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