(Topic ID: 240360)

Computer Power Supply to Bench-top Power Supply


By oldschoolbob

77 days ago



Topic Stats

  • 16 posts
  • 8 Pinsiders participating
  • Latest reply 62 days ago by Strohz
  • Topic is favorited by 4 Pinsiders

You

Linked Games

No games have been linked to this topic.

    Topic Gallery

    There have been 27 images uploaded to this topic. (View topic image gallery).

    IMG_3393 (resized).JPG
    IMG_3391 (resized).JPG
    IMG_3371 (resized).JPG
    IMG_3369 (resized).JPG
    IMG_3347 (resized).JPG
    IMG_3361 (resized).JPG
    pic_68_3 (resized).jpg
    pic_68_2 (resized).jpg
    pic_68_1 (resized).jpg
    IMG_3435 (resized).JPG
    IMG_3433 (resized).JPG
    IMG_3443 (resized).JPG
    IMG_3442 (resized).JPG
    IMG_3441 (resized).JPG
    IMG_3423 (resized).JPG
    IMG_3422 (resized).JPG

    #1 77 days ago

    I’m not a big fan of computer power supplies but I had so many extra parts from building my other power supplies, I thought I’d give this a try. The only thing I needed to purchase was a couple of switches. I thought I could pull this off without any assistance but I seem to have run into something that don’t make sense.

    I didn’t want to build your typical ATX power supply so I de-soldered all the output wires and only kept the wires I needed – 3.3V, 5V, 12V and ground. Here’s a rough wiring diagram.

    PC PS 1 (resized).jpg

    My plan was to run the three voltage wires to a 3 position rotary switch then connect the switch output to a terminal on the case front.

    The voltages were a little low but I read that I need to add a 10 ohm – 10 W resistor to the 5 volt line. That worked fine as I now have the voltages I need.

    The problem occurred when I tried to connect the rotary switch. When I switch from 12V to 5V or 3.3V to 5V the power supply kicks off. If I start at 5V it’s fine but when I switch to 12 or 3.3 it kicks off. If I disconnect the 5V wire and just have 12V – space – 3.3V it works fine. The switch is a “make before break” so I thought that might be the problem. So I opened the gap between the connectors but that didn’t help. The switch is a 4 pole so I moved the 5V wire to another pole and connected the 2 output terminals together. That didn’t help either. I have another switch (4 position – 3 pole). I connected that switch and still get the same results.

    I’m out of ideas. Anyone have any suggestion?

    Thanks

    Bob

    IMG_3357 (resized).JPGIMG_3375 (resized).JPGIMG_3380 (resized).JPGswitch (resized).jpgpc box (resized).jpg
    #2 76 days ago

    Just put separate output posts for each of the voltages and eliminate the need for the switch. That way you can use more than one voltage at a time which may come in handy. That's what I have done and it works great. You may need a minimum loading resistor (like you used on the 5v) on all of the outputs to keep them stable.

    Mac

    iu (resized).jpg
    #3 76 days ago

    Thanks Mac, but I really wanted to use the switch. That's what makes it a little different and also will allow me to use the meter.

    #4 76 days ago

    I would think you would need something like this. You need a break before make switch (non-shorting) so you don’t short the power leads when changing position.

    On computer power supplies one of the outputs need to have a load on it so all the outputs will regulate. Most need to have a load resistor on the 5 volts but some use the 12 volts to regulate. If you don’t have it the outputs will float around until you put a load on the one that is used to regulate the outputs. Research your supply to make sure it is the 5 volts that needs loaded for it to go into regulation. Looks like you have done that already. That resistor needs to stay in circuit all the time.

    Tie all your grounds together and tie this to your common (ground) jack. Measure your outputs to make sure they are correct and stable with nothing else hooked up. Now take each output to your break before make switch and the common pole of the switch to your power jack. Your meter will be tied to this. I’m not very good at drawing circuits but if you search for break before make (or maybe non-shorting) switches you will find some example circuits to use to guide you on how to connect things.

    Make sure the switch you come up with can handle the current you will be sending through it.

    Good luck.

    B712387C-2A6A-4961-9EB5-BA5F96E96A57 (resized).jpeg
    #5 76 days ago

    Nice Idea, . here's a nice one .

    #6 76 days ago

    Wiz,

    I did a bunch of test today. I’m sure my switch is the problem (make before break). If I just strike two power leads together I get the same results (power supply kicks off). I’ll order a new switch tonight.

    I added a 10 ohm 10 watt resistor to the 5 volt power lead. That seemed to stabilize all the voltages.

    Tony,

    That’s a neat power supply. I saw it before. As a matter of fact that’s where I got most of my ideas for building mine. But I don’t like all the extra wires bundled together. I de-soldered and removed all the un-needed wires. I also connected the green wire directly to ground and use only one switch to turn on the AC power (through a fuse). I also don’t like all the power jacks. I know that limits me to just one voltage at a time but I don’t think that will be a problem. And I don’t like the looks of the ATX power supply box so I’m going to put mine in a plastic case.

    Bob

    #7 76 days ago
    Quoted from oldschoolbob:

    Wiz,
    I did a bunch of test today. I’m sure my switch is the problem (make before break). If I just strike two power leads together I get the same results (power supply kicks off). I’ll order a new switch tonight.
    I added a 10 ohm 10 watt resistor to the 5 volt power lead. That seemed to stabilize all the voltages.
    Tony,
    That’s a neat power supply. I saw it before. As a matter of fact that’s where I got most of my ideas for building mine. But I don’t like all the extra wires bundled together. I de-soldered and removed all the un-needed wires. I also connected the green wire directly to ground and use only one switch to turn on the AC power (through a fuse). I also don’t like all the power jacks. I know that limits me to just one voltage at a time but I don’t think that will be a problem. And I don’t like the looks of the ATX power supply box so I’m going to put mine in a plastic case.
    Bob

    I guess we think much alike oldschoolbob. I just took my old computer power supply and put a wire nut on the green wire to a black wire. Then, I use alligator clips to tie whatever voltage I need to the test item before I plug in the power supply, being careful that no wires are shorted or touching something that they should not. I didn't really see a need for an on/off switch. The power supply project box looks a lot better and is probably a lot safer however. Still gonna need an alligator clip to tie the DC to the test item though.

