First, all ATX power supplies are switching DC supplies, and as such, they don’t really work without a load. Assembled Variable Dummy Load. For a real bench I'd be a little curious about what the traces on the PCB are rated for. Note: While the diagrams show fuses on all voltage rails and no fuse on the ground line, when I actually built my power supply… Power supply dummy load resistors. But now you have to factor in the power rating... New formula: Power (in watts) is determined by I (current) multiplied by E (voltage). However, when I attach a load (I'm using a PS3-controller for testing purposes), I can see Voltage across it, but no current. Simply connect the load to the power supply and turn it on. For the price, I would expect a power switch, and active 5v SB bus LED as well., but considering it just plugs into the stock ATX MB connector it's not bad. A completed 145 watt ATX power supply with switch, binding posts, labels and feet. Connecting this wire to ground (a black wire) causes the voltage to drop down to logic low (0), and the monitoring circuitry starts up the supply. Joined Apr 5, 2019 17. Notice the zip ties in the ventilation slots that hold the load resistor. It was actually my very first successful electronics project. Most of the power supplies in use today do not require as much of a load as the original IBM AT power supply. Versatile 5V and 12V rails, with -5V and (perhaps) -12V (low current) too. Establishing an accurate load is critical to testing and evaluating a PC power supply. In this video show converting computer ATX Power Supply to Lab Bench Power Supply. Inside the power supply, you will find a lot of different colors of wires. I wanted a power supply to use on my desk with a breadboard for electronics- based projects. It’s a converted ATX PSU, I cut the cables off and added binding posts to use as a bench-top power supply, I could have simply bought one of those cheap ones on ebay from china for ~£40 however I had this lying about and it cost me about £6 in parts. My roommate Adam told me about somebody online who had converted a spare ATX computer power supply into a lab bench power supply, ... 10 Watt power resistor between +5V and Ground. Your garden variety ATX supply has a +5, +12, +3.3, -5 and -12 volt rails. I'm reading up all the various youtube videos, websites, etc on converting a surplus PC ATX power supply to be a benchtop supply, and all of them note the ATX requirement for a dummy load between 5V and ground or the PSU will turn off. Bench power supplies are expensive and therefore we usually use what's available. Pros: Low cost. In our experience most modern ATX supplies don't require a significant load on the 5 volt rail to start. The motherboard would draw +5v at all times, but +12v would normally be used only by motors, and the floppy drive motors would be off most of the time. To test real capacity of a power supply, we need a load with variable current consumption. So a 5 volt supply under 1 amp load would require a 5.0 ohm power resistor. Thread starter Napalm1432; Start date May 22, 2019; Search Forums; New Posts ; Thread Starter. High current output. Intermediate Full instructions provided 5 hours 4,461. My roommate Adam told me about somebody online who had converted a spare ATX computer power supply into a lab bench power supply, ... 10 Watt power resistor between +5V and Ground. The choice was mainly based on the fact that I could find a manual that specifies the minimum load for each output of this thing. The early ATX supplies (circa 1995) had a minimum load requirement of 1 amp on the 5V line and 0.3 amp on the 3.3V line. This DIY project will give you a power supply that produces a +3.3V, +5V, and +12V current, as well as some practice assembling basic electronics. The ATX breakout board routes the -12, 3.3, 5 and 12 volt ATX outputs to screw terminals, each protected by a 1.25 amp resettable polyfuse. These four voltages cover many common electronics needs, there's even a negative voltage (-12 volts) for op amps and audio projects. These four voltages cover many common electronics needs, there's even a negative voltage (-12 volts) for op amps and audio projects. A lot of these supplies won't give you the full 12 volts unless there is a load on the 5 volt rail. Very good if to test a power supply you got or if you are trying to make one. The most well known power supplies of a high current low voltage are AT or ATX supplies from computers. The ATXbreakout board routes the -12, 3.3, 5 and 12 volt ATX outputs to screw terminals, each protected by a 1.25 amp resettable polyfuse. I assume that is what the missing resistor is for right in the middle of the break out board. Pretty much any working power supply will be fine. You also need to have a load on the power supply. What do you think about using an ATX PC power supply as a bench unit? ATX Supply Breakout An ATX power supply can make a good cheap bench top power supply, and this breakout and is also good for testing ATX power supplies. .. Thus if you plan on powering LED's or other such low-power device exclusively, you'll need a resister to waste power. If the load resistor were missing, the system would intermittently fail to start up or operate properly. Recycle an ATX computer power supply into a beefy bench tool that powers your projects. This seems rather a low … If we have high power variable resistor such as tapped wire-wound resistor, we can directly connect this resistor and make some measurement. At first I thought this was because I did not have a load-resistor across the 5V-rail. Computer PSU's supply a good range of low voltages, which is useful for all sorts of smaller electronics projects. The ATX power supply we are going to use is one of the brand: GMI Power Supply, model: ATX500, 500W of power. I used an 18 ohm 10-watt resistor as a load and applied 19-volts to the input of each converter. Things used in this project . Recycle an ATX computer power supply into a beefy bench tool that powers your projects. If you tried