Easy Power Supply For Your Model Railroad

Here is an easy way to convert an old computer power supply to use on your model railroad work bench or layout. It can be used either way with a few common inexpensive parts. You can power anything from 3.3 VDC to 24VDC with ample amperage available by combining the many leads available for the outputs.
Computer power supplies are a great source of DC voltage for our model railroads. We can operate almost everything imaginable from one source.
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Intended for viewers over the age of 14

[@MMRails]

Aw man, I just threw out my old computer. Wait until you see THAT video! You're a wealth of knowledge Tom. I don't know where you find the time to film all of these videos but us rookies appreciate it. -Mark

[@TomsTrainsandThings]

Oh No, you didn't! Hey, I'm retired, I have a lot of time on my hands and all this knowledge leaking out my brain. I have to put it somewhere. lol 😃

[@thomasdwyer6128]

Well, found your You Tubes quite by accident one night while just mucking around looking up information for my then proposed train layout. Well, I'm in the process of building a modest 13' X 10 foot layout and doing it on a reasonable budget. Your "how to's" have saved me a lot of money by solving problems in a practical, sensible way. I've have my eyes peeled for an unused PC power supply that should be able to run my accessories lighting. Well Done Thomas! Your efforts are appreciated.

[@TomsTrainsandThings]

Thank you Thomas. Glad I could help!

[@awizardalso]

Thanks for posting this even though it was a few years ago. I have an electronic and electrical repair bench in my basement and a few junk computers. I could use the outputs from a computer power supply for my work bench, and not to mention what's left of my model railroad.

[@anthonynewman1601]

By far the most straight forward instructional video for conversion that I have seen. Thanks for your knowledge

[@TomsTrainsandThings]

Thank you

[@maxpayne0369]

Absolutely amazing! very ingenuous way of reusing older computer supplies. I agree with previous posters, there is a great deal of wiring involved... but this is model railroading scratch building at its finest, put into even more of a practical use. Cheers!

[@TomsTrainsandThings]

Mike The Train Guy thank you. A little bit of work goes a long way

[@aaronb4936]

This channel in general has been really informative and helpful.. appreciate the work you put in to make these videos 👍🏻

[@TomsTrainsandThings]

I appreciate that!

[@danorley5575]

Thanks Tom as always I learn something when watching your videos.

[@TomsTrainsandThings]

Your welcome Dan. Glad I can help

[@bobshobbiesandcamping5614]

I appreciate this video. I never thought about using the power supply from an old computer for a power supply for my railroad.

[@TomsTrainsandThings]

Bobby Davis thanks for the comment. Glad it helped.

[@1955bluemoon]

Many thanks Tom from the UK for this very informative video, now to get started

[@TomsTrainsandThings]

Glad I could help Ronnie.

[@DavidShallcross]

great info, well described, made easy, and comical too. Thanks Tom

[@TomsTrainsandThings]

Glad to help!

[@kiwibjg]

Good to see you used the 3.3 volt section which I use to run LED lights in buildings or on control panels. Newer power supplies are rated at over 30 amps for the the 3.3 volt section which is more than enough for the several hundred LED's on my layout. That leaves the 5 and 12 volt sections to run control electronics and all of my Cobalt switch machines. Waste not what not. Cheers Brendon.

[@TomsTrainsandThings]

Glad you were able to use yours. The hidden features of what most people throw away!

[@samhane11]

Awsome ! great video. I learned a lot. Thanks for sharing. Im going tommorrow to ask a Computer Repair shop close to my house for any old power supply. Or My brother has tons in Al. works in computers for the Government. They demo them all the time. Great Idea and THX again.

[@TomsTrainsandThings]

Thanks for watching and your comment. Most people just get rid of their old computers and never realize what they can salvage inside.

[@mikerich68]

Great video on wiring. I learned a lot that I didn't know about the wiring of the power supply. Thanks for your time and information. Mike

[@TomsTrainsandThings]

Thank you Mike. Glad I could help!

[@bruteforce76]

Thanks For the great tips Tom. Never thought about using a 'load' resistor on these switching power supplies but I guess it does make sense, Mouser has some nice ones. Thanks again.

[@TomsTrainsandThings]

Glad I could help

[@frankmolina8660]

THANKS FOR ALL YOUR HELP IN UNDERSTANDING THE POWER SUPPLY 👍

[@TomsTrainsandThings]

Glad to help

[@Ax89]

Tom, Thank you for another interesting and informative video.

[@TomsTrainsandThings]

+Ax89 Your welcome

[@ChadAmI80]

First time viewer. Just subscribed. Thanks for sharing a great use for a computer supply. I am a novice when it comes to wiring. Thanks for your explanation!

[@TomsTrainsandThings]

Thanks for watching and subscribing. I have a lot of videos on wiring, just check out my playlists.

[@sirracer2005]

This is great. That solves my problem for a mini n scale layout. Thank you for showing this.

[@TomsTrainsandThings]

Thanks for watching and your comment. Glad I could be of help

[@sirracer2005]

Toms Trains and Things your are a huge help. I literally don't know anything about this stuff and I have been learning slowly by videos. And your videos have been a huge help.

[@grandparails8858]

Thanks for the video this is something I can use in the future.

[@TomsTrainsandThings]

Your welcome John. Refer back whenever you need to!

[@jodacious46]

Enjoyed this. I'm a newbie and learning as I view. Subscribed TY.

[@TomsTrainsandThings]

Your welcome Joseph. Glad I could be of help.

