Need someone good with math involving watts and amps

[SiGfever]

This forum is one of the best (if not the best) for sharing knowledge amongst members. We all have different skill sets/training and remember different things from school so it is nice to be able to share that with each other. Asking a question should never be an offense on this forum. Questions asked, no matter how simple to "Google", start up a conversation that can go in many different directions and open up areas of thought that Google can't.

So the next time someone asks a question here, please show them and the world that Xtreme Systems is not the run of the mill forum, here knowledge is taken to a higher level and manners still mean something.

P= Power (Watts)
I= Impedance (Amperage)
E= Electromotive Force (Voltage)

P
_________
I | E

P = I x E
P / I = E
P / E = I

[BeepBeep2]

shush, Creekin made fun of a dude who should've used 5min on google. Case closed.

No, look back through Creekin's other posts. He talks about the US being "illiterate" as well as just makes immature, snotty remarks in almost every post he makes.

Lets grow up, children.

[skeyo]

shush, Creekin made fun of a dude who should've used 5min on google. Case closed.

Bud take it easy. It's not that easy to calculate. Every fan has peak current when is turned on so that's why it's uses more power. So you can easy burn your fan controller. Most of controllers have over current protection but for 24/7 use sometimes is not good to use them on their limits. So there is no reason for anger.

[Diverge]

Bud take it easy. It's not that easy to calculate. Every fan has peak current when is turned on so that's why it's uses more power. So you can easy burn your fan controller. Most of controllers have over current protection but for 24/7 use sometimes is not good to use them on their limits. So there is no reason for anger.

His fan controller probably has a peak current rating as well. Look at the datasheet of any power transistor or fet. they have peak ratings as well.

If the OP wants to get technical, try to find out the transistor/fet that is used for the each channel of his fan controller, and find the datasheet. The fan controller manufacturer might just underrate their max current rating. never know, unless you look at a datasheet ;p

[OldChap]

The way I was taught...

W= Power (Watts)
I= Current (Amperage)
V= Electromotive Force (Voltage)
R= Resistance (ohms)

W
_________
I * V

W = I*V
W/I = V
W/V = I

then there was the resistance triangle too

V
_________
I * R

V = I * R
V/I = R
V/R = I

Over the years here in UK they have messed with the education system loads
It would not surprise me if this kind of info is missed off the curriculum entirely

Just by the way all you FAN boys ...when you put a fan in open air it will pull a lower current than when you put it on a rad. If you want to demonstrate this lay your fan on the bench blowing down and measure the current then do the same standing the fan in free air. Ok so it is not huge but it is different just the same...The higher the density of rad finnage the higher the current will creep

Anyone know if there is a mod for the original Lamptron fc2 to stop the induced motor noise?

[Waterlogged]

Anyone know if there is a mod for the original Lamptron fc2 to stop the induced motor noise?

Hammer?

[Creekin]

No, look back through Creekin's other posts. He talks about the US being "illiterate" as well as just makes immature, snotty remarks in almost every post he makes.

Lets grow up, children.

I apologise if you misinterpreted my comments,
I made no allegations about US literacy, for the record it is 99%, same as here in Oz, and for the record, I don't give a flying banana about your literacy or
lack thereof, nor anything else that happens in Sarah Pallin land for that matter.

As for my "snotty remarks" , It is not my problem if you don't understand my sense of humour.
Your choices are A) Laugh B) Ignore C) Take offence

My 1st comment in this thread, may have been misinterpreted by some, as I neglected to end with a as intended. This oversight has now been corrected, but I note that the intended recipient got the implied joke anyway.

The OPs Q

So, I have a Lamptron fan controller that handles 45 watts per channel, how do I figure out how many amps that is?

06:47 AM

Can,and was answered with 2 mins on google.

06:49 AM

P = U x I
P - Power (Watts)
U - voltage (Volts)
I - Current (Amps)

So, at the best, you could draw about 3.75 amps at 12V before the controller would be officially overloaded.

The OP did his research but also wanted to ask the opinion of his peers to confirm. Thats what forums are for!
The question had been answered well, TWICE when I came along, so all that was left for me to do was make lol's
If YOU take offence to someone else's comments and want to make an off topic comment, use PM. I would for this also, except for the fact I have the right of reply.

