The Controllers & Circiuts I've Built

[Charles B]

Hi!
I've worked in broadcast engineering, industrial electronics and then in medical electronics. I was involved in Amateur radio for many years. Therefore I'm used to designing and building my own eqipment and know the safety rules

But I would not recommend doing so unless you have had proper training! And all of the equipment I shall present here is powered through commerical 'Titan 208' model railway transformers; no, I never touch the mains!

Here is a controller I built for my test workbench and for a small H0 point to point shunting layout



It's difficult finding project cabinets now-a-days therefore sometimes I build them out of 3 mm plywood if heat is no problem.





The cooling block on the rear keeps the 2N3055 power transistor cool. But it's really sized too big as the supply is built for 2 Amps (for reserve) but fused off at 1.5 Amp on its output.

The circiut is pretty simple: The unit has a rectifier, filters, a divider and then a LM358 OpAmp. One side to the OpAmp samples the desired voltage off of the divider and controll while the other side samples a Zener reference voltage. Therefore it doesn't let the controller's output exceed this pre-set reference. (I have it set for 12.5 VDC.) The output drives a pass transistor the 'good old' 2N3055. The LM358 is also very useful in other model railway circiuts as well as it only needs a single polarity supply and can handle a supply voltage up to 24 VDC.

Here is my light wood construction in it's industrial 'Safety Yellow' livery. In the old days one could have purchased a nice metal project case from the Canadian company 'Hammond' which had a good selection in the 1960's - 70's. But not anymore.
So I resulted to wood.



I built this controller for the rebuild of my Fleischmann 4000 shunter 'Anna'



I'll add more to this thread later off and on.
Cheers!
Charles

[Rog (RJ)]

I've only ever built 1. It was a circuit in one of the electronics mags. It used a 2n3055 transistor for the output. Worked OK but I much preferred my ancient H & M duetted.

[Charles B]

...Worked OK but I much preferred my ancient H & M duetted.

Hi Rog(RJ)!
I used to like my old 'MiniTrix' and 'Fleischmann' power packs until I discovered how 'Pulse Power' (half wave rectication at the lower voltage range) was causing massive sparking between my motor comutators and brushes and overheating and burning out motors.

Another problem is that I bought a new diesel shunting loco from the German manufacturer 'Piko' where only 12 volts maximum was allowed. Alas my 'Fleischmann' pack topped out at 16 VDC thus burning out a SMD transistor in my loco! (They repaired it free of charge anyway, thank Heavens!)

So my old power packs had to go!

And then I bought the N-Scale Terrier from Dapol which runs like a watch! But if I read the instructions sheet properly it too has a maximum of 12 volts tops. But I only ever ran this wee loco on controllers of my own design with pure, filtered and regulated DC and a maximum of 12.5 VDC without anything on the tracks at all. The resistance of a loco pulls that down to about 11.75 VDC. So mine are safe!

My old 'Fleischmann' was then screwed to the back of my wife's 1:12 doll house for lighting service! Haha! (Good recycling!)

My big N-Scale point to point layout is so big it requires two controllers at two large control panels therefore I built my own controllers into these panels. I got better at it each time too! Alas, this third one I built seen here has a box which was too small for everthing stuffed inside and outside of it.
My advice: Never scrimp on box size for a project!
Also the knob should have been larger in diameter. Mabye?

Cheers!
Charles

[Brian]

I also built simple DC train controllers (2 off) using instead of 2N3055 I used a MJ2501 mounted on a suitable heatsink. Worked extremely well on an exhibition layouts fiddle yard.
https://www.brian-lambert.co.uk/Electri ... in_control