[@ianturner2229]

Hi Tom THANK YOU SO MUCH FOR SUCH A DETAILED AND **ACCURATE** VIDEO I just followed thru using the pause button as I made all the connections as per your instructions, even the Blue and Yellow to give me 24V and it all works just fabulously, exactly as you say, although I do not have a spare 5W 5 ohm. resistor around, but I am still getting slightly higher voltages than your readings ! I have tried this process several times based on watching other videos, but frankly it all got into a knot as they sortta left you in the lurch at important points in the process.. SILLY QUESTION PERHAPS - I have the purple and a black connected separately to a 2 point terminal block, and that gives me 5.1V approx standby voltage, but I must say I was a little mystified when it still worked not only when I turned OFF the switch on the Black and Green wires, BUT IT STILL SUPPLIED THE SAME VOLTAGE EVEN WHEN I UNPLUGGED THE POWER SUPPLY FROM THE MAINS ENTIRELY ? is it just providing what it can for as long as it can from a large capacitor in the power supply (HENCE STANDBY) or what ? Totally brilliant presentation, you have saved me a lot of money and a great deal more in headaches as my layout uses several Arduino mini's for control functionality (hence my need for a decent 5v supply) and several CDUs' that can take the 24V supply as their inputs, so right now I can power most everything from my good ole PC Power supply. THANKS, THANKS THANKS THANKS................................. You are a star....:-)))

[@TomsTrainsandThings]

Thanks for watching and your comment Ian. The stand by power was used on the computer to be available all the times even before booting up. you may be experiencing the residual voltage from capacitors holding the voltage after unplugging. It will eventually dissipate.

[@steveandrews4275]

Hi Tom, I found your video on building a DCC + + controller with raspberry pi very interesting and helpful. I am new to model railways, I have now ordered all the components and looking forward to building this command station.

[@TomsTrainsandThings]

That sounds great Steve. Keep me updated on your progress.

[@EagleValleyModelRailroad]

Thanks for sharing Tom.....Ed.

[@TomsTrainsandThings]

My pleasure Ed. Thanks for watching.

[@robertdoetterl7507]

Thanks Tom for the great info!

[@TomsTrainsandThings]

Your welcome Robert

[@JoeG-firehousewhiskey]

That is a pretty neat device for model railroading. Great for accessories too.

[@TomsTrainsandThings]

I use this on my bench and layout

[@bravolavoro3002]

Thank you very much and I also love your explanation

[@TomsTrainsandThings]

Glad I could help

[@flyboy2610]

Hi, Tom! I had an old Windows XP computer that worked when I mothballed it. I pulled the power supply out of it after watching this video a couple weeks ago. Tried hooking up the green wire and a a ground through a SPST switch. No joy. Tried using a resistor to fool the power supply. No joy. No voltage on any of the wires. Methinks it be kaputsky! I bought a new power supply for $26.95 off eBay (shipping included). Jumpered the green to the ground, plugged it in, and we have power! I'm going to add the resistor, though, to stabilize the voltages. Thank you for a very helpful video!

[@TomsTrainsandThings]

Your on your way to more possibilities now!

[@jackmason7518]

Thank you. I find it very helpful. Jack

[@TomsTrainsandThings]

Your welcome Jack

[@trainroomgary]

Hi Tom / Looks like a lot of wire work "Wow" / I use 4 Lionel Bricks, one for each main line. • Cheers from The Detroit & Mackinac Railway 🚂

[@TomsTrainsandThings]

Thanks for stopping by Gary. Once you splice them all together it's a piece of cake. This is all for operating accessories on your railroad.

[@DelayInBlockProductions]

Love your videos!

[@TomsTrainsandThings]

Thank you very much, that means a lot!

[@jamurphy8386]

You Sir, are a real wealth of information! Thank you for sharing. OMG! We've got old computers. My friend and his kids have computers.... I always thought it would be a waste to just throw out all that wiring, components, and I didn't even think about that power supply!! Pardon my ignorance, but you plugged that into a 120v wall socket? Just the fact that one of those can supply so many different volt outputs, is going to make my head spin! 😨😲😵😵 I mention him so often, you're gonna think we're *married!!* But Carmine's my go-to electronics guy... He got me some free sound in my Layout room, using a wall wart, an old amplifier, and an old CD/ROM, from an OLD Windows 95 computer!!! I need to keep this video handy, and watch it often. I'm sure ideas will start flowing... Murph 🚂

[@TomsTrainsandThings]

Thank you for the kind words Murph. MY old Windows XP computer that I used for 5.1 surround sound and JMRI died right before I did my video on JMRI. I'll have to put my sound card in another computer now to get my sound fx going on my layout. Haven't been having too much luck with computers lately. They are all 6+ yo now. The power supply plugs into 120V outlet. It drops the voltage down to several DC voltages. Even though there are some modelers that already use old computer power supplies, I was surprised that there were so many that didn't! I have an old home theater/ tuner that got zapped by lightning a few years ago that I'm going to be pulling all the components out of for spare parts. That should be an interesting video to do.

[@jamurphy8386]

Yup!! All my computers are at LEAST that old... I'm pretty surprised that I'm one of those who didn't know! 😑😥 I already knew to grab wall warts from ANYTHING being thrown out. I need to take a closer look at other electronic gadgets. Doing scavenging, I learned that the vibration motor in earlier Nintendo hand controllers (that don't have transducers instead), are a *perfect* drop-in replacement for the ooold Tyco locos, with truck mounted, crappy 3-pole motors!! They're the same "pancake style" motor that the Tyco has, but is a *7-pole* with less 1/5th the amp draw. I realize that you'd have to REALLY love that old locomotive.... But hey! The price is right.

