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atx power supply wrong voltages

I've done some experimenting with an ATX power supply, trying to turn it into a bench top, and I've come close.  I have 1 more problem, the voltages are off.  Instead of 5v I'm getting 5.25, instead of 12 I get 11.4 and most dramatically of all instead of 3V I get 4V. Has anyone had this problem before and learned to solve it? 

Topic by bobobano    |  last reply


I currently have a HP 6623A bench top PSU which is amazing to say the least but I never end up using all of the features and its pretty big. It regulates voltage and amperage but I really only need a really good variable voltage bench top PSU. What I need: 3x 0-12V 3A outputs What I have: tons of computer PSUs, wall warts, and everything in between. What I was suggested to use: 3x LM350T 3x 5k pot running off the 12V rail of a PSU. Does anyone have a suggestion for a better configuration? Is there a better variable regulator you suggest? -Thanks!

Question by newrev426    |  last reply

Could i use pwm to vary voltage for a benchtop power supply? Answered

I wanted to create a variable benchtop supply from a computer atx supply. Could i use a MOSFET with an arduino to vary the voltage coming from a 12v power supply? Initially i wanted to use a LM317 but since that would be inefficient. The mosfet in question is IRF540N Here is the circuit diagram

Question by qwerty156    |  last reply

Using a Benchtop PSU to heat wires?

I modified a 300W ATX power supply that I got for $1 the other day to use as a benchtop power source, much the same way the people who have posted Instructables for this have done.  I want to do some experimenting heating up wires, but I don't want to harm the PSU.  I believe it has built-in short circuit protection, but I want to be safe anyways.  I think that if I put in a high-wattage resistor in parallel with the heating wire, that might save the PSU.  If I did this, what value resistor (ballpark range) would I need so that power would flow through the wire until it heated up too much (thus increasing resistance across it), causing the power to go through the resistor instead?

Question by Radioactive_Legos    |  last reply

ATX PSU to Multi-Volt power supply and I have PROBLEMS! Chirping/cicking and jumping voltage.

Clicking from voltage regulator, jumping voltage, I'm stumped! Heres a video of the problem, any help is GREATLY appreciated!!

Question by flyinfinn    |  last reply

Are high power resistors really neccessary on a benchtop PSU conversion?

Was looking through the site and I was just wondering--why all the huge resistors on the bench-top power supply conversions of PC Power supplies? From personal experience this seems like a waste of perfectly good electricity.I know that they require some current to just stay on however in designing a project for my school's Engineering Technology department I found that the heat generated by such a small resistance (Around 10 ohms) was unacceptably high. Originally I was looking at Instructables and this sitethis site for inspiration but all the cooling measures taken to prevent the high power resistor from becoming a hazard seemed rather silly. A few calculations and experiments later with the 250 watt power supply and I determined that 160 ohm1 watt resistors and 1K 1/2 watt resistors were perfectly acceptable for the purpose of keeping the PSU awake and functioning. I connected one of each between each voltage and ground. According to calculations I can get away with dissipating a grand total of two watts or less spread across multiple resistors.The current divider rule dictates that if you add resistances in parallel, the resulting resistance will be smaller meaning more current will flow through the overall circuit. However this increased current will divide itself across the parallel resistances according to the rule Ix= RtIT/(Rx+Rt). The current through and power dissipated by the resistor you've soldered into the PSU will not change enough to be significant no matter how large or small a resistance you attach in parallel with it--with the exception of an effective short and what in God's name are you doing intentionally shorting the terminals of your bench-top PSU? Now several months later, the PSU is still operating happily and powering multiple micro-controller projects on a display board. Therefore I can reliably conclude that the high-power 10 ohm resistors in many computer power supply conversions are probably a gratuitous waste of wattage. You can get away with using a higher resistance and a resistor that dissipates much less current.

Topic by Psickattus    |  last reply

Jewelry tools for sale

My boss recently purchased all the tools from a jewelry shop that was going out of business and subsequently has a lot of tools that he is parting with. While these are primarily jewelry tools many of them are perfect for prop building. He has some nice workbenches, casting equipment, benchtop laser welder, a large polishing station, plating rectifier, rolling mills, benchtop lathe, flexshaft motors/handpieces, microscopes, engraving tools and all kinds of small hand tools. There's too much to list here- I have a complete listing of everything with photos and pricing. Some of this equipment is pretty big/heavy so local pickup would be preferred (Boulder, Colorado) but he said he'll ship equipment if need be. After downloading and viewing the list if there are any questions just message me and I'll try to answer them as best as possible or have my boss email you. Thanks!

Topic by Honus    |  last reply

the right resistor?

Hey guys got a question. I want to add an ultra bright LED from my mini mag light to my atx benchtop power supply. The LED ran off 3v (2 AA’s.) The line I want to use is the 3.3v (14 amp) from the atx to power it. What size/power rating resistor should I use?

