Fan control DIY?

[spwath]

How can i control speed of fan. On fan i have red yellow and black, and im using yellow black and red wires from a molex conector.

Can i change the order of the wires to run at different speed?

 

[phillrulz]

How can i control speed of fan. On fan i have red yellow and black, and im using yellow black and red wires from a molex conector.

Can i change the order of the wires to run at different speed?

get a potentiometer aka a variable resistor, cut the red wire place the resistor there... you increase resistance fan will get slower reduce it fan will get faster. 

[spwath]

get a potentiometer aka a variable resistor, cut the red wire place the resistor there... you increase resistance fan will get slower reduce it fan will get faster. 

but isnt there some thing you can do with wire order?

[phillrulz]

but isnt there some thing you can do with wire order?

well if its a 12v fan running it on 5v will slow it alot but thats obiously only a one set speed. for that you would change the pins

[spwath]

well if its a 12v fan running it on 5v will slow it alot but thats obiously only a one set speed. for that you would change the pins

Right thats what i meant. Thanks, ill try changing stuff.

[phillrulz]

Right thats what i meant. Thanks, ill try changing stuff.

be extremely careful you dont use that moded molex on another device you could fry a 5v device if you pump 12v into it. 

[spwath]

be extremely careful you dont use that moded molex on another device you could fry a 5v device if you pump 12v into it.

I won't.

I tried changing wires.

With no 12v runs same speed as with 12v.

With no 5v it won't run

[phillrulz]

I won't.

I tried changing wires.

With no 12v runs same speed as with 12v.

With no 5v it won't run

guess its a pot for you then 

[W-L]

I won't.

I tried changing wires.

With no 12v runs same speed as with 12v.

With no 5v it won't run

 

You can try setting up the molex to 7v if the fans don`t spin up at 5V.

[Scheer]

well if its a 12v fan running it on 5v will slow it alot but thats obiously only a one set speed. for that you would change the pins

 

For clarification, that color code is for the MOLEX ONLY!

 

This would be a 3 pin fan pinout (motherboard side I believe). The third wire is the RPM sensor.

 

 

You can take the 12V pin on the fan, and connect it to 5V on the molex to see if it will still spin, but most will not go that low.

Or do as W-L says and take the fan 12V and go to the molex 12V, and the fan ground and go to the molex 5V to give the fan 7V of power (DC works as differences, so if you connect to -5V and 12V you will give the device 17V of power. The black wire in DC technically isn't ground, it is a return/0V)

[phillrulz]

For clarification, that color code is for the MOLEX ONLY!

 

 

OP did say molex connector

 

How can i control speed of fan. On fan i have red yellow and black, and im using yellow black and red wires from a molex conector.

Can i change the order of the wires to run at different speed?

[spwath]

For clarification, that color code is for the MOLEX ONLY!

This would be a 3 pin fan pinout (motherboard side I believe). The third wire is the RPM sensor.

You can take the 12V pin on the fan, and connect it to 5V on the molex to see if it will still spin, but most will not go that low.

Or do as W-L says and take the fan 12V and go to the molex 12V, and the fan ground and go to the molex 5V to give the fan 7V of power (DC works as differences, so if you connect to -5V and 12V you will give the device 17V of power. The black wire in DC technically isn't ground, it is a return/0V)

Ah great thanks, this explains it

[gylmir]

well if its a 12v fan running it on 5v will slow it alot but thats obiously only a one set speed. for that you would change the pins

 

tell me how to make a fan spin at 7 volt when you take +12 and +5 volt is equal to 17v

everybody talks about the -5v but i have never seen a molex with a -5 volt rail.

 

The positive voltages seemingly power everything in the system (logic and motors), so what are the negative voltages used for? The answer is, not much! In fact, –5 V was removed from the ATX12V 1.3 and later specifications. The only reason it remained in most power supply designs for many years is that –5 V was required on the ISA bus for full backward compatibility. Because modern PCs no longer include ISA slots, the –5 V signal was deemed as no longer necessary. However, if you are installing a new power supply in a system with an older motherboard that incorporates ISA bus slots, you want a supply that does include the –5 V signal.

 

Your +5V feed will be being over-powered by +7V.

This is bad

You will probably be doing damage to the internals of your power supply.

