Permafrost
Compo Whore
hahaha i really look forward to seeing this and might even get a cheap psu just to play with
ZEUS (Fractal R4 | blue/black | internal UT60 Rad) - by alpenwasser
- Thread starter alpenwasser
- Start date
hahaha i really look forward to seeing this and might even get a cheap psu just to play with
alpenwasser
New member
Yeah this PSU wasn't very expensive, so if I screw up colossally I won't lose that much money
(although quite a bit of time, but of that I have quite a bit at the moment).
Besides it's a good practice project for HELIOS.
(although quite a bit of time, but of that I have quite a bit at the moment).
Besides it's a good practice project for HELIOS.
Permafrost
Compo Whore
I'm going to watch the videos and read up about tomorrow, i need to sleep
alpenwasser
New member
Mgutierrez33
New member
How did you determine the type of variable resistor you needed for that quantity of fans? I am familiar enough with the math surrounding electronics to get the idea, so feel free to be technical if you like x-).
alpenwasser
New member
To be honest I didn't.
I bought a few of those resistors a couple of years ago and just had them laying around.
It's this model (100 Ohm), although I didn't buy it from caseking.
I did actually work on this a while back trying to figure out what sort of fixed resistors to use,
but I scrapped that part of that project and changed plans. I might try to do the calculations
nonetheless just out of curiosity and for being thorough.
Mgutierrez33
New member
To be honest I didn't.
I bought a few of those resistors a couple of years ago and just had them laying around.
It's this model (100 Ohm), although I didn't buy it from caseking.
I did actually work on this a while back trying to figure out what sort of fixed resistors to use,
but I scrapped that part of that project and changed plans. I might try to do the calculations
nonetheless just out of curiosity and for being thorough.
LOL I love it x-). That tends to pretty much be how all of my projects lately have been turning out; Plug and Pray, as it were x-). Glad all of that worked out for you tho, pretty clean job all things considered. I would imagine that ensuring a parallel circuit makes things significantly easier, assuming that all of the fans you will be using generally have the same specs and resistances to overcome in the circuit.
alpenwasser
New member
"Plug and Pray", haven't heard that one in ages, but it's still a good one. :lol:
Yes the circuit itself is not that complex and should certainly be doable to calculate.
Thanks mate!
Most stuff I've seen has been done by people who've had professional experience with cable
lacing and their results were accordingly complex. Of course when you lace something that
has to last for years, decades even (especially when it's supposed to be an "install and forget"
type of thing were you no longer might have access to it), you want to do it absolutely right
and as solidly as humanly possible.
However, whatever techniques I've seen from that area have not been ideally suited for my
purposes because they just didn't look right. Of course I want my result to be solid, but it
also has to look pleasingly (at least to me
), which means I can't make any convolutedknots between cables that are going to ruin the aesthetics of it
And of course making a nice parallel bundle in free air isn't really something that's usually
done. Whatever bundles I've seen that sort of look similar to my 24 pin have always been
tied down to a rack, which I don't have here. That changes a lot. And whatever I've seen
that hasn't been tied to a rack (or whatever other tie down point) was usually just an actual
bundle of cables (i.e. round-ish in diameter).
Zoot
Active member
Nice job on the fan controller!
If you simply use Ohms law you get an effective resistance of the fan of 12/0.1 = 120 Ohms. Since the fan is just a DC motor, and all motors rotational speed is a function of the current flowing in them. If you assume a linear relationship between fanspeed and current, halve the current and you'll halve the speed.
To do that, just make your resistor 120 Ohms (same as the fan), for 66% fan speed, make it 80 Ohms etc.
Most fans have some sort of power rating. I think the Akasa ones I had lying around were rated for 100mA at 12V.
If you simply use Ohms law you get an effective resistance of the fan of 12/0.1 = 120 Ohms. Since the fan is just a DC motor, and all motors rotational speed is a function of the current flowing in them. If you assume a linear relationship between fanspeed and current, halve the current and you'll halve the speed.
To do that, just make your resistor 120 Ohms (same as the fan), for 66% fan speed, make it 80 Ohms etc.
Mgutierrez33
New member
Figured that was how you could do it. Been so long since I touched on Ohm's Law... plus I've been delving deeper and deeper into Calculus for my Engineering degree (Computer Engineering) and haven't yet gotten to take my Physics courses to get me refreshed on it (my community college has some terrible scheduling, seemingly put in place to ensure that the students have to stay there for as many semesters as is humanly possible). I studied it heavily though while I was in automotive school, really enjoyed it then and am finally starting to see more applications for it again x-).
But her I am spouting exposition... NEED more of this build to get posted up (but in your own time).:crazy:
Zoot
Active member
If you do anything in regards to electronics you'll see it again and again, it comes into everything.
But yes, all you're doing is just limiting the current that the Fan is pulling with the resistor.
alpenwasser
New member
Thanks!
The SP120's quiet are rated @ 0.08 A @ 12 V, which equals to 150 Ohm if my math is correct.
Taking three of them in parallel would yield 50 Ohm for the fans in total. Connecting the
potentiometer (100 Ohm @ max R) in series, that would give you 4 V over the 3 fans and
8 V over the Potentiometer.
I don't know the minimal resistance of the pot though.
True, the voltage divider is a rather important concept.
