One of the things I've been intending to do is provide an integral controller for British Oak. For some time now, I've been trying out various small and inexpensive PWM speed controllers. There are a wide variety now available, sometimes also labelled as LED dimmers. The most useful I've found are the type called "Mini DC Motor Speed Control Driver Board 3V-35V 5A PWM Controller / LED dimmer" or some variation thereof, usually costing between £3 & £4 from a UK seller on eBay, cheaper from overseas.
It's important that the controller has a PWM duty cycle of 0% to 100%, which means that at the lowest setting, no power is applied to the track. Some don't go right down to 0% which can leave a small voltage present causing some motors to creep. If you're very interested in PWM, then a pretty good explanation can be found here
Suffice to say that the controllers I've used give a precise degree of control, very good slow running and don't cause any noticeable motor heating or noise, unlike the feedback controllers which rely on low voltage AC input to provide a waveform at 50 or 60Hz. These controllers typically have a PWM frequency of 10KHz and require a DC feed. This means they can be used as battery controllers if necessary. For this application, the control pot usefully includes an off switch. Ths photo below gives some idea of the size. Being a bare controller, a reversing switch is required.
For British Oak, I tapped into the 12vAC feed already provided for the plug-in controllers I use, like the Pentroller. The AC feed is taken to a small solid state bridge rectifier
(the black box at the bottom of the case) and from there, the rectified feed is fed in the controller, which has screw terminals to make the job easy. The output from the controller is taken into a DPDT reversing switch with a centre-off. This serves to isolate the controller when a plug-in unit is in operation. If this is not done, there is a strong possibility the two controllers will interact with each other.
Just to be on the safe side, I added some sleeving to the terminals of the rectifier. The controller also has screw terminals for the output. The wiring follows my particular convention of red & black for track power, green for AC and in this case I used orange for the DC where the polarity is changed by the reversing switch.
It all fitted into a small project box which is screwed to a convenient location in the fiddle yard.
Incidentally, those who joined in the 2mm VAG Zoom conference the other day will have seen an unusually tidy workbench. Below is much more typical, although there's actual bench still visible, not always the case...