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DC toy motor as cooling fan Answered

i used a dc toy motor to make a cooling fan. i made the connections to draw power using usb.but 3rd time when i plugged , the laptop didnt start. i called service centre and they said to replace motherboard. fortunately i had warranty. why this happens ?????

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Downunder35m

3 years ago

I simply guess you neither checked how much currrent the motor uses, nor included any form of protection for your USB port.

A DC motor like yours has carbon brushes to make the contact to the windings - they love to produce interference, enough to kill your laptop if unprotected.
Lesson learned I guess - don't use stuff on a USB port that shouzld not be plugged in it ;)

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robo10302

3 years ago

was this an old laptop? Because this shouldn't happen no matter what the load is because if the laptop detects that too much power is being consumed by the usb port it shuts the power going to the usb off and displays a message. So I'm assuming that this was an old laptop. Sorry to hear that it died

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mpilchfamily

3 years ago

Basic motors pull a lot of current. Especially as they first turn on.
USB is only able to offer you 5V at about 400mA. I'm sure the start up
and constant draw of the motor exceeds that burning out the power
regulation circuits on the main board of the laptop. See you laptop
takes in about 19V from the battery/brick and then regulates that down
internally to the 3.3, 5, and 12 volts needed by most of the
components.

You say the motor is from a toy. I'm guessing
something small that ran on a couple of AA or AAA batteries right? So it
uses about 3V. So you figured the 5V from USB wouldn't be a problem
right. Well lets say that motor is pulling about 2.4W. So 3V @ 800mA. On
5V USB it's still needs 2.4W to run. So it's pulling 480mA from a
system that is suppose to only offer about 400mA. Like i said before at
start up the motor pulls a lot more. It could be pulling about 3W or
more. So on 5V it needs 600mA.

Know the amount of power your
device needs and how much your power source can offer before bringing
the 2 together to avoid problems like this in the future.

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bravoechonovember1

3 years ago

you might want to change the title to some thing like "why did my laptop die when I plugged a toy motor into it" you will get more help that way