It would be possible. Taking 12 SP120 Quiets in parallel would yield 150 Ohm/12 = 12.5 Ohm
total resistance for the fans without the potentiometer. From there you can take whichever
potentiometer suits best your needs. A 12.5 Ohm potentionmeter would give you 6 V voltage
drop over the fans and 6 V over the resistor, a 25 Ohm pot would give you the same behavior
as in my circuit (provided I haven't made a mistake somewhere, I am admittedly a tad rusty
when it comes to electronics, haven't done anything since last August), meaning 4 V over
the fans and 8 V over the resistor.
What you need to pay attention to is that the potentiometer is specified for the power draw
for your circuit. For example, let's say I have my potentiometer (so, for the circuit with 3 fans)
set at 50 Ohm, meaning I have 6 V over the pot and 6 V over the fans.
Going by each fan having a resistance of 150 Ohm, this would give me a power draw for
each fan of 6 V/150 Ohm = 0.04 A. Since we have three fans, and the entire current for those
three fans needs to pass through our potentiometer, the current through that will be 0.12 A.
This will give us a dissipated power in the resistor of P= 6 V * 0.12 A = 0.72 W. Since the
resistor in my circuit is specified for 4 W (according to caseking's site), this is all good.
As for cost, I think the PCB cost about 4 bucks and the potentiometer another 4 bucks.
Provided you already have a soldering iron it would certainly be cheaper than a prebuilt
controller.
If it would be helpful and desired, I could make a drawing of the circuit, I usually have
an easier time understanding a circuit diagram than a long text describing said circuit
(both together are optimal, of course).
Disclaimer: As mentioned, I'm rather rusty when it comes to electronics. Since
this is rather trivial stuff, I hope I haven't made any errors (that would be rather
embarrassing
), however, Zoot knows this stuff inside out, I'm sure he'll call me outon any BS.
Update: I will probably have one either tonight or tomorrow, depending on how
well things go. I'm more or less done with the PSU, still need to test it though. Besides
that I'm working on the new back panel and trying to get everything to fit together.
Zoot
Active member
Nah, no need. What you've said is correct.Zoot knows this stuff inside out, I'm sure he'll call me out
on any BS.
alpenwasser
New member
Nah, no need. What you've said is correct.
*sigh of relief*
Considering I'm starting a degree in electrical engineering next fall I really should be able to do
this, rusty or not. This is stuff from my high school days. :lol:
On another note: I got my first studio light today and have been experimenting around with that.
Unfortunately my camera's batteries have decided to quit after a day of playing around.
I'll give the PSU a good clean and take some proper pictures tomorrow morning along with a
status update for the back panel.
Until then,
-aw
Throbbi
New member
Gotta say, I wasn't familiar with cable lacing and I must look into that for my since I hate cable ties with a passion but i'm forced into used them at present. Looking forward to what else you come up with.
FYI - 1174 holes drilled (no, I wasn't sat with nothing to do before work, honest)
FYI - 1174 holes drilled
(no, I wasn't sat with nothing to do before work, honest)
alpenwasser
New member
It is indeed not something one usually just stumbles upon. Originally I started with a Google
search about "Sewing Cables", which after a little while lead me to cable lacing. It's definitely
not as prevalent these days as it used to be.
FYI - 1174 holes drilled
Oh dear god, that got an actual, literal :rollinglaugh: from me! I've thought about counting
them, but so far couldn't get myself to do it. :lol:
*gives cookie for achievement of the day*
Hm, this gets me thinking: 1174 holes, and for each hole I
- drilled a small hole for centering (yeah, yeah I know they're not all properly centered ),
- drilled the actual hole,
- deburred both sides,
which gives me 1174*4=4696 drilling operations.
No wonder my wrist hurt for two days after I was done.
alpenwasser
New member
Fan Controller & PSU
Fan Controller - Finished
I've strengthened the fan controller with quite a substantial amount of epoxy glue. It might
not be the prettiest, but it won't be visible and it's pretty much bomb proof at this point.
PSU - Finished (More or Less)
There's still some very minor finishing touches to be applied, but it's as good as done.
24 Pin - Detail
There's a minor mistake in my lacing in the middle lacing section, but I'm not sure if I'm going
to redo the thing just for that. It depends on whether or not it will be visible in the final configuration
when everything is in the case. The lacing is not 100% straight at this point, that will be done
once everything is mounted, there's enough flex to do that.
Fan Cable
This cable will connect to the fan controller, hence only the 12 V wire. Obviously I couldn't
use the same technique for this as for the 24 pin.
Fan Controller - Finished
I've strengthened the fan controller with quite a substantial amount of epoxy glue. It might
not be the prettiest, but it won't be visible and it's pretty much bomb proof at this point.
PSU - Finished (More or Less)
There's still some very minor finishing touches to be applied, but it's as good as done.
24 Pin - Detail
There's a minor mistake in my lacing in the middle lacing section, but I'm not sure if I'm going
to redo the thing just for that. It depends on whether or not it will be visible in the final configuration
when everything is in the case. The lacing is not 100% straight at this point, that will be done
once everything is mounted, there's enough flex to do that.
Fan Cable
This cable will connect to the fan controller, hence only the 12 V wire. Obviously I couldn't
use the same technique for this as for the 24 pin.
