Anyone else get a wp40 wave maker yet?

[blanden.adam]

That's an interesting post. However, I'm a touch confused about the assertion that the wattage is maintained (which would necessarily cause current to increase with decreased voltage). Because the speed is lower, won't both the wattage and the voltage be lower? I feel like I'm missing a crucial piece of information.

 

[reefboarder]

Mine came in today and my first thoughts are that it is great. I have it on wave 1 which is the biggest of the flow settings. My torch is swaying this way and that instead of the laminar flow pattern of three k-4's blown at various angles but in the same general direction
With those running and the wp40 it seems to keep stuff suspended in the column a lot more and it breaks up the flow pattern which was what I really wanted to do.

 

[ReeferSteve78]

Can you use the outlet that comes with it or you have to order one?

 

[reefboarder]

I ordered mine from eBay for 118.00 and it was here from Pensacola Florida in three days. But Yes the cord and power supply were ready for 115v and the US standard plug end.

 

[Conesus_Kid]

Here's a link to my poorly paraphrased explanation: http://www.reefcentral.com/forums/showthread.php?t=2259644&highlight=wp40&page=108

 

[blanden.adam]

OK, I get it now. The whole crux of the early wear thing is because of the assumed constant power consumption. IDK how that could be true considering the pump runs slower, so it stands to reason power consumption should be reduced, but I am by no means an electronics expert, so I could be completely off point. However, I'm still going to run the pump with the variable power supply and see what happens.

Pumps just came in today. 7 days from Hong Kong, not bad. Now to go play with them

 

[SkiFletch]

Has anyone figured out what the motor is? Are we dealing with a Brushed motor with some kind of MOSFET and/or PWM control circuitry inside the pump housing itself? Or is this a Brushless 2 or 3-phase motor?

 

[der_wille_zur_macht]

The "constant power assumption" is 100% false in this application. You can disregard that argument. It's based on the assumption that the work done is constant. With a pump, that is not the case. As the RPM decreases due to a lower voltage, the work performed (water movement) also decreases, and hence the current drawn decreases.

In other words, taking his example, if the pump draws 30w at full speed at 24v, it will draw way less than 30w if you drop the DC voltage down to 12v.

 

[der_wille_zur_macht]

so it stands to reason power consumption should be reduced, but I am by no means an electronics expert

Your reasoning is correct - and this is arguably a fluid dynamics problem, not an electronics problem. I assume that's why the poster quoted above got it wrong, he probably has an electronics background - when an EE studies motors, they're shown graphs that correlate low RPM to high torque because the assumption is that the load is constant regardless of speed, i.e. the work done is constant. In that case, this would be true - at a lower speed the motor would "have" to produce more torque to create the same work. And since current has a linear relationship with torque (similarly to how RPM has a linear relationship to voltage) the motor WOULD draw more current at a lower speed.

If you can visualize motor performance in three dimensions (torque (aka current, in amps) vs. speed (aka voltage) vs. work (aka power in watts) this will make sense. The poster above is talking about the torque/speed plane, assuming power stays the same. He's missing the fact that the third variable (power) is not constant in this application.

 

[der_wille_zur_macht]

And just to be totally clear and give that poster some credit, his logic is somewhat true when comparing constant voltage to PWM at a partial duty cycle. The current in the PWM example will be lower than the constant voltage example. But the key point here is that FOR BOTH examples, the current will ALWAYS be lower than under "full speed" at the nominal voltage.

So if the problem is choosing PWM vs constant voltage because of concerns over current, it's a totally moot point. There very well may be other arguments to using PWM but that isn't one of them.

 

[ReeferSteve78]

Just ordered mine. And now to wait for it in the mail

 

[007Bond]

Where did you order from, if you don't mind

 

[ReeferSteve78]

Fish street website. A lot more cheaper

 

[007Bond]

Thank Youuuu!

 

[octopus737]

I dont know squat about programming. However i will be getting an Arduino and will try to replicate a cresting reef. Trying to gather as much information from what is out there and it is overwhelming.

 

[SkiFletch]

Agree with DWZM. Motors operate similarly to resisitive devices in most cases. R is constant (or nearly so) in ohm's law V=IR. So if V drops and R is constant, I (current) must reduce. Lower current and lower voltage therefore equals less power, less heat, and less wear on the motor. Pumps that are frequently started (moving from zero inertia to positive ineritia) can have some current issues with starting, but we're not starting motors here all the time. These things run constantly, we're just varying how much they run. You can run a DC motor (either brushed or brushless) at a lower speed via a lower voltage with no extra wear on the pump. That's one of the beauty of DC motors. I've been running DC motors at voltages lower-than-rated for years via variable linear power supplies. They run quieter, cooler, and last longer at lower voltages...

 

[Conesus_Kid]

Pumps that are frequently started (moving from zero inertia to positive ineritia) can have some current issues with starting, but we're not starting motors here all the time. These things run constantly, we're just varying how much they run.

Most of what you guys have posted is over my head, however I believe that the W1 mode on these pumps is a start/stop wavemaking cycle. I don't know if this has any impact at all, but just wanted to make sure everyone knew this.

 

[der_wille_zur_macht]

Obstacles with respect to starting torque will be both obvious (it won't start) and easy to fix (start it at a higher speed, then ramp down to the speed you want).

octopus, this would be a good first Arduino project! I'm sure there are already people working on something.

 

[SkiFletch]

It might Scott, but in a submersed aquarium environment where the pump is always heat-sunk to water, the slightly higher current required to start the motor from zero inertia wouldn't cause a heat problem which is most of the trouble with long-term wear. That would of course depend on the type of motor (brushed or brushless) if it was even a possible concern.

 

[der_wille_zur_macht]

Startup at partial voltage is not going to cause appreciable extra wear due to excessive current in this case. There's very little inertia, the "extra" current is going to be less than a fraction of a second. Go plug a maxijet in and see if you can determine how long it takes it to get up to speed. It's probably so quick that you don't even notice. That's the timeframe that it'll be drawing extra power.

Again, this is a valid concern, just not in this application. If you were talking multi-HP motors that were started hot with no cooling and were spinning gigantic heavy pieces of machinery I'd be worried. On a pump motor pulling a few hundredths of a HP sitting immersed in relatively cool water it's not an issue.