Cheap DCS / track power option - Laptop 100 w DC power supply

The laptop supply should work fine, obviously you'd be running on DC.  Personally, I'd use the 50W to power the TIU through the aux port so the entire 100W is available for the trains.  Note that you will only be able to run fixed voltage for command with this, the TIU can't vary the voltage of DC supplies using the variable channels.

I'm presuming you're running PS/2-PS/3 stuff on this layout?

I never had any luck using a switching power supply.

Have you tried a laptop supply as he's suggesting?  I have a 4A one, and on the bench it delivers 4A at the rated voltage just fine.  I can't imagine why it wouldn't work, DC is DC, unless you overload it.

I've had quite good luck with my Z-4000 switching power supply

I believe you said elsewhere you have a relatively compact layout and this is a temporary solution.  To your point, it's probably true that your switching supply frequency is in the range of the DCS signaling frequency.  But perhaps your DC "brick" has a EMI filter blob near the output plug or you can add one for a few dollars.  I'd run the DCS signal quality test and if you don't get all 10's then add a filter before the fixed TIU input.  Let us know how it works out!

FWIW, I just did a quick test of a DCS locomotive with a laptop power supply, mine was the Kingston Model# 33197 Universal 120W Power Adapter.  It's a slim portable universal laptop supply that runs off either 12VDC or 110VAC.  It ran a PS/2 locomotive flawlessly, maybe smoother than the 180W brick that I normally use.

Hi all,

Carl,

The laptop charger may or may not work.  Go ahead and try it.  If you can add an engine to DCS with that power supply everything else will be fine.  If you can't add an engine it probably will never work because the switching frequency is incompatible.  I have tried a number of different DC switching power supplies over the years for HO display setups with mixed results.  Switching supplies intended for PC's tend to be higher frequency with smoother power output.  Your chances of success are pretty good.  Either way you won't harm the TIU.

I'd be cautious with the 16 VAC power supply running on 230V 50HZ.  I built two display layouts for MTH that are now touring Europe.  Europe's power grid has turned out be quite a problem.  We provided MTH with step-down transformers so they could use Z-1000 brick power supplies.  Unfortunately, EU standards allow anywhere from 216-253V 50HZ, which is far more deviation than what is allowed in the US or Canada.  They have had more than one TIU failure due to excessive voltage.  I have no experience with South Africa's power grid, but I would be interested to assist you as I can in order to learn.  If you have a digital volt meter that can capture MIN/MAX voltages I would suggest you test the actual voltage from your outlets.  Check the ratings of the transformer to calculate the step down ratio (e.g. 230 input / 16 output = 14.38).  Apply this ratio to you actual outlet voltage to find your expected output from the transformer.  As long as this figure is below 18 volts I'd feel pretty comfortable using the transformer.  This is somewhat lower than the acceptable voltage we might use in North America due to your lower frequency.

No I haven't tried that particular brand but I have tried a Cherokee 40 amp 30 volt DC switching power supply and a Meanwell 24 volt 10 amp DC switching power supply and both didn't play very well with DCS. Both of those models do well with DCC though.

As I understand it the chopped sine wave coming out of a swp feeding a TIU is detrimental to the DCS signal as the TIU chops it again...and a double chopped sinewave is no good.

A Z-4000 is a pure sinewave AC power supply 

If you stick a scope on the laptop power supplies, you'll see you don't have the hash you see on other switching supplies, at least the two I checked looked pretty clean, even with a load.

Dave has a good point, I'm spoiled by the US power supply, so caution is advised.

As far as the noise on the other supplies, a healthy choke and capacitor would clean that right up if you have a suitable DC supply in other specifications.

You can also set the variable channels to fixed mode to have more TIU outputs and capacity.

I like your "power line conditioner" application of a UPS.  But note that modern UPS systems - those that generate sinewave-like waveforms - are...wait for it...switching power supplies running at tens or hundreds of kHz.  Your audio friend might find it amusing that the PS2/PS3 audio amplifiers are...wait for it...switching power converters (class-D type) running at hundreds of kHz.  Yet, the end-result is "clean" sound pressure levels in the audio frequency range.

As I see it, the issue is compatibility  - specifically if DCS works if powered by a source that internally uses high-frequency switch-mode components.  Since I don't think you'll find relevant technical specs on either side, the consensus is for you to just try it and if it doesn't work to consider some additional filtering. 

As to your wondering about PS3 current, I don't think there's a simple answer.  I have not seen any published information showing power requirements for different engines under different condition (speed, load, grade, smoke, etc).  As was suggested earlier 100 Watts might be all you need for a flat, low-speed, single-train layout.  You benefit from the...wait for it...switching power supplies used inside the PS3 engines which effectively makes it a power issue.  This means that, to first order, if your engine needs 28.8 Watts to do its thing, then this can come from 16V at 1.8 Amps or 18V at 1.6 Amps...symmetrical numbers chosen to illustrate the point.  Most hobby meters can make DC-current measurements to 10 Amps so you might activate different features on the engine and jot down the incremental power.  A PS3 engine in shutdown draws only a few Watts.  Audio takes less than you think...also a few Watts even with the Horn blowing.  Smoke takes a bit more...5 Watts or maybe a bit more.  The motive power is what gets you.  An engine by itself slowly moving might draw only, say, 20 Watts with audio and smoke on but add some metal diecast cars and hit a grade and it's "More power Scottie!" as Captain Kirk would say.  I'd think if you identified the specific consist you have and asked here on the forum someone may be able to report how many Volts/Amps are reported on their Z-4000 or whatever running that exact load.

I think you said you have lighted passenger cars. Cars with incandescent bulbs can draw 10 Watts or more.  If you do the LED conversion as many of the guys have done, you easily get less than 1 Watt per car - a dramatic power savings.  If your tester/meter has a current measurement function compatible with the power (AC or DC), try measuring the lighted car current (and hence power).  Or identify the exact cars you have and someone here might be able to give you some numbers.  This might get you motivated to start the LED conversion while you wait for your TIU.

Yet another way to look at it is to consider that MTH starter sets include or have included 50W/75W Z-500/Z-750 transformers for engines (with smoke) and a few cars.  The rub is a PS2/3 engine operating in DCS draws essentially the same power pulling the same load at the same speed as one operating in Conventional.  Again, because of the switchmode power conversion techniques used in the engine, it's the Power in Watts or Volt-Amp product that's important. 

All of this is in my opinion.

Thanks guys, Gunrunnerjohn so it sounds like a good laptop charger will do a pretty ok trick for now if it works, found a 120 Watter rated at 6.5A.  Thanks Stan, very interesting, I will mainly just run for now a train or 2 with sound, and odd occasion smoke.  No I don't yet have lighted passenger cars, but will consider doing led replacement before they go near the track.

Ps:  My DCS system just landed this morning, and I got my local SA tracking number for it, it seems like currently in customs, so hoping there's no issues or excessive charges, should have it tomorrow or Wednesday.

Let the adventure begin!

Ye can't wait.

I spoke to a guy who has tested South African mains wall socket power quite thoroughly, and he said our power is pretty stable, it's actually rated at 220 V but has never fluctuated above 230 V.  In some areas we do have voltage dips though, I've never experienced that.

And there's the irony.  It remains to be seen how the high-frequency switching affects DCS signaling, but in contrast to fixed-ratio AC transformers a switching regulator will at least compensate for line voltage dips (within reason) and keep the DC output stable!  

I have a HP 19.5 4.6 A 90W laptop charger and an Apple 18.5 V 6 A 110 Watt charger, wonder which would have matching switching frequencies for DCS?  Will have to try when the DCS arrives.