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Forum Index : Electronics : homemade dump loads again

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niall1

Senior Member

Joined: 20/11/2008
Location: Ireland
Posts: 331
Posted: 11:30pm 12 Jan 2009
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lots of talk about keeping costs down , reclycling etc at jimmys workshop in ireland resulted in some experiments with dump loads ...some good ,some bad ,some their own mothers could,nt love ....but all cheap (important) and hopefully ok to use in a room as recycled heat

after dismembering an old 220v emersion element at the workshop a piece of the nichrome wire was sealed into a piece of copper pipe
with spark plugs used as connectors (insulators) ,the pipe was filled with oil ...stood well back and lit it up with a 24v 60ah battery ..it pulled about 200w (7 ampsish) and took about 30 seconds to get hot (to hot to touch) ..looked promising but at this temp the oil started to expand to much ,the filler hole had to be used as a kind of bleed instead of keeping it sealed...the ends were only soldered on so the temp needed to be kept at about 70 or 80 to be on safe side ...not much good as an air heater , was,nt able to dissapate enough heat without some kind of heat exchanger around it ... salvaging old nichrome had potential though







next up will be the same thing but with a solid insulating core inside



simplest so far and almost cost free is this attempt using stainless steel wire (stainless steel rope)


seemingly stainless has a fairly high resistance close to nichrome (news to me ) ..the piece wrapped around
the tile pulls about 100w at 26v and gets (warm/hot) ... playing about with the number of
strands used in each section winding ...more strands less resistance more heat (used 4 above) and then paralleling the sections ... should leave the full tile able to dissapate about 900 watts (...i think)
without running too hot ...


must be true if its in the bible ......

From Wikipedia, the free encyclopedia
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Resistance wire is electrical wire used for its resistance. It is routinely used at high temperatures, so normally also has high melting point. Resistance wire is usually used for high-power resistors and heating elements, which produce heat used in electric heaters, electric ovens and toasters, and many other appliances.

Nichrome, a non-magnetic alloy of nickel and chromium, is commonly used to make resistance wire because it has a high resistivity and resistance to oxidation at high temperatures. When used as a heating element, resistance wire is usually wound into coils.


Many elements and alloys have been used as resistance wire for special purposes. Copper is also included for comparison.

Material        &nbs p;     Resistance
                                                    ( oh m- cmil/ft ) (ohm-cm)

Aluminum        &nbs p;        15.94   2.650 e-6
Brass         & nbsp;         4 2.1    7.0 e-6
Carbon (amorphous)        & nbsp;   3.8-4.1 e-6
Constantan        &n bsp;   272.97 45.38 e-6
Copper          &nbs p;         10.09& nbsp;  1.678 e-6
Iron         &n bsp;          5 7.81   9.61 e-6
Manganin        &nbs p;        290     48.21 e-6
Molybdenum        &n bsp;   32.12   5.34 e-6
Nichrome        &nbs p;        675     112.2 e-6
Nichrome V           ;  650     108.1 e-6
Nickel          &nbs p;         41.69& nbsp;  6.93 e-6
Platinum        &nbs p;        63.16   10.5 e-6
Stainless steel (304) 541     90 e-6
Steel (0.5% Carbon)   100     16 .62 e-6
Tungsten        &nbs p;        31.76   5.28 e-6
Zinc         &n bsp;          3 5.49   5.90 e-6



this ones wound with 2 equal sections in parallel to pull max 20 amps at 26v ...for the mill 2 tiles like this in parallel would be needed


the 6mm stainless rope (5.5 meters ,16 euros worth) is made up with 7 groups of wire wound in a spiral.....one full group (5.5 meter ) was used for each section,
in the pic the mills dumping about 8 amps ...



it spiked over the full 20 amps once or twice and was almost fully furled (early)
at the full 20 the heat in the tile builds up fairly fast ...a floor tile would be a better job

i,m not sure if having the dump composed of so many single strands might increase the inductance ...is there a simple circuit i could add across the dump to be on the safe side ? ...i see lots of tryistors in power supplys but have no idea if i need to add one Edited by niall1 2009-01-15
niall
 
GWatPE

Senior Member

Joined: 01/09/2006
Location: Australia
Posts: 2127
Posted: 09:48pm 13 Jan 2009
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Hi Niall,

I have used the stainless steel [fishing trace] solid type wire for heating elements.

Gordon.
become more energy aware
 
niall1

Senior Member

Joined: 20/11/2008
Location: Ireland
Posts: 331
Posted: 01:48am 14 Jan 2009
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hi Gordon

found this downstairs ...its not solid kindof more woven   ,dad was using it to brace model biplane wings a loong time ago ....funny when your racking your brains looking for something to experiment with and cant find any
.....its usually under your nose ...all 30 meters of it ....funny that    

Edited by niall1 2009-01-15
niall
 
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