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DC brushless Fan issue?

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dknguyen

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Is it normal for a 12vdc fan not to spin freely?
You mean if you flick the fan blades it while it's off? That's normal. What you're feeling is a magnetic cogging in the motor that makes the fan want to prefer certain positions evenly spaced around it's rotation while at rest.
 

Xn35

Member
I uploaded a video.
It's like it doesn't stay on constantly and only spins every second. 12vdc 1Amp fan connected to a 12vdc 1amp adapter. What am I missing here?

Suppose to be 50cfm.
 

dknguyen

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Most Helpful Member
I uploaded a video.
It's like it doesn't stay on constantly and only spins every second. 12vdc 1Amp fan connected to a 12vdc 1amp adapter. What am I missing here?

Suppose to be 50cfm.
I see no video. But it sounds like it's having trouble starting up. Does it start running okay if you take a pencil and flick the blades to get it going? (don't use your fingers!)

And how many pins are on the fan? And are you plugging into a motherboard or straight into a battery or other power supply?
 

Xn35

Member
Sorry I'm on my phone and didn't see you full post.

It's plugged into a wall adapter for now because I wanted to see how much air it would move.

It is a three wire fan but the third wire is for a locked arm signal.
 

dknguyen

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It sounds busted to me then unless it's a new fan or your wall adapter is somehow a bit too finicky (too much ripple messing up the startup or something like that) or insufficient current for the fan.
 

Xn35

Member
It's all brand new stuff. If I fastly tap the fan power wire to the adapter connections it still only gets power every second.
 

dknguyen

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Well try plugging it into your motherboard or a different adapter. Sometimes, cheap wall wart power supplies don't always supply the thing we think they do.
 

dknguyen

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When I get a minute here I'm going to stick my multimeter in the adapter
Try it under load. But it may also not tell you too much since it might be something like ripple really screwing around with the fan's startup.
 

AnalogKid

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it still only gets power every second.
The fan startup current is greater than its running current. During startup, it might be driving the power supply into an overcurrent shutdown and automatic restart.

As suggested above, connect the fan directly to the power supply, then spin the fan blades by hand to get them going.

ak
 

Xn35

Member
I'm guessing that's what the problem is until I get some more time. Because 120v AC at 60hrtz would make sense.
 

Xn35

Member
It's like the fan only can receive power once its slowed down enough. Because it can start and time from a spotted position
 

Xn35

Member
So every once and a while if I keep tapping the power source it will build fan speed and run properly. So am I going to have to get some capacitors for a cap start set up? Is there anything else I can do?
 

dknguyen

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So every once and a while if I keep tapping the power source it will build fan speed and run properly. So am I going to have to get some capacitors for a cap start set up? Is there anything else I can do?
This is a DC-fan it's not a "cap-start" in the sense where you need to produce a phase shift between voltage and current to begin to get a motor spinning. A big cap could help the wall-wart deal with that initial inrush current but I'm feeling it's probably going to need to be too big. I would just try another wall-wart.

What are the specs writen on your wall-wart anyways? Or just use some batteries to test it.
 
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