# Buying a new 24V supply



## jt2048 (Jan 14, 2009)

I'm looking at buying a new 24VDC track power supply. I use constant track power plus on track charging battery power. I'm currently using a couple of 6.5A supplies and starting to run out of juice under certain conditions. I'm aiming for something in the 15 to 20A range. The Meanwell SP-500-24 seems to have all the right specs and can be had for a decent price for the class. Datasheet here http://www.trcelectronics.com/Meanwell/pdf/sp500.pdf. I've had good experiences with Mean Well in the past.


Does anyone have any experiance with this supply or alternatives in the same class they might like to suggest?

JT


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## Greg Elmassian (Jan 3, 2008)

I have several, and I am very happy with them, have run continuously for several years... 

I think they are a good balance between price and quality. You can find cheaper ones, but I do not think they are made as well. 

Regards, Greg


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## blueregal (Jan 3, 2008)

Greg what is the model # or part# of what you are recommending????? Don't make me call you AGAIN!! Hah LOL The Regal


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## Chucks_Trains (Jan 2, 2008)

I use Bridgewerks.


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## Greg Elmassian (Jan 3, 2008)

Question was: 

Does anyone have any experiance with this supply or alternatives *in the same class* they might like to suggest? 


I don't think anyone would put the Meanwell in the same class as Bridgewerks. 

They are not really comparable, one is a high end, expensive, super high quality analog power supply with a throttle and not regulated, the other is a small, inexpensive regulated switching power supply. 


Regards, Greg


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## jt2048 (Jan 14, 2009)

Not only are they not in the same class, they aren't even used for the same thing. The Bridgwerks are lovely supplies but would be a waste of money for my application, I just need a supply that puts 24VDC on the rails so I can fry frogs







Train control is handled by other means so that nice throttle would go to waste.

Thanks Greg!

JT


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## Chucks_Trains (Jan 2, 2008)

Well this topic is posted in the Traditional Power Forum and you did ask about alternatives..


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## jt2048 (Jan 14, 2009)

Fair enough. I debated on where to post and ended up here. Might belong in the radio battery area but then again it is track power. Just constant track power vs variable. 

JT


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## Chucks_Trains (Jan 2, 2008)

But when the trains are running and you're mingling with the guests having a drink isn't the track power constant?? Just kidding..









You got it figured out..


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## Randy Stone (Jan 2, 2008)

Posted By jt2048 on 14 Nov 2009 04:19 PM 
I just need a supply that puts 24VDC on the rails so I can fry frogs









JT

Humm, great idea. I wonder how this would work on cats? Might need more volts.

Randy


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## blueregal (Jan 3, 2008)

Greeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeg!!!!!!!!!!!!!!!!!!!!!!!!!!!!look up







Regal


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## Totalwrecker (Feb 26, 2009)

Mr. George S. directed me through a post to these guys: 
http://www.mpja.com/ 

Similar to Meanwells but cheaper... I picked up a 24v 13.5 amp for aprox $30 plus power cord 

Last I heard they were on backorder, but I haven't checked recently. 

I kinda trust his suggestions.... 

John


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## jt2048 (Jan 14, 2009)

Doesn't work worth a darn on cats, mine run through the tunnels with impunity. Also doesn't work on rattlesnakes. But frogs have nice moist skin.....

At one point I did build an exotic disconnect for the (ground level) main line and hooked a fence charger to one rail, theory being I'd keep my cats off the line when no trains were running. They very quickly learned to *step over *the rails and thus became well trained trainman qualified cats but it didn't keep them away. Don't know if it worked for the rattlesnakes, we only get a couple a year in the yard .


JT


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## jt2048 (Jan 14, 2009)

Posted By Totalwrecker on 14 Nov 2009 05:12 PM 
Mr. George S. directed me through a post to these guys: 
http://www.mpja.com/ 

Similar to Meanwells but cheaper... I picked up a 24v 13.5 amp for aprox $30 plus power cord 

Last I heard they were on backorder, but I haven't checked recently. 

