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#1 jeff heck

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Posted 19 February 2013 - 05:35 PM

I plan to add a controller for my two boundary layer fans on the Teeter scope to allow them to operate continuously at lower rpm's. Can I use a simple rheostat/pot or should it be an active circuit to prevent battery drain? Maybe it is cheaper and easier to buy a fan controller online. :question:

#2 Mirzam

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Posted 19 February 2013 - 05:41 PM

Here's one way to do it. More power efficient than a rheostat:

Off-the-shelf fan controller

JimC

#3 De Lorme

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Posted 20 February 2013 - 04:22 AM

From Digi-Keys{really cheap, work great} I got 3 39cfm's
for $2.60ea. I also bought 3 low to high fan controllers for $6.50ea. Because they don't turn completly off I put
in a toggle switch for each one{Walmart}
They have higher CFM's if 39 won't work for you. De Lorme

#4 gpelf

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Posted 20 February 2013 - 09:58 AM

Need to be careful on power rating of POT that is used, A common power rating on an average size pot is 1/2w. At 12volts DC this translates to about 42ma of current. I have seen some of the 120mm fans draw around 250ma of current, Far exceeds the power rating of most pots. Not saying this wouldn`t work for a while, Lot of Variables involved, like, How good is the pot heat sinking itself. I would go to a adjustable switched mode power supply to control fan speed (Do a google on "1amp adjustable switched mode power supply") Not only will this run cooler, It will draw 1/3 to 1/2 less power from the battery.

Just had to put in my :penny: :penny:

Clear Skies,
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#5 gpelf

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Posted 20 February 2013 - 10:03 AM

Oh yea if you are needing 12v instead of 120vac from a wall wart type supply, you would need to google "12v Adjustable buck converter"

Greg

#6 Steve OK

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Posted 20 February 2013 - 12:05 PM

I got one of these:

http://www.coolerguy...0556089537.html

It controls two 40mm fans on the back of my C11. Easy to wire up.

#7 Mark Peterman

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Posted 20 February 2013 - 01:23 PM

I got one of these:

http://www.coolerguy...0556089537.html

It controls two 40mm fans on the back of my C11. Easy to wire up.


Steve,

I tried that same controller on my fan and it does not have an effect on the speed at all. It seems that I read somewhere that the newer fans cannot be controlled this way. :question:

This is the fan that I use: http://www.silenx.co...p?sku=efx-12-15

Mark

#8 gpelf

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Posted 20 February 2013 - 01:24 PM

Looks like that would work great, For 6 bucks how could you go wrong !!!

#9 jeff heck

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Posted 20 February 2013 - 02:45 PM

Thanks for all of the replies and links. I am trying to find one locally but will order online if need be. Good to know, Mark, I will hook up my Kendrick control box to a 9v battery and see if the fans operate.

#10 Steve OK

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Posted 20 February 2013 - 03:56 PM

I guess I got lucky!

#11 jeff heck

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Posted 20 February 2013 - 07:36 PM

The SilenX controller looks like a steal at $4.95. Why the three pin connector, is there a positve, negative and ground for reversible fans? :question:

#12 De Lorme

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Posted 20 February 2013 - 09:38 PM

I have a couple of small deep cell gel batterie{from a wheel chair} that fit inside the base. Although there older they seem to have lots of power. There are smaller ones that are not so heavy but these are free and I need{want!}
a 8mm Parsdgim!. De Lorme

#13 Mark Peterman

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Posted 21 February 2013 - 09:35 AM

The SilenX controller looks like a steal at $4.95. Why the three pin connector, is there a positve, negative and ground for reversible fans? :question:


I purchased that controller too thinking it would work with my fan since it is from the same manufacturer. However, the three pin connectors are meant to plug into the motherbaoard of a computer and the fan. I cut the connectors off and tried every possible wiring combination that would get the fan running and the controller was never able to adjust the speed of the fan.