[@TomsTrainsandThings]

I have a collection of wall warts also. Always good to have a dozen or two laying around. lol

[@davidgreen1299]

I knew that old power supply from my PC would come in handy one day.

[@TomsTrainsandThings]

I still have a computer that came loaded with Windows 98 sitting in the corner. I upgraded to Win 2000 Pro and it was my work horse for many years. It still works, so, I'll leave it alone for now. lol

[@frankcullen3471]

Tom, Suggest the 5 Ohm 5 Watt Resistor leads be covered with shrink tubing to protect from chassis shorts. Also apply heat sink compound to the underside of the resistor body for better heat dissipation. Frank WB8JWE

[@TomsTrainsandThings]

Thank you very much for the suggestions Frank. Good information is always welcome!

[@mikedebany2904]

Outstanding presentation!!!!! *****

[@TomsTrainsandThings]

Thanks Mike.

[@EricJones-yh4sx]

Thanks Tom

[@TomsTrainsandThings]

You're welcome

[@WiSLTWTR]

Awesome vid!

[@TomsTrainsandThings]

Thanks Anthony.

[@dongarman4548]

Thanks!

[@TomsTrainsandThings]

Thank you very much

[@norcalman01]

About 20 years ago, I tried to re-purpose an old computer XT power supply. I could not get sufficient voltage from the 12 volt wiring, so I "s-canned" the supply. Later I found the absence of a load on the 5 volt wiring influenced the rest of the available voltages! Later I re-purposed an old AT supply to power general illumination 12 volt LED lighting in my garage workshop. Instead of using a large resistor for a 5 volt load, I used a 6 volt incandescent lamp such as what is was on a motor scooter, golf cart, or a building emergency lamp. Mine was a type 4510, case style PAR36, 6 volt lamp, which worked for me. I know an incandescent lamp's cold resistance (off) and hot resistance (on) are different, but the bottom line is that my one lamp solved the problem for me. The 5 volt circuit does need a load, and mine did useful work in providing some illumination!

[@TomsTrainsandThings]

Good information. Thank you.

[@collinsullivan1517]

Interesting topic. I never know this could be something to use for the layout. I'm not very electronic literate. I always wonder how folks figure out these things. Thanks for the info.

[@TomsTrainsandThings]

Thanks for watching. Have more videos coming up on the same subject.

[@bigdon1a1]

good job

[@TomsTrainsandThings]

Thank you Don

[@railbuilderdhd]

This is great resource for power to the model railroad. Can you tell me if you have a video on how to connect this to your railroad for accessories and such? Love to see that.

[@TomsTrainsandThings]

I have several videos that cover items that can be hooked up to the power supply. I don't recall having a dedicated video that covers everything.

[@dacuzzz]

hi Tom... does the 5ohm 5watt resistor need to be on the 5V or can it go on any of the voltage out puts.. i have my LED in line with one of the yellow wires with no resistor.. seems to work just fine... great video thanks for sharing.. vinny

[@TomsTrainsandThings]

Hi Vinny, Yes! Any Red +5V wire to black will do. The Grey wires only function is an indication that the power supply is working properly.That's why I put the LED there. The resistor in line with the LED is to limit the current to the LED so it doesn't burn up. You can also control the intensity of the light by changing the value of the resistor. Some LED's are sold with a current limiting resistor already attached.

[@legionfrog]

can u assist me with some info on a 262 Arnold steam engine? Thx

[@edwinkowalinski4337]

I am really learning a lot watching your videos. Keep up the good work. I have a question that I know you have the answer to. I have a twenty year old IHC CORKEY'S CARNIVAL CARAVAN set that was made in Slovenia. Can it be converted to DCC? If so which decoder should I get?

[@TomsTrainsandThings]

Thanks for watching Edwin. Wow, you have "The Happiest Train Set Ever Made." My first question for you is; how does it run now? Putting a DCC decoder in a locomotive isn't going to make it run any better. If it runs poorly now, it will also run poorly with DCC. If it runs fairly well, you will have to be careful while installing a decoder as to not short it out. Assuming it doesn't have a plug since it was made in the 90's you would have to wire it by hand and that includes changing the lamps to LED's. There are a lot of variables involved in choosing a decoder. If you would like to discuss it further send me an email at [e-mail]

[@garylester55]

Edwin Kowalinski hi, I just read your comment and question, well, running a dc layout, as you know the tracks don’t have power to them all the time, only when you turn the control knob on the power supply to make the train move, with DCC, the tracks have power all the time, your loco, fitted with a decoder, weather it has sound or not, the decoder operates the loco, it depends on the quality of the decoder as to how well the loco runs, I’ve seen tests, SoundTraxx make a Tsunami2 decoder that leaves the others behind, changing some cv settings you can have the sounds come automatically on like the Proto, if you want to check it out search for SoundTraxx on KZbin, George from SoundTraxx demonstrates and explains all the settings and sounds, how it works. Track and wheels must be clean, as you know for good conductivity. Regards Gary

[@lloydcoltman1624]

Well, I just completed modifying the a PC power supply using a 10 ohm 5 watt resistor (couldn't get a 10/10). I let it run a few minutes, and took some readings with an Infra-red thermo. Surprise! The 10 ohm 5 watt runs at about 80f (yes, warm! I wouldn't want my grandson to touch a 5/5 used for this) and the major heat sink cycles around 90f. I'll use some tie-wraps to suspend the resistor on the inside of the cover, in the cooling fan flow.