I kinda trust his suggestions.... 

John 
John, I'm going to guess that was the Potran, correct? They unfortunately no longer carry it. They do have an excellent price on the unit I'm planning on buying, but are out of stock. JT


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## krs (Feb 29, 2008)

Potran told me a while back that they have gone out of the switching power supply business. 
MPJA was one of the distributors liquidating their stock - that's why it was so cheap. 
But once they are gone - they're gone. 

I use Meanwell supplies as well - can't do any better for this application I don't think.


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## Totalwrecker (Feb 26, 2009)

JT, 
Yep, but I just checked and the model I got isn't listed anymore...only saw a 24v 8.3a ...19.95. I know you run larger 2motor deisels and cameras so probably need more amps. Could ya put 2 in parallel? 

I find this funny that I'd be 'helpng' in electronics... I look up to youse guys usually... 

John


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## jt2048 (Jan 14, 2009)

Posted By Totalwrecker on 14 Nov 2009 10:58 PM 
JT, 
Yep, but I just checked and the model I got isn't listed anymore...only saw a 24v 8.3a ...19.95. I know you run larger 2motor deisels and cameras so probably need more amps. Could ya put 2 in parallel? 

I find this funny that I'd be 'helpng' in electronics... I look up to youse guys usually... 

John Hi John, Yeah, that's what I'm actually doing right now with similar supplies. The biggest thing I run is an SD45 4 motor unit and it's not all that bad but the number of units is catching up with me. I also pull 24V off the track to run the signaling system and track side cams, it all adds up after a while. The reason I've been able to put off upgrading is that the batteries in the locos pull the load when the power supplies start to sag or limit. But that gets annoying because the track side video units don't like voltage sag at all. So I'm going for that 20A Mean Well I talked about in the first post, people seem to like it. I'll use the smaller supplies to power the yard where the units sit overnight and charge, they are fine for that.

You need to bring your loco down someday and take it out for a spin on the H&N, it will work fine here









JT


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## jt2048 (Jan 14, 2009)

As a followup to my original question, I did indeed get one of these units and it's working like a champ. One nice feature of using regulated switching power supplies is that they normally have a true common ground as this one indeed does. So ground is ground and all other system voltages (from several other switchers) are referanceable to it and can run with a common ground buss. So at the cost of a larger wire on the ground buss as it carries the sum of all current from all supplies, there can be only one. Makes life simpler. 

You do want to check potential between grounds before doing this, I got surprised a few years back by the Aristo CRE-55465, its ground is better than 2V *below* common reference. Which is one of the reasons that it's currently taking up space in the dead equipment pile. The other is that it died for the second time some time back and I got sick of sending it back in to get repaired. In fairness to Aristo, I do run all my stuff 24x365 and a good telco or computer switchers are much more suitable for that sort of operation. 

JT


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## Nicholas Savatgy (Dec 17, 2008)

Bridgewerks RULES BROTHER peroid,,,,,,







You pay more but you get far more in return?







Tell me i'm WRONG ........... NOT.. he he he


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## JPCaputo (Jul 26, 2009)

If you want good quality, go for Astron, they make almost bullet-proof power supplies. The linear supplies have good sized transformers, weigh a lot, and provide pure DC past full load capacity.


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## Nicholas Savatgy (Dec 17, 2008)

Bridgewerks rules Brother........... Period







Pay for the best get the best............


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## krs (Feb 29, 2008)

Posted By Nicholas Savatgy on 03 Dec 2009 09:18 PM 
Bridgewerks rules Brother........... Period









Not if they still use linear supplies.


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## Greg Elmassian (Jan 3, 2008)

in the old days, there were only linear regulators and ac variable transformers. 

early switching power supplies had electrical noise 

modern switching supplies have virtually taken over the market. there's reasons for this. 

the only segment of the hobby that seems to demand highly filtered DC is MTH, and since the DCS system runs at fixed speeds thanks to the optical tachometer feedback system, it does not need a regulated supply. 