Topic by jmille38    |  last reply

how would you make a powernet model pwp 165h computer power supply turn on with out the motherboard?

 i am trying to make a benchtop power supply from a powernet model pwp 165h computer power supply. the power supply wont turn on unless its connected to the motherboard, and the whole computer is powered up. i would greatly appreciate any help or advice.

Question by knexer87    |  last reply

power inverter: help? Answered

I have this power inrter, and i once hooked it up t a mac power supply converted to a benchtop power supply. i didn't know i yet, but the power supply was surging, and it started making he inverter smoke. i turned it off, but the inerter never worked again. can i reuse any of these parts to make a new one? i dont think it was the actual inverter piece, but one of the others p.s. this inverter was from a hp scanjet scanner

Question by zack247    |  last reply

Custom Power Supply for Lemax Products

Curious if it would be possible to make a custom power supply for the Lemax Halloween town.  We end up with a tangle of wires every year, and I saw recently This on Amazon and thought it might work.  The only problem I run into is that the bigger Lemax products (houses and spot lights) use 4.5v where as the smaller figurines use 3v.  I've seen a lot of computer PSUs used for benchtop power supplies but none have a 3v or a 4.5v output.  I'm fairly competent with electronics, so I understand this might be more difficult than it's worth.  

Topic by cyranohadden    |  last reply

Bench top power supply with 9 volt and 1.5 volt outputs? Answered

I am buidling a benchtop power supply from an ATX power supply.  I understand using the color codes how to accomplish  12v, 5v, and 3.3v connection connection ports. How could I add 2 more power ports for 9v and 1.5 volt? Basically I am trying to minimize the use of batteries in my testing with most common power sources. I have read a little about the -12v and -5v being obsolete power options.  Is there any need for these voltage outputs for a newbie electronics hobbiest? Thanks, TRU

Question by DiyWaterDog    |  last reply

I am looking to build a cheap (under $300) CNC machine that won't involve too much precise cutting... Answered

I have been interested in CNC for a while now, and now that I have a fairly good supply of money I think it's time to try my hand at building one. My criteria for the CNC are: *It has to be smallish (about 20" deep and up to 36" wide...) *I don't want to do too much precise cutting as I don't own a bandsaw. My cutting methods are hacksaw, Miter Saw, Jigsaw, and Circular saw... A kit would be nice (as in one with all parts included like the one oomlout will eventually come out with...) *I would only use it for foam most of the time, but it would be nice to be able to cut and carve wood and other materials as well. *A Hotwire machine might be nice... *I would like to build my own controller for it, because the prebuilt ones are expensive, right? *I would like it to have 30 inches x travel, 20 inches y travel, and up to 6 inches z travel. Like I said, it will probably do sheet foam most of the time, so even 6 inches or less z travel would probably be fine. Any of these sizes could be adjusted, I'm not set on the exact size... This machine would have to be able to work off of free or relatively inexpensive software. It would also have to be able to be stored 4 inches off the ground. I might bring it up to my benchtop when I use it, but it would be nice if it could stay down there on the shelf.

Question by snowpenguin    |  last reply

Any of you more seasoned build-o-philes have tips, mods, or tricks for an 8"(or any size) drill press? Answered

I was recently given a very well taken care of 8" Craftsman 1/3hp 5 speed drill press. It works fine, but it's a little grimy. So I'm currently cleaning it. Actually I wanted to ask someone if it's okay to clean that gunky layer of grease off of it because the grime has mixed in and it's essentially "sanding" the post. If it IS okay to clean off, do I replace it with different or newer grease once it's been cleaned? Also, ever since I was a kid, I was captivated by the swirling grinder or polisher pattern on the drill press table. Mine has a thin layer of rust on the table. Is there any way to remove the rust without ruining my beloved swirly pattern? So to wrap up here is the list of questions... 1. What are some modifications, tips, tricks, jigs, etc. for an 8" Benchtop Drill Press? 2. Is it okay to clean the grease off of the entire machine? If so, do I regrease it afterwards? What's the best product to use? 3. Is there a way to remove small layer of rust off the table without compromising the original swirl pattern? ANY and ALL help or suggestions will be greatly appreciated. Thank you Instructables community!!(That made me think of a town whose entire population was comprised of Instructables members. Ha! Got a question about robots? Go to Ted's three doors down. Building a welder from car batteries? Oh Tom two streets over would be more than happy to help! I know...ridiculous.)

Question by Mister Wolf    |  last reply

basic wiring, (for a home made benhtop injection molding machine? help?

