Callandor is correct, iris2000 - what you ask really shouldn't be attempted...
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How To build a USB heater?
Hi all,,
I am planning to do a simple USB heater that drives its power from USB port and heats up a continer containing water/coffee,, so any ideas in how to do such a project??
thanx
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Answers
AlbertaBeef - No, this not a serious question even if they may have bought the points. I just do not believe it - sorry. Just because someone has asked a question does not necessarily mean it is a serious one. At times people just have a laugh at how seriously others take themselves.
I reckon that if the heating element can chosen to draw not much more than 100mA it should be able to heat water in say a thermos mug to ensure heat losses are kept to a minimum. The USB connection can certainly cope with that level of current (ref: http://www.usb.org/faq/ans
Good luck with this ambitious project iris2000. Do let us know how you get on with the development of this innovative product.
I've seen a USB-powered personal cooling fan and a USB-powered reading light. This sounds like a serious question to me. I'd use the device if it kept hot coffee from getting cold, or delayed the inevitable cooling for 30 minutes or so.
The device could be called "Keep-It-Hot" and come with the cable *and* the thermos mug. You could make good money from that idea.
You only have 2.5watts available.
Since I haven't got a kettle I warm my coffee in the microwave and it takes 1.5 minutes at 900W so you need 1350 watt-seconds so at 2.5 watts it will take 10 minutes to warm the water except that if left for 10 minutes a hot cup of coffee goes luke warm so USB doesn't have enough power in itself to make a cup of coffee.
You wll have to encorporate a rechargable battery, the USB charging side is covered at http://www.national.com/ap
The USB standard specifies a MAXIMUM power draw of 2.5 watts.
As a comparison, my microwave requires about 700 watts for two minutes to heat up a large cup of tea.
So a USB-powered heater would take about 700/2.5 times two minutes to do the same, assuming no heat loss.
That's about 500 minutes, or lets just round it out to SIX BLEEPPIN HOURS!
(And that's with no heat loss, like with a very good vacuum thermos teacup)
Basic law of thermodynamics, no way around it.
--------------------------
Aother question is can USB power a cup warmer, something to jsut keep the tea warm. Well, yes and no. 2.5 watts might keep a very well insulated cup (with insulated lid) warm. Probably not even a well-insulated cup with no lid (evaporation takes away much more than 2.5 watts I'd estimate).
So maybe think of something else to do with 2.5 watts.... A fan to cool off too-hot tea would work.
My three 'puters each have about four USB ports in them That's 12 cables, each supplying 2.5 watts.
Next, you will need to acquire 12 *powered* USB hubs. Plug each one into the mains and attach one standard USB cable to each hub. You now have 24 cables, each supplying 2.5 watts for a total of 60 watts, which will give you a nice hot cup of tea in about 25 minutes, maybe less if you sit the mug on a hot radiator
If this is a serious question, then the poster is not well informed about the power capacity of USB (although given the above posts, he should be now...)
If you need to warm something with USB, then I assume you are using a portable device with no external power available (otherwise you'd use a normal heater). Best bet is to use the battery in the portable to power a heating element directly (and don't stand too close!). Ultimately a bad idea.
The ultimate solution is to develop a small, high-capacity power supply for your portable, which is not yet readily available - let us know how it turns out (I can't wait to use it to power my handheld laser pistol).
Cheers,
-Jon
They already make a USB powered mug warmer
http://www.cyberguys.com/t
The world is full of people who loudly proclaim "It can't be done!" But their words are are seldom heard by those who are out there pretending to have done it.
To be a "warmer" it has to heat the water, the Japanese one shows a flat graph for 20 minutes then it tails off at the same speed (2.5 watts difference maybe) so it must have a battery or two in it, you can see the thickness of the mug so it must be heavily insulated.
The plate thing must be the same. What they don't show you is how long it takes to charge the battery up again, I would guess about 2 hours.
I see all the usual suspects are chiming in with illogical babble.
The fact that some people once said something " can't be done", and they might have been wrong, in no way implies that "anything can be done". Especially in areas that have been studied to death by thousands of physicists, until they're convinced enough to form "the law of conservation of energy", and "the laws of thermodynamics", laws that have stood for over a century.
Preliminary results with a 2.5 watt heater in a cup of coffee:
Coffee in regular cup, with heater on, goes from 124 degrees F to 84F in about 2.5 hours (room temp is 78)
Insulate the cup with three layers of bubble wrap, coffee slowly rises to 96F in about 2 hours.
