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#21
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PSU load tester
On Fri, 30 Jun 2006 20:23:26 GMT, VWWall
wrote: kony wrote: On Fri, 30 Jun 2006 19:21:42 +1000, "Rod Speed" wrote: Well headlamps are typically 110W or less, IIRC, and that only on the 12V rail. Nope, they're fine on the other rails too. Yes, but I meant using _one_ headlamp, was why I'd mentioned the upper wattage I'd seen per one. It's going to be quite the contraption to hook up enough headlamps to put a full load on all rails of a 750W PSU, particularly the 3.3V and 5V rails. That doesn't make it undo-able but not so convenient either unless one worked for a place that makes or sells headlamps. You don't need a "headlamp", all you need are the bulbs! Old time headlights,(and taillights), did use separate bulbs. Ok, but then you need a way to mount them and/or either to solder or sockets. Finding suitable sockets might be a chore, but you can easily solder 12 gage wire to the bulbs. You don't need that size for the current, but it's stiff enough to hold the bulbs where you want. Left "floating" in the air, they will easily dissipate their rated wattage. I'm not arguing that bulbs couldn't work, but rather the resulting project could be a little nicer looking, sturdier, more compact, by avoiding bulbs. It may also be easer to select different current going another route (depending on the control method). Old fashioned "knife" switches are ideal for connecting as many lamps as required in parallel, and they have terminals, so you don't even have to solder! Yes if he has some, but if not, the project budget is getting pretty tight as it is. You can still find 6V lamps if you like to "see the light" on the 5V rail. :-) Google for "automobile lamps" to find amperage specs. The "inrush current" of ~1A taillight is ideal for simulating the 12V start-up of a hard drive motor. (Don't look for the 12V rail droop with a DVM, in spite of what w_tom says!) ;-) I'd think the inrush current would be better than nothing, but not long enough duration (at an elevated level) to be a good simulation. |
#22
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PSU load tester
kony wrote
Rod Speed wrote kony wrote Rod Speed wrote Well headlamps are typically 110W or less, IIRC, and that only on the 12V rail. Nope, they're fine on the other rails too. Yes, but I meant using _one_ headlamp, was why I'd mentioned the upper wattage I'd seen per one. Still cant see what you are getting at there. I meant your specific reference to the 12V rail. For one, the # of headlamps isn't necessarily lower than other types of resistors, could go either way, lower or higher. There arent too many 100W class resistors readily buyable. The one thing which seems more certain is it could end up either costing more, or being very very large. Dunno, most obviously with surplus bulbs from car wreckers. Suppose a typical 55W headlamp, it's roughly 4.5A at the slightly over 12V electical system of an automobile. You'll need at least 6 for the 12V rail alone. Next we need a way to re-rate the resistance for what it would be (slightly higher) Lower, actually. due to the element not getting as hot from the other (lower voltage) PSU rails, but for simplicities' sake let's consider it a constant, 2.7Ohm 750W PSU is bound to have a fairly high 5V current (unless we were told otherwise, that wattage rating has to account for it, else we'd need even more amps on a different rail instead which is still more bulbs). So let's suppose a fairly modest 30A on 5V rail and 20A on 3.3V rail. Do you see that we're now talking about a LOT of headlamps Dont have to cost much tho if you get them from a car wrecker. and that this entire setup may require a whole table or more? Only if you use sealed beam headlights. Sure it doesn't need heatsinks anymore but it requires it's own zip code instead. Cant see that its going to be any bigger than those TO220 resistors if you dont use sealed beam headlights. If anything bulbs give you more flexibility since you can plug in a variety of different bulbs to get the load you want on a particular rail. "Plug in" is easier written than rewired. You must have noticed that headlights have sockets for the bulbs. Yes it can work, and work fine at that. It does have it's own set of trade-offs though, and that many headlamps are not going to be so cheap unless there is a lower-than-normal cost source for them. Thats what a car wrecker is. Even being conservative and thinking $5 each, You dont pay anything like that at a car wrecker. that's well over the budget. Nope. That was only