# Wiring Diagram Question



## Bwells (Mar 30, 2014)

I want to light some HO passenger cars and have been watching Lostsouls thread but my case is a little different. I want to use only the first two cars as track pickup with the first picking up one side and the second picking up the other side. I would like it to work on both DCC and DC but drew up a picture and thought I could use some input. Here it is:


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## highvoltage (Apr 6, 2014)

That's a plan, one comment though. Both of those cars will always have to be in the consist. Otherwise there won't be path to complete the circuit.


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## Bwells (Mar 30, 2014)

I understand that but I want to minimize rolling resistance at the added expense of miniatronis micro connectors, they are PRICEY. This way I would only have two cars with pickup but a lot of plugs. It would give me plenty of pickup using just two cars. Not sure what is better though. Thanks, Brian


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## Tom_C (Jan 8, 2016)

From your drawing and the criteria that you want to use it for dc and dcc, I would probably use a full wave retifier on the front end, and then connect + and - on each car.


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## Bwells (Mar 30, 2014)

So a bridge instead of the diode and then to the cap, etc? That was my first thought but that would mean a 3 pin connector between car 1 and 2.


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## Tom_C (Jan 8, 2016)

Yeah, I guess that is true, if you want to use 2 cars to pull track power. 

But, a full wave on the front end means you don't need to worry about how you put the cars on the track, it will work regardless.

ADDED: I guess if you use each car with + on one and - on the other then you could still use a 2 pin connector...I need to think about that more. You are still required to have the front 2 cars always connected together, and not connect the other cars to those front cars if they aren't connected together, and that may cause future problems if the connectors are the same.

ADDED AGAIN: If it were me, I wouldn't want to use the same type of connector for 2 different applications/voltage connections, because it will just create problems later.


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## traction fan (Oct 5, 2014)

*Batery power*



Bwells said:


> I want to light some HO passenger cars and have been watching Lostsouls thread but my case is a little different. I want to use only the first two cars as track pickup with the first picking up one side and the second picking up the other side. I would like it to work on both DCC and DC but drew up a picture and thought I could use some input. Here it is:
> View attachment 278473


Bwells;

If you're going to use LEDs to light your cars, then I think it would be simpler to power them with batteries. No track pick ups = no drag from them. No bridge rectifier, or capacitor needed. Constant lighting regardless of whether you're running DC or DCC. An HO passenger car is big enough to hold two or three, AAA size batteries. Or. if you have interior detail in the cars, you could use one of those tiny, three volt, disc batteries. A switch on the bottom of the car could turn the lights on and off. Also, if you have a battery for each car, you won't need any connectors between cars. With no track pickups, there would obviously be no "track pickup cars" and you could run any consist you wanted. You might even be able to mount a twelve volt, "N cell battery on the outside of the car, under the floor, just like the prototype. With a dropping resistor, it would power several LEDs easily. The battery, and the resistor could be painted flat black, and disguised as under car machinery. That way, you wouldn't even have to open the car to change batteries. Also the interior would not have to hide a battery somewhere inside the car.

regards;

Traction Fan:smilie_daumenpos:


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## Lemonhawk (Sep 24, 2013)

You do realize that LED's are a current device, typically 20 ma. Hence you need to have some sort of voltage regulation and resistors to achieve this. Or, use a CL2 which is an LED driver that puts out 20 ma. Another possibility is to use a buck converter that will take any voltage and up/down convert to a constant voltage like 12v that you could then drive 12v LED strips (the strips contain the resistors). To me it would be easier to pack all the pickup and drivers in a single car (the baggage car) and then supply the 20 ma or 12v via connectors to all the other cars. No matter which way you go you will need a fullwave bridge and cap to supply the unregulated voltage to the CL2 or buck converter.


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## Bwells (Mar 30, 2014)

Tom_C said:


> Yeah, I guess that is true, if you want to use 2 cars to pull track power.
> 
> But, a full wave on the front end means you don't need to worry about how you put the cars on the track, it will work regardless.
> 
> ...