Back OT

You never want to run gear at its capacity, especially if its on 24/7
Going by Wl's math of 6, I would run no more than 3 per channel, that is my plan for my Aquaero also, and i have seen channel wattage specs for it ranging from 5w per to 25w per! (I know my AQ4w/powerbooster does 25w on channel 1 and 15w on 2-4.)

if you don't go over 50-75% of the theoretical load limit, you shouldn't have a problem with start up current or overloading.

The fan controller manufacturer might just underrate their max current rating.

Good point Diverge, BUT, even if the tranny can take a bigger load than the channel specs, doesn't mean the rest of the circuit can! pcb,plug pins,cabling.
In my experience of lighting loads, the plug pins are usually the weakest point in the circuit. I have spent YEARS replacing pins in 10 pole wieland plugs!

That's the same way i was taught OldChap but we're OLD!
All they teach these young whipper snappers is how to type "g o o g l e"

Good idea WL!

[fgw]

leaving comments aside and going back to topic:

as i'm currently in the process of building my own fan controller, i doing some math for selecting the correct output transistor.

the goal is to keep the power dissipated by the transitor in focus and not the total power the fan will use. if the fan is running at full speed (at 12V and draws about 1A) the transistor needs to be able to run the full current, but it will drop just something below 1V, thus needs to be able to dissipate less than 1W!

the story gets interesting when the fan is running at half speed which might be at 6V and in this situation the fan is drawing about 0,5A. you can see it coming: the transistor needs to drop 6V off the 12V supply to feed the requested 6V to the fan. at this time the transsitor dissipates about 6V x 0.5A = 3W.

as you can see, running the fan at full speed is not the point to take care of!

anyway, in any case we are far away from the advertised 20W, 30W or even 45W a fancontroller is able to control.

even the increased power draw during startup, should not be that much of a problem. its very likely the transistors used are able to handle a magnitude of the required current the fan will draw at startup. especially if you take into account, this will last just for fractions of a second in most cases.

this all holds true for so called linear voltage regulation!

coming now to your lamptron. as far as i know the lamptron is not utilizing linear voltage regulation but using PWN control instead. which most fancontrollers are as its the cheaper solution. when running in PWM mode, the transistor is by far NOT stressed as in linear mode. think of switching the fan on and off rapidly within a certain time interval, eg, 10sec: if you switch it on for 3sec and off for 7sec the fan will get only 30% of the energy it would get when it is switched on for 10 sec. thats pretty much what PWM control is about.
the transistor has to dissipate much less power as it is either switched off

current is 0A thus dissipated power is 0W

OR

switched on, where current might be 1A but voltage drop is far below 1V which gives a dissipated power of less than 1W

did some experiments with PWM control myself, but unfortunately the circuitry needs to be tuned for a certain powerrange of fans.it worked seemlesly with some fans but did not work at all with other fans. either the circuitry is designed to control standard case fans or it is designed to control powerhungry fans like some deltas, but it most likely wont be able to control both of them!

also the base frequency used in PWM control is an important factor. low base frequency let you control a wider range of fans, but has the disadvantage of generating this ticking and annoying sound and also prevents correct rpm readings at lower speeds.

to make a long story short:
powercapabilities of fancontrollers using PWM is more or less a marketing gag. if PWM is working as expected you want run into a problem here.

this is different for linear voltage control, but as stated above, the power used by fans is much overrated.

here is an example of a delta fan (the most powerhungry fan martinm210 recently tested. look at the figure:
fan voltage / dissipated power in the transsistor (linear voltage control)
5V / 1.7W
6V / 2.1W
7V / 2.2W
8V / 2.1W
9V / 1.9W
10V / 1.5W
11V / 1.0W
12V / 0.4W

as you can see, the most demanding range is 6V to 9V but the total power dissipated is still just above 2W and far away from the advertised limit of most fancontrollers.

the advantage of linear voltage control is, it will work for all fans without the problem of this ticking sound but at higher cost. also rpm readings will work almost the whole rpm range.

when you are in search of a fan controller i recommend to look for one which is not working in PWM mode.

will keep you posted somewhere on this forums how i proceed with my own project and findings regarding fan control.

[Utnorris]

Ok, so just for the record, I did not take any offense, hence my response, I can give as well as take unless it gets personal and then I hit the "ignore" button. It was not my intention to start a flame war, just ask a simple question. Yes, I could have just relied on Google, however I like to get more info than what is posted by who knows on the internet. I had two conflicting sources of info, so i wanted to verify, no need to have a fire even if the system is water cooled, not my idea of fun.