So, I've tried two controllers that are intended to control the speed of a fan, and one off the shelf potentiometer and none of them have worked.

:tonofbricks:

#14 tnranger

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Posted 21 February 2013 - 10:33 AM

FWIW, I just went through all this with the Fox conn fan I scavenged from an old PC. I ended up using this:

http://www.amazon.co...0_i04?ie=UTF...

It controls the fan speed well, but has a mild squeal when the speed is slowed.

Hope this helps.

#15 lbsgville

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Posted 21 February 2013 - 01:04 PM

I got the same thing and had the same problem with the squeal. I think the fan is the reason. The fan has to have a minimum amount of power to run without the squeal. I just use mine at full speed now. I tried to use the control on my dew controller and my mirror dewed up.

#16 Sebastian Quirk

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Posted 21 February 2013 - 01:38 PM

Another option is to replace the current switch with a double pole double throw switch (On-off-on), and wire the two fans in series on one end, and in parallel on the other. Most fans start up ok with 6 v and run much quieter with less vibration. 12 v for cooling, 6 v for boundary scrubbing.

Q

#17 Quest

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Posted 21 February 2013 - 04:31 PM

I used this:
http://www.amazon.co...0/ref=cm_ciu...

with this fan:
http://www.amazon.co...0_i01?ie=UTF...

...on my Orion XT8i.

The controller didn't turn the fan off so I removed the plastic housing and mounted it in an altoids tin with a toggle switch to the bottom of the scope. I then wanted a larger knob and an LED to indicate power so I went with a project box from Radio Shack along with the knob, LED, etc.

Here's the end result. So far so good. The fan starts up at even the lowest setting.

Attached Files



#18 Mark Peterman

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Posted 22 February 2013 - 04:44 AM

FWIW, I just went through all this with the Fox conn fan I scavenged from an old PC. I ended up using this:

http://www.amazon.co...0_i04?ie=UTF...

It controls the fan speed well, but has a mild squeal when the speed is slowed.

Hope this helps.


From the name, PWM, I believe that is a Pulse Width Modulation unit. Most companies that market 'quiet, vibration free' fans do not use this technology because:

<snip>
PWM works by pulsing the full power at rapid speeds. Imagine turning a light switch on and off rapidly. The overall brightness over a period of time will be less than having the light on steadily. In fact, most LEDs are lit using this technique. However, on moving parts such as motors, this has a detrimental effect and causes the motor to rumble. They introduce more noise by creating vibration. Instead of a smooth running motor, you have a pulsing one.
<snip>

All that being said, thanks for the link. I think I will give it a try for myself.

#19 jeff heck

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Posted 27 February 2013 - 11:57 AM

Another option is to replace the current switch with a double pole double throw switch (On-off-on), and wire the two fans in series on one end, and in parallel on the other. Most fans start up ok with 6 v and run much quieter with less vibration. 12 v for cooling, 6 v for boundary scrubbing.

Q

I like this idea. I will see how my fans run at 6vdc and if ok will go with the switch method you suggest.

#20 jeff heck

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Posted 27 February 2013 - 04:26 PM

I made a dc voltage divider and found the supplied SilenX fans (120mm/72cfm) run quiet down to 7.3v, anything below that they either squeal or will not start. I think I will try the regulating dc to dc converter.

#21 jeff heck

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Posted 09 March 2013 - 01:49 PM

I installed one of the Radio Shack style devices (rheostat?) and had a chance to test it Thursday night. I noticed the fans now imparts a slight star wobbling effect when power is on, even at the 12v setting. There is no wobble when the fans are switched off. I plan to remove it and test the boundary layer fans again to see if the lobing takes place.

#22 thetortoise

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Posted 09 March 2013 - 05:16 PM

super cheap and adjustable directly on the fan: Adjustable USB Computer Fan

A bit tricky to mount because you need to take off the cage and stand but great for adjusting the fan speed. I put it on full blast until it's time to observe and then turn it down to minimum speed while observing. I like it.






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