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.
Quote from: Red_Raven on Feb 06, 2012, 11:16 pmthere 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?
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.