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From what I understand they are switchmode power supplies. They don't like running without a load, just like any switchmode laser diode driver.
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PC PSU into a Lab PSU
- Thread starter LaZeRz
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From what I understand they are switchmode power supplies. They don't like running without a load, just like any switchmode laser diode driver.
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The difference is that laser drivers are constant current. You can't maintain constant current without a load, but you can maintain constant voltage without a load.
I've found they tent to shut down with sudden changes in load. So putting a power resistor on one of the rails makes any additional load less of a change.
I've found they tent to shut down with sudden changes in load. So putting a power resistor on one of the rails makes any additional load less of a change.
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I've got an old 300W Dell ATX power supply and converted it into a bench power supply. I added an LED + resistor across the PSU-is-plugged-in lines for an indicator and used a simple rocker switch to turn on the PSU. It doesn't care about having a load. Many of the older switched power supplies did care, but many newer ones have resistors built in that allow them to turn on without load.
LaZeRz
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Also, some psu's have sensing lines on the 3.3v rail (orange) so if all the orange cables aren't connected it won't switch on.
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What if you don't use all the cables in your computer?
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so im working on a project similar to yours and i cant find how you make it cc and cv i can only find one or the other
help??
hahhah im a noob when it comes to electronics, i only know the very basics.
so take it easy please:thanks:
help??
hahhah im a noob when it comes to electronics, i only know the very basics.
so take it easy please:thanks:
LaZeRz
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IIRC you will have two make two circuits. one with a current regulator and one with a voltage regulator
I might be wrong though, im pretty tired
The 3.3v sensing cable is already bridged to another 3.3v cable in your 20 or 24pin connector
I might be wrong though, im pretty tired
The 3.3v sensing cable is already bridged to another 3.3v cable in your 20 or 24pin connector
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He means the orange wire connections in the ATX motherboard connector. There aren't any orange connectors in any of the other cables.
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so yesterday i bread-boarded some circuits a cc and a cv using the lm317 while waiting on my 338's i found that under a load w/ the multimeter still attached i don't get the correct reading so my question is how do you make it like the ones you would buy are ( where the meter displays the correct current fed to the load) ?
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You need to be way more specific.
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ok so i set up a voltage regulator w/ a 1m117 i had laying around i used a pot and i could adjust the voltage up and down. so i set it to 10v added a load( in this case a fan) with the DMM still attached and the multimeter went from a 10v reading to all over the place
better?
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thank you :beer: how big does my dump resister need to be the only high W resisters i have is 1 ohm 10 W i'm guessing that's not enough resistance
EDIT: also are there any other lm317 variants like the lm338 that go above 5A
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LaZeRz
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I used a LD1084 because it can handle 5 amps of draw and has lower voltage dropout than the LM series.
I also used a ceramic plate resistor (10ohm, >10watt) thermally glue'd to a heatsink.
I also used a ceramic plate resistor (10ohm, >10watt) thermally glue'd to a heatsink.