a 55W headlamp, but beggers can't be choosers, a much higher wattage lamp may cost a lot more too. Again, these were (@ 55W) about 2.7 Ohm each, so you may be paying $5 (or more) per 2.7Ohm. Contrast that with 29 cents each for the first 10 Ohm resistor I'd linked. So you need 4 of them to reach close to 2.7Ohm, but it's still closer to $1 than =$5. Pity about the car wreckers. It's going to be quite the contraption to hook up enough headlamps to put a full load on all rails of a 750W PSU, particularly the 3.3V and 5V rails. The resistance of the bulb wont change that much, if anything the ones running on the the 3.3V and 5V rails will have a lower resistance than they will on the 12V rail. Agreed, but he'll still need to know how much it changes for determination of load, for # of bulbs to buy, Nope, just get a box full from the wreckers. and it's still a whole lotta bulbs and space to build this to test a 750W PSU. Maybe that's within the acceptible project needs for the OP, I don't know... but if he has a way to heatsink something else, it will tend to be more expensive than other alternatives. Nope. That doesn't make it undo-able but not so convenient either unless one worked for a place that makes or sells headlamps. Dunno, in some ways bulbs are more flexible since you can just plug in different wattage bulbs as required. Does he have different wattage bulbs? You can obviously get them from wreckers. I don't recall this being introduced into the thread yet, and wouldn't expect the average person to have several different wattages of 12V bulbs lying about, at least not more than their own automobiles/etc needed. Of course he can buy them but then the costs keep going up. Wreckers dont charge much. |
#23
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PSU load tester
Okay.. time to throw in some more details I think..
The 750W PSU I will likely be testing is this one: http://www.silverstone-usa.com/products-75zf.htm If the company decides to send me a 650W model instead, it will likely be this one: http://www.silverstone-usa.com/products-65zf.htm I just need a way to load either of those supply's close to their maximum ouput rating.. 600W is probably sufficient though.. (80% of 750W) Budget is the number one consideration.. I want to building something to generate a suitable load, but I don't want to spend a fortune.. If I have to spend like $50 to build something suitable then so be it.. as long as I can re-use it.. I don't mind at all how I accomplish the end result.. resistors just seemed 'the norm' for this kinda thing.. if I can use headlamps from a wreckers or resistance wire then so be it.. whatever is cheapest and least complex.. Bottom line: I will be recieving a brand spanking new power supply for absolutely nothing, and I don't want to screw up my relationship with the company by doing a lame review with no real stats.. (ie. idle voltage readings and reading at 100% cpu aren't gonna cut it all.. I need much more info and much more load) Chris |
#24
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PSU load tester
On Sat, 1 Jul 2006 08:21:37 +1000, "Rod Speed"
wrote: kony wrote Rod Speed wrote kony wrote Rod Speed wrote Well headlamps are typically 110W or less, IIRC, and that only on the 12V rail. Nope, they're fine on the other rails too. Yes, but I meant using _one_ headlamp, was why I'd mentioned the upper wattage I'd seen per one. Still cant see what you are getting at there. I meant your specific reference to the 12V rail. That you can plug the 110W lamp into 12V and expect close to 110W, but have to recalc for lower wattage on 3.3 or 5V rails. For one, the # of headlamps isn't necessarily lower than other types of resistors, could go either way, lower or higher. There arent too many 100W class resistors readily buyable. How many types does he need? I linked a few, but 100W isn't needed per se, but high wattage per $ is, if it is to be within the budget. That's part of why I linked that surplus 'site resistor because it is not only inexpensive (if he has a way to 'sink it) but also a smaller contraption to built which unless this is only a one-time test, means less costly wood/metal/whatever enclosure to hold all these parts. If it's going to be built, it might as well remain a whole modular device rather than just a string of bulbs spread out across a workbench. That makes storage, transportation, and setting it up again much easier too. The one thing which seems more certain is it could end up either costing more, or being very very large. Dunno, most obviously with surplus bulbs from car wreckers. Yes, that'd be a good way to cut costs