Hi, I’m doing a University group project based on a train set and I was wondering whether it is possible to independently control several trains using Pulse Width Modulation. I am aware that DCC is one method of doing this, however this does not suit our needs. Is there some way of using PWM generated by a PIC microntroller that receives instructions via a computer terminal and power from a dc supply? Any suggestions would be much appreciated, thanks
There were some analog systems that used an FM type carrier with multiple channels. Keller Engineering was one of them. Theirs was called “Onboard”.
Sure. It’s the basis of most multichannel radio control. Look up the three “words” PWM radio control on Google. You’ll get any number of hits.
If you still need an explanation, let me know.
-Ed
PWM IS what dcc is - at least one form of it.
To use a non-DCC source wll require receiver modules that match. Do you have?
CVP has a non-DCC digital system that some say is better than Lenz’s. You might want to investigate.
The main limitation to DCC is depending on track/wheel contact for commands and off-table sound compatibility with moving product.
DCC decoders use PWM to control the motor in the locomotive.
There have been many PWM throttle designs over the years, the vast majority limited due to using 60Hz line frequency.
There is no practical way to send PWM from a central control to multiple outputs over the same wires (track). All industrial applications have the PWM output seperately generated for each motor. There will be a single PIC for the system, with individual PWM boards for each motor.
Take a look at the NMRA website for information on the DCC signal, you may be able to have the PIC generate the required wave form, which is 9600 baud. The serial port of a PC is capable of generating the control signal (and there is Linux and other software available for this), which can then be feed into a power booster (basically an audio amplifier).
The CTC-16 and its progeny were systems which superimposed an R/C type signal on top of a filtered DC supply. The R/C type signal was a train of pulses of varying width, each one corresponding to the desired throttle setting for one particular locomotive. The receivers in each locomotive counted the number of PWM pulses in the control signal, and responded to the signal of the appropriate pulse for that particularly numbered receiver. While it may not be the best solution when specifying an industrial control system, it worked for model railroads for years before DCC. Although the CTC-16 did not use PIC technology, the RailCommand system by CVP Products did use micro-controllers. I believe that most current DCC systems use micro-controllers in some capacity.
You should have no trouble getting a PIC to generate a DCC signal. You wouldn’t have any trouble getting a PIC to generate a train of R/C type PWM pulses either. Micro-controllers in each receiver could interpret the signal and
Thanks guys for the replies, I will be researching the pointers given further and I’ll provide an update soon. Cheers