The first two cars are RPO and baggage with plenty of room for electronics, minimal windows. I live 200 miles south of San Francisco so I do understand the male/female thing and how it works. The connectors I am planning on are these:
http://www.miniatronics.com/Merchant2/merchant.mvc?Screen=CTGY&Category_Code=4.
I like the bridge idea cause I think it is true DC and not done by "cheating". I'll draw that up and see if I can get away from a 3 pin between car 1 and 2.. Traction Fan: I thought about the battery route with a magnetic reed switch for turning it off and on and just don't like the battery route. Thanks for the input, I'm still in the thinking stage.


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## MtRR75 (Nov 27, 2013)

Tom_C said:


> If it were me, I wouldn't want to use the same type of connector for 2 different applications/voltage connections, because it will just create problems later.


The electronics is over my head, but couldn't the OP paint the connectors different colors (black, brown, gray, rust?) to indicate which ones could be connected to each other?


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## Bwells (Mar 30, 2014)

It won't be a problem, Male pointing back and female pointing front. The first two cars are a given as the front car has one connector and the second is the baggage and match the connector. The rest will follow suit. I'm trying to get as much pickup and span the greatest distance yet keep the rolling resistance to a minimum. I could eliminate the connectors and make every car separate with it's own pickup but this would add resistance and have more of a tendency for flicker, which I cannot stand, even with a large cap.


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## Tom_C (Jan 8, 2016)

MtRR75 said:


> The electronics is over my head, but couldn't the OP paint the connectors different colors (black, brown, gray, rust?) to indicate which ones could be connected to each other?


Sure, he could do anything like that to keep them straight, and it sounds like Bwells has a connector plan anyway.

Bwells, I like those connectors you posted, but they're pricey. I just bought some of these that are small, but maybe not small enough for your liking. They are also cheap.

http://www.ebay.com/itm/272195249542?_trksid=p2057872.m2749.l2649&ssPageName=STRK:MEBIDX:IT


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## Bwells (Mar 30, 2014)

Those are cheape but I couldn't see a size, only the pin spacing of 1.25. Are they flexible so as to not derail cars?
Why would I need a bridge when lostsoul used only a diode? The strips have the resistor so I should be covered there. I do like the bridge rectifier, then a BIG cap then a 7812 then the strips but I think I would still need the third wire for the second car pickup.


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## Tom_C (Jan 8, 2016)

Bwells said:


> Those are cheape but I couldn't see a size, only the pin spacing of 1.25. Are they flexible so as to not derail cars?
> Why would I need a bridge when lostsoul used only a diode? The strips have the resistor so I should be covered there. I do like the bridge rectifier, then a BIG cap then a 7812 then the strips but I think I would still need the third wire for the second car pickup.


The connectors are small enough for my purpose connecting 2 On30 cars, but they might be too big for HO.

I looked up Lostsouls thread and scanned through the first page, and if I understand he is running 3 rail O gauge (AC) and you are running DC and DCC. The diode in his circuit it used to protect the LEDs in reverse polarity. In forward polarity they will work fine.

You need a rectifier so you can put your cars on the track and it will work in either direction (on DC) and to turn the DCC into DC.

ADDED: The 7812 will work, but for your purpose I'd just experiment with a series resistor and call it a day. WAY cheaper.


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## gunrunnerjohn (Nov 10, 2010)

Why not have both sides powered from the lead car, then you can simply run the two wires for the remaining cars?


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## DonR (Oct 18, 2012)

You might consider using both trucks on
the first car for power pickup. With your
rectifier and cap in that car, you would need
only 2 pin connectors for following cars.

There is another way though. Use axle 'wipers'
instead of wheel wipers for power pickup on
each car.. One
truck would be R rail other L rail. The rolling
resistance is a bit lower. That way you could
do away with the intercar wires.

