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Electrical help with cooling fan design

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#1 tnranger

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Posted 27 January 2013 - 08:46 AM

I'm trying to build a cooling fan assembly for an XT10i. I have a repurposed 12 volt fan and am looking for a switch to control the fan. I would like to be able to do a high/ low/ off configuration, and wonder if this switch would work:

http://www.amazon.co...0_i1?pf_rd_m...

I plan on using 8 AA nicads for power.

Any help/suggestions are appreciated.

#2 bob71741

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Posted 27 January 2013 - 11:01 AM

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#3 tnranger

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Posted 27 January 2013 - 12:16 PM

The fan does have 3 wires. (now I know why!)
Thanks for the suggestion. How would I wire to this switch?

#4 jerwin

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Posted 27 January 2013 - 04:07 PM

I didn't do a high low switch in mine but this is my wiring diagram.

This is what mine ended up looking like when completed. I used a coiled phone cable that I pumped the power over so I could leave the power supply on the ground rather than attach it to the OTA. I've also revisited the design to add a cap over the switch so I know it's turned off when transporting.

http://www.cloudynig...5502411/Main...

Good luck.
Jim

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#5 tnranger

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Posted 27 January 2013 - 04:33 PM

Thanks, Jim. Your set up is the most elegant I've seen. I plan to use an old phone cord I have laying around. I would just like to be able to slow the fan down while I am observing, hence the 2 speed switch. BTW, shouldn't there be another wire coming from the fan?

#6 jerwin

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Posted 27 January 2013 - 05:20 PM

Thanks, I did make one later modification that I didn't list in that post. I replaced the machine screws in the mirror cell with longer screws (had to special order them) but that let me attach the fan and plastic cover to the ota a lot easier than with the stock screws that where just barely long enough.

My fan does have 3 wires coming out of it, I just never knew what the 3rd wire was for. I typically leave my fan running when viewing and I don't see any vibration which I'm sure is what you're trying to avoid with the dual speed.

I've seen some fans that have a switch built into them for speed.
http://www.amazon.co...ef=sr_1_7?ie...

I just don't know how to wire that into a homemade switch (which is what your original question was about)

Wish I could be more help, I'm just not electrically inclined enough to understand what does what. My only tip to you is to draw it out as you experiment because I probably couldn't have put it back together properly once I moved it from the test table to the install table.

Jim

#7 Gene7

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Posted 27 January 2013 - 06:38 PM

8 rechargeables, Naaa, that is a lot of grief. Use 3 4 volt lithium rechargeable cell # 18650, a much better battery. Get special size cell holder from e-bay. Use special lithium charger. Cells will hold a charge for a year. Not expensive now. Gene

#8 tnranger

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Posted 27 January 2013 - 07:24 PM

I appreciate the tip Gene.

I'm trying to make use of the 20 or so rechargeable energizers we have in circulation in the house now, but will check the lithium batteries out.

#9 wirenut

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Posted 28 January 2013 - 11:33 AM

I didn't do a high low switch in mine but this is my wiring diagram.

This is what mine ended up looking like when completed. I used a coiled phone cable that I pumped the power over so I could leave the power supply on the ground rather than attach it to the OTA. I've also revisited the design to add a cap over the switch so I know it's turned off when transporting.

http://www.cloudynig...5502411/Main...

Good luck.
Jim

something doesnt look right in this drawing. when the switch connects the battery feed to the wire on the left side, it should be shorting out battery. thinking about it, if its a potentometer and not just a switch it would work fine but would need to be sized to motor.
the speed switch in our cars heaters are wired so high goes straight to the fan, medium goes thru a resistor then to fan,low goes thru a bigger resistor then to fan. the resistor arent part of the switch they are located in the cars duckwork to help keep them cool and not part of the switch. this might be how you snowmobile switch be intended to work.

#10 tnranger

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Posted 28 January 2013 - 03:17 PM

That is my concern.
Would I be better off to get a cheap potentiometer and forget the switch in my original post? Remembering this fan has 3 wires, how would I wire a 3 post pot in this circuit?

#11 gpelf

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Posted 28 January 2013 - 03:33 PM

If the 3rd wire is yellow it may be from a PC, In which case the wire is used to monitor the fan speed and not a secondary speed line......

Clear Skies,
Greg

#12 tnranger

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Posted 28 January 2013 - 03:54 PM

This is a scavenged computer fan (I forgot to mention that in my original post). If the third wire is a speed monitoring line, how would I wire this fan to control the speed?

#13 tnranger

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Posted 28 January 2013 - 06:39 PM

Just got home, it does indeed have a yellow lead. It is a Foxconn DS90SM-12 rated at 35 CFM and 0.18A.
Any ideas on wiring to control speed?

#14 Mxplx2

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Posted 28 January 2013 - 07:50 PM

In a pinch you could experiment. First measure the resistances between all three wires. If there are no dead shorts or very low resistances, hook up 12 volts between two at a time and see what happens. Perhaps introduce a potentiometer and experiment with that.

#15 Gene7

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Posted 28 January 2013 - 08:17 PM

Yes, forget the third wire and control the power with a Buck Converter from e-bay,NOT a pot, which wastes power. The adjustable Buck converter does not, it converts excess power to amps. Costs $1.52 on the Bay. Get several. Gene
http://www.ebay.com/...&_trksid=p39...

#16 gpelf

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Posted 28 January 2013 - 09:04 PM

I hate to be a Naysayer, But.....
The yellow line cant be used for speed control, It is hooked to a hall sensor that produces a square wave on this line when a very small magnet on the motor armature spins (This is how the computer monitors the speed). I use one of the true DC fans (NO small circuit board under sticker and frame) and for a second reason, I use a DPDT center off switch and a variable supply. This way I can adjust to any speed and Reverse the fan as well. Hope this helps some.
The buck converter mentioned by Gene7 is also a very good idea if you dont care about reverse.


Good Luck,
Greg

#17 Mark Peterman

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Posted 28 January 2013 - 10:58 PM

Greg,

Do you have a make/model or part number for that fan you use? I can't find any that are reversable.

#18 gpelf

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Posted 29 January 2013 - 08:35 AM

Mark,

Not sure if they make a small modern fan that will, The one I use came out of an old circa 1970`s oscilloscope. I will be glad to look in my garage and see if I have another.

Clear Skies,
Greg

#19 gpelf

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Posted 29 January 2013 - 08:40 AM

Found one here, but i`m not sure about the availability.
Link

Greg

#20 Mark Peterman

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Posted 29 January 2013 - 09:16 AM

Thanks Greg, I appreciate the help.

#21 tnranger

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Posted 30 January 2013 - 09:57 AM

Just out of curiosity, how long could I expect the fan to run on 8 rechargeable AA batteries?

#22 Project Galileo

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Posted 30 January 2013 - 10:28 AM

I solved power switch ability with one of these.

Posted Image

#23 gpelf

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Posted 30 January 2013 - 11:26 AM

That would be directly related to the current draw of the fan you choose, The newer lithium batteries would be a much better choice....

Greg

#24 Mirzam

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Posted 30 January 2013 - 02:37 PM

I created a thread on using this type of converter for a fan speed controller. This method uses power more efficiently than a potentiometer.

Off-the-shelf fan speed controller

JimC

#25 taylornate

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Posted 31 January 2013 - 04:07 PM

There have been a couple options mentioned in this thread that will work, but the most appropriate method is a pwm controller.






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