Reducing fan voltage for molex
- Thread starter APM
- Start date
Soldato
- Joined
- 6 Feb 2010
- Posts
- 14,583
I think this is what you are looking for:
http://www.techpowerup.com/articles/other/137
http://www.techpowerup.com/articles/other/137
Depends on the load on the circuit.
For 5v swap the yellow and red on the Molex to use the 5v rail. Some people also swap the red into the black position next to the yellow to give 7v but it's not a great idea. I would never do it to my power supply. +5v is meant for positive voltage rails and not as a return path for your fans.
Far easier is to solder a few diodes in series in the circuit. You'd get 0.6-0.7v drop per diode. So eight would give a near 5v drop and 11 would give a 7v drop.
A 1N400x series diode costs about 1p.
Another simple option is to get a 1W zener diode of say 5.1v
Or just use a fan controller like everyone else.
For 5v swap the yellow and red on the Molex to use the 5v rail. Some people also swap the red into the black position next to the yellow to give 7v but it's not a great idea. I would never do it to my power supply. +5v is meant for positive voltage rails and not as a return path for your fans.
Far easier is to solder a few diodes in series in the circuit. You'd get 0.6-0.7v drop per diode. So eight would give a near 5v drop and 11 would give a 7v drop.
A 1N400x series diode costs about 1p.
Another simple option is to get a 1W zener diode of say 5.1v
Or just use a fan controller like everyone else.
Last edited:
Thanks chaps,
I'm looking to fit a HDD fan to an old Compaq Presario pc circa 2006 and all the cheap ones I see on flea bay are all rated at 3300 rpm and up so I imagine they'd be quite noisy but what I think I'll try is to just sit an 80mm fan on top of the HDD and use a molex to 3 pin converter to drop the voltage to that to 5v or 7v.
Thank you very much for your replies though and I think I'll just go and order a few of the 1N400x diodes for my parts drawer as they sound useful,the link to the easy 7v mod is going in my bookmarks too.
Is this what I'm looking for regarding the diodes?
http://www.ebay.co.uk/itm/1N400x-1A...mponents_Supplies_ET&var=&hash=item43bd50c038
Cheers
I'm looking to fit a HDD fan to an old Compaq Presario pc circa 2006 and all the cheap ones I see on flea bay are all rated at 3300 rpm and up so I imagine they'd be quite noisy but what I think I'll try is to just sit an 80mm fan on top of the HDD and use a molex to 3 pin converter to drop the voltage to that to 5v or 7v.
Thank you very much for your replies though and I think I'll just go and order a few of the 1N400x diodes for my parts drawer as they sound useful,the link to the easy 7v mod is going in my bookmarks too.
Is this what I'm looking for regarding the diodes?
http://www.ebay.co.uk/itm/1N400x-1A...mponents_Supplies_ET&var=&hash=item43bd50c038
Cheers
Cheers,just picked these up,
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=120917745136
good enough for me to play with if not the cheapest available.
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=120917745136
good enough for me to play with if not the cheapest available.