Anyway, I have gone back to what I was doing previously and running 6 of the San Ace fans off the Koolance controller and 3 off a 5v converter board. Not what I wanted to do, but i can't seem to find a decent fan controller for 18 San Ace fans.

Anyway, this thread looks like it should be closed based on the comments. For those that gave advice, thank you, for those that did not, it's ok, no harm, no foul.

[Creekin]

i doubt you will find any one controller that can run 18 fans, why not just use 2 fc5's or something?

do u need to control them? if not just hard wire the lot

[fgw]

Anyway, I have gone back to what I was doing previously and running 6 of the San Ace fans off the Koolance controller and 3 off a 5v converter board. Not what I wanted to do, but i can't seem to find a decent fan controller for 18 San Ace fans.

which san ace are u talking about, 9G1212H101?

took currentreadings from martinm's tests again and come to a max power dissipation of less than 1W for this san ace! dont think this is a real problem for a correct constructed fan controller .

i need a fancontroller for my build anyway. so i will build one for sure!

would recommend you run the system as described for now. may be i come up with a solution within the next two month. otherwise you can still look after a fancontroller with the requested capabilities after this time.

pm me if you have further questions ...

[OldChap]

SWC, among others, sell a rheostat (variable resistor) or two that might just do the trick for a lot of fans (probably not all 18 though) and do it the old fashioned way by inserting resistance in the circuit. This will dissipate power too so might be best mounted in a position where there is airflow but I would venture that for your immediate needs, Ut, it would resolve the problem. Big (high power) versions have little use these days though and will therefore be less common and more expensive....probably $30 or more

[Utnorris]

The only one I have found was the FC-2 that does over 30 watts per channel. Assuming the calculator I used is correct, I need 6 watts per fan, which comes out to 108 watts, however that would be on one channel and I figured I could run 6 per channel on the FC-2, so that would be ok. The problem is the whine it produces. They did redesign it with digital vrm's, however it's hard to tell who has the new one and who has the old one and even then there is no guarantee it won't make the same whining noise with 18 fans connected to it. I could do two controllers, which I may end up doing, but I was trying to keep it simple. I would just hard wire them all at 5v, but I would rather have the ability to adjust the voltages. Anyway, any suggestions would be welcomed.

[terramir]

45 W per channel would be 45/12=3.75 amps, however I got to warn you if your running at max draw your going to be running into problems of a different sort, you'll be creating heat!
Also I assume this controller uses some sort of digital PWM to control the fans and yes that can cause a whine if it's not properly capacitor'ed at the output. ( properly sized capacitor and a diode to prevent chargebacks into the controller is a must for any fan controller that wants to avoid the whine factor. Zahlman fan controllers used a method that created alot of heat but avoided the whine (this was the first commercial single fan controller) that allowed tach signal pass through.
the start-up factor could also be alleviated by using a smoothing capacitor. however if 45W is the max per channel you should use no more than about half of that for daily use (i.e. no more than 4 fans per channel and that is pushing it)
the problem with fan controllers is that they tend to design them to spec, to save money hence they usually dun spend the extra money for a good really oversize smoothing cap.
so some noise tends to get through.
just one question though WTF do you need 18 fans I'm right now designing a new case and it will have 5 fans 3 in the water cooling compartment, two in the main board compartment.
there comes a time when more fans are overkill.
Directed airflow would get you better results.
well good luck
terramir

[Utnorris]

Why 18 fans? Because I have 60 or so San Ace fans sitting around and figured why not. And this is xtremesystems, so there is no such thing as overkill.

[Creekin]

ok, so better question then
WhyTF do you have 60 fans!??!?!

and more importantly..
SHARE ya bastard!

why not use all 60?

[Martinm210]

FYI, You might consider some sort of PWM controller option instead. I haven't tested it yet, because I can't figure out how to run one without a computer, but according to Bing on OCN, PWM is better for the big fans for reducing motor noise. You might check with the gurus over at crystalfontz, their forums are generally pretty helpful.

[terramir]

Why 18 fans? Because I have 60 or so San Ace fans sitting around and figured why not. And this is xtremesystems, so there is no such thing as overkill.

Ehhh are those the 127x38 fans or the 120x25 ? aluminum frame or plastic?
these are like classics if there the ones I'm thinking of.
I could use five or six for a project if they are the ones I'm thinking of
terramir

[Utnorris]

They are 120x38mm, model 109r1212h1011, the ones they do not make anymore.

[MagisD]

Isn't the new fc-t pwm?