Other than that particular system, I cannot see the extra cost incurred by a large linear supply. 

Regards, Greg


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## Nicholas Savatgy (Dec 17, 2008)

Hmmmmmmmmm...........







I still like my Bridgewerks and they rule........


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## krs (Feb 29, 2008)

Posted By Greg Elmassian on 04 Dec 2009 08:06 AM 

the only segment of the hobby that seems to demand highly filtered DC is MTH, and since the DCS system runs at fixed speeds thanks to the optical tachometer feedback system, it does not need a regulated supply. 





I don't quite follow you.
Are you saying that a switching power supply is not suitable for MTH because the ripple is too high?

Brudgewerks shows a graph on their web site which "suggests" that the ripple at 8 amps is about 0.1 to 0.15 volts.
Hard to read since the Y-axis scale seems to be offset from zero and there are no horizontal grid lines.
Also, there is no indication if this value is rms or peak-to-peak 


The Meanwell 24 volt 10 amp switching supply specifies maximum peak-to-peak ripple at 150 mV, so definitely the same type of magnitde as the Bridgewreks as far as ripple is concerned. Measurements I and others have taken on the Meanwell supply show that the actual ripple is less than half the maximum specified.


One big problem I have with large linear supplies is the poor efficiency; I in general think the world needs to cut back on energy use and linear supplies certainly don't help in that respect.


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## lownote (Jan 3, 2008)

MeanWell stuff has been excellent for me, and it doesn't generate a lot of heat. Very high efficiency


Digital switching amps--they're a miracle! I'm a semi-professional musician, and I play a lot of gigs on bass. Back in the day, being a bass player meant lugging BIG, HEAVY gear. A 300 watt tube bass amp weighs around 75 lbs--and that's just the amp! Solid state linear amps were much lighter, but now I have a digital switching amp that puts out 800 watts and weighs less than 4 lbs. The old tube amps sounded great, but I don't like the way they sounded terrible loading them out at 2 am. 


I can't really see a good argument for Bridgewerks stuff except that they are small company and stand behind the product. That's a real advantage, but the price diferential is huge


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## Torby (Jan 2, 2008)

I'd side with lownote. Get something from the electronics market. Meanwell are very nice.


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## George Schreyer (Jan 16, 2009)

note that any power supply that you use to provide "constant" power to the track needs a GOOD overcurrent trip capability. There will be derailments and there will be short circuits. If you power supply does not shut down QUICKLY you will get smoke. 

Further, you wiring and rail resistance needs to be low enough so that you CAN draw enough current to trip the supply in the event of a "short." In the spacecraft biz, we had a term to describe a serious problem. It was called a "smart short." A smart short is one that draws a fault current that is high enough to cause damage, but not high enough to trip of the power source. Whatever is causing the smart short then just sits there and cooks until it causes serious damage to itself or causes collateral damage to other things. 

Most DCC boosters trip off in 100 mS or so after the load current has reached the trip point. Then they retry every few seconds or so until the short is cleared. The short bursts of fault current do not typically do any permanent damage to things that have not failed already. Sometimes a short is caused by the failure of load in which case the load is damaged already. Simple derailments are correctable if the energy resulting isn't high enough to burn wires or melt down contact springs. 

Many moons ago, I used an Ultima power supply to supply 21 volts to the track. I had a derailment that burned up wiring in an FA and the contacts of a Lionel Atlantic in one shot. That experiment ended quickly. 

In the 11 years that I have used DCC, I have had many track shorts, NONE of them caused any damage. 

It's not that DCC is magic, it is because that the boosters are designed to anticipate short circuits as normal events and they react to them gracefully. I regularly test my track wiring by laying a screwdriver across the rails. HO folks use a quarter, but the result is the same, the booster should shut down immediately and then recover a few seconds after the short is cleared. 

Your DC power supplies should do this too.