[@TomsTrainsandThings]

That's a great idea Lloyd

[@MoosesWorkshop]

Great idea! I have done it for robotic projects but never thought about using a PC power supply for my railroad. Do you show in any other video where you mounted it? Or had any problems later on using it?

[@TomsTrainsandThings]

Never had an issue with it. I did a live stream several months ago showing how to use the break out boards for it. Currently my layout is dissassembled since I'm between houses.

[@f.glenskidmore1678]

I am finishing up my own ATX train power pack project, and I thought I should share an insight I gleaned: you can (and probably should) replace the 5 or 10 ohm resistor with a 14 volt ba9s lightbulb which is 11 ohms, and use it for a "power on" pilot light. Kill two birds with one stone. It glows perfectly with only 5 volts!

[@TomsTrainsandThings]

Thanks for your idea. Using an incandescent bulb defeats the purpose of the resistor. The resistor is in place to supply a constant resistance across the 5 vdc power bus to regulate the power supply. Unfortunately, an incandescent bulb changes resistance as it heats up.

[@04fys513]

Thank you for this tutorial. I’m just starting out with trains, and am going to use a computer power supply to provide as much of the power as possible. Is there any way to convert one of those computer power supplies into a digital (dcc?) controller?

[@TomsTrainsandThings]

Thanks for watching. Take a look at my videos on DCC++. kzbin.info/www/bejne/j3PXiqeZjJikiaM

[@HillBillyRailRoad]

thanks this video help me set up a power supply i used a 10 ohm 10w 10% from radio shack will be doing two more again thanks

[@TomsTrainsandThings]

Your welcome Scott. The 10 Ohm 10 watt resister works just as well as the 5 Ohm resister. You have plenty of power in those computer power supplies!

[@lloydcoltman1624]

There is an advantage to using a 10 ohm resistor, if it will work. If you run a 5 ohm 5 watt resistor on 5 Volts, you will be dissipating 5 watts at the resistor, 100% of its rating (HOT!) However, if you can use a 10 ohm 5 watt resistor across 5 volts (IIRC) the power dissipated drops to 1.25 watts, and the resistor should remain relatively cool. Lloyd - Kelowna BC [e-mail]

[@lloydcoltman1624]

What was I thinking? On a 10 ohm @ 5 Volts it.s 0.5 Amp. Watts = IxIxR (.5x.5x10) = 2.5 watts His 10 ohm, 10 watt resistor would be almost cold, and a 10 ohm 5 watt would just be warm

[@lloydcoltman1624]

This should really help my son. I have an old PS (250 watt) that should solve problems with trying to add LED building and tunnel lighting to a layout powered by a wimpy 17 output watt PS. Now, if we could find a way to use the +12 V to power the Loco Nothing fancy, it's straight DC.

[@cokidjazz]

Very interesting use of an old computer, Tom. Did you use this on your layout or workbench? I could see this being used on a layout. Especially with all the lighting and accessories being incorporated in layouts today. Do you run a bus of 12 volt wires for your turnout machines?

[@TomsTrainsandThings]

I currently have my work bench on a portion of my layout so I'm using it for both. I have another work bench in another room where I will be using another power supply. Right now it's easier to film my episodes in the train room so I set up a filming work bench on the layout. I operate most of my turnouts with a Digitrax DS64 so I run a common 12 volt to all the units.

[@yuryschkatula9026]

Attention! You should be really care while connecting together wires of the same voltage. Reason is simple: if you get two "+12" wires that came from two different keys this may give you "+12.01" on one wire and "+11.99" on another. Shorting together that two wires would cause dissipation of the voltage difference. Heat dissipation. The bigger the delta - the shorter is the power supply life. So, connect the wires together if and only if you clearly understand underlying schema of your power supply unit. Another option is to put ballast resistor between the wires (usually less than 1 Ohm, calculate it according to actual voltage delta).

[@TomsTrainsandThings]

Thanks for the info Yury. In this particular power supply all the wires from each voltage are coming from the same source inside the power supply. When I opened it, I made sure to bundle each source together, but they were soldered to the board at the same potential for each voltage.

[@ripjeffhanneman5838]

Hey Tom! Quick question.. I want to run a bus wire for street lamps and another bus for buildings. How many volts do I need off of this power pack? Like which "branch" of power would be sufficient?

[@TomsTrainsandThings]

That depends on how you plan on controlling your LED's. Have you tested any circuits yet? If so, what voltage do they require?

[@ron045]

Thank you for the video... But I feel like there needs to be a part two showing the true application. Demonstrate various accessories and which voltages to use. How many accessories can use the same pole? I have a string of buildings with lights. Some are LED and some are incandescent. Can they be mixed? Must they be seperated? Which voltage do I use and at what point would I overload something? Thank you for the time.

[@TomsTrainsandThings]

There are many follow up videos on the subject including basic electrical theory and projects.

[@mikedebany2904]

would love to see dcs options....

[@johnfeet5476]

Tom, can I combine a red, yellow for ~18 volts to run my Arduino DCC++ base station at the required "18v"? What would the available amperage come to? (more than enough I would suppose) if I could do that? Thanks much. This is an awesome video but I will always put the salvaging the printer at the top of the list!!:)

[@TomsTrainsandThings]

No, it doesn't work that way.

[@charlesmayer7097]

Can you do video on how to hook some of the accessories up to this power supply?

[@TomsTrainsandThings]

Will do!

[@alfredcollins87]

Thanks for the reponse i meant to say the train lights up but dosent move is possibly a easy fix or just toss them thanks

[@TomsTrainsandThings]

The only way to tell is to open it up and look at it.