Don


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## gunrunnerjohn (Nov 10, 2010)

Don, read the post above. 



> There is another way though. Use axle 'wipers' instead of wheel wipers for power pickup on each car.. One truck would be R rail other L rail. The rolling resistance is a bit lower. That way you could do away with the intercar wires.


No reason that wouldn't work for the first car to power the whole string as well.


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## Bwells (Mar 30, 2014)

Yeah, I thought about 1 car pickup for both sides but the axle wipers are easy however the wipers for the insulated wheels is a different story. That would be the best. Having all cars with pickup is a good idea as it would save $45 dollars in connectors but also greatly influence the rollability of six. I don't mind the connectors, I am just thinking about minimizing the drag by too many wipers.
Okay, a bridge it is then cap then 7812. The problem with DC is that the engine runs at a decent speed around 7-8 volts so the strips may not even light. I see DCC in it's future but until then, I'm stuck. What does a buck converter do? It wouldn't by chance increase voltage would it?


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## Tom_C (Jan 8, 2016)

I'm not familiar with them, but I think you can use a *buck-boost* converter to do that.


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## Tom_C (Jan 8, 2016)

Here is one from Amazon:

https://www.amazon.com/DROK-Adjustable-Non-isolated-Buck-Boost-Transformer/dp/B00GWCC6S4

Here's some on ebay, from a US seller:

http://www.ebay.com/itm/2-PCS-DC-BO...096286?hash=item3ccd66ae1e:g:DnQAAOSw0HVWDsvC

Here's some on eBay from China, so you decide:

http://www.ebay.com/itm/DC-DC-Boost...864741?hash=item258c7e1b65:g:-soAAOSw9GhYfJW8

http://www.ebay.com/itm/DC-DC-Boost...73a96fa&pid=100005&rk=1&rkt=6&sd=161270864741


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## Bwells (Mar 30, 2014)

Thanks Tom. That is interesting and I guess I need to read up on them. The width looks doable but the power plant car is going to be loaded with a bunch of cool stuff! I assume that once the loco goes DCC, I would remove the buck converter. While in DC mode, the input would change and I wonder if the output would also change?


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## Tom_C (Jan 8, 2016)

Bwells said:


> I assume that once the loco goes DCC, I would remove the buck converter. While in DC mode, the input would change and I wonder if the output would also change?


Thats a good question about the DC voltage changing and I guess you'll need to experiement. I'm sure there are probably high quality converters that will hold your set voltage, but on anything this inexpensive I would not trust it blindly.

As for removing it on DCC, why bother? If it works then just leave it... particularly if you use a 12v led strip and then you'll need a voltage regulator anyway, and the converter will do that job.

It looks like you need a bridge, a cap, and a buck-boost and then what ever connectors you decide to use.


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## Lemonhawk (Sep 24, 2013)

The idea of the boost-buck converter is that at low voltage the converter boost the output to 12 volts and as the input voltage increases it can change modes and reduce the voltage to 12v. Why change it when going to DCC? it will will take whatever come in via the bridge and cap and convert it to 12v, so the cars would work on both DC and DCC! If it all fits in the the baggage car then that's the place for it, just connectors to the other cars. Some day after you have DCC installed and when you have nothing better to do, you could replace the bridge and buck converter with a decoder so you could turn the lights on and off from your throttle. You would really needed to be bored to do this


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## Bwells (Mar 30, 2014)

Hmmmm, those things seem to good to be true. Once the output is set to 12, the input can vary and not effect the output? If so, that is the way to go for DC. It sounds like you guys figured it out. I think it is a keeper and I'll need to draw up a schematic while I wait for it to show. $12 Amazon Prime with free two day shipping. Done deal! The size was listed in both mm and inches and the two didn't jive. I guess I'll know when it shows!


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## Tom_C (Jan 8, 2016)

I just bought the one on eBay from the US seller, $9 for 2 pieces.

