Model Railway Forum

I've only just joined this forum (although I'm not new to model railways) so apologies if my questions already have answers on here and I've just not found them yet.

I'm restarting my hobby after a break of many years and starting with a very small and basic setup to get back into it. Once I've completed my small project I hope to have learned enough about scenery making to move onto to grander things.

Time for my first question though.

I intend to build my own control panel that will have an input of 12V DC and a knob or slider built in to control the train's speed. My question is, what specification of potentiometer would I need, i.e. how many ohms to give complete control from full speed to a stop? There will only be one loco per track/section so I'm assuming about 250mA.

Also, does anyone have any recommendations about the best places to obtain these, along with DPDT switches and the like?

I am keen to get the electrical side of things sorted early on so that when I want to start on my bigger project I won't be having to spend lots of time sorting out these aspects.

Cheers

Hi
You cannot use a slider or rotary potentiometer (pot) to just control a locos speed. It would burn out almost instantly!
The slider or rotary pot needs to operate other devices such as a power transistor. The base current of the transistor being adjusted by the pot and in turn the transistor adjusts the output volts to the rails between 0 and 12v DC. The transistor should be able to pass 5Amp and a higher amperage is better, In addition there needs to be overload/short circuit protection provided too set normally for DC to 1.0Amp.

Unless you're adapt and building electronics, I would suggest you look at the excellent Gaugemaster panel mounting controllers or their Hand Held controller - Examples are their single panel controller GMC-100 or twin track GMC-UD Hand held is GMC-HH. These all are usually feed with 16v AC at around 1.0 to 1.5Amp. But 12v DC at 1.0A or above could be used, but will result in a lower top speed. Note; Gaugemaster also sell cased mains to 16v power supplies the GMC-M1 is an example Link to GM controllers https://www.gaugemasterretail.com/magen ... 5.html?p=3 Its also worth looking on the www for Gaugemaster products and a lot of their stockiest sell these products cheaper then GM themselves!

I think there is a lot more to a train controller than just a variable resistor, in fact the basic models used to use a variable transformer.

I was looking for a replacement DC controller recently and stumbled upon the site below:

https://www.scottpages.net/ReviewOfControllers.html

Because of the amount of current that a model loco motor takes, a simple potentiometer cannot be used as it would burn out but you can use the pot to control a transistor (for example) which would then send power to the layout.

Wow, I'm impressed!
Seriously, three great replies and my question hasn't even been on here for an hour yet.

I take all your points and have just taken a look at those Gaugemaster controllers. The panel mounted ones are pretty neat!

Thanks everyone!

I really like their Hand held controller, as it allows more freedom to move about around the layout.
16v AC input and controlled DC out all by a 4 core flexible cable. Frequent connected to the panel via 4 or 5 pin DIN plug and socket (5 pin doesn't normally use the central pin 3!)

I have used both panel mounted and handheld Gaugemaster DC controllers and though I totally agree that panel mounted controllers really do look neat, I do admit that the hand held ones I preferred as they were more practical, as if a train stalls it nearly always is out of reach of ones conteol panel, and if one ups the speed to provide the loco a chance to go once one gives it a gentle tap, one has to quickly run to ones panel to slow it down before it flies off the layout! Haha. Ok. Maybe a little extreme but it has been known!
With a hand held controller one can usually just go to where the locomotive is, and if ones layout is larger, one can provide multiple sockets to just plug them in.
One thing I did do was to glue a piece of velcro on the back of the handheld controller (The hooked part of velcro) and one can add a whole strip along the edge of ones layout with the softer side of the velcro, so one can simply stick the hand held controller wherever one wants to use it.
I did have two independent control panels which both had duplicated cab control with indicator lights as I wired for common return so the other side of the switches were dedicated to panel light indication. It took a bit of thinking and a lot of wire to do this for both stud contact point control and cab control section switches, but the results and ease of operation I think were actually easier to use then my later venture into DCC. I was just about to add the probe part of the stud and probe point control to my hand held controllers to make it easier when I had to take my layout down as my brother wanted the larger room.
By then I had sold the hand held units to go into DCC but never did make another 00 gauge layout due to circumstances I was in.
By the time I changed to 7mm narrow gauge I decided to go back to simple DC control and use a very simple controller which is not yet finished and will run on a 12volt battery. (I do have a Gaugemaster panel controller but it did not really work well from a 12volt battery which is why I decided to make my own... Not quite finished as I want to build part of it into a backscene structure of my little portable layout).

I agree 100% with Mountain Goat about the hand-held units. I have an ancient Gaugemaster WS unit which I must say is quite poorly built and I have had to make several mods to it. However, I must say it is a very good controller and they are still in business so they must be doing something right.

The idea of the velcro strip is brilliant! I fixed a loop on the back of the controller and use strategically placed hooks to hang it on. However, I will switch to velcro at the first opportunity.

The most important things with Gaugemaster DC controllers is ...
A) They just work so well.
and
B) They have a lifetime warranty.

I’ll second that.