<div dir="ltr">I have a whole box full of high wattage resistors (some as big as 25w I think), if you need some more to play with let me know. <div><br></div><div>Alternatively, if you decide a cleaner solution is needed, here's an example of what's available commercially: <a href="http://www.alliedelec.com/mean-well-usa-lrs-75-5/70696528/">http://www.alliedelec.com/mean-well-usa-lrs-75-5/70696528/</a> 70W 5VDC power supply for under $20. </div></div><div class="gmail_extra"><br clear="all"><div><div class="gmail_signature"><div dir="ltr"><div>--</div>Wyatt Zacharias<div><br></div></div></div></div>
<br><div class="gmail_quote">On Wed, Feb 17, 2016 at 3:51 PM, Trevor Cordes <span dir="ltr"><<a href="mailto:trevor@tecnopolis.ca" target="_blank">trevor@tecnopolis.ca</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><span class="">On 2016-02-17 Wyatt Zacharias wrote:<br>
> Do the resistors have their power rating on them? 1.6A at 12V is 19.2<br>
> watts total. You'll need some hefty resistors to sink that much power<br>
> into.<br>
<br>
</span>10W resistors, 2 of them should take 19.2W. These are the biggest<br>
resistors I've ever personally seen.<br>
<span class=""><br>
> Out of curiosity, how much power do you actually need from the 5V<br>
> rail? Single voltage switch mode power supplies can be had for under<br>
> $50 with decent amperage ratings.<br>
<br>
</span>I need 10A 5V. I don't want to use a wall-wart as they don't usually<br>
put out very clean power compared to a "real" power supply. As for<br>
buying one, the idea here is try the "free" stuff first, buy something<br>
second.<br>
<span class=""><br>
On 2016-02-17 Gilles Detillieux wrote:<br>
> half the heat of a 40 W incandescent bulb. Any load you use will put<br>
> out that much heat for the same amount of current.<br>
<br>
</span>I thought maybe I'll try putting in a .5A fan to take up a chunk of the<br>
12V output, and have it blow on whatever hot resistors I need for the<br>
rest :-)<br>
<span class=""><br>
> It seems to me a decent switching power supply should be able to<br>
> regulate voltage with much less draw than that, though. I'd try a<br>
> single 15 Ohm resistor and see how well it holds the +12 & +5 V, and<br>
> if it's good, try even higher resistor values than that. You might be<br>
> able to get the current draw down below 100 mA (1.2 W) without any<br>
> loss of stability.<br>
<br>
</span>That's voodoo territory for me. I'm not sure what the characteristics<br>
of the PS are with different loads on the unused lines. I'm not<br>
certain I could a) reliably measure stability in a short amount of time<br>
and b) project those results out over the (offsite) usage lifetime of<br>
the PS.<br>
<br>
What I could easily do is check if I have some other PS's with a lower<br>
min 12V rating on their label. Maybe I just picked the wrong one with<br>
the initial grab.<br>
</blockquote></div><br></div>