On Wed, 08 Nov 2006 07:30:59 -0800, T-n-T wrote:

In article , PeterD
wrote:

On Tue, 07 Nov 2006 07:02:47 -0800, T-n-T wrote:

In article , T-n-T
wrote:

In article , PeterD
wrote:

On Mon, 06 Nov 2006 07:46:14 -0800, T-n-T wrote:

In article , PeterD
wrote:

On Sat, 04 Nov 2006 15:09:41 -0800, T-n-T wrote:

Thinking more about it now I do want to err on the side of not
killing
my terrarium inhabitants. So a wall wort transformer is the way to
go.
the purpose of using wire and a resistor is so the wire can be sealed
in silicone tubing for fish tanks and siliconed on the ends., it just
seems easier to seal up. what theory do I need to apply to heat up
say
4 feet of wire not just the resistor?



Okay so I now know how to come up with the length of wire and
transformer. If I wanted to use a long wire and coil it, do the coils
absolutely have to not touch? What if they do? I believe a smaller wire
that is longer and coiled will give me a more pliable cable.

lildog


Ok, i don't know if this falls within the realm of electronics but you
guys may be able to point me in the right direction. Is there a formula
to determine the amount of heat coming off of on eof these cables?

What unit of measure do you think you'd like to see? If I say 15
Joules will that make sense? If I say 15 watts then how about that?
Or, are you interested in temperature rise? Or BTUs? Or Calories?

bg

There are so many ways of saying that!

Errrr... I guess I would like to be able to calculate how hot in
degrees F a length of said wire will get given voltage of X at Y amps.
OR the number of degrees F the wire will get above it's non-charged
state.

Humm, that's not likely to happen. Too many variables such as
insulation, insulation diameter, etc. You could get an approximation
but it would be free air values, and not somethign that you will see
in a real application.


Also if I wanted to coil a long wire to effectively make it shorter do
the coil need to not touch or is that okay? And if they do what would
be the effect?

If you coil, the coils MUST NOT TOUCH. That assumes bare wire, of
course. If the wire is insulated, and if the insulation is rated for
the temperature that will be found at contact points, then the
*insulation* could touch--but never the bare wires.

Also, if you are running this as a coil, I'd recommend a couple of
turns in one direction and then a couple in the other direction to
minimize magnetic effects and inductance.


Once again, thank you guys for your patient help. I know this is a
simple question I have probably not made so clear.

You're not doing that badly now...

Check:

http://www.aeroconsystems.com/electronics/nichrome.htm

Look at their 26 gauge nichrome wire. It is 2.6 ohms a foot, so for
your 14 ohms, you'd use about 5 feet of wire. Their prices are Ok and
they are able to deal in smaller quantities too.

Note: this is bare wire, so you will have to make sure it doesn't
short anywhere.