Cheap dump load
By frackers, Section Diaries Posted on Mon Jul 21st, 2008 at 09:01:41 AM MST
The picture as promised

As promised, a picture of the 'wire wound resistor' made from fence wire. Its 1m long and 0.5m in diameter and with something like 45m of wire on it - it presents a resistance of 1.88 ohms I might try it if we get any wind - its really for testing the genny off the tractor PTO

Cheap dump load | 7 comments (7 topical, 0 editorial)

Re: Cheap dump load (3.00 / 0) (#1) by wooferhound (tim((NoSpamAt))wooferhound.com) on Mon Jul 21st, 2008 at 08:41:06 AM MST (User Info) http://wooferhound.com

Looks like a great idea for a Camp Fire Starter W o o f -={(

Re: Cheap dump load (3.00 / 0) (#2) by Bruce S (bruce(dot)stahl <at>gmail (dot)(com)) on Mon Jul 21st, 2008 at 08:47:37 AM MST (User Info)

Hey wooferhound;    I was going to say something of the same :-) Depending on the heat, I'm thinking those wood stand-offs will do just that. Cheers Bruce S [ Parent ]

Re: Cheap dump load (3.00 / 0) (#3) by ghurd on Mon Jul 21st, 2008 at 09:08:42 AM MST (User Info)

Sounds safe to me, for 12V.  About 7.7A, 110W. Only ~1W in 16" of wire? G- [ Parent ]

Re: Cheap dump load (3.00 / 0) (#4) by TomW on Mon Jul 21st, 2008 at 11:50:12 AM MST (User Info)

Interesting. So at say, at 10 amps its 188 watts [not a problem] but at 100 amps it will be creating 18.8KW? Spread out over that length I wonder how hot any one point of contact will get? Likely quite safe for a lot of testing use before it chars too much. How many of you push 100 amps for long? Great use of stuff on hand especially in spring during fencing season. I don't see the gage mentioned? Tom "Education consists mainly of what we have unlearned."--Mark Twain

Re: Cheap dump load (3.00 / 0) (#5) by DamonHD (d@hd.org) on Mon Jul 21st, 2008 at 11:56:03 AM MST (User Info) http://www.earth.org.uk/

Could be an alternate way to keep the deer out...  First 300V on the nose.  Then 300C on the nose if they don't wise up... Rgds Damon [ Parent ]

Re: Cheap dump load (3.00 / 0) (#6) by SparWeb (sparweb at ANTISPAM_hotmail_com) on Mon Jul 21st, 2008 at 12:43:41 PM MST (User Info)

Don't people hang those things over their patios to zap bugs?  Hehe  Looks nice. Steven Fahey

Re: Cheap dump load (3.00 / 0) (#7) by frackers (g8ecj at *nospam* gilks dot org) on Mon Jul 21st, 2008 at 05:54:09 PM MST (User Info) http://www.gilks.org

Seems like it was one and a half hours well spent :-) And all scrap materials - even the nails were reclaimed from a bunch of pallets! It will be on a 24volt system so I expect that I'll only run it up to about 35volts (i.e. without a battery bank, just the genny on the PTO) where the full length will be dissipating 650watts (35^2 / 1.88). For higher current tests where I want to load the genny to about 40amps at 28volts (max design charge current on a fully charged bank) the 1120watts will be spread over about a third (0.7 ohms for that load of course) of the wire length so I expect it will cook then - so long as the smoke isn't the magic variety that makes all the electrons go round I think I'll be OK... Robin - Down Under (or are you Up Over)

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