I built a circuit to supply 3v power to a string of LED lights from a passenger car, and this would have been much easier... Just dial in the output voltage and finished.

I didn't really participate to solve it, Lemonhawk planted the seed. I'd never even heard of a buck (or buck-boost) converter until he mentioned it


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## DonR (Oct 18, 2012)

GRJ

Sorry, I wasn't ignoring your post...I started my
reply before your post but got a phone call in
the middle, so posted after yours.

Great minds think alike...

Don


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## Bwells (Mar 30, 2014)

Here is version 2 and 3. I like version three but I'll wait for the buck converter and see what it does. Version three would allow me to crank up the buck to 14v and pack the cap solid and the 7812 would take care of the 12v deal. The diode will keep the cap from bleeding back into the tracks on shut down and power the lights for a while until they dim. To borrow a Las Vegas saying, what goes on in the circuit stays in the circuit! The cap I have in mind is a 10,000µF one, about the size of a C cell tad bit smaller. That should do it.


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## gunrunnerjohn (Nov 10, 2010)

You do realize that a buck converter has to have a higher voltage in that it does out, right? Will your track voltage always be more than 12 volts be at least a couple of volts?


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## Bwells (Mar 30, 2014)

Damn it John, no I did not! So it is too good to be true, I suspected that. What the heck good is it? I can do that with a LM78XX, it's worthless! Back to the drawing board, AGAIN!


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## Lemonhawk (Sep 24, 2013)

Don't panic! The Amazon item were talking about, John, is a buck boost converter so it will take about anything you throw at it. At really low voltage it just does not supply much current, but were talking about powering LED's.


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## Tom_C (Jan 8, 2016)

Lemonhawk said:


> Don't panic! The Amazon item were talking about, John, is a buck boost converter so it will take about anything you throw at it.


Correct. There are buck converters, and there are buck-boost converters. The one I posted earlier (and I think the one Bwells bought) are buck-boost. 

If you look at the differences in the circuit boards, the buck has fewer parts than the buck-boost.

Buck (step down converter)

https://www.amazon.com/LM2596-adjus...qid=1486729414&sr=1-3&keywords=buck+converter

Buck-boost (step up/step down)

https://www.amazon.com/DROK-Adjusta...GWCC6S4?tag=vs-collectables-convert-amazon-20


Bwells, I don't think you need the diode in your updated circuit. The output of the buck-boost will always be +dc. Also, me personally, I would tie power straight through to each car, and not daisy chain it like you are showing. It may not be noticeable, but you may get some voltage drop at each car if you daisy chain it like your diagram. 

Eliminate version #3, you won't need the 7812 and you don't need the caps in each car, but the caps won't hurt, either, they just aren't necessary if you have enough capacitance up front.

The only change I might do is put the cap between the bridge and the buck-boost. Not sure it will matter one way or the other, but it will smooth out the complete drop-outs of input voltage to the converter.


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## gunrunnerjohn (Nov 10, 2010)

I only saw buck supply, so that's what I based my comment on. 

It will depend on the buck/boost supply you use, some don't have sufficient input capacitance and will require bulk capacitance after the bridge.


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## Bwells (Mar 30, 2014)

I hope this buck boost does what I think it does. No idea how it can but I'll find out! Here is the latest using Tom's suggestions. The first cap, 470µF, is a smoothing cap, the second cap is my storage cap, 10,000µF, and I did keep the diode in the circuit to act as a check valve. I don't want the stored juice to backfeed into the circuit but want to keep it all to power the LEDs after shutdown. If I can get 15 seconds out of it, great, if not, I'll throw some 470s in every car and a 3000 at the end(I like capacitors). Check it out and hopefully this will work as I am out of paper!


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## Tom_C (Jan 8, 2016)

Oh ye of little faith. 

You don't need the diode, but you can leave it if you want. I might put the 10k uf cap between the bridge and converter, but it will probably work either way.

