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Combining AC and DC on the one output? Answered

I have a variable 0-12v DC output which has a maximum output of 1 amp.
I have a fixed 16v AC output which has a maximum output of 1 amp.

I am looking at how to combine the two so as to power a model with the variable DC output and also power lighting on the AC through a capacitor to filter the DC out.

Also, I would rather it was nearer 6v AC at the output. Would this just be a matter of a simple step-down transformer before they are combined?

Essentially, I am looking to replicate the functionality of this product for less than £42.95. This is too expensive especially when I need two of them.



You could use diodes so that the train was powered by cathode and lighting was powered by anode. I had a slot car set a long time ago where 4 cars would run on 2 tracks.

Then no train could backup.

Lionel trains had 3d rail and a 4 way step relay in each engine that advanced on
each track power down and switches the engine to


5 years ago

In my opinion, the very best train control is PWM. 
It lets trains creep into stations without jerking.

Lighting on a train and around the track is a matter of collecting DC energy
with a bridge to a "small large capacitor" and directing addressed pulse
coded commands to the miniaturized electronics LED lamp lightning assets.


I take it you don't want to go DCC then ?

I've spent a happy hour or so looking at model railway circuits. I think if you look for model railROAD circuits you may have more success.


That doesn't work with 50Hz. To make the trick work with components that fit in less than a small cupboard, you need to run at high frequency.

How would I go about increasing the frequency?

Presumably this would take it into the kilohertz range where it could cause interference if not appropriately shielded?

If it's a decent shaped signal, it won't generate RF to speak of, say at 10kHz.

IIRC there was an article in Wireless World back in the 1970s that did just what you want.......

Thanks. Do you have any idea where I could expect to find this article seeing as I wasn't even born in the seventies?

I've just had a quick look on line to see if there's any kind of index out there, but no luck yet.


5 years ago

I like your idea about AC in the rails for LEDs and  picking it off with a capacitor.

However LEDs run on DC ..... So you need to put a DC Bridge after the capacitor before the LEDs.

BUT ..... The real difficulty .... is the Motor will try to run on the AC at the same time as the DC.
This would HH your motor ( Heat & Hum ).


I knew that but I only stated up to where the signals were separated.
I know I would need a resistor also.