TechTools Archives: Re: Dummy load on power supply

From: Tom Miller <tmiller_at_skylinenet.net>
Date: Wed Aug 08 2012 - 01:21:48 EDT

Get two 5 ohm 10 watt resistors and put them in series. Put the 6.3 volt
bulb across one of the 5 ohm resistors. Connect the series pair to the 12
volts. It will draw about 1,3 amps and the bulb will light..

regards,
T

----- Original Message -----
From: "David Shoemaker" <davids@oz.net>
To: "'Technical Tools Mail List'" <techtoolslist@flippers.com>
Sent: Wednesday, August 08, 2012 1:12 AM
Subject: Re: [Techtoolslist] Dummy load on power supply

Ok I thought I would be smart and put a light in series with the resistor,
draw a little more and let me know everything is on.

I put a #1847 6.3v 150ma bulb in there along with a 10ohm 10watt resistor
(figured I would get 650ma draw). Light turned on but 12v was only around
10v. Regulation wasn't stabilized.

I dropped back to a 1ohm 25w resistor. Lamp was a little brighter but still
the same 10v.

Pulled the lamp out and left the 1ohm resistor in there. 12v was nice and
steady at just over 12v.

This leads me to believe that the wattage rating is the max current the bulb
will pass (and consume). I never really thought of it before (haven't built
anything using an indicator bulb before :)

Am I right or just confused?

Thanks,
David

-----Original Message-----
From: techtoolslist-bounces@flippers.com
[mailto:techtoolslist-bounces@flippers.com] On Behalf Of David Shoemaker
Sent: Thursday, August 02, 2012 9:32 PM
To: 'Technical Tools Mail List'
Subject: Re: [Techtoolslist] Dummy load on power supply

Yep a 15A unit. Thanks that was what I thought but it was gut not knowledge
:)

-----Original Message-----
From: techtoolslist-bounces@flippers.com
[mailto:techtoolslist-bounces@flippers.com] On Behalf Of Brad Gass
Sent: Thursday, August 02, 2012 8:44 PM
To: Technical Tools Mail List
Subject: Re: [Techtoolslist] Dummy load on power supply

In the non-arcade SMPS part of my world, as a general rule 5% of rated
output is usually more than sufficient to stabilize cross-regulation -
sometimes it's a lot less actually. However, I can't speak directly to the
cross-regulation performance of the Peter Chou supplies as I've never loaded
them in that manner. But if it's one of the 15A units, I think 1A should be
more than enough.

----- Original Message -----
From: "David Shoemaker" <davids@oz.net>
To: "Techtoolslist@Flippers. Com" <techtoolslist@flippers.com>
Sent: Thursday, August 2, 2012 9:56:02 PM
Subject: [Techtoolslist] Dummy load on power supply

I am testing a board that takes 12v in. I am using a Peter Chau supply on
my bench. As the voltages follow 5v on those I need to load the supply
somewhat to stabilize Is 1A enough?

Thanks,
David
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