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Author Topic: Controling a laptop cooling pad (first project, need some guidance)  (Read 1021 times)
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Hello all. I recently finished the Sparkfun Inventors Kit tutorials, and I want to start my first project. I have a USB laptop cooling pad. there is a switch on its cable that turns it off, low, and high. I want to put a temperature sensor on the arduino and plug the cooling pad into it. Then i will leave the pad on high, but control its speed with the arduino based on the temp sensor. Later on, once this part is finished, I want to add indicator LEDs and temp logging functions, but that's not the main focus. I just need some help because I'm not sure what kind of voltages I need, and what components i need to supply them. Can someone help me out with a list and general layout of parts I should probably be using? oh, and for connection i have a USB female plug with nothing but striped wires on the end that i will attach to the arduino/breadboard, and the arduino itself will draw power over a typical USB connection to the laptop.

Thanks!
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there is a switch on its cable that turns it off, low, and high. I want to put a temperature sensor on the arduino and plug the cooling pad into it. Then i will leave the pad on high, but control its speed with the arduino based on the temp sensor.

I'm not sure what that bit means. The cooling pad is powered by USB? There is a three position switch on the USB cable? What does the switch do in electrical terms? How are you planning your Arduino to control the pad? Just turn it on/off by disconnecting the power, or what?
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there is a switch on its cable that turns it off, low, and high. I want to put a temperature sensor on the arduino and plug the cooling pad into it. Then i will leave the pad on high, but control its speed with the arduino based on the temp sensor.

I'm not sure what that bit means. The cooling pad is powered by USB? There is a three position switch on the USB cable? What does the switch do in electrical terms? How are you planning your Arduino to control the pad? Just turn it on/off by disconnecting the power, or what?

yes, the pad is cooling usb. but i would plug it directly into the arduino, which in turn would be powered by usb. there is a 3-position, sliding switch built into the cooling pad's USB cable. position 1 is off, 2 is low speed, and 3 is high speed. I am not sure if it has two resistors that it switches between, or how the switch works. I can't easily dissemble/reassemble it, and i'd rather not as it was a gift. my plan is to leave the switch on high the whole time because I am assuming this will allow the most voltage through. Then i will regulate the voltage with the arduino based off the temp sensor. (I dont want the arduino to set it on high/medium/low, but i want it to increase/decrease based on the temp. for example, at x temp, set y voltage based off an equasion that i'll figure out later)

I hope this helps. I know its not terribly precise. if this helps, here's the model i'm using: http://www.logitech.com/en-us/notebook-products/cooling-pads/devices/cooling-pad-n200
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So you're planning to make up a USB flying lead and wire that to the Arduino somehow? If the pad only needs power, that could work. But I suggest you confirm it's that simple before you get any further. If you just connect the USB ground and 5V pins to a 5V supply that can provide enough current, and it works properly, you know you're in with a chance. How much power does it take, by the way? A USB port is usually only rated for 2.5W in high current mode, which is eff all compared to the amount of heat your laptop will produce.

(In other words, a USB powered cooling pad is a fundamentally flawed idea and about as useful as a USB powered coffee cup heater i.e. no use at all.)

Assuming you decide to press on anyway, the Arduino won't supply enough power to power that cooling pad directly, you'd need to connect an external supply regulated down to 5V. You'd be powering this from the laptop, I suppose? Adding to the heat generated within the laptop?
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So you're planning to make up a USB flying lead and wire that to the Arduino somehow? If the pad only needs power, that could work. But I suggest you confirm it's that simple before you get any further. If you just connect the USB ground and 5V pins to a 5V supply that can provide enough current, and it works properly, you know you're in with a chance. How much power does it take, by the way? A USB port is usually only rated for 2.5W in high current mode, which is eff all compared to the amount of heat your laptop will produce.

(In other words, a USB powered cooling pad is a fundamentally flawed idea and about as useful as a USB powered coffee cup heater i.e. no use at all.)

Assuming you decide to press on anyway, the Arduino won't supply enough power to power that cooling pad directly, you'd need to connect an external supply regulated down to 5V. You'd be powering this from the laptop, I suppose? Adding to the heat generated within the laptop?

I may sound like an idiot here, but the arduino has a 5v output which works while its running off USB, so why would I need an external power supply? and I don't think the USB hub really generates that much power, or else no one would ever make cooling pads.
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I may sound like an idiot here, but the arduino has a 5v output which works while its running off USB, so why would I need an external power supply? and I don't think the USB hub really generates that much power, or else no one would ever make cooling pads.

You need to consider how much current is being drawn, not just the voltage.

A standard USB port should support up to 500 mA in high current mode. If it's on an unpowered hub, it will provide much less. So, best case you have about 2.5 Watts of electrical power available. That's ample to power an Arduino and a few LEDs.

Peltier coolers aren't very efficient and you probably have somewhere between 10% and 30% of that electrical power actually available as cooling. So that's probably less than 1 Watt worth of cooling. Your laptop probably puts out 100 Watts of heat when it's thinking hard.

When you are thinking about whether they're likely to work or not, consider that somebody bought you one without any idea how effective it would be. If people are willing to buy them, people will sell them, regardless of whether they do any good.
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oh its a fan-based cooler. never heard of a laptop cooler with a peltier (sp?) unit.
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So you have a 2.5 Watt fan pulling air past the outside of the laptop case? Well, it's probably better than having it sitting on your lap. If you supply the fan directly from the Arduino's USB power in line, I expect that will work about the same as before (the Arduino will add a few tens of milliamps to the load, not enough to worry about). Just don't try to supply it via the Arduino's voltage regulator, or from any of the I/O pins.
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These cooling pads never made sense to me.

When your laptop gets hot the fan starts to cool it, but doing so it has draw power from the laptop, which must generat more heat.

So the only thing achieved is using more power ? 

Or am i just being "gadget salesman" paranoid ?
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