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## Nicholas Savatgy (Dec 17, 2008)

So i need and want high volts and amps, What would you reccomend Goerge as a good DC power pack that can give 24 to 30 volts and at least 25 amps of power to match my Bridgewerks TDR. I ran a few weeks ago at a show 2 E-8s and 12 passenger cars all lit and with sound and they drew 17amps. no other power pack that i know of can handle that kind of power...... Any suggestions


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## George Schreyer (Jan 16, 2009)

anything with similar ratings. I haven't looked them up. 

What does your Bridgewerks do when you short it out?


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## Nicholas Savatgy (Dec 17, 2008)

It always pops the auto fuse i have inline between track and pack.


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## jt2048 (Jan 14, 2009)

As near as I can tell most switchers are pretty smart about shorts. There seem to be two modes of short protection in general use for this class of supply, hiccup mode and output current limiting. Hiccup mode supplies always auto recover when the short is lifted, constant current mode *may* require a reset. I have supplies of both types in operation here and prefer the hiccup mode supplies for operational reasons. 

As a side note, although it's extra work, secondary fusing on locos and other powered units is always a good idea. Since I back up all units with on board battery I fuse both track power and battery power, belt and suspenders engineering. Thermal self resetting fuses. And since I have to open them up to install the battery in any case installing the track power fusing is not a big deal. 

Power supply technology has come a long way in the past 20 or so years. Time was where I'd not consider using anything but a model railroad manufactures supply, they were engineered to our specific needs. That time has passed. Advanced control methods like DCC and radio have also changed the equation as well. Since I'm a constant power guy (track power + local battery controlled by radio) commonly available and inexpensive switchers make a great deal of sense for my requirements. I'd suspect that they may well work as 'back end' supplies for DCC folks. Variable track DC folks are still better off with purpose built power supplies from specialist manufacturers. 

JT


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## Greg Elmassian (Jan 3, 2008)

Knut, belated reply. 

I do not understand why the DCS folk insist they need linear power supplies, but I bow to their greater experience using the system. It does not make sense to me, but, again, I defer to people like Chuck and Raymond. 

Regards, Greg


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## krs (Feb 29, 2008)

I do not understand why the DCS folk insist they need linear power supplies, but I bow to their greater experience using the system. It does not make sense to me, but, again, I defer to people like Chuck and Raymond. 


Thanks for the reply, Greg, 

I did a bit of googling to see if I could find anything that would shed some light on this, but I came up empty. 
Your site showed up, so did Raymond's, but no technical reason(s) why a switching supply would be unsuitable. 
The MTH web site didn't provide ant clues either. 

Two differences between the linear and switching supply output could possibly affect the DCS signal (although they shouldn't), one is the difference in the frequency component of the output ripple and the other the output impedance of the supply. I don't know how the DCS signal is actually (circuit-wise) superimposed onto the DC signal and how it is detected - using a 2 volt or so very high (MHz) control signal in the noisy model railroad environment doesn't seem to be a very robust solution in my opinion. Didn't the early command systems like Astrac work this way (but with a lower frequency) and one of the DCC innovations, if you can call it that, was to get away from this concept. 

Knut


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## Greg Elmassian (Jan 3, 2008)

Yes, you are right on all counts (in my opinion) Knut... of course now there will be more nasty emails to the moderators that I am picking on MTH and DCS. 

Yes, a fundamental weakness is the low level signal on a carrier... as FM is far superior to AM radio, DCC is the same thing, the power is the modulation, and you have to really mess up the signal to not be able to decode it, whereas a low level signal on a carrier is easier to "wipe out"... 

Yes, Astrac (I still have my 1963 Model Railroader where it was reviewed) did this with 60 Hz AC, and my X10 control system which is a 700 millivolt signal on my 110v AC powerline is also similar and dated. 

Regards, Greg


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## Torby (Jan 2, 2008)

Doubt it. Just a myth. Like "I don't dare use pulse width!"


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