[@nikkibiddle]

As an electrically challenged individual, I found the video very helpful and done in such a way that even I could follow what needs to be done. Just a quite question is there an advantage to grouping the wires together in the terminal block? I think you mentioned somewhere that this was done to maximise the amperage. Could you you use single wires to power different power busses on the layout. One again many thanks for the video.

[@TomsTrainsandThings]

There are break out boards that use individual wires for each voltage. Yes, the reason to group them together is for more amperage. These power supplies will handle more amperage with the wires together, but you may use them independently, but you have to pay attention to the maximum amperage for the individual amperage.

[@nikkibiddle]

@@TomsTrainsandThings Most helpful, many thanks for your help

[@johnfeet5476]

Tom I had another question, sorry. When you combine three of the same voltage wires, did you do that just to use them up or to increase the ability to get the most amperage out of the power supply? I don't think you can multiply the amperage, and I know you didn't say that. So for instance, what is the benefit of putting the three yellow wires together? Neatness, or does it help with pulling all the the 10 amps out of the ps for the 12 volt wires? I know, I'm kinda stupid on that. thanks!

[@TomsTrainsandThings]

I combined the same color wires to be able to draw the higher amperage. Each wire can only handle a small portion of the amperage.

[@TheGamingEevee8]

Wish I knew these things like you, it's like Greek to me.

[@TomsTrainsandThings]

It used to be Greek to me also until I started taking an interest in it and studying about it

[@OlympusHeavyCavalry]

I am wondering for even more neatness, if molex crimps and crimping terminals, or similar, can be used. I really prefer neatness in wiring as it not only looks good, cable management and troubleshooting is made easier. Nice job. :-)

[@TomsTrainsandThings]

I removed the original molex connectors to consolidate the wires

[@haroldhunt7260]

Hi I'm am wondering when you bud lines is that a main feed to all your conrolers like working up a switch track an you train switch

[@TomsTrainsandThings]

This is for any accessory that operates on either 3.3 VDC, 5 VDC, or 12 VDC.

[@chrisworkman5288]

Tom, your videos have helped me a lot. I want to put LED traffic lights on my layout. I have a DCC layout. I don't have any DC transformers, manufacturers say I could hook to. It's requires a 18v AC power supply. Any suggestions?

[@TomsTrainsandThings]

Chris, you can see if you can find and AC wall wort or pick up a used transformer cheap at a train show.

[@chrisworkman5288]

Toms Trains and Things Going to a show this Sunday, will check. Thank you.

[@dennistaylor7191]

Tom what digatrax decoder do I use on my HO Bachmann decoder ready GG1 Thank You

[@TomsTrainsandThings]

Bachman does not make it's own decoders. You have to do a search of different manufacturers by your loco model. This video may help: kzbin.info/www/bejne/a6q7iX5oqLOSo68

[@christopherkingsland4604]

Great video - to think I threw out so many old computers when they became obsolete! DOOOH!

[@TomsTrainsandThings]

I never throw away anything until I get tired of moving it from one place to another. I still have the first computer i ever bought in 1987.

[@christopherkingsland4604]

@@TomsTrainsandThings Wize move for sure!

[@andrewgladfelter4298]

You actually don't need a resistor or toggle switch on the power supply to do this. Shorting pin 15 and 16 on the ATX supply (black and green wires) provides an "always on" load. If the PSU is plugged in (if it doesn't have a switch on the back) or is plugged in and turned on (if it has a switch on the back), a load is supplied and the PSU will provide output. No resistor or toggle needed. I use this setup for powering an RC battery charger. However, if you want to have a remote switch that you can mount somewhere away from the supply like your single pole switch, then your method is probably the best.

[@TomsTrainsandThings]

Thanks for the info Andrrew

[@lloydcoltman1624]

Well damn! By the time the PS arrived at my son's, it had been bounced around so much, it wouldn't run. But he got one from a friend for free (seemed the +3.3 V was 7.0 V though). A little bit of experimenting showed that the +5 V would just nicely power 2 LED's in series, with just the desired brightness (and easy trouble shooting). I'm hoping that 5 pairs of LED's (.1A draw) will be enough to activate the regulation circuit , thus cancelling the need for the resistor. Thoughts?

[@TomsTrainsandThings]

How much resistance are your 5 pairs of LED's?

[@lloydcoltman1624]

E= IR: 50 ohms?

[@ICUNA22]

What load can be placed on a power supply's 24v circuit when the +12v is rated at 20amps and the -12v is rated at 1 amp?

[@TomsTrainsandThings]

The -12 is the weak link. 1 amp. If you need more voltage with more current use a buck converter. I show how in this video: kzbin.info/www/bejne/Y4qpfWOnjLZ4b5o

[@bradm1508]

Any tips / way to use the rack power on a random car. I wanted to try to take five volts off a moving car and wanted to use the power. Any way this is possible?

[@TomsTrainsandThings]

Buck converter. I've discussed this several times in other videos. You can take any power source, even AC, and get the desired result with a rectifier & buck converter

[@tom7601]

The power supply is a switch-mode device and the resister on the +5V line guarantees the power supply will "wake up" and regulate reliably.

[@TomsTrainsandThings]

Thanks for your input Tom

[@kevinsymss8373]

Hi Mate ,Just a quick question about the resistor. I know you need a load , what is the max lead you need , can you put in on any outlets or do you have to put it on the one with the highest current ?

[@TomsTrainsandThings]

Hi Kevin, The resistor has to go between 1 black wire and 1 red wire with nothing else on those wires to keep the load steady. I may be doing another video similar to this one shortly for adjustable output.