to turn it on with nothing plugged in, it’d probably just fail into protect mode. This breakout provides +3.3, +5, +12, and -5 volts. Topic: Need help for approriate dummy load on ATX bench power supply (Read 5888 times) previous topic - next topic. ronnyandre. You possibly already have a spare one lying around. It is used to provide a small load to keep the power supply in the On mode. Their disadvantage is a poorly regulated output voltage and often a need to load both of the two main outputs (5 and 12V) at the same time. A pull-up resistor ensures that this wire carries a TTL-compatible "logic high" (or logic 1) value, which a small circuit within the supply monitors. If you find building your own desktop powersupply from a recycled PSU and a few parts from the local electronics store appealing, then grab some tools, pour yourself a cup of coffee (or personal preference) and let's get started. Power good and enabled indicator LEDs. An ATX power supply contains a green wire (known as PS_ON) which is used to turn on the supply. Napalm1432. I know this can be done using a 10ohm/10W power resistor, but i was wondering, … On the ATX connector you want to tie the green wire to ground. ATX BENCH SUPPLY This is a great way to get a cheap lab power supply, and serves as an introductory project in electronics. Make a dummy load for a lower voltage DC power supply. Otherwise you could damage the PSU. I have a couple of pragmatic questions about this - typically they're looking for 5-10 ohms in a 10Watt resistor as the load. A power resistor from 5v (red wire) to ground will do the trick. So your 5Volt Supply loaded by the 5Ohm resistor drawing 1 Amp will need to dissipate 5 watts. The min. With this modification we can easily build a bench power supply, boost electric motors, amplifier circuits, among many other things. May 22, 2019 #1 Hi there, I'm converting a ATX power supply to a "lab power supply" and found i need to have a dummy load to be able to use it. Recycle an ATX computer power supply into a beefy bench tool that powers your projects. The load requirements are different for every PSU. How to convert an ATX power supply to a lab bench power supply 30 March 2013 . The ATX breakout board routes the -12, 3.3, 5 and 12 volt ATX outputs to screw terminals, each protected by a 1.25 amp resettable polyfuse. On-Off button and control circuit. Optional load resistor included but NOT soldered. Any ATX power supply can be plugged into the adapter. I have a few old power supplies lying around, so I picked one to become a bench power supply. as to the possible need of a load resistor some power supplies do need one but most do not. May 11, 2017, 05:24 pm. I then used my multimeter to measure the output. Open source (CC BY-SA) Note: A 9 Watt load resistor is included but not soldered to the board. Components. the 5 and 12 volt supply lines of modern ATX supplies are capable of some pretty serious current. Hardware components: Darlington High Power Transistor × 1: Texas Instruments General Purpose Dual Op-Amp × 1: Buy from Newark; Buy from … We will take a step by step to facilitate our understanding. First of all, load resistors. Lab bench power supplies are very cost-prohibitive, but luckily power supplies for desktop computers can easily provide 30A for under $20. 1 × Power resistors I didn't have the right values so rather than order anything, I just grabbed a bunch that I could find and strung them together to get the right values. As such, you need to prevent this by using a small ballast on at least one of the rails to essentially burn a little power and complete the circuit. If you increase and decrease the load you should hear a change on the noise, and the output voltage should always keep on the same value. Computer power supplies cost around US$30, but lab power supplies can run you $100 or more! Before we begin, here is some background information on computer power supplies. load for mine is around 0.8 amps. Most of the parts were salvaged from old equipment. 1 × ATX power supply Mine is rated for 575 watts max, but that's probably overkill for most bench use. TheATX breakout board routes the -12, 3.3, 5 and 12 volt ATX outputs to screw terminals, each protected by a 1.25 amp resettable polyfuse. Unfortunately, this kind of high power resistor is expensive and not so flexible getting wide adjustment range. I assume that is what the missing resistor is for right in the middle of the break out board. .. I've done some reading about using ATX supplies as bench supplies, so I think I'm roughly familiar with the considerations I need to make for this project, but I'd just like to check here and see if I have my bases covered. It won't produce the same power that a standard lab power supply … The minimum load specification varies depending on which version of the ATX spec the supply adheres to. Power Supply Dummy Load. I'm currently trying to create bench power supply (for small projects) from an old ATX-PSU.. So I cannot recommend any one resistor to use. These four voltages cover many common electronics needs, there's even a negative voltage (-12 volts) for op amps and audio projects. Of course you could use the power brick instead of a bench supply, especially if you don’t already have one (which could well be the reason you are building this one). I am planning on converting an ATX PSU into a lab bench power supply, and I've seen plenty of videos and read numerous articles about how easy it … It is used to provide a small load to keep the power supply in the On mode. PCPerspective’s power supply test bench can place a precise DC load on the PSU under test. A computer power supply converts the AC power from the wall outlet into smaller DC voltages that power the various components of the computer. Newbie; Posts: 13; Karma: 0 ; Need help for approriate dummy load on ATX bench power supply. In picture 3 and picture 4 I made a test to show, how the voltage behaves between load and no-load operation. 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