if he is inclined to go that route. Suppose a typical 55W headlamp, it's roughly 4.5A at the slightly over 12V electical system of an automobile. You'll need at least 6 for the 12V rail alone. Next we need a way to re-rate the resistance for what it would be (slightly higher) Lower, actually. Yes I noted my error in a followup post. due to the element not getting as hot from the other (lower voltage) PSU rails, but for simplicities' sake let's consider it a constant, 2.7Ohm 750W PSU is bound to have a fairly high 5V current (unless we were told otherwise, that wattage rating has to account for it, else we'd need even more amps on a different rail instead which is still more bulbs). So let's suppose a fairly modest 30A on 5V rail and 20A on 3.3V rail. Do you see that we're now talking about a LOT of headlamps Dont have to cost much tho if you get them from a car wrecker. Maybe, he'll have to try it and see. I don't know that they'll be gathering up old light bulbs for resale though, it might take a lot of work to collect bulbs out of cars. and that this entire setup may require a whole table or more? Only if you use sealed beam headlights. It's not going to be all that small no matter what headlights you used. "maybe" but it all depends on the source, and the cost, other parts, etc... the whole design. Sure it doesn't need heatsinks anymore but it requires it's own zip code instead. Cant see that its going to be any bigger than those TO220 resistors if you dont use sealed beam headlights. If you say so. You must only be referring to the 10 ohm resistors though, right? There were 100W in TO247 package too. Further he may be able to create a load but it'll be fiddly to hit any exact load with a random assortment of bulbs... he might end up using resistors anyway to get that last few % accuracy. If anything bulbs give you more flexibility since you can plug in a variety of different bulbs to get the load you want on a particular rail. "Plug in" is easier written than rewired. You must have noticed that headlights have sockets for the bulbs. yep, all this is still a lot more work. Maybe easier, maybe not. Yes it can work, and work fine at that. It does have it's own set of trade-offs though, and that many headlamps are not going to be so cheap unless there is a lower-than-normal cost source for them. Thats what a car wrecker is. Maybe, he'll have to call a few up and see. Some people might be fortunate to have an accomdating junkyard nearby and others might not. Even being conservative and thinking $5 each, You dont pay anything like that at a car wrecker. Probably not, but there's still a lot of time involved, and not knowing what that wrecker has, we can't draw a conclusion yet on what support parts he'd need. Agreed, but he'll still need to know how much it changes for determination of load, for # of bulbs to buy, Nope, just get a box full from the wreckers. You figure those guys are going around collecting bulbs for resale? I kinda doubt it. They'll be in cars still and if he wants to spend an evening collecting them, so be it... or if he had to pay the cost of having someone else go around collecting them (for insurance reasons of no other), the cost goes up some. Probably still cheaper than new bulbs but it ends up being a lot of time and BS to go through just to save $10 for some resistors or whatever. I don't recall this being introduced into the thread yet, and wouldn't expect the average person to have several different wattages of 12V bulbs lying about, at least not more than their own automobiles/etc needed. Of course he can buy them but then the costs keep going up. Wreckers dont charge much. I guess we have completely different ideas about the best way to tackle a project. |
#25
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PSU load tester
www.xbitlabs.com has a detailed description of its PSU testing
methodology and also the hardware they built for the purpose. Instead of fixed resistors they used MOSFETs mounted on big, fan-cooled heatsinks and controlled each set of MOSFETs by a computer so its resistance could be varied. Where does it have all this info ? I can't find two words about their test rig ! Chris |
#26
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PSU load tester
On Fri, 30 Jun 2006 19:38:48 -0400, "Skeleton Man"
