# DC motor, Run on AC



## T-Man (May 16, 2008)

Ok, this is the last time. I have my 8604 that has a DC motor. TOnight I got it to work on AC with one Radio Shack part. It goes forward and works. I just have to display the pictures but that puter is upstairs. It will take longer to post it than it did to get it to work. 
I have another project to finish too.


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## T-Man (May 16, 2008)

First you but this part for under 3 bucks.
You have four connections. The two inners go to the frame ground and center pickup. 
The red from motor goes to the + side and the black goes to the other side.
Easy.











The nice thing about these motors is that it has only two screws and you can replace it.
It ran like a champ.










You just installed a bridge rectifier.


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## imatt88 (Jan 31, 2010)

OK, I suppose this will work on my 8625?:thumbsup: 

T-Man, was this directed at me, by chance?

Now I have to make a road trip to the nearest Radio Shack....2 hours away:laugh:


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## T-Man (May 16, 2008)

I aim to please.


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## tjcruiser (Jan 10, 2010)

T-Man,

Just out of curiosity, any idea on how "pure" of a DC signal comes out of the bridge? I.e., is it true steady voltage, or does it have a pulse / step signal of high frequency?

Thanks!

TJ


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## T-Man (May 16, 2008)

For electronics Chips need filtered DC. To my knowledge it is not enough and needs capacitors. Look for my DC power supply.


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## T-Man (May 16, 2008)

I have been thinking with a DTDP switch it can be made to work AC or DC.
DOn't know if you are interested in it.


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## tankist (Jun 11, 2009)

TJ, what rectifier does is invert the "negative" part of the sine wave. so resulting DC is pulsed. which i guess not an issue for a motor.however to reverse direction there should be some sort of switch on the Loco, otherwise its always forwards.


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## Reckers (Oct 11, 2009)

Anton, does that mean the negative side's new sine wave is in step with the original sine wave? As in, do both curves peak at the same time and place? Or does one rise as the other falls? I can't think of any reason I'd need to know that, but you made me curious!


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## tankist (Jun 11, 2009)




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## Reckers (Oct 11, 2009)

Got it---thank you. What piqued my interest was that it would seem to make a more powerful motor.


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## tankist (Jun 11, 2009)

Reckers said:


> Got it---thank you. What piqued my interest was that it would seem to make a more powerful motor.


not really,you can't get something from nothing.
but compared to smooth DC, pulsed DC might be better for low speed control - breaking the stiction since the Vpp voltage is higher then average voltage (Vrms i think its called).


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## Reckers (Oct 11, 2009)

I was thinking in terms of pulling power. Since both seem to be pulsing, the more rapid pulse would seem to be an advantage when pulling a train uphill, for example. Or am I wrong?


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## Stillakid (Jan 12, 2010)

Interesting explanation here.......
http://www.authorstream.com/Present...-pulse-wi-pmw-width-education-ppt-powerpoint/


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## tjcruiser (Jan 10, 2010)

Guys,

Just back from a business trip and catching up. Thanks for the dialog above, and the explanations of what the bridge rectifier is going. Makes sense, especially if one considers the diodes that make up the rectifier as simply one-way valves that open and divert current in only one direction.

I know that there are other devices that are "regulated power controllers" that not only invert AC to all-positive, but filter it somehow to generate a much cleaner steady-state DC output.

As a sidenote, I was amazed to learn recently how DCC works. To my surprise, it's not via DC power at all, but actually a stepwise (square wave) AC signal, with the duration of each step (and it's +/- component bias) triggering each loco's unique onboard decoders. Quite clever.

Cheers,

TJ


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## T-Man (May 16, 2008)

I believe MRC uses the pulse to slow the motors down for more realistic speeds. Model motors tend to be too quick.


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## T-Man (May 16, 2008)

*Run AC and DC with a DPDT Switch*

Without the e unit, I took the DC motor one step farther. With a double throw, double pole, switch and a bridge restifier, I can wire the motor to run forward on AC and DC current. The advantage of DC is that I can reverse the motor by reversing the current at the transformer.

