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large axial fans: power used is less at higher voltages?
- Thread starter 80251
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Looks like 24V is the optimal voltage for such a design geometry.
What would happen if you were to connect the positive lead to +12V and the negative lead to -12V on the 24-pin ATX power connector? Most PSU's still seem to have a -12V lead.
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The -12V line can normally only carry a rather low current.
Just use a 12V fan and move on.
Just use a 12V fan and move on.
There are +24VDC PSU's that could be used, some of them are pretty small considering you don't need a lot of current to power +24VDC fans, but I only have 2 or 3 fans that come in +24VDC models.
I believe the +24VDC models of these fans can be had cheaper than the +12VDC models though (at least on ebay).
I believe the +24VDC models of these fans can be had cheaper than the +12VDC models though (at least on ebay).
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Most PSUs don’t like high load on the -12V side. It’s a leftover relic from older communication ports and protocols.
Why is -12V needed on an ATX power supply
Checking the standard ATX connector pinout it mainly gives out "standard" positive voltages, like +3.3VDC, +5VDC and +12VDC. There is one exception, pin 14, which actually gives out -12VDC: Based o...
You would achieve your 24V difference, but not at enough wattage to do anything. I experimented with a older PSU once and the voltage drops back to 12 quickly as the load increased, and then it tripped since it believed it had a short circuit.
I'll bet -12V was for the old RS232c serial ports (which initially required +/- 12V to work).Most PSUs don’t like high load on the -12V side. It’s a leftover relic from older communication ports and protocols.
Why is -12V needed on an ATX power supply
Checking the standard ATX connector pinout it mainly gives out "standard" positive voltages, like +3.3VDC, +5VDC and +12VDC. There is one exception, pin 14, which actually gives out -12VDC: Based o...superuser.com
You would achieve your 24V difference, but not at enough wattage to do anything. I experimented with a older PSU once and the voltage drops back to 12 quickly as the load increased, and then it tripped since it believed it had a short circuit.
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Last edited:
@Shrek
That's a great idea except for two things:
1. every fan would need it's own AC power cord.
2. you can't control the fan speed
I do use two high power 127mm fans though and only at full speed. If I could convert those to 115AC it would reduce the power draw on my PSU by 66W (even more on start-up) and save power over using the +12VDC models it would be a winner.
That's a great idea except for two things:
1. every fan would need it's own AC power cord.
2. you can't control the fan speed
I do use two high power 127mm fans though and only at full speed. If I could convert those to 115AC it would reduce the power draw on my PSU by 66W (even more on start-up) and save power over using the +12VDC models it would be a winner.
eidairaman1
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Considering POTS established the TRS then 3.5 (POTS used 48~53VDC Ring Battery)Most PSUs don’t like high load on the -12V side. It’s a leftover relic from older communication ports and protocols.
Why is -12V needed on an ATX power supply
Checking the standard ATX connector pinout it mainly gives out "standard" positive voltages, like +3.3VDC, +5VDC and +12VDC. There is one exception, pin 14, which actually gives out -12VDC: Based o...
You would achieve your 24V difference, but not at enough wattage to do anything. I experimented with a older PSU once and the voltage drops back to 12 quickly as the load increased, and then it tripped since it believed it had a short circuit.