Fan Speeds

Grimm · 17-February-03, 04:58 PM

Hey Pimps,

Since I've spent way to much money on building my new rig, I really don't want to buy a rheobus for me fans, but I want some control over their noise, so......I was thinking of putting in either a rotory pot or a double throw switch so that I could have Hi, Med and Low.

I'd rather use the pot (beacuse I have one) so I don't have to buy a switch (which would upset the wife even more).

Question: is it stupid to control all 5 case fans (Antec 80mm 12 watt) with one pot, or should each fan or group of fans (ie. front fans, back fans and side pannel fan) be controled with it's own pot?

BigAkita · 17-February-03, 07:30 PM

Group them. You will usually keep the exhaust fans low, but there are times you will want to kick up the RPM on your side fans.

Grimm · 17-February-03, 09:05 PM

Damn, I thought this would have been easy!

putwig · 17-February-03, 09:13 PM

It is easy!

Run all your exhaust fans on 7V (this is essentially free), and hook all your intake fans up to pots or rheos.

Make sure the total wattage of the intake fans does not outstrip the wattage rating for the pot ...... you may need multiple pots (like one per fan) if they are big powerful fans.

What are the specs of the pot you have?

Grimm · 17-February-03, 09:28 PM

Hey putwig,

I was refering to the fact that I didn't want to have to buy a rheo. I have one pot leftover from a previous project on my old case and thought that I could get away with just using it.

Looks like I'll have to buy two more pots. Good thing they are cheap.

putwig · 17-February-03, 10:43 PM

What are the specs of the pot?

What are the specs of the fans?

The answers to the above questions will answer whether or not you need more pots.

Grimm · 17-February-03, 10:54 PM

Well, from what I can remember....The fans are the standard Antec case fans you get at best buy. 12 watt, 34 CFM. I got 5 of em.

The pot is linear 0-100K ohm rotory.

I was going to wire it into the 7 volt (or FAN Only) line from the PS. When the pot is turned all the way to the left, the fans will essentially be off, and all the way to the right they will be running at full tilt.

putwig · 17-February-03, 11:34 PM

Most 80mm case fans are about 2 watts (I think you mean .12 amperes).

Anyhow, if you have 5 of them you would in theory need a pot rated to 10 watts ...... 15 if you want a cushion. The problem with pots is they tend to be really low wattage ....... 1/2 watt 10 Kohm is common. I don't know that I have ever seen a readily available pot greater than 2 watts.

The only difference I know between pots and rheos is the wattage ...... rheos tend to be much higher wattage (I am sure Wixx or CarbonGraphite would know the actual technical difference).

The problem is a lack of middle ground ...... low wattage rheos are hard to find!

I used 5 watt 100 ohm rheos (from Caseetc) with good results, but even there I only put 2 x 80 or 1x120 on each rheo.

This site lists 100 ohm rheos in 25 watt ( and 50 watt ) flavours that would handle your needs:

http://www.alltronics.com/rheostats.htm

Also, I would recommend this little read:

http://www.fanbus.com/

Look under "The Lab" and then "Rheostat Quick Tips"

17-February-03, 04:58 PM		#1 (permalink)
Grimm Apex Master Tech Apprentice	Fan Speeds Hey Pimps, Since I've spent way to much money on building my new rig, I really don't want to buy a rheobus for me fans, but I want some control over their noise, so......I was thinking of putting in either a rotory pot or a double throw switch so that I could have Hi, Med and Low. I'd rather use the pot (beacuse I have one) so I don't have to buy a switch (which would upset the wife even more). Question: is it stupid to control all 5 case fans (Antec 80mm 12 watt) with one pot, or should each fan or group of fans (ie. front fans, back fans and side pannel fan) be controled with it's own pot?

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17-February-03, 07:30 PM		#2 (permalink)
BigAkita n00b-ass reviewer	Group them. You will usually keep the exhaust fans low, but there are times you will want to kick up the RPM on your side fans.

17-February-03, 09:05 PM		#3 (permalink)
Grimm Apex Master Tech Apprentice	Damn, I thought this would have been easy!

17-February-03, 09:13 PM		#4 (permalink)
putwig Dr. Hydro Pimp	It is easy! Run all your exhaust fans on 7V (this is essentially free), and hook all your intake fans up to pots or rheos. Make sure the total wattage of the intake fans does not outstrip the wattage rating for the pot ...... you may need multiple pots (like one per fan) if they are big powerful fans. What are the specs of the pot you have?

17-February-03, 09:28 PM		#5 (permalink)
Grimm Apex Master Tech Apprentice	Hey putwig, I was refering to the fact that I didn't want to have to buy a rheo. I have one pot leftover from a previous project on my old case and thought that I could get away with just using it. Looks like I'll have to buy two more pots. Good thing they are cheap.

17-February-03, 10:43 PM		#6 (permalink)
putwig Dr. Hydro Pimp	What are the specs of the pot? What are the specs of the fans? The answers to the above questions will answer whether or not you need more pots.

17-February-03, 10:54 PM		#7 (permalink)
Grimm Apex Master Tech Apprentice	Well, from what I can remember....The fans are the standard Antec case fans you get at best buy. 12 watt, 34 CFM. I got 5 of em. The pot is linear 0-100K ohm rotory. I was going to wire it into the 7 volt (or FAN Only) line from the PS. When the pot is turned all the way to the left, the fans will essentially be off, and all the way to the right they will be running at full tilt.

17-February-03, 11:34 PM		#8 (permalink)
putwig Dr. Hydro Pimp	Most 80mm case fans are about 2 watts (I think you mean .12 amperes). Anyhow, if you have 5 of them you would in theory need a pot rated to 10 watts ...... 15 if you want a cushion. The problem with pots is they tend to be really low wattage ....... 1/2 watt 10 Kohm is common. I don't know that I have ever seen a readily available pot greater than 2 watts. The only difference I know between pots and rheos is the wattage ...... rheos tend to be much higher wattage (I am sure Wixx or CarbonGraphite would know the actual technical difference). The problem is a lack of middle ground ...... low wattage rheos are hard to find! I used 5 watt 100 ohm rheos (from Caseetc) with good results, but even there I only put 2 x 80 or 1x120 on each rheo. This site lists 100 ohm rheos in 25 watt ( and 50 watt ) flavours that would handle your needs: http://www.alltronics.com/rheostats.htm Also, I would recommend this little read: http://www.fanbus.com/ Look under "The Lab" and then "Rheostat Quick Tips"