wrote: Okay.. time to throw in some more details I think.. The 750W PSU I will likely be testing is this one: http://www.silverstone-usa.com/products-75zf.htm If the company decides to send me a 650W model instead, it will likely be this one: http://www.silverstone-usa.com/products-65zf.htm I just need a way to load either of those supply's close to their maximum ouput rating.. 600W is probably sufficient though.. (80% of 750W) Budget is the number one consideration.. I want to building something to generate a suitable load, but I don't want to spend a fortune.. If I have to spend like $50 to build something suitable then so be it.. as long as I can re-use it.. I don't mind at all how I accomplish the end result.. resistors just seemed 'the norm' for this kinda thing.. if I can use headlamps from a wreckers or resistance wire then so be it.. whatever is cheapest and least complex.. Bottom line: I will be recieving a brand spanking new power supply for absolutely nothing, and I don't want to screw up my relationship with the company by doing a lame review with no real stats.. (ie. idle voltage readings and reading at 100% cpu aren't gonna cut it all.. I need much more info and much more load) Well you probably already have a hint about the direction I'd go... I'd use TO220 or TO247 resistors arrays. I'd use a circuit board and mount PSU connectors on it (though come to think of it I don't have any 4-pin (12V) connectors like motherboard use, or at least I don't know where they'd be, but probably Digikey would have them or you might be able to get samples from Molex/etc). You wouldn't necessarily need a circuit board for anything, but, I'd think you would at least want the whole *whatever* mounted somehow whether it be on a circuit board, on a piece of plywood or other wood planking or whatever. I've built quite a few one-off projects and can tell you that the incidental expenses add up quick, depending on what parts you have around already. I tend to buy not only what I need for a project but whatever else I might need someday if/when the prices are good, as it can cut down costs in the long run not to have to mail-order a 15 cent resistor or whatever to finish something. If you already had the wire, screws/bolts/nuts/etc, it helps towards your budget but if not there are lots of incidentals that can end up costing near what a bunch of resistors would. Incidentally here's another example of some potentially useful resistors from a surplus 'site, http://www.goldmine-elec-products.co...?number=G14510 With those, unlike the TO220 parts I'd linked previously, if you give them a little margin you don't have to try to heatsink them. For example on the 12V rail with paralleled series of those you'd have each series as 4 of them, so 3A through that series is 36W / 4 resistors = 9W each. Since you have 18A rails, that's 6 paralleled groups of 4 in series per each 12V rail. The entire PSU has 60A 12V limit though instead of 72A, so the total cost to load all 12V rails is 80 resistors, $8. Personally I always buy some spares of parts *just_in_case* something went wrong but that's up to you. For the 5V rail, it's only 30A and that takes up most of the current available for the combined 3V +5V rating too (180W total combined rating), so for a thorough test you'd have to unload the 5V rail some so you can then have 24A on 3.3V (almost 80W) and only 20A on the 5V to pull that addt'l 100W. So with 1 ohm resistors on 5V rail, paralleled series of 2 in each series, 2.5A per series and 6.25W per resistor. You'd need 12 paralleled series of 2, 24 resistors is $2.40 or $3 in groups of 10/$1. Same math applies for 3.3V rail, 1 resistor (no series needed since 3.3V/1= 3.3, * 3.3 = 11W, still enough margin on one 20W resistor. So for 24A, 7 resistors in parallel. So you'd need 111 resistors or $12 worth. The extra 9 might come in handy to load the other lower current rails or even buy another 10 or 20 more while you're at it (I'm too lazy to do the math as to how many you'd need for the other low current rails but with so many USB devices these days, I'd at least be sure to test the full rated 5VSB current. That's a lot of resistors of course, but it is only $12 total cost (check my math though, I might have easily made an error) and while the number seems awefully high, it also allows a finer granularity for testing not only this PSU but any others you want to put a different load on (which would be practically any PSU, since most are not 750W). Light bulbs would work though, I just won't go that way myself. I have oddles of leftover heatsinks though, aluminum sheeting, a metal brake, etc, so I can easier forsee what I'd do... if you feel more comfortable mounting na bunch of light bulbs on a piece of plywood, then explore that angle more. If you were going to be posting a picture of your PSU loading setup, I'd tend to think going with resistors or another electronics-parts method would look a little more