(96F coffee feels cool to the finger)
Actual charts and graphs and photos of the experiment coming soon.
baldrick made a point ... the standard says that 2.5 watts is the max, but imagine that you have two devices each pulling 2.5w or four devices... Clearly that single plug is CAPABLE of putting out MORE than 2.5w And even if the 2.5 is for *all* attached devices, then consider that most PC's have TWO outlet plugs. So there's 5.0 watts. Further consider that nearly everything everywhere has some built-in tolerence. Going outside the standard and pulling 3w or 4w or more is probably feasible, as long as you don't expect to get some sort of certification.
Anyway, all of the discussion has basically been around whether or not it is possible. Assume for the moment that it *is* possible... then it might be fun to consider: What would be the next step? How would you go about developing such a device?
> the standard says that 2.5 watts is the max, but imagine that you have two devices each pulling 2.5w or four devices...
Not quite, here's what the standard says:
A NORMAL USB load is 100 milliamps at 5 volts, that's 500 milliwatts, half a watt.
A USB device may negotiate for more power-- it can send a USB request to the USB controller. The USB controller will return a packet telling the USB device how much power it can have, depending on the number of other USB devices plugged in, the amount of extra power available may be from 1 to 4 additional standard USB loads-- that's an absolute MAXIMUM of 500 milliamps total that may be available from that controller/hub.
Every USB device has to pass a rigorous set of certification tests before the USB Organization will allow the device to claim it's "USB compatible" and use the USB logo on its products and packaging. You can't get USB certification if your device draws more than 2.5 watts or fails to honor any lower limit imposed by the USB controller/hub.
How about you just go to the "dollar Store" and get one of those immersion heaters? They're not very safe, but at least they don't claim to violate the laws of physics or USB.
Regards,
grg99
Thanks for the details -- I was just guessing anyway...
Still, if it plugged into both USB ports, one for each of two heating elements, then that would be within spec. And there is always the option of marketing without the USB logo ("It plugs right into the USB port on your computer!" does not claim compatibility with, only use of the USB port :-)
I believe what you’re looking for is BTu's
Short for British thermal unit, a British standard unit of energy. One Btu is equal to the amount of heat required to raise the temperature of one pound of liquid water by 1 degree Fahrenheit at its maximum density, which occurs at a temperature of 39.1 degrees Fahrenheit. One Btu is equal to approximately 251.9 calories or 1055 joules. The heat output of computer devices is often expressed in Btu’s.
If you used the USB wattage posted in here, USB power is not a good choice.
2.5 watt = 0.0023695 Btu/second = .14217 Btu/min = 8.53 deg F rise per hour = approx 8 hours for 1 pound (16oz) of 95 degree water
This rate would become progressive and time would fall as the water increases in temperature
It would be my suggestion to dump the USB concept and get your heat from the sources that are already consuming energy and generating heat as a waste product. ie .... CPU, power supply, ram chips, ..etc. The normal CPU puts out 60 to 80 WATTs of heat. The new Intel P4 3.6 chip is generating 103 WATT's. The normal RAM Chip puts out 30 to 50 WATT's of heat. A 450 watt power supply heat sync can reach 156 degrees F.
If I were to build anything it would be a water cooler for the processor that sends the heated water to a desktop coffer warmer. Thus performing a dual duty, and ease of installation would be just replacing the CPU fan. Incorporating chemicals capable of transferring heat energy more proficiently, in lieu of water, would enhance the process.
Here's the best option. Mod your case to include a coffee maker. This is my all time favorite case mod. www.frontier.net/~wixx/caf
OK, nobody else will answer the question... amazing! So I will:
>> am planning to do a simple USB heater that drives its power from USB port and
>> heats up a continer containing water/coffee,, so any ideas in how to do such a project??
1) Go to a parts catalog and find a heating element.
2) Find a USB Cable
3) Locate a coffe mug (perhaps borrow one from neighboring cubical)
4) Attach item #1 to item #2
5) Fill item #3 with coffee (#5)
6) Put item #1, attached to item #2 into item #3 filled with item #5
7) Plug the other end of the USB cable into the computer
I hope this helps.
I don't think you should get the points back, you were provided with two independant sets of calculations that came out with similar lengths of time to heat the cup (although I dropped a factor of 60.) You were given the spec of the USB power and provided with a method of storing the minimal power available until it would be needed to heat the cup.
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by: CallandorPosted on 2004-02-20 at 07:43:03ID: 10413272
I would say it's not a good idea - USB is intended for signal-level voltage and current, and what you want requires amps. Look at the power ratings of electrically heated devices, like a hot plate or toaster. You will blow up the USB circuit if you try this, and maybe take the motherboard too.