Here is the diagram. The motor is connected to the center of the switch. The top leads are connected to the frame and center pickup. The bridge is wired between the switch and the frame/center pickup. The two track polarities are attached to the two center connections of the bridge . Not shown.










The motor and switch.









The bridge epoxied to the frame and the completed wiring. It runs great.








If you look at the plus sign above.T he black is from the center pickup, the red goes to the switch for DC power. The unused lug to the left is the converted AC that goes to the other side of the switch.


A better diagram


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## tjcruiser (Jan 10, 2010)

T-Man,

Neat ... Very clever use / combination of the switch and the rectifier to toggle the AC or DC option. Very clever, indeed.

Although it's running AC, rather than DC, the old-school manual toggle that came with my "new" Lionel 1681 is essentially a double-throw-double-pole switch, albeit in a circular disc design.

TJ


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## T-Man (May 16, 2008)

It gives on less excuse not to have a DC trolley setup on a table. To have an engine that can do both is rather cool.


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## Reckers (Oct 11, 2009)

Nice work, T-Man!

You know...I've heard that certain older manufacturers used AC motors, and those would run on either AC or DC. Now THAT sounds like a superior product! Have you ever run across anything like that? *innocent look*


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## T-Man (May 16, 2008)

Any motor with a coil can work DC. The problem is the reversing units.I can't explain why but if removed they work.


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## Reckers (Oct 11, 2009)

Reckers said:


> Nice work, T-Man!
> 
> You know...I've heard that certain older manufacturers used AC motors, and those would run on either AC or DC. Now THAT sounds like a superior product! Have you ever run across anything like that? *innocent look*


Actually, T-Man, I was fishing for "Oh, that's right....with AMERICAN FLYER S SCALE, you can run on ac or dc!"


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## T-Man (May 16, 2008)

I know. Sort of. 
They do run, but I was thinking. The draw back is in the field winding. WIth DC the winding has to stay the same and the armature current has to reverse to make the engine go in reverse. This can't happen unless you wire it that way.
ALso the DC may magnetize the e unit. Just a theory based ona guess.


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## T-Man (May 16, 2008)

To carry on, a 25 amp bridge rectifier is needed. It took me this long to find out. Here is the latest thread on the subject.


Not bad only two years.


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## servoguy (Jul 10, 2010)

T, I think a 25 amp bridge is a bit of overkill. If you put 25 amps through the field coil, the smoke will come out. A 5 amp bridge should be sufficient. Also, I posted a comment about a better way to wire up the motor with the bridge.


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## gunrunnerjohn (Nov 10, 2010)

Gosh, even 5A through the field coil sounds like overkill!



> ALso the DC may magnetize the e unit. Just a theory based ona guess.


I've seen this happen, T-Man. It was just using a rectifier to run the E-Unit on DC to eliminate the buzz, but it's the same as running the whole locomotive on DC.


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## T-Man (May 16, 2008)

I pulled the wrong thread. I used a scout motor once and had no luck. Just too much heat for the bridge. SOmething was wrong. I gave up on that and did this thread..


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## infernisdiem (Nov 12, 2011)

as someone suggested to me, just go buy a DC out put transformer, I have one that runs my 8902 engine, and because I am lazy, I have a main line that goes to my track, then off from that line, I have my AC transformer on the left, and my DC transformer on the right... so far no issue, just can't use them both at the same time, nor even unplugged, can i have the AC transformer set to on, and vise versa, it seems to slow if not stop my trains dead on their tracks.


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## T-Man (May 16, 2008)

Er OK. 

I have a trollley line that runs on DC. I use this engine on it. 

Then if I get another DC engine I can flick my switch and run it on the main line.  Two unconnected blocks.

If you run MPC era engines it is nice to have the DC transformer.


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