[@kevinsymss8373]

thanks ,

[@mycrazygrandpa]

Hey Tom, just ran across this video and the question I have is I'd like to run a series of led's on my layout, light poles, etc. and was wondering if the 3 watt output would be okay to use straight to the led or would I still need a resistor? If not, how many led could I run in parallel or if that can be done? My only experience with electricity is when I was 3 and stuck a fork in an outlet :-O the 12v I'd like to use for 2 linear actuators for bridges so I won't have to duck under (Yeah I'm old) Thanks!

[@TomsTrainsandThings]

kzbin.info/aero/PLjjhnrIKSTShIsUhAHn1O6eUIIqJ45gS5

[@mycrazygrandpa]

@@TomsTrainsandThings WOW! I can't thank you enough, looking forward to your next offering, "Same Tom time, same Tom station"

[@billvassar7473]

i have an old digitraks zypher that the power supply died on can i use this for it?

[@TomsTrainsandThings]

Unfortunately no Bill. You need 15VAC for your output and this has only DC output. If you can't find a suitable power supply online, you can always try your local thrift store. They sometimes have many wall wart available, you just have to root through them unless they take the time to separate them by voltage.

[@sueb.f.8349]

I am trying to figure out how to connect a transformer to a g scale track for a g scale christmas trolley. The trolley is in the family, I bought the track and the transformer at a thrift store. I dont know how to connect the transformer (120 Volt Lionelle) to the tracks. Thanks!

[@TomsTrainsandThings]

Make sure you have the correct output voltage. You may want ot watch some of my other videos Model Railroading for Beginners kzbin.info/aero/PLjjhnrIKSTShrzvkLrtppcNJ0zObTcDyv

[@steamy1225]

Good idea on this . Now can you use one that has failed to power the computer? I got one of them from my Dell.

[@TomsTrainsandThings]

You have to determine what is wrong with it. Is there no power out on any of the leads? Did it blow a fuse? Some have internal fuses.

[@steamy1225]

@@TomsTrainsandThings dont know. Will have to test.

[@willievanstraaten5801]

Hi Tom, I bought my trains about 40 Years ago. Me and my son used to play a bid but then we had to pack it up again and put it away because we didn't have the space to permently build a lay out. I watched your video and read thru all the comments. My question is: Can I use the 12V output to drive the DC lokomotives if I build some type of speed controler between the power supply and the rails? Thanks. Willie. (Bloemfontein, South Africa.)

[@TomsTrainsandThings]

Willie, unfortunately 12 VDC is not high enough to run your trains. Power packs are typically 16V and up. I use my power supply to run accessories, usually the 3.3v and 5v. I also have a few on the 12v.

[@willievanstraaten5801]

Thanks Tom. I tested the power supply that came with the train sets that I bought and its max. output is 12V to the rails. The problem with the power supply of the set is that it seems to me the output watts is to low because the power supply cuts out when I try to run two trains with it. Thanks any way for your help. Willie.

[@TomsTrainsandThings]

Willie, Those older power supplies that come with train sets were made for running the train set only. Power supplies that you purchase separate from a set are more powerful, higher wattage and higher voltage.

[@CajonSub]

What do you with the brown wire if your power supply has one? Thanks

[@TomsTrainsandThings]

It's the 3.3v sense wire. Connect it to one of the orange wires. It helps to regulate the power.

[@CajonSub]

Toms Trains and Things Thanks Tom!

[@JoeG-firehousewhiskey]

What would you use negative power for?

[@TomsTrainsandThings]

I don't use it on mine but you can use the -12 as the Gnd and the +12 to make 24 volts. This would be a low amperage situation since the -12 is typically 1amp or lower. In this situation you can not use the Gnd wires in that circuit, and this would have to be isolated from any other circuit. I would not recommend using this method though. Too easy to mess things up!

[@titustracy3342]

What can you run on something like that if you don't mind me asking

[@TomsTrainsandThings]

Any accessories that would take the different voltages. You can also use a buck converter to boost the voltage to run your trains. I have additional videos on this

[@matmarsden7276]

Hi Tom, I could only get a 5w 5.5 ohm resistor would this still work

[@TomsTrainsandThings]

That will still work

[@kevinstroud5216]

Hi there - great video, I'm in the process of sorting out all the leads right now! Quick question - my power supply has a switch on it anyway, so do I NEED to add a switch on green/black, or can this just be a permanent connection. Any advantages, other than the ability to place a switch somewhere else for convenience? THanks

[@TomsTrainsandThings]

Test your outputs with the switch on. Some of the older power supplies used the on-off switch and not a pushbutton

[@kevinstroud5216]

@@TomsTrainsandThings hmmm. Just blown a row of 4.5v strip leds, all connected to a 3.3v bus (yellow, black). No idea how that happened, possibly because I've been impatient and not waited for the 5v resistor to arrive in the post! Ah well, all part of the learning curve!

[@TomsTrainsandThings]

You better rewatch the video especially at 12:53. Yellow is 12 Volts. You want the Orange & black for 3.3 volt

[@kevinstroud5216]

@@TomsTrainsandThings sorry, I meant orange and black (which is what I did). I'm wondering whether switching directly from the power supply without the resistor on place have a surge? But the leds are 4.5v (using 3xAA batteries) so plenty of spare on a 3.3 supply. Mystery continues

[@hdrjunkie]

i have an older Tyco #899V transformer and its got A/C outs and D/C Outs on it but it does not say which terminals are Negative and which are Positive... is there any way to test them to determine which is which?

