OFF OFF G off 3 Ampere
ON OFF N on 1 Ampere


The tranformer or power supply (=ac/dc adapter) for this unit should minimal 50VA.
The table below shows the best voltage regarding to the used scale.

Voltage ac out power supply dc out scale
12-20V 15-30V N
15-20V 18-30V HO
18-20V 21-30V G

Note :
Transformers do NOT have dc out! Except the speed/control output from any train transformer for two rail systems.
Using DC supply is no problem, polarity is not important.

Housing for ORD-3

RBS-Modellbau made a nice housing for ORD-3.
This picture shows a demo model, text must be corrected.
Housing is available as long stock will hold, Price €17,50 (excl Porto). Ask Peter

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