Path: csiph.com!eternal-september.org!feeder.eternal-september.org!nntp.eternal-september.org!.POSTED!not-for-mail
From: Christopher Howard <christopher@librehacker.com>
Newsgroups: sci.electronics.design
Subject: thermal resistance, dummy loads
Date: Thu, 23 Apr 2026 13:33:01 -0800
Organization: A noiseless patient Spider
Lines: 19
Message-ID: <874il1tl9u.fsf@librehacker.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 8bit
Injection-Date: Thu, 23 Apr 2026 21:33:02 +0000 (UTC)
Injection-Info: dont-email.me; posting-host="41ccae71c0bea6c6d34a8b4c755fc055"; logging-data="3510255"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX19B62AQAGu2vGNFf3rdKZF+4zKrSOZ0QVo="
User-Agent: Gnus/5.13 (Gnus v5.13)
Cancel-Lock: sha1:vYR2Zh92jhGRNJrL0McqDp2Aid8= sha1:fzk6Cwq/gAI/ue+5on5HLcNRv1I=
Xref: csiph.com sci.electronics.design:743286

Hi, I'm wondering what could be used as a dummy load for testing low
voltage, high wattage DC power supplies. E.g., I have a 12V 500W DC PS I
wanted to test under heavy load. I see 50 ohm dummy loads for ham stuff
are easy to get, but that would be too high a resistance for something
like 12V.

I see 1 ohm, 200W resistors are easy to find, like the HS200 1R J. But
in the fine print you've got to provide a correctly rated heatsink. When
I did the calculations for maximum total thermal resistance, assuming
200W power dissipation, and some non-conservative values of standard
room temp and a max junction temp of 200 ℃, I'm looking at less than 1 ℃
/ W total thermal resistance, and the heatsink ends up being five times
the cost of the resistor.

So I'm wondering what is the practical way forward. Like, put the
resistor in mineral oil? Or get some nichrome...?

-- 
Christopher Howard