MichaelT

Not only price. As there is generally more railway traffic going on 4 mm scale layouts the nature of the TX is very important: it determines how trains are operated. Do you want cab control or one master computer controller, or both? A low-level approach gives this flexibility whereas I believe the existing products, particularly because they are closed-source, do not. However, please correct me if I am wrong!

Hi Frank, BG John, Robin Thanks for the positive comments! Yes, sure, everything is built using open-source tools (CC license as I mentioned in previous post) and the whole point of the exercise, at least from my point of view, is to make BPRC freely available for others to use. The model rail hobby is big business these days and although there are cases where it is worth paying more for quality, it is generally expensive. Also, for new products, paywall = slow adoption, unless there is a critical mass. The idea of electronic modules + motherboard is that a beginner can get the system up and running with minimal work. You do not need to know how the modules are connected together, but if you wish to find out, it's not kept a mystery. I can provide the build info but at this stage it may be easier for me to provide you "kits" at the cost price since I have lots of spares. You will spend less time sourcing components and more time building/using the setup. It would be very useful if you can provide some feedback on this forum or other suitable place. RE size of the locomotives: I can easily fit this control system into coal tenders, DMUs, class 37s in 4 mm scale. This is not a problem for me, though I can appreciate some people model smaller locos. Sound: open-source tools including Arduino/Teensy make this possible already. You should need to pre-load the sound files onto an SD card and carry an SD reader plus loudspeaker on board the locomotive (space is premium!). Then it is a matter of writing the microcontroller code. I have never used DCC so don't know what sound card you are referring to, anyway the point is that you won't need it.

Hi Robin and all, Robin's project is very nice. I know a number of people who have been playing with nRF24L01 and locos (as well as other forms of model transport). Here is a quick overview of what I have been doing. About three years ago someone at my workplace showed me Arduino and its capabilities. So then I started off trying to control my trains: first with an OO gauge loco, an Arduino UNO and a transistor: As I had little experience with electronics, this design was a great pleasure to see working but was terrible on many accounts: The locomotive could only run in one direction. The 9 volt battery did not have a high charge capacity, so could not supply current to drive the motor for very long. For power and to send control commands to the Arduino, the Arduino was connected to a PC using a USB cable. All in all, the operation was not prototypical. Some time later I had been successful in learning to use nRF24L01+ radio transceivers. One of these could be carried with each locomotive plus an Arduino for control and an L298 pulse-width-modulation motor driver module (the red circuit board in the photo below, you can see the twisted orange wires going to the DC motor of an HO scale loco). The system was powered by 2x 3.6 – 4.2 volt Li ion cells in series. This worked but needed some miniaturization in order to be hidden under the loco body shell. In 2016 I shrunk the design down to use SMD (surface mount device) version of the nRF24L01+ module (black circuit board in photo). I had a smaller PWM motor driver module (Pololu TB6612FNG, green circuit board in photo, 2 A peak current) and was using an Arduino pro mini (blue circuit board) as the microcontroller. These components are all mounted on a custom-made PCB (purple circuit board, fabricated by OSHpark) to avoid wires trailing everywhere. This is how it looks: The photo shows the battery-powered radio control system added to a dash-9 locomotive in HO scale from Athearn. At the bottom of the picture is the DCC socket board that came with the locomotive. My system is pretty much the same width and length, but half the thickness (even without the DCC decoder added) and I am sure further miniaturization is possible. There was enough space inside the loco shell for two 750 mAh Li ion cells, which is enough capacity to allow between 8 and 10 hours loco running at full speed. This is fine for my needs! The design is very similar to that of Robin, so costs about the same to build. The most expensive part of the whole operation is the lithium ion cells. I’m at the stage where I would like other people to help test and develop the RC system. Please get in touch with me! The nRF transceivers have a maximum data packet length of 32 bytes, so can be used to transmit standardized DCC strings and integrate with established layout control softwares such as JMRI. There is a full writeup of all this work as a “how to guide” which I’d like to publish in a magazine, e.g. MRJ. If that takes too long I will find another place to distribute. Unless otherwise specified the design is licensed under Creative Commons CC-BY-NC-SA 4.0.