[@TomsTrainsandThings]

It doesn't matter on the old transformers. Your DC is for track power, its toggled by the fwd/rev sw and the AC is for you accessories.

[@hdrjunkie]

@@TomsTrainsandThings thanks... I’m guessing when you choose forward or reverse, it just switches the positives and negatives which would make the engine run in forward or reverse... so I’m guessing I’ll hook up the positive to the right side Terminal and if the engine runs in forward with the switch I. Forward, it’s correct lol !

[@barryporter7563]

Tom, I have a IP-P350AJ2-0 power supply for model railroad, I have one question on my P1 I have a brown wire attached to 3.3 volt wire at pin #11 do you know what that wire is for.

[@TomsTrainsandThings]

Barry Porter it's for the remote sensing of a voltage drop when connected to the motherboard. May not have a practical use for mrr. I would just cap it off.

[@barryporter7563]

Tom, thanks for a quick response, if I had watched your video a little closer you had memtioned it so I did a little research and found out it was for remote sensing but will cap it. Thanks, really enjoy your video's. Thank's again

[@TomsTrainsandThings]

Your welcome Barry

[@joe-ut7ee]

Where can I buy that 5 watt resistor?

[@TomsTrainsandThings]

Thanks for watching Joe. I got mine through MCMelectronics.com 5 Ohm 5 watt resistors 46-000500 $1.16 per 5 pk. 220 Ohm 1/4 watt resistors 287-10790 $2.06 per 10 pk.

[@johnbutler8388]

Thank you

[@rollingh8809]

Question: Is there a less expensive relay that will do the job of an atlas relay? These atlas relays are getting very expensive and there are no hobby shops within miles, so I have to order them from Ebay or elsewhere and pay on top of that a very high shipping price. These prices are eating my lunch and on top of that atlas relays are not that great, they get contact problems after awhile. I'm referring to the double pole Atlas Snap Relay.

[@TomsTrainsandThings]

I don't use the Atlas products so I'm not sure what voltage they operate at but here are a few options on Amazon: amzn.to/3FoNwKF

[@rollingh8809]

@@TomsTrainsandThings Thankyou, I will look into this.

[@titodalessandro1909]

that looks like my old comp. my wife through out on me.

[@TomsTrainsandThings]

That was my old Windows XP computer. It was pretty old. I'm surprised it lasted so long. It died on my right before I was planning this video.

[@leeroyexcavator9149]

havnt bought a transformer yet for my new track set up. how many feet of track will a train transformer power? like a mrc 2500?

[@TomsTrainsandThings]

Leeroy, how many feet of track do you plan on running and how complex of a track plan? How many locomotives do you plan on running at one time? How many accessories do you plan on powering from the transformer at one time? If your talking about a Tech 2 2500, it's rated at 16 VA which comes out to about 1 amp give or take depending on what voltage your running at. If your just starting out, I wouldn't worry about how many feet of track it could handle. If your planning on buying a use power pack, I would hope you can test it before buying.

[@leeroyexcavator9149]

Toms Trains and Things.. thanks for replying back. At the moment it is a very simple straight forward track around my living room. No extras. except for maybe a couple turnouts to an area to add and take away trains off the main line. will be a total of about 120ft in whole thing. As I said last time we talked this is the first time I have ever fooled with trains since I was a kid. So I know nothing of how much power it takes to run the train for that distance. Will just be one train running at this point.

[@TomsTrainsandThings]

With one train running you should be okay with any MRC power pack!

[@leeroyexcavator9149]

Toms Trains and Things .. ok. great! . how many feet of track will a power pak like that supply? Is there a formula for power vs distance? Got a recommendation for a controller by mrc or another company that would be better?

[@TomsTrainsandThings]

Any power pack will work fine. There is a formula for calculating all the variables involved such as amp draw of your locomotive, accessories used, track resistance, and resistance of the wire used. I=V/R

[@STEAMBOLTANNIE]

wow...I can do all the building of tables and all the artistic stuff...sculpting, painting, and scenery but im going to have trouble here wiring everything...im lost...lol

[@TomsTrainsandThings]

That's what I'm here for, I have a lot of videos in playlists on everything you need to know about wiring; DC, DCC. and electrical projects.

[@BsrlinMAZ]

I know this is very old video, so may not get an answer -- but hoping someone can explain this to me like I'm 5: you indicate you have some wires giving you +12 volts and others giving you -12 volts...does that mean the polarity is reversed? So if, for example, a motor was attached to -12 volt wire it would run one direction, and if then attached to +12 volt wire it would run in opposite direction? And would it matter which of the black 'ground' wires it was attached to? I just used a motor as an example in my question, as a simple way to try to explain what I am asking (don't know if there is a 12-volt motor), since I can understand fwd/reverse on a small electric motor. Sorry for the dumb questions -- my knowledge of electrical stuff is such that I know how to plug something into an outlet in the wall and I can (usually) change a light-bulb ha-ha; but beyond that I need to educate myself to understand what's being shown in the video. I am retired and have wanted to build a model railroad layout since I was a young boy -- but the current state of the hobby is beyond ridiculous and unacceptable regarding price gouging and over-inflated greed by companies providing consumer goods (it's everywhere, not just R/R hobby); so being able to re-purpose a power supply from an old computer looks like a good way to save a few dollars. Thank you for your time and assistance. Liked/subscribed.

