# Ac to dc conversion



## Terminator1983 (Sep 10, 2013)

Hello, I am not really a beginner have been into model railroading for couple years but I have a question regarding lgb trains and Lionel transformers. I am well aware that Lionel is ac and lgb is dc but I have several zw transformers and only a few Lionel o scale train set ups. I am currently running my lgb with the Lionel zw-l which I have hooked up to a Lionel ac to dc converter box. The train runs great with lots of power. My question is will I encounter any problems I may not be aware of with this even though it works fine and I converted the ac to dc to run it?


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## Cougar Rock Rail (Jan 2, 2008)

I see no reason why that wouldn't work just fine and if it runs smooth with no strange buzzing etc., then I'm sure it's OK. LGB trains are designed for


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## alvin harris (Oct 3, 2018)

what type of ac/dc adapter would I need if I used a lionel zw-l transformer to run my dc trains?
is at all possible.
thanks much


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## alvin harris (Oct 3, 2018)

what type of ac/d adapter would I need if I used a lionel zw-l transformer to run my dc
trains? is it all possible?
thanks much


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## dbodnar (Jan 2, 2008)

Alvin - all you need is a bridge rectifier (rated at several amps, minimum) and a few filter capacitors (the caps are not strictly needed but are a very good idea!)


You will also need a Double Pole Double Throw toggle switch to change direction.


dave


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## East Broad Top (Dec 29, 2007)

Dave, do you know of a basic schematic to wire this up? A Google image search for "AC to DC converter schematic" turned up a bunch, but the input and output voltages as well as capacitor values are all over the place, making it hard to figure out what would be suitable for voltages common to large scale.

Later,

K


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## fredlub (Feb 7, 2010)

Look here for a AC/DC box I made, with drawings: https://ogrforum.ogaugerr.com/topic...-dc?reply=77734316000252819#77734316000252819
Regards
Fred


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## Dan Pierce (Jan 2, 2008)

To get DC without much of a ripple, a capacitor is needed on the DC output of the bridge rectifier. I would suggest a value of 1,000 microfarad for each amp. If you have a transformer rated at 4 amps, make saure the bridge rectifier is more than that (5 amps or more) and use a 5,000 UF (microfarad) capacitor.
Note that the more current you draw, the bigger the ripple, however, the capacitor on a 16 volt AC source will give you over 20 volts DC (16 times 1.414 minus the diode drop).


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## Dennis Cherry (Feb 16, 2008)

Connect the capacitor to the output of the diode bridge and before the reversing switch. Observe polarity of the capacitor. + goes to + and - to -.


Use a 10 amp or higher bridge rectifier and also add a fuse on the output to the track say around 5-7 amps.


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## dbodnar (Jan 2, 2008)

East Broad Top said:


> Dave, do you know of a basic schematic to wire this up? A Google image search for "AC to DC converter schematic" turned up a bunch, but the input and output voltages as well as capacitor values are all over the place, making it hard to figure out what would be suitable for voltages common to large scale.
> 
> Later,
> 
> K



The folks who chimed in are spot on - take the output from the Lionel transformer and connect those wires to the AC input terminals on a large bridge rectifier -- run the + and - output from the bridge to the + and - on the capacitor - that goes to the DPDT toggle for direction.


I would try a bridge rectifier similar to this one I found on Amazon:
https://www.amazon.com/BLS-KBPC3504...e+rectifier&refinements=p_85:2470955011&psc=1


A 10,000 uf, 50 volt cap (or two in parallel) should clean up the AC - 

https://www.amazon.com/Nichicon-100...d=1538662722&sr=8-2&keywords=10000uf+50+volts


Good luck!


dave


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## Dan Pierce (Jan 2, 2008)

If using a smaller scale AC power source, then 35 WVDC (Working Volts Direct Current) Capacitor is OK.
These do have a 20 percent tolerance and I always assumed it was for capacity and voltage. SO, 35 volts is ok for up to 28 volts DC.


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## dbodnar (Jan 2, 2008)

Dan Pierce said:


> If using a smaller scale AC power source, then 35 WVDC (Working Volts Direct Current) Capacitor is OK.
> These do have a 20 percent tolerance and I always assumed it was for capacity and voltage. SO, 35 volts is ok for up to 28 volts DC.



That is likely OK, Dan, but I was always taught to double the expected max voltage just to be safe.


dave


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## krs (Feb 29, 2008)

Dan Pierce said:


> If using a smaller scale AC power source, then 35 WVDC (Working Volts Direct Current) Capacitor is OK.
> These do have a 20 percent tolerance and I always assumed it was for capacity and voltage. SO, 35 volts is ok for up to 28 volts DC.



Dan,


The tolerance for capacitors relates to the value of the capacitance only, not the voltage.
The voltage specification is the maximum the capacitor is designed, tested and guaranteed to tolerate.
I spent the first ten years of my professional life designing electronics for the telecommunications industry - we used as a rule-of-thumb for capacitor voltages 50% over the maximum design voltage of the circuit.
So for a 24 volt circuit that would be 36 volts.
Depending on the life expectancy that was required for the design - a commercial product would use a 35 volt capacitor in that circuit, a telecommunication product would probably use a 50 volt capacitor unless space doesn't allow that.


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## krs (Feb 29, 2008)

dbodnar said:


> That is likely OK, Dan, but I was always taught to double the expected max voltage just to be safe.
> 
> 
> dave



If space or cost is not an issue, that is certainly fine.


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## Dan Pierce (Jan 2, 2008)

When I looked at the specs, it said 10,000, 25 volt 20 percent tolerance. This led me to believe it was for both. I will always up the voltage on my caps, it is not worth destroying equipment for the little extra cost. And most capacitors now come from other countries, not the USA.


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## krs (Feb 29, 2008)

> When I looked at the specs, it said 10,000, 25 volt 20 percent tolerance.


Yes - I can see where the confusion comes from.
Retailers do a lousy job when they put specs on their website.
Mouser for instance also uses the order of capacitance, voltage, tolerance....... in their capacitor selection table - https://www.mouser.com/Passive-Comp...apacitors-Snap-In/_/N-75hr0?P=1z0wqs8Z1yx4avv


But if you look at an actual manufacturer's datasheet like this one:
http://www.cde.com/resources/catalogs/SLPX.pdf


it's much clearer.
There are also a number of other capacitor parameters listed that we usually don't worry about in our applications.


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