Computer fan

[smiler]

Not boat related, but I'm in need of a little advice....

I'm building a small project and need a computer fan to only run only when the sun shines.

Is it possible to connect (via a fuse) the pc fan directly to a small (20w?) solar panel without problems.

I'm concerned whether the fan motor will be damaged when not getting 12v always(comparing varying voltage during sun up/sun down, overcast or full sun)

Will this work?

Alternatively I could use a battery to provide constant 12v and a light sensor to switch on/off with light levels.

TBH I would rather keep it simple if possible.

Any thoughts?

 

[Machpoint005]

I'm a fan of computers but lockdown prevents me from running anywhere even if the sun is shining!

 

 

[TheBiscuits]

29 minutes ago, smiler said:

I'm building a small project and need a computer fan to only run only when the sun shines.

 

Does it have to be a separate panel and computer fan?  I'm thinking of those solar mushroom vents that are a solar panel and fan, and wondering if that's any use to you.

[Detling]

Most '12 volt' solar panels put out 18 volts on no load and are held down by the battery, I doubt if the fan would like 17 odd volts for long. Maybe try a suitable zenner and a low ohm resistor to limit the volts at 12 the fan will not take much power.

[smiler]

11 minutes ago, TheBiscuits said:

 

Does it have to be a separate panel and computer fan?  I'm thinking of those solar mushroom vents that are a solar panel and fan, and wondering if that's any use to you.

It has to be separate - the fan will be mounted in a plastic pipe.

[smiler]

12 minutes ago, Detling said:

Most '12 volt' solar panels put out 18 volts on no load and are held down by the battery, I doubt if the fan would like 17 odd volts for long. Maybe try a suitable zenner and a low ohm resistor to limit the volts at 12 the fan will not take much power.

That's what I'm concerned about - too high/low voltages.

Thanks for the input, but zenners and resistors are above me.

Mechanically I am well experienced, but I'm not so good with electrickery. I know sparks, heat and smoke should stay inside the wires - any more complicated than that just confuses me. ???

24 minutes ago, Machpoint005 said:

I'm a fan of computers but lockdown prevents me from running anywhere even if the sun is shining!

 

 

"I'm an ex-tractor fan" is the punchline - the rest you probably heard already.

[OldGoat]

FWIW - I have 24V old style mainframe computer fans that move a lot of air at 24V but run quite well on 12V, would probably run reasonably at lower voltages as well.

Computer fans have generally  magnets in the rotor (the fan bit) and thus do not get hot as the current is always limited.

IMO the standard PC fan - although  reasonably well made can be quite 'rubbishy' when bought on fleabay.

[Richard10002]

What is the fan doing that you only want it to run when the sun shines?

 

There might be a different solution to a directly connected panel, or a battery and a light sensitive switch.

[Jen-in-Wellies]

2 minutes ago, OldGoat said:

FWIW - I have 24V old style mainframe computer fans that move a lot of air at 24V but run quite well on 12V, would probably run reasonably at lower voltages as well.

Computer fans have generally  magnets in the rotor (the fan bit) and thus do not get hot as the current is always limited.

IMO the standard PC fan - although  reasonably well made can be quite 'rubbishy' when bought on fleabay.

24V is probably the way to go. It will be under run at 19ish V, but will last a very long time and be quieter. If the air flow is sufficient for the OP's needs, then this is a simple way to do it. I have a solar hot water 24V pump that is run from a single 20W 19 ish V panel in this way. The fans that @OldGoat is talking about are connected to +12V and -12V, in a computer, giving 24V across them. Alternatively, have two 12V fans in series across the panel. As per ASCII circuit diagram below.

  _________________+ Fan -__

  |  +                                             |

Panel                                          |

  |    -                         -    +           |

  ---------------------------Fan---------

 

Jen

[smiler]

13 minutes ago, OldGoat said:

FWIW - I have 24V old style mainframe computer fans that move a lot of air at 24V but run quite well on 12V, would probably run reasonably at lower voltages as well.

Computer fans have generally  magnets in the rotor (the fan bit) and thus do not get hot as the current is always limited.

IMO the standard PC fan - although  reasonably well made can be quite 'rubbishy' when bought on fleabay.

Thanks

How big are they?

I want to mount one in a 4" soil pipe so needs to be no more than about 100mm diameter.

9 minutes ago, Richard10002 said:

What is the fan doing that you only want it to run when the sun shines?

 

There might be a different solution to a directly connected panel, or a battery and a light sensitive switch.

Cooling air

[smiler]

9 minutes ago, Jen-in-Wellies said:

24V is probably the way to go. It will be under run at 19ish V, but will last a very long time and be quieter. If the air flow is sufficient for the OP's needs, then this is a simple way to do it. I have a solar hot water 24V pump that is run from a single 20W 19 ish V panel in this way. The fans that @OldGoat is talking about are connected to +12V and -12V, in a computer, giving 24V across them. Alternatively, have two 12V fans in series across the panel. As per ASCII circuit diagram below.

  _________________+ Fan -__

  |  +                                             |

Panel                                          |

  |    -                         -    +           |

  ---------------------------Fan---------

 

Jen

That's an idea - thanks.

I take it a pc fan won't be damaged with under-voltage?

[Jen-in-Wellies]

3 minutes ago, smiler said:

Thanks

How big are they?

I want to mount one in a 4" soil pipe so needs to be no more than about 100mm diameter.

Here you go. No shortage of choice. Should select 24VDC and 92x92mm. Adjust to suit. May need to be smaller to fit within a soil pipe. Other fan styles may be more suitable as these are square, not round.

https://uk.rs-online.com/web/c/hvac-fans-thermal-management/fans/axial-fans/?searchTerm=fan&applied-dimensions=4294573405,4294380160,4294380194,4294376192

 

Jen

1 minute ago, smiler said:

That's an idea - thanks.

I take it a pc fan won't be damaged with under-voltage?

Should be fine. It is a common thing on computer fans to vary the voltage (actually pulse width modulation) to adjust the speed to the temperature.

Jen

[smiler]

6 minutes ago, Jen-in-Wellies said:

Here you go. No shortage of choice. Should select 24VDC and 92x92mm. Adjust to suit. May need to be smaller to fit within a soil pipe. Other fan styles may be more suitable as these are square, not round.

https://uk.rs-online.com/web/c/hvac-fans-thermal-management/fans/axial-fans/?searchTerm=fan&applied-dimensions=4294573405,4294380160,4294380194,4294376192

 

Jen

Should be fine. It is a common thing on computer fans to vary the voltage (actually pulse width modulation) to adjust the speed to the temperature.

Jen

Thanks