[@TomsTrainsandThings]

Do not use the -12, that's for computers, and it's only 1 amp. To reverse a motor, one would just revers the leads I have some more videos after this that explains it more. Check in my Playlists

[@johnbutler8388]

What do they use at for Tom do they use that for lights tortoise switch machines what

[@TomsTrainsandThings]

Hey John, anything you want to power on your model railroad. Switch machines, lighting, stationary decoders, Power management boards. Just about anything that runs on DC voltage.

[@shamiester]

How do you use negative voltage.

[@TomsTrainsandThings]

Use the negative voltage lead as the - and add the + voltage for a higher voltage Make sure you don't exceed the Amp rating of the lower rated voltage!

[@KerleyExpress]

How did you know those was the right wire for the switch an light?

[@TomsTrainsandThings]

There is a pin out diagram available for all power supplies which are common to all computers. I think I overlayed one in the video

[@KerleyExpress]

Thanks Tom I saw that after I ask the question lol

[@jackgale1403]

Should use shink wrap on all connections.

[@TomsTrainsandThings]

Thanks for the information Jack.

[@ozarksfarmerhansen8782]

All you have to do on any old Power supply is touch the green wire to a ground, been using old power supplies for years to run 12 volt fans in a stereo component cabinet and a big closet where I have tomato plants.

[@TomsTrainsandThings]

Yep, that will do it for fans and anything else that doesn't need a regulated voltage. When you use electronics that way, they have issues.

[@oneiltomlinson]

How do you know what wires to connect the switch to and the wires to connect the resistor to?

[@TomsTrainsandThings]

It's explained at 5:32

[@oneiltomlinson]

But still don’t see my the green wire (for the switch). Why not add the switch to a red and black wire? And why the grey for resistor? Why not a yellow and black?

[@TomsTrainsandThings]

If you put a switch between the red and black wires, you will cause a dead short and fry the wires when you turn on the switch.

[@lloydcoltman1624]

Now that I've figured out how, I'll add my comments as posted (reply) to Scott Macdonald. If a 10 ohm resistor will work as stabilizing load, there are advantages. A 5 ohm 5 watt resistor on 5 volts will be dissipating 5 watts (100% of rating- HOT!) A 10 ohm 5 watt on 5 Volts will be dissipating 2.5 watts (50% of rating- barely warm) and Scott's 10 ohm 10 watt will be almost cold.

[@TomsTrainsandThings]

Yes Lloyd, that's true. I thought I mentioned it in the video that a 5 ohm 5 watt or 10 ohm 10 watt could be used. I had both but used the lower value or the video.

[@ajb07]

@@TomsTrainsandThings LOL - Now you say! - I missed that on the video and have been hunting hi and lo for an apparently specific 5/5w when all I could find (in the UK) are 10/10w or 10/5w :| Search over :) Great video btw and so well explained. Thank you!

[@brucew.5177]

Tom , you are a genius ... I am not. Is there a video that explains your explanation of this ? lol

[@TomsTrainsandThings]

Not a genius. Just a few colored wires, each wire represents a different voltage.

[@csxroch4lyf]

can i use any pc power supply an can it be any watts

[@TomsTrainsandThings]

Yes you can.

[@csxroch4lyf]

@@TomsTrainsandThings thanks so much love your video's they are very helpful

[@594208]

what is the differance between + 24 volt and - 24 volt on the supply cheers

[@TomsTrainsandThings]

Hi Bob, thanks for watching. It's actually +12 and -12 to make the 24 volts. If you tap into the blue and yellow you'll get the 24vdc, as opposed to black and yellow for 12v or black and blue for -12v. Check the amperage on the data plate, the -12vdc is normally about 1 Amp. When you combine the -12 with the +12 your limited to the lowest amperage value.

[@594208]

cheers for that if i need 24v just put the two together and i have my 24v brilliant thank you for being so quick with a reply all the best Bob

[@michaelbarbone9310]

I am confused. How would +12v and -12v combined = 24v ? Do you connect both together for one item lead and a black for the other item lead? Or connect yellow to one item lead, then blue to the other lead of the item?

[@57dent]

Michael Barbone Do NOT connect the yellow and blue together. The voltage between yellow and black is +12v(the yellow wire is 12v above ground potential). The voltage between the blue wire is -12v or 12v below the ground potential. So the difference between the yellow and blue +12v - (-12v)= 24v so your item would connect between yellow (+v) on the item and the blue (-v) on the item. Just make sure no electrical part of the item touches anything connected to ground (black)

[@michaelbarbone9310]

That was what I was asking. I would connect the yellow to one connection (lead) on the accessory and then the blue wire to the other connection (lead) on the accessory, and the item with those wires will be getting 24v? I see in your reply " +12v - (-12v) = 24v" I did not know that was how the electric worked. I was thinking that the voltage between the two wires would like "cancel each other out" somehow, that they wouldn't be additive, but switch between +12 and -12. Thank you.

[@martyndavison5259]

Hi Tom, I think you should mention that there are dangerous voltages inside the case, much of the circuit is at mains voltage and the large filter caps have 300V dc on them and can store this even when the supply is switched off and disconnected. Also you do not make it plain for beginners that you can only combine a positive with a negative supply and the neg supply can only supply low amps. combining two positive supplies will result in a short circuit and BANG !!!!!!! SMOKE !!!! etc. cheers Martyn

[@TomsTrainsandThings]

There is no need for the viewers to remove the cover of the power supply. I removed it to show how it is wired. If you watch again you will see I refer to the amperage of all the voltages. Also, the way I present the terminal block it would be hard to short out the wires of different voltages unless they were deliberately shorted together. I have other videos on basic electrical theory and electronic projects for everyone to see. Thanks for your input!