DWiDCC - Direct Wireless DCC Are you looking for the DWiC page? Experiments with wireless DCC on a budget Introduction
With track laying on my garden railway nearing completion my attention turned
to how I am going to control my locomotives on a track that is subject to the
elements. I determined my main requirements... A quick browse through the Jaycar catalogue provided the answer - 433MHz Wireless
Modules! But how should I use them? Most DCC manufacturers have in their range
a wireless throttle where the control path is only wireless between throttle
and command station except for CVP who have a wireless decoder for G scale.
I feel this is the way to go - direct wireless DCC - DWiDCC. Current thinking includes two methods for wireless
control as shown in this diagram:
Click here to link to the DWiC (Direct WiFi Control page)
copyright Bob Backway 2006
Are you looking for the DWiC page?
Experiments with wireless DCC on a budget
With track laying on my garden railway nearing completion my attention turned to how I am going to control my locomotives on a track that is subject to the elements. I determined my main requirements...
A quick browse through the Jaycar catalogue provided the answer - 433MHz Wireless Modules! But how should I use them?
Most DCC manufacturers have in their range a wireless throttle where the control path is only wireless between throttle and command station except for CVP who have a wireless decoder for G scale. I feel this is the way to go - direct wireless DCC - DWiDCC.
Current thinking includes two methods for wireless control as shown in this diagram:
DWiDCC enables track independent control (and/or power) of a loco. The receiver is located within the loco and its output is directly attached to the decoder.
Experiment 1 - DWiDCC
In this experiment an existing DCC Command Station designed by Robert Côté was modified to fit in a smaller case, powered by batteries, and drive a 433MHz transmitter module. An old Lenz LH100 decoder mounted on a HO chassis with a sound module and headlamp was modified to take its command signal from a 433MHz receiver module. Note that the receiver, decoder and sound module would fit on a properly designed PCB in a mid to large HO locomotive. I will have no problems fitting it into little 1:24 logging locos. The design is very simple and yet - it works!
Parts for 1 x MiniDCC© system by Robert Côté
1 x Plastic Case 150x80x30mm - Jaycar HB-6034
1 x 433MHz Wireless Transmitter Module - Jaycar ZW-3100 $A9.95
1 x 433MHz Wireless Receiver Module - Jaycar ZW-3102 $A9.95
4 x AAA NiMH rechargeable batteries and flat holder
1 x 78L05 Voltage Regulator IC
1 x Red LED
1 x Yellow LED
1 x Diode
1 x 470R Resistor (Yellow,Violet,Brown)
1 x 2K2 Resistor (Red, Red, Red)
1 x 3K3 Resistor (Orange, Orange, Red)
Circuit Diagram of Transmitting Handset
Construction of Handset
The protype MiniDCC based handset was built on eurocard with all components either soldered or plugged into this board. With no loose wires the final PCB will make construction a breeze. The extra components for DWiDCC are the battery holder, a diode to drop the battery voltage to a suitable level for the PIC and a LED to indicate handset and transmitter power which also drops voltage to near the 3 Volts required by the transmitter. The DCC signal is reduced to 3V maximum by a resistor divider before entering the transmitter module.
Here is a front view of the circuit assembly
Here is a rear view of the circuit assembly
Here is a left view of the circuit bassembly
Here is a right view of the circuit assembly
Circuit Diagram of Receiver and Decoder in Locomotive
Construction of Locomotive Receiver-decoder
Again the prototype was built on Eurocard. A long thin strip was used as a base with the Receiver and its power supply soldered in. The decoder and sound module were stuck on with double sided tape and connected with their standard flying leads. A LED was added to notify the tester that the loco has track power. The board contructon is as simple as the handset but there is one complication...
**Modifying the DCC decoder
For the initial experiment on a HO diesel chassis I used an early Lenz decoder LH100 because I had one lying around and I have a circuit for it that was provided to DCC WG members in the early 1990s by Lenz. The relevant parts of a typical decoder are shown below:
The track power is full wave rectified by the four diodes and the resultant DC voltage limited to 22Volts by the zener diode. At the positive end of the zener diode the standard decoder accessory wire (blue) is usually attached. It is this line that is regulated to 5Volts to power the receiver. For test purposes the negative end of the zener diode , which is the decoder ground, had a wire soldered to it to provide a ground for the receiver. If you are willing to keep poking around your decoder with a soldering iron you could probably find the output of the decoders 5 Volt regulator and use it to power the receiver.
Now comes the tricky part. The DCC signal line has to be traced from a track wire via a resistor to the microcontroller. This line has to be isolated at the microcontroller end. This end is where the receivers data output, the DCC signal, is connected.
For my 1:24 Fairymead Mill 4wD loco I used a Digitrax decoder. On examinination it was found to be similar to the Lenz decoder and in fact easier to find a suitable point to cut by drilling out a via on the printed circuit.
I have a circuit for the MERG decoder and although it is a bit more complex (they have added a Schmidt Trigger to the line) it is very similar in design. Afterall each manufacturers decoder has to perform in a similar fashion. That's the beauty of standards!
If you are brave enough to poke around in another brand decoder I would like to hear from you
Of course in the long term it would be nice if the manufacturers provide an "External DCC Data In" option - just think of the extra sales and the step in the door to the future of DCC.
This information is provided for individual use only. Commercial production of this design may only be undertaken under licence from ADCC.
© ADCC 2005