professional than a bunch of lights, but inevitably no matter what you do, *somebody* will be finding fault with an article while the majority will instead welcome the information you provide whether it is, or isn't, as thorough as it could be- some information always beats _no_ information, so long as the wrong conclusions are drawn prematurely. For example, running a PSU at 600W load for a few hours is a better method of indicating a problem rather than declaring the PSU is suited for long term use at that wattage. Even a poor generic may have sufficient output into a resistive load for a day but in an actual system might fail in a few weeks time. I don't suppose you really want to have a 750W project running for months though, so back to that part about any info being better than none. I tried to download that PSU spec sheet but it seems unavailable or perhaps the link is mangled, they didn't seem to spell "download" right on the link but the correct spelling didn't work either. Anyway, with all the independant 12V rails it would be good to make sure they're up to spec. Likely they're all essentially duplicates of each other internally so it may not matter as much that all are simultaneously tested for 18A (indeed, they also mention the 60A max for 12V so it couldn't apply), but putting at least 50-60 amps of load on the rail would be a useful test, as I doubt anyone would want to pay a premium for the PSU if it doesn't actually perform better than a lower cost, 550-or-so watt alternative. |
#27
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PSU load tester
Skeleton Man wrote: www.xbitlabs.com has a detailed description of its PSU testing methodology and also the hardware they built for the purpose. Instead of fixed resistors they used MOSFETs mounted on big, fan-cooled heatsinks and controlled each set of MOSFETs by a computer so its resistance could be varied. Where does it have all this info ? I can't find two words about their test rig ! I searched their website for "power supply" and found this article from Jan 16, 2005: http://www.xbitlabs.com/articles/oth...thodology.html Here's the page where the test hardware is shown: http://www.xbitlabs.com/articles/oth...dology_11.html |
#28
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PSU load tester
1) Article cited by larry moe 'n curly provides useful background
information such as how voltage may vary both with load (wattage) on this voltage as load (wattage) changes on other voltages. That is a static load test where voltage is measured and compared to Intel ATX specs. Also pictured is a dynamic load tester. Power supplies must not maintain voltage just for a static load. Supply must also respond fast enough for dynamic loading. A meter excellent for static testing will not be sufficient for dynamic testing. However your description only asks for static testing under full load. 2) Motor load inside a computer is all but nil. Motors have a large startup current. Power supplies (circuit breakers, fuses, etc) are specially designed for this startup current. But computer supplies are not because that large startup current does not exist. Some mistakenly think a disc drive is a large load. Those motors draw so little as to make startup current trivial. However, if loading a power supply 12 volts with maybe 200 watt lights (16 amp load) may first demand more than 100 amps (for a short period). This might put a power supply into current foldback limiting - a protective lockout function. IOW a power supply would fail test even though that supply is perfectly OK. A partial load created by incandescent lights would be better if part or majority of that load is resistors or transistors; to create a smaller startup current. 3) BTW, if paralleling transistors (as shown in the picture), then use FETs (not bipolar) transistors for reasons only provided if relevant. 4) Paul makes an important point about maximum current per Molex pin. Too much current through one pin can create excessive heating and connector damage. What he has posted is informative - especially the numbers. 5) How to measure load of more than 10 amps with a meter only rated at ten amps: put a 14 AWG solid copper wire in series between power supply connectors (all pins brought to a common point) and the load. This is a current shunt. If that wire is about 5 feet long (ballpark numbers from memory), then the DC voltage between both ends of that wire might be 0.2 volts with a 16 amp current draw. Use a long wire so that wire temperature changes are minimal. Better accuracy might be obtained with 8 feet of 12 AWG wire. Calibrate the current 'shunt' by loading 8 amps. The wire 'shunt' might measure 0.1 volts. Therefore 1) no need to break and make connection for measuring current (no additional connectors required), and 2) your meter is not at risk for too much current. 