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radkins
05-21-2012, 08:27 PM
I have a control box from a friend's John Deere hay baler with a broken resistor, the box was physically damaged. The only parts we need to fix this thing is a couple of Bosch type relays which are easy to find but one of them was pushed down onto a resistor and ruined it also. This thing is a .03 Ohm 10 Watt resistor with a 5% tolerance. Been searching the net and can't come up with a thing, found a few .03 Ohm but only in 1, 1/2 and 2 Watts. Any suggestions on where to find something like this or some type of substitute?

lakeside53
05-21-2012, 08:32 PM
3 of these in series : http://www.ebay.com/itm/10x-Ceramic-Wire-Wound-Power-Resistors-0-1-Ohm-5-5W-/330734434569?pt=LH_DefaultDomain_0&hash=item4d014ef909

or one of these (bigger, but)... http://www.ebay.com/itm/Gold-Tone-Aluminum-Case-Resistors-50W-Power-0-03-Ohm-5-/370568406877?pt=LH_DefaultDomain_0&hash=item564799275d

2 of these in parallel : http://www.ebay.com/itm/5W-0-06-ohm-0R06-Aluminium-clad-Resistor-R-5-W-Watt-x-1-/230583791114?pt=LH_DefaultDomain_0&hash=item35afdd6e0a

radkins
05-21-2012, 08:47 PM
Not sure how you did that, I bet I searched E-Bay for over half an hour and came up with nothing close to that! The 50 Watt one will be just fine since we have lots of room in the case and even if it won't fit inside I will still find a place to mount it. :)


Thanks!

lakeside53
05-21-2012, 08:48 PM
lol... I just typed in "0.03 resistor" (no quotes)

J Tiers
05-21-2012, 09:30 PM
In stock at Mouser Electronics if you can tolerate a 1% instead of the less precise 5%...... ;)

http://www.mouser.com/ProductDetail/Vishay-Dale/LVR10R0300FL03/?qs=sxHCE4x4v6aOcUFB%252b7m%252bwHwAjVk0TbrM2Zbwa6 XPLCA%3d

radkins
05-22-2012, 01:56 AM
lol... I just typed in "0.03 resistor" (no quotes)




I typed in .03 resistor, danged thing sure is picky! :mad:

Evan
05-22-2012, 11:43 AM
Just use ten feet of 14 gauge copper wire.

beanbag
05-22-2012, 04:07 PM
Just use ten feet of 14 gauge copper wire.

Just make sure it isn't copper coated steel wire ;)

H380
05-22-2012, 04:54 PM
You can search your heart out here.

http://www.newark.com/fixed-value

J Tiers
05-22-2012, 08:11 PM
Just use ten feet of 14 gauge copper wire.

Tempco of resistance is a killer on copper. Most all resistors are made of a low tempco material so that the resistance stays pretty close.

Don't believe it? Try copper as a meter shunt someday.........

Evan
05-22-2012, 09:27 PM
10 watts (probably much less) dissipated over ten feet of 14 ga wire might raise the temp a couple of degrees, if that.

J Tiers
05-22-2012, 10:56 PM
10 watts (probably much less) dissipated over ten feet of 14 ga wire might raise the temp a couple of degrees, if that.

In this case, yes..... in the general case, copper isn't a great resistor material because of the tempco. One doesn't often have the luxury of unlimited space for long pieces of heavy wire.

If it has to fit in a smaller space, it might be coiled up...... heats more that way. A goodly length of 14 ga wire is a tad larger than a wire-wound resistor, as well, might not fit. Then one is tempted to use a shorter piece of smaller wire, which is obviously worse off for heating effect.

One generally de-rates a resistor considerably, perhaps to 50%. Then at 5W dissipation, that would be 13A carried, with a voltage drop of 0.387V..... no idea what that would be for on a hay baler.

One usually uses a small resistance for a good deal of current.... or else as a meter shunt. As a 50mV meter shunt, it could carry just 1.6A, which is obviously not much issue for 14ga.....although I don't know what good that would be on a hay baler, either.

Evan
05-23-2012, 01:15 PM
I didn't make a general case suggestion. It was specific to this application and will work just fine. 10 feet of wire can be coiled loosely and will not heat enough to matter. It also has a positive tempco so will self limit any heating.

It's a perfect farmer fix.

radkins
05-23-2012, 01:23 PM
This is all interesting, keep it coming!! :)

About using the Copper wire, what difference would it be between using 14 ga. solid or multi-strand wire?


BTW, I ordered that resistor.

oldhat
05-23-2012, 01:51 PM
Wire Gauge Resistance per foot and Amps per AWG copper

AWG Ohm Amps
4 .000292 135
6 .000465 101
8 .000739 73
10 .00118 55
12 .00187 41
14 .00297 32
16 .00473 22
18 .00751 16
20 .0119 11
22 .0190 7
24 .0302 3.5
26 .0480 2.2
28 .0764 1.4

Maximum amps for chassis wiring only not power cords.

Bill:cool:

lakeside53
05-23-2012, 02:51 PM
BTW, I ordered that resistor.


The correct choice.;)

Forestgnome
05-23-2012, 03:10 PM
Why not just use Nichrome wire?

http://www.pelicanwire.com/resistance-wire-alloys/nichrome-60/

Forestgnome
05-23-2012, 03:11 PM
Too late...

wierdscience
05-23-2012, 07:16 PM
Also too late,but still neat:)

http://www.youtube.com/watch?v=hu7bQdcHUZg&feature=related