Here's something to read in your spare time. Scroll down to the bottom of the page and there is an animation of how the buck-boost works.

http://www.learnabout-electronics.org/PSU/psu33.php


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## Bwells (Mar 30, 2014)

Hmmm, interesting. I see there is some ripple current in the output so wouldn't the cap behind the buck smooth that out?


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## gunrunnerjohn (Nov 10, 2010)

If we're talking this one, it should work with low output currents as it does have some filtering. I'd probably give it another 1,000uf capacitor anyway.


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## Bwells (Mar 30, 2014)

Yes, that is the one. When you say another 1000 do you mean on the input side in addition to the 470 or a total of 1000µF? I do have a 1000 and a couple 3000µF caps, I guess more is better?


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## gunrunnerjohn (Nov 10, 2010)

I'm seeing 220uf on the input of the one linked earlier that I pictured, but I was talking about 1,000uF extra. You can use 3,000uF as well, the larger the input cap is, the more current it'll handle before the supply gets upset about the input ripple.


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## Bwells (Mar 30, 2014)

Okay I see. the shiny things on the PCB are caps? Then a 1000 on the input side should do it or 3000, not a big deal.


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## Tom_C (Jan 8, 2016)

The ripple is of no concern, you'll never notice it in the lights. As long as you have enough capacitance to overcome the dropout of track power then you're good to go. That's why I would put most of the capacitance in front of the converter so it will have a relatively constant voltage regardless of track power dropouts. I don't think you even need caps on the output, but it won't hurt.


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## Bwells (Mar 30, 2014)

In DC mode, the cap in front of the buck will only be getting 7-8 volts and my way of thinking is that this is what takes care of the smoothing and whatever else the cap does. The one on the output side is for storage and it needs the boosted voltage to be of any use for the strips. I want then to continue to burn and then slowly go out on power down. Looks better than just slamming the circuit off.


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## gunrunnerjohn (Nov 10, 2010)

The ripple is a concern because the switching regulator will drop out if you have too much ripple.


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## Tom_C (Jan 8, 2016)

gunrunnerjohn said:


> The ripple is a concern because the switching regulator will drop out if you have too much ripple.


I guess I was replying more to Bwells comment about ripple on the output. Putting most of the capacitance on the front end will help with your point.



Bwells said:


> In DC mode, the cap in front of the buck will only be getting 7-8 volts and my way of thinking is that this is what takes care of the smoothing and whatever else the cap does. The one on the output side is for storage and it needs the boosted voltage to be of any use for the strips. I want then to continue to burn and then slowly go out on power down. Looks better than just slamming the circuit off.


 In DC mode you won't need any smoothing, and the storage is going to work on either side of the converter, more or less. There will be insignificant lost in the converter so any storage in the cap will transfer through to the output. IMO.

Added: I guess a cap on the output will smooth any ripple created by the switching in the converter, if there's anything worth smoothing. That's why I *think* any ripple on the output isn't of concern because it won't be noticed in the lights, but admittedly I have zero experience with these converters.


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## gunrunnerjohn (Nov 10, 2010)

Yep, ripple on the LED's isn't a big deal, I was suggesting the extra cap on the input side.


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## Tom_C (Jan 8, 2016)

OK, so to summarize all this info, Bwell, put your 3k-10kuf cap between the the bridge and the converter. If you want extra storage put a 470uf-1kuf cap on the output. Those 2 caps will smooth most of the ripple on the front end, and also smooth the output of any switching ripple created in the converter... which may not be necessary but won't hurt.

If you get >1 second dropouts of track power then you may get flashing LEDs in your passenger cars, but I think you'll be about as good as you can get short of using batteries (which would not be my preferred solution... track power all the way, baby!)