6) Voltage using a volt meter is not only a great tool for testing a power supply under full load (static load). Same meter is effective at identifying a defective power supply when power supply remains inside a computer - fastest method to confirm power supply integrity and without disconnecting anything. Excessive AC ripple would also cause bad DC voltage on meter - but only when power supply is loaded either by computer or test fixture. IOW detect computer failures before those failures start intermittently crashing the computer later. Skeleton Man wrote: Okay.. time to throw in some more details I think.. The 750W PSU I will likely be testing is this one: http://www.silverstone-usa.com/products-75zf.htm If the company decides to send me a 650W model instead, it will likely be this one: http://www.silverstone-usa.com/products-65zf.htm I just need a way to load either of those supply's close to their maximum ouput rating.. 600W is probably sufficient though.. (80% of 750W) Budget is the number one consideration.. I want to building something to generate a suitable load, but I don't want to spend a fortune.. If I have to spend like $50 to build something suitable then so be it.. as long as I can re-use it.. I don't mind at all how I accomplish the end result.. resistors just seemed 'the norm' for this kinda thing.. if I can use headlamps from a wreckers or resistance wire then so be it.. whatever is cheapest and least complex.. Bottom line: I will be recieving a brand spanking new power supply for absolutely nothing, and I don't want to screw up my relationship with the company by doing a lame review with no real stats.. (ie. idle voltage readings and reading at 100% cpu aren't gonna cut it all.. I need much more info and much more load) |
#29
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PSU load tester
Paul wrote: In article , "Skeleton Man" wrote: The 750W PSU I will likely be testing is this one: http://www.silverstone-usa.com/products-75zf.htm If the company decides to send me a 650W model instead, it will likely be this one: http://www.silverstone-usa.com/products-65zf.htm There are (3) 3.3V and (4) 5V wires on a 20 pin ATX power connector. There are (4) 3.3V and (5) 5V wires on a 24 pin ATX power connector. You are allowed 6 amps per pin. I would aim for 5 amps per pin for a small safety factor. Molex pins for HDs are rated for 6A apiece, those for motherboards 8A or 9A apiece. That's not to say I'd want to operate them at those limits. Contact the lamers at Silverstone and get the manual. Silverstones are actually very good and made by Etasis. |
#30
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PSU load tester
Skeleton Man wrote:
Okay.. time to throw in some more details I think.. The 750W PSU I will likely be testing is this one: http://www.silverstone-usa.com/products-75zf.htm If the company decides to send me a 650W model instead, it will likely be this one: http://www.silverstone-usa.com/products-65zf.htm I just need a way to load either of those supply's close to their maximum ouput rating.. 600W is probably sufficient though.. (80% of 750W) Budget is the number one consideration.. I want to building something to generate a suitable load, but I don't want to spend a fortune.. If I have to spend like $50 to build something suitable then so be it.. as long as I can re-use it.. I don't mind at all how I accomplish the end result.. resistors just seemed 'the norm' for this kinda thing.. if I can use headlamps from a wreckers or resistance wire then so be it.. whatever is cheapest and least complex.. Bottom line: I will be recieving a brand spanking new power supply for absolutely nothing, and I don't want to screw up my relationship with the company by doing a lame review with no real stats.. (ie. idle voltage readings and reading at 100% cpu aren't gonna cut it all.. I need much more info and much more load) Chris Forget using filament lamps. They eat in the region of 10x rated current on start up, and would make your test results junk. And maybe open you up to legal charges, depending on where you live. A bit of sheet wood & metal with 3 screws and 2 bolts would do it, plus resistance wire. In fact you could likely do it with nothing more than 2 metal rods/plates and a bucket of water. Water conducts some at 12v after all. Or one rod and a metal bucket. Fully variable. NT |
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