heating resistors

[adsl1981]

Hello,

I want to build a circuit primarily for heating. I need some advice on the best things to use like heating resistors, resistor wire and power and some way of getting it working on a USB. I basically need it to be a effective heater for things like water and not take up too much power?

Can anyone please help me there is a lot of intelligent people on this forum and i need some help

Thank you very much

[Externet]

Hello.
If I understand your question, you are trying to electrically heat something in the most efficient way.

To heat water (or something else) as you say, there is NO more efficient way.
Any electrical heater will work THE SAME. How many Watts you put in; and the temperature will rise the same amount with a modern ceramic heater, or a carbon resistor, a light bulb or a 1920 coffe brewer.

The efficiency can be improved by confining the heat and eliminating heat losses with insulation, but a given power will always produce the same amount of heating. Go to a store and look for plain room heaters, you will see many models. If all are 1500Watts, all will yield the same heat, no matter if modern or antique or whatever the advertisement in the box says.
Hope it helps,

Miguel
-I do not know what you mean by USB-

[Cap'n Refsmmat]

-I do not know what you mean by USB-
By USB I think he means he wants it to run off of a 5-volt USB plug in any regular computer.

[adsl1981]

Hello,

Thanks for the help. Basically i do really want to be running it of USB on a standard computer. Will i be abled to do this and what resistor will be best suited etc.. ?

Thank you

[Externet]

¿ Heating something with the power source from a Universal Serial Bus connection ?

Well, you will be able to connect a 6 V portable flashlight bulb, maybe two as a heat source. That is about how much heat you can obtain from it.

The USB power is +5Volt, current limited to a number of milliamperes determined by the USB chosen integrated circuit specifications used by the manufacturer of the motherboard.
If the current is limited to 500mA, the maximum power obtainable is 2,5 Watts.

You may try to connect a rheostat and measure at what resistance the voltage drops 5% to 4.75V. That is as low resistance as you can connect to drain power from it. Should be around a couple of watts.

But all this near senseless aproach can be done much better by tapping to the +5V PC power supply line, capable of much, much more current, maybe 50 extra watts, instead of playing with a power weak USB port.

Miguel

[5614]

You can get things like a USB coffee warmer which works:
http://www.sunbeamtech.com/PRODUCTS/USB%20COFFEE%20WARMER.HTML

Or even a grill, see here:
http://www.thinkgeek.com/stuff/looflirpa/igrill.shtml

So it is possible. The first site says it runs from 5V at 10W... so obviously that is a 2A current, which obviously a USB is capable of supplying.

The iGrill sounded interesting; "Using the USB current to directly charge high voltage capacitors" gives you a design idea.

[Externet]

Hey Scientist 5614 :

¿Can you read the word after " /stuff/ " in your link ?
Try in reverse ! Still believe it possible ? :-p :D

Miguel

[5614]

What??? The top of my 2 links no longer works for me (it did work when I posed it), oh, I see, if you go to http://www.sunbeamtech.com then it asks to instal chinese... was my link in Chinese? I wouldn't have done that! There would have been sufficient English or images to make sense of it (otherwise I wouldn't have posted it), either way it doesn't anymore (for me anyway).

So I did another google search and found the same product here:
http://cruftbox.com/blog/archives/000748.html