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## Bwells (Mar 30, 2014)

Alright, I understand the cap in front of the buck boost, I'll plan on a 3000µF, no big deal. The cap on the back end is the kicker here. I want it to act as a BIG battery that will supply power to the LEDs on shutdown. I want them to continue to burn for awhile, slow dim if you will. Whether the cap will pass voltage back through to the buck and through the bridge and into the track, I don't know. Hence the diode to remove all doubt. I know that a 7809 and 7806 do that so I added a diode to stop it. Either way is fine I guess, I'm just looking out to not pass my stored stuff where it does not need to go. I'll check the buck for that first off as I have no idea what state the schotky diodes are in when powered down. Never checked to see on a bridge even though it is loaded with diodes, hitting it backwards may create a different path. I do think I'm good to go on this one and with a little fine tuning, it should do both DC and DCC.


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## Tom_C (Jan 8, 2016)

The bridge will prevent any feedback into the track. I think you would need a BIG capacitor to keep the lights on for more than a few seconds, but that is based on my experience with incandescent lights in passenger cars. With a 1kuf cap I get dimming when it goes over a dead spot (dirty or misaligned track). Not complete outage, but a little dimming. I guess you just need to experiment to adjust to your liking.


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## Bwells (Mar 30, 2014)

Yep Tom, I agree, by the way, you can call me Brian if you wish, or whatever! I found that caps deplete real quick with incandescent bulbs but with LEDs, they seem to last longer. I haven't tried out my 10K on a six foot strip of LEDs but it should do something, if not, more caps! Just to throw a monkey wrench in, I see Tomar Industries has drumheads for the observation car but they are 1.5 volt incandescent. Oh boy, I see a whole other circuit brewing at the end of the train!


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## Bwells (Mar 30, 2014)

Update: I received the buck-boost converter yesterday and looked at it and measured it. It is the perfect size for my application but that was it for yesterday. Tday, I decided to run it thru the mill and hooked it up to the track with jumpers. Turned up the DC controller to 6 volts and measure the output. It was near 12 so I adjusted it down to 10 and then checked the track power. 13.5 volts!! What the heck, I disconnected it real quick and then figured it needs a load. Glancing around I spotted a half used roll of 5050 RGB so I hooked them up and they burned bright. Check output, 12, check input 14! look at the controller with analog ammeter and volt meter, yep 14v and the ammeter is reading 2 amps! Turn every off and proceeded to scratch my head. Okay, the LEDS are RGB so I assume there is 3 LEDs within each 5050 so triple the milliamps. Hopefully that accounts for the high amp draw. The voltage thing is weird. It is like the boost is making a bunch and passing it down the road as well as backfeeding it into the track. I gave up for now but will be back tomorrow with some 3528 warm white in the correct length for what I need and see what happens. I did not add any caps as I figured the transformer should be putting out filtered DC.:dunno:


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## Tom_C (Jan 8, 2016)

I just remembered about this thread and came back to look. I also bought a couple buck-boosts to play with but I haven't gotten around to messing with them.

I don't think they are feeding back into your track power, but that's just a guess with nothing to back it up.


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## Bwells (Mar 30, 2014)

As far as backfeeding into the track, I can't think of anything to explain the 14v on the transformer as it was set for six. If the buck-boost is backfeeding into the track a diode should stop that but pulling 2 amps! That is crazy and doesn't sound good for DCC. Let me know what you get with yours. Mine is in a ziplock bag and skewered onto a pegboard hook, for ever.


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## Tom_C (Jan 8, 2016)

If you put that bridge on the front end that would prevent the possibility of backfeeding.


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## Bwells (Mar 30, 2014)

Good thought, I was using DC so I hooked it straight to the track. I was just thinking that maybe the amp reading was coming from the boost also. I may give it another shot with a bridge in front.


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## Bwells (Mar 30, 2014)

Tom, any info on the tests you did with your buck-boost converter? I was thinking about my last idea and it seems wrong. Normally you pull amps and not push them so still in a quandary as to why the ammeter read so high.


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## Tom_C (Jan 8, 2016)

Sorry, I've had other things going on and have been wasting a lot of time doing nothing, so I haven't done any tests on the circuit yet.


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