Sent from my X10a using Tapatalk

[terramir]

They are 120x38mm, model 109r1212h1011, the ones they do not make anymore.

Hmm you willing to part with 6 of them and well how much for the 6 PM me please
terramir

[Martinm210]

Isn't the new fc-t pwm?

Sent from my X10a using Tapatalk

That's what we heard, but after watching this video, @3:33 it clearly show Voltage as an indicator option.

PWM doesn't operate at lower voltage, so I'm lost... As far as I can tell it's voltage controlled.

[terramir]

That's what we heard, but after watching this video, @3:33 it clearly show Voltage as an indicator option.

PWM doesn't operate at lower voltage, so I'm lost... As far as I can tell it's voltage controlled.

Actually PWM does operate @ a lower voltage (not really but bear with me)
what PWM does is either switch it on or off so on the axis of time you have a bunch of 12 states and a bunch of 0 volt states, now if you capacitor filter that output sufficiently Before the capacitor you will see a bunch of 12V states and a bunch of 0V states, but on the other side of the circuit where the filter capacitor is you will see an average voltage that can be anywhere from 0 to 12V.
Let's say the 12V is on 75% of the time hence 0V is on 25% then the voltage after the filter capacitor should be around 9V if you use a filter cap that is too small you will get spikes in that voltage (that's where the humming comes from in some pwm controlled fans). Now let's say 12V is on 66.6% of the time then you'll get about 8V after the filter I think you see where I'm going with this.
So while the PWM circuit IS a 12V circuit because of the charging curve of a capacitor the voltage that is output is lower than 12V, there is also another danger, if you design the filter capacitor to high then it will take a long time for the voltage desired to be reached, however; unless you use one that is way over sized the delay should be no more than a few seconds. There is a way around that though. You measure the voltage after the filter cap and base the on off cycles on this voltage. So it will start basically always on till it reached the desired voltage.
terramir

[Martinm210]

Actually PWM does operate @ a lower voltage (not really but bear with me)
what PWM does is either switch it on or off so on the axis of time you have a bunch of 12 states and a bunch of 0 volt states, now if you capacitor filter that output sufficiently Before the capacitor you will see a bunch of 12V states and a bunch of 0V states, but on the other side of the circuit where the filter capacitor is you will see an average voltage that can be anywhere from 0 to 12V.
Let's say the 12V is on 75% of the time hence 0V is on 25% then the voltage after the filter capacitor should be around 9V if you use a filter cap that is too small you will get spikes in that voltage (that's where the humming comes from in some pwm controlled fans). Now let's say 12V is on 66.6% of the time then you'll get about 8V after the filter I think you see where I'm going with this.
So while the PWM circuit IS a 12V circuit because of the charging curve of a capacitor the voltage that is output is lower than 12V, there is also another danger, if you design the filter capacitor to high then it will take a long time for the voltage desired to be reached, however; unless you use one that is way over sized the delay should be no more than a few seconds. There is a way around that though. You measure the voltage after the filter cap and base the on off cycles on this voltage. So it will start basically always on till it reached the desired voltage.
terramir

Interesting, thanks for sharing

So, in essence, the fan will see voltage control, but the controller is converting 12V to a lower voltage through PWM + Capacitor?

The advantage of this is simply not generating heat in the controller?

Sorry for the dumb questions, just trying to get at least a little pinky around the topic. I've had a few people indicate on my 38mm fan tests that the problem is lower voltage, and PWM is the better way to go....yet it sounds like this controller is converting PWM to lower voltage. Why not leave it PWM if PWM is better?

[Church]

Why not leave it PWM if PWM is better?

Because some analogue, not pwm fans might get extra noise under pwm regulation. IIRC In normal 4pin pwm fan there is separate wire for pwm synchronisation, that solves that issue, but with analogue fan with normal 3pin these voltage spikes might differ at different rpm at which point coils should actually charge and push to turn rotor and at one position have more voltage, at different less, so possibly resulting in that extra noise.
Otherwise pwm of course is better then analogue regulation in several ways - it's circuitry is cheaper, as doesn't require monstrous heatsinks to dissipate redundant power, it can handle much higher current, with pwm minimum rpm-s can be lower (as less of a problem minimum startup voltage to start turn motor, because it's always full 12V or 0V). But probably because that pwm rpm regulation is newer, and many analogue fans/pumps exist, some choose analogue regulation as safe bet for everything. (eg. Aquaero).