    #8 76 days ago

    I use this, it's like $12...

    ebay.com link

    #9 76 days ago
    Quoted from ZEN:

    I use this, it's like $12...
    ebay.com link

    I was about so suggest one of those.. I got something very similar off amazon. It works great.

    #10 76 days ago
    Quoted from ZEN:

    I use this, it's like $12...

    That takes all the fun out of building a power supply.

    #11 70 days ago

    My new switch came in today. This is what I ordered:

    ebay.com link » 4 Pole 3 Position Rotary Switch Non Shorting Rbs1 4

    The ad says "non-shorting" but when I hooked it up it shorted my power supply - just like my other switch. I took it apart and I don't think it's "non-shorting".

    IMG_3400 (resized).JPG

    Looks like the wipper would connect two points at the same time.

    I tried to open the space between the contact points (see the top of the wafer) to make it non-shorting but I don't think I should trust it.

    This is the next one I ordered.

    ebay.com link » Alpha 4 Pole 3 Position Premium Rotary Switch 1 Deck Pc Mount Usa Seller

    This look like it has insulators between the contact points. Hope this works.

    1 week later
    #12 63 days ago

    My new switch arrived the other day. I hooked it up temporarily and it worked great. The new switch IS non-shorting. I decided to make a small PC board to mount on the back of the switch to make it easier to connect all the inputs and LEDs. It would also eliminate a bunch of wiring. After I etched the board, I tested it. It worked fine. Now all that’s left is the meter, power switch and assemble the box.

    IMG_3415 (resized).JPGIMG_3419 (resized).JPGIMG_3422 (resized).JPGIMG_3423 (resized).JPG
    #13 62 days ago

    I finished up the ATX power supply and it works and looks great. Not your average looking computer power supply.

    IMG_3433 (resized).JPG
    IMG_3435 (resized).JPG
    IMG_3441 (resized).JPG
    IMG_3442 (resized).JPG
    IMG_3443 (resized).JPG

    On the scope it looks like a pretty steady voltage.

    pic_68_1 (resized).jpg
    pic_68_2 (resized).jpg
    pic_68_3 (resized).jpg

    In case you’re interested this is how it was made. Last winter I built a power supply especially for testing MPU boards. This is the build for that project:

    https://pinside.com/pinball/forum/topic/meteor-resets-with-rottendog-solenoid-driver-board

    So I had a bunch of parts left over.

    Lately I’ve been messing with Arduino’s and they are mostly 3.3 volts and 5 volts. I had an old Dell power supply so about the only parts I needed were a couple switches. I didn’t want to use the metal ATX box so I made my own enclosure from some white Plexiglas I had. I removed all the unnecessary wiring to clean it up. I added the USB power ports for Arduino’s. The LED power indicators were completely unnecessary but they add a custom look.

    IMG_3347 (resized).JPG
    IMG_3361 (resized).JPG
    IMG_3369 (resized).JPG
    IMG_3371 (resized).JPG
    IMG_3391 (resized).JPG
    IMG_3393 (resized).JPG

    This was a fun project – after I got the non-shorting switch worked out.

    #14 62 days ago

    Wow, was following along. That came out very cool looking!

    #15 62 days ago

    Thanks for the compliment and thanks for posting. I was beginning to think no one was watching.

    It was a fun project. I really enjoy building stuff like this.

    Bob

    #16 62 days ago

    I'm sure I'm not the only one. Very impressive, it was much more polished than I ever expected. The custom-formed shell put it over the top

    Promoted items from the Pinside Marketplace
    $ 269.00
    Cabinet - Other
    PinGraffix Pinside Shop
    From: $ 9.00
    $ 14.95
    $ 7,499.00
    Pinball Machine
    Star Wars Premium Out of stock
    Operation Pinball
    $ 495.00
    Cabinet - Armor And Blades
    MI Pinball Refinery
    $ 224.99
    $ 750.00
    Flipper Parts
    Mircoplayfields
    $ 4.95
    Apparel - Unisex
    ULEKstore
    $ 69.99
    Playfield - Toys/Add-ons
    Lighted Pinball Mods
    $ 23.00
    Cabinet - Shooter Rods
    The MOD Couple
    $ 11.95
    Playfield - Toys/Add-ons
    ULEKstore
    From: $ 7.49
    $ 11.95
    From: $ 42.00
    Cabinet - Shooter Rods
    ModFather Pinball Mods
    $ 99.99
    Lighting - Other
    Lighted Pinball Mods
    $ 89.99
    Lighting - Led
    Lighted Pinball Mods
    $ 86.95
    Cabinet - Shooter Rods
    Super Skill Shot Shop
    $ 37.00
    Playfield - Toys/Add-ons
    The MOD Couple
    $ 7,999.00
    Pinball Machine
    Little Shop Of Games
    $ 69.00
    $ 89.99
    Lighting - Led
    Lighted Pinball Mods
    $ 10.95
    $ 129.00
    Lighting - Led
    LED OCD
    $ 14.95
    Playfield - Toys/Add-ons
    ULEKstore

    Hey there! Got a moment?

    Great to see you're enjoying Pinside! Did you know Pinside is able to run thanks to donations from our visitors? Please donate to Pinside, support the site and get anext to your username to show for it! Donate to Pinside