26 Oct
2015
26 Oct
'15
12:09 p.m.
Well, we indeed know the voltage (V or E) but not
the current (I) used in your formula; since I is
E/R then power is simply E^2/R, so 20 Ohms at 12V
has to dissipate 144/20 = 7.2 W.
m
----- Original Message -----
From: "Ian Finder" <ian.finder at gmail.com>
To: "General Discussion: On-Topic and Off-Topic
Posts" <cctalk at classiccmp.org>
Cc: <General at classiccmp.org>
Sent: Monday, October 26, 2015 2:32 PM
Subject: Re: Model 152 PSU dummy loads - Re: NeXT
Cube - powers on briefly then off again
Not sure how much of a noob you are, although
you repeatedly claim to be
one so just on the safe side we'll cover some
Engineering for Poets (or
Programmers) to reassure you ;) --
V = I * R
Power (watts) = I * V
You know the voltage of the monitor. You know
the resistance of your
resistor. So, you also know the maximum power
the resistor needs to be
rated to dissipate.
If the spec says the single air-cooled resistor
you're buying is good to
dissipate X watts into ambient temperature Y,
I'd just go ahead and believe
it.
Make sure the numbers work out and you're fine,
no heavy duty HVAC needed.
:-P
Cheers,
- Ian
On Mon, Oct 26, 2015 at 10:52 AM, Toby Thain
<toby at telegraphics.com.au>
wrote:
On 2015-10-26 1:23 PM, Ian Finder wrote:
--
Ian Finder
(206) 395-MIPS
ian.finder at gmail.com This thread took a turn for the absurd. Oil?
Water? What a practical
bunch of people. /s
They make resistors with adequate cooling...
Almost as if they're
rated for a certain number of watts of
dissipation and you can buy
them based on that. They are resistors after
all.
And if they overheat-- oh wait, they're heavy
duty resistors, not
ICs. Get a couple, put them in a metal project
box, put it inline
with the cable, and call it a day.
Damn, I already ordered a pile of HVAC gear.
j/k - yeah that was what I was basically
planning, Ian ... just as a noob,
I'm not totally confident with what a single
air cooled part can dissipate.
(The thread was kind of interesting anyway!)
--Toby
Sent from my iPhone
On Oct 26, 2015, at 09:24, simon
<simski at dds.nl> wrote:
please skip this ridicule and grab yourself a
couple of headlights from
a car.
On 26-10-15 17:16, Dale H. Cook wrote:
> My recommendation of oil is based upon my
> decades of experience with
> broadband dummy loads from 60 watts to 2.5
> kilowatts. The dummy loads that
> I have worked with for medium wave and below
> and from 5 kilowatts down have
> all been convection air cooled. Broadband
> dummy loads that I have used for
> higher powers (up to 25 kilowatts) have been
> forced air cooled.
>
> I prefer to stick with what I have
> experience with. As for water, YMMV.
>
> Dale H. Cook, Radio Contract Engineer,
> Roanoke/Lynchburg, VA
> http://plymouthcolony.net/starcityeng/index.html
>
--
Met vriendelijke Groet,
Simon Claessen
drukknop.nl