Hey I have a bit of a home project here...I'm building a benchtop (hobby sized) plastic injection molding machine (or at least trying to :) ) well, I've been working on it for quite a while (including gathering all the components) and I've come to the wiring aspect of the project, I've made this wiring diagram, with some questions attached to it..can you help me by telling me whats right or wrong and what i perhaps might need. PS. I LIVE IN EUROPE, AND THE WIRING SHOULD THEREFOR BE EUROPE-STYLE... I have some questions:1)the thermostat has three(3) "taps" marked as on my drawing (1,2 and c), A,B and C1(my own made up symbols) should all be connected to it, can you say which goes where? 2) as you see in lower left corner (the plug) i know which wire should be ground, but can you tell me which one should be neutral? # or % (made up symbols) 3) as you mouse over some of the components, you can see how much power it uses etc, I DO NOT know how to use these informations, like should i need some kind of converters etc.? 4) does the rest of it look correct to you?, something i need or something i need to change? thanks I really hope you can help me, I've come so far machining most of the parts, so I almost only need to assemble it, when the wiring is done :) - Ps. as you might have guessed i am not that much into electrical surcuits :/ so bear with me

Question by lordl9999    |  last reply

What do I need to start getting into electronics?

I saw an instructable on here for an 8x8x8 LED cube, and was completely inspired. When I was younger (I'm 19) I built a few things out of those snap-together electronics kits, but nothing involving a soldering iron or a breadboard. I've bought myself a breadboard and a few little pieces to try to start out, but I know I need more--and I'm not totally sure what. On my list is a soldering iron (I have one but it's a piece of junk), red/black wire, a multimeter, and an assortment of resistors, and an arduino, but past that I still feel like I'm missing something vital. My current project list is: A 4x4x4 LED cube (just so I can know the fundamentals before jumping into an 8x8x8) A stereo (I have 2 car speakers that are just laying around, I'm hoping to turn them into something useful) Touching up my benchtop power supply (I built one out of a computer PSU but it looks.... not good) A high-power LED flashlight (my mom is into photography and saw a post about using an LED for an improv light source--the pictures turned out great, so I want to build one that has enough brightness to be used in a real photoshoot) An LED visualizer (This is one of the more daunting ideas I've had, I realize programming will be a bit difficult... I was hoping to use RGB LEDs and a microcontroller to handle the logic) I have a bit of experience in coding, nothing too impressive, but enough where I feel that I can grasp at least the programming of an Arduino (which so far looks user friendly and relatively simple [to me]), and on top of that I've been into computers and done a bit of tinkering with electronics before and so I know the basics of resistors (and LEDs together), capacitors, relays etc. Any advice would be greatly appreciated :)

Question by ninjatails    |  last reply

Motorized Monitor Lift idea - could I use a 775 motor (or 2) to power a lead screw lift?

Okay so I have a couple of extra 775 motors laying around (12V-36V, roughly 8A and 10K rpm). Also some cheap lead screws and some fittings, and I'm wondering if I can use them for sort of a crazy idea I'm formulating (which I'll explain more later if you're curious). I'm not sure if I've ever seen a lead screw actuator with BLDC motors, which makes sense because lead screws are for precision and that's what steppers are for. But I don't really need precision at all. I'm not sure which kind of motors they use in the actuators that are pre-built for things like this, they're usually hidden inside a housing. I've seen the DIY Perks build on YT where he used a 775 motor and a pulley system, and I realize pulleys are probably easier/better for a higher RPM motor. But I'm under the impression that BLDCs have more torque at lower speeds, and I want the whole lift assembly to be more compact than his if possible. Could my idea work if I was using a PWM controller to set the speed and some limit switches to shut it off? The load per monitor is about 10-15lb (5-7kg) and I have 8mm T8 lead screws. I basically have two of everything so if I figure out a lift that works well, I'd like to do a double monitor lift. Is this viable or no? Would it need reduction gears or something and just be too complicated? I'm about to mock something together and test it, but wanted to ask around first. I'm willing to scrap the lead screw idea if there's a better way. My crazy idea if anybody's interested: I want to build the most over-complicated electronics station/desk PC ever. (If you haven't heard of a desk PC, it's exactly what it sounds like - a PC inside a desk.) I'm thinking the PC portion will remain static, but it will have the hidden double monitor lift, an adjustable height KB + M surface, and an extra ATX PSU inside the desk. With a remotely wired access panel for all of the switches, some binding posts, volt/ammeter displays, etc. A very literal take on the "benchtop power supply." Oh and also maybe a hidden wireless charging surface somewhere in there too. I realize it will take wayyyyy more work than it's worth, but it would sorta be the culmination of several different skills I've been learning... but I'm still trying to learn some of them. There are two ways I can go about it. 1) If the lead screws work, I have more or less everything I need to build a version of it. But it would be a janky, bulky, heavy version with a lot of wood (I get tired of seeing wood, I like a more industrial look). 2) My dream come true would be to build the whole frame with 8020 aluminum, then use polycarbonate or something for the top. More expensive for sure, but it would be much more rigid and compact. I built my sim racing rig with 8020 a couple years ago. Love that stuff. And you can get it for close to 50% off from their ebay store.

Question by formVfunction