Especially if the +5V section is using capacitors that are rated at less than 12V... pop

[Grrizz]

tell me how to make a fan spin at 7 volt when you take +12 and +5 volt is equal to 17v

everybody talks about the -5v but i have never seen a molex with a -5 volt rail.

 

The positive voltages seemingly power everything in the system (logic and motors), so what are the negative voltages used for? The answer is, not much! In fact, –5 V was removed from the ATX12V 1.3 and later specifications. The only reason it remained in most power supply designs for many years is that –5 V was required on the ISA bus for full backward compatibility. Because modern PCs no longer include ISA slots, the –5 V signal was deemed as no longer necessary. However, if you are installing a new power supply in a system with an older motherboard that incorporates ISA bus slots, you want a supply that does include the –5 V signal.

 

Your +5V feed will be being over-powered by +7V.

This is bad

You will probably be doing damage to the internals of your power supply.

Especially if the +5V section is using capacitors that are rated at less than 12V... pop

The fan sits between the 5V and 12V, the 5V remains at 5V and the 12V remains at 12V but there is a 7V drop over the fan (12V - 5V = 7V) basically your fans "ground" level is 5V relative to the PSUs ground and the fans positive side is 7V relative to its own "ground" but 12V relative to the PSUs ground. Using the -5V and +12V would give you 17V (12V - (-5V) = 17V).

As long as the current being pulled from the 5V is greater than what you are feeding back in (via the 7V bridge) you shouldn't have an issue (and this is usually the case with fans).

[Scheer]

tell me how to make a fan spin at 7 volt when you take +12 and +5 volt is equal to 17v

everybody talks about the -5v but i have never seen a molex with a -5 volt rail.

 

The positive voltages seemingly power everything in the system (logic and motors), so what are the negative voltages used for? The answer is, not much! In fact, –5 V was removed from the ATX12V 1.3 and later specifications. The only reason it remained in most power supply designs for many years is that –5 V was required on the ISA bus for full backward compatibility. Because modern PCs no longer include ISA slots, the –5 V signal was deemed as no longer necessary. However, if you are installing a new power supply in a system with an older motherboard that incorporates ISA bus slots, you want a supply that does include the –5 V signal.

 

Your +5V feed will be being over-powered by +7V.

This is bad

You will probably be doing damage to the internals of your power supply.

Especially if the +5V section is using capacitors that are rated at less than 12V... pop

 

Grrizz explains it very well, but in most simple terms your output is the difference of the voltages of the two input wires.

[phillrulz]

tell me how to make a fan spin at 7 volt when you take +12 and +5 volt is equal to 17v

everybody talks about the -5v but i have never seen a molex with a -5 volt rail.

 

The positive voltages seemingly power everything in the system (logic and motors), so what are the negative voltages used for? The answer is, not much! In fact, –5 V was removed from the ATX12V 1.3 and later specifications. The only reason it remained in most power supply designs for many years is that –5 V was required on the ISA bus for full backward compatibility. Because modern PCs no longer include ISA slots, the –5 V signal was deemed as no longer necessary. However, if you are installing a new power supply in a system with an older motherboard that incorporates ISA bus slots, you want a supply that does include the –5 V signal.

 

Your +5V feed will be being over-powered by +7V.

This is bad

You will probably be doing damage to the internals of your power supply.

Especially if the +5V section is using capacitors that are rated at less than 12V... pop

it works on a differential, to make 12v you use +12 and 0 the difference being 12v to make 7 volts you use 5v as your 0 rail and 12 as your positive, the difference is 7. 

EDIT: i can "make" a 7volt rail and measure the other 5 volt rails on my psu if that will make you happy? 

 

[gylmir]

it works on a differential, to make 12v you use +12 and 0 the difference being 12v to make 7 volts you use 5v as your 0 rail and 12 as your positive, the difference is 7. 

EDIT: i can "make" a 7volt rail and measure the other 5 volt rails on my psu if that will make you happy? 

 

 

if you can show me in picture or video i will be glad to see that since i'm also interested in lowering fan speeds.

i always thought since DC goes one way it won't return true the 5 volt.

 

i got 1 more question it is probably the best to have it on a single connector with no other parts like hdd connected.