Motor control

[kamlesh barot]

Hi,

For my aquarium hobby at home, I'd purchased the below fan (motor) to circulate the water in my aquarium, for flow. There are two problems I need to request just an approval, if I can go ahead or not.

The first problem is that when I start the AC 220v circulation motor, sometimes it rotates clockwise and sometimes anti-clockwise. When I switch it on and off a couple of times, the desired rotation is achieved.

The second problem is the motor rotates very fast and the entire plants, soil and fish keep getting blown away. It consumes 6 watts per hour, which with the speed control I'd also like to bring down the 6 watts to 2 or 3 watts power consumption, per hour.

I had come across the attached motor controller on amazon, which says it will make the rotation in the correct direction and the speed can be regulated. On the internet I found in a chat that if there's a mistake made, the motor could catch fire, though the motor is immersed inside the water.

I need only some expert on the is forum to read both specs and tell me if it's ok to buy the controller, for my wavemaker motor. Thanks in advance!

Wavemaker motor already installed:
Size:WP-200M
Sobo Wave Maker WP-200M

Sobo Wave Maker WP-200M provides powerful water circulation for strong and consistent flow. Energy Saving and Eco-Friendly, Excellent for both marine and fresh water, Does not overheat and operates quietly, suitable for coral decorations, Also great for waterfalls, fountains, skimmer and multi tank aquariums. High performance with minimum power consumption. It can be easily mounted with its powerful suction cup, Reliable, extremely silent and easy to maintain.

MODEL: WP-200M

Voltage: 220V - 240V
Freq: 50/60Hz
Power: 6W
Amount of water displaced at a height of H.MAX: 0.8m, F.MAX: 5000L/H
Dimensions: 16*10*10

AC motor controller to buy is in the attachment: https://www.amazon.in/gp/product/B01EF2XMMQ/ref=ox_sc_act_title_2?smid=AT95IG9ONZD7S&psc=1

Description of this controller I want to buy: With reverse polarity protection, high current protection high temperature fr-4 circuit board maximum power: 2000w voltage: Ac 110-220v voltage regulation: Ac 50-220v size(lx w): Approx. 46 x 35mm how to use: This product series with the lamp or electrical circuit, table lamps, appliances disconnect any firewire or zero line (ie a "product" two wires connected to both) rotary potentiometer spin rod, you can play light and shade adjustment, speed, pressure, the role of the thermostat, use very convenient. This product is applicable to: The use of new two-way high-power thyristor can be very convenient to adjust the mains current up to 25 a, and solve the the overcurrent problem of the heating wire resistance is too small in the case of cooling causing good, the output voltage is adjusted anywhere between 90 to 220 volts for use with electrical appliances. Such as: Electric stove, water heater tune thermal, lighting dimmer, small motor speed, electric iron thermostat. So as to achieve dimming, thermostats, pressure regulator effect. Large appliances available, power consumption is less than 2, 000 watts of power has sufficient home appliances or small factories. (Inductive or capacitive load power should be reduced, the regulator is equipped with two-way high-power thyristor, potentiometers are with nuts, do not have to add any components will be able to use, very convenient and practical). Package includes: 1x high-power controller.

Thanks,
Kamlesh

 

[c_mitra]

Your regulator is for high power loads (typically 2 kW) and it MAY not work for loads that are very small (your motor is 6W). You may just use a couple of power resistors to reduce the speed.

By the way, your motor, with power of 6W, can pump 5000 L/H - surely an overkill. Unless your fish tank is like a small pond.

Can you please share a photo of the motor (and pump)?

 

[kamlesh barot]

Your regulator is for high power loads (typically 2 kW) and it MAY not work for loads that are very small (your motor is 6W). You may just use a couple of power resistors to reduce the speed.

By the way, your motor, with power of 6W, can pump 5000 L/H - surely an overkill. Unless your fish tank is like a small pond.

Can you please share a photo of the motor (and pump)?

Thank you so much for your reply c_mitraji. PFA the pictures.

If you could please guide me, how and what to use for the couple of power resistors to reduce the speed, I'll do that immediately. Will that reduce the watt consumption as the motor has to be kept on 24x7? I know a bit of soldering etc.

Would request you earnestly to give a few details, as I'm not an engineer.

 

[c_mitra]

The motor voltage is 220V and the power is 6W. Hence the current is about 30mA. This is going to run the motor at full speed.

To get the motor running at 1/2 speed, you need a series resistor that will drop about 1/2 the voltage. How much resistor value will be needed?

Approx value will be 220V/30mA=6.8K (nearest standard value). What will be the power rating? About 1/2 of the motor power, say 4W.

If you cannot find a 4W resistor easily, just get 4 1W 6.8K resistors and connect them in 2S2P. If the speed is too low, you can reduce the resistor value, say 4.7K. If you want it still slower, just incrrease the resistance value, say 8.2K.

Try to put these resistors inside the power plug and wrap them with a generous PVC insulation tape.

If you want a variable control, use a 10W power potentiometer with a 10K value. Connect it like a adj resistor. Please ensure electrical safety (wrap with lots of insulation tape).

 

[KlausST]

Hi,

Safety first: mind that you handle with dangerous voltage
Knowledge of safety, proper isolation while maintaining air flow at the power resistors is essential.

@c_mitra: you did not care of motor phase shift.
Anyway .. a good start for the OP.

Klaus

 

[Kajunbee]

CMitra , Klaus , The OP states that motor turns different direction each time he starts. This sounds to me that it is a synchronous motor which doesn’t make since for a pump. If so how do you make it start in same direction every time. Or could there be another reason.

 

[Kajunbee]

From what I understand in the red circle there is a rubber piece that bumps the prop backwards when it starts it wrong direction.

 

[c_mitra]

@c_mitra: you did not care of motor phase shift.

Small low power motors running at 220V appear mostly resistive in nature.

For a rough (means crude) regulator, a simple resistor may be sufficient - he just wants to reduce the speed somewhat.

Accurate speed control is =not possible without detailed idea about the motor.

Thanks for the reminder about the safety. I have received electrical shock from an aquarium.

 

[kamlesh barot]

Thank you all for your guidance. Yes, I've a problem of the fan motor rotating in the wrong direction, I've to restart it 2-3 times to make it start blowing instead of pulling.

I found a potentiometer as per the reply from c_mitra on Amazon with three connectors, which I'll have to ask how to connect it to my two pin plug. Have attached the picture. Should I buy it?

 

[c_mitra]

I cannot guess why the motor starts rotating in the wrong direction at random; but the potentiometer does not appear to be 10W rating.

It will burn off very soon. Not worth even trying.

If you cannot get a suitable power potentiometer, better to use a series dropping resistor.

 

[KlausST]

Hi,

And again: safety!!.
This tiny potentiometer with metal shaft surely is not suitable for mains applications.
You risk electric shock ... worst case death...

Klaus

 

[d123]

Hi,

I sort of can see a lot of ignorance in the following question, based on my only having used simple DC motors where polarity defines direction, but I'll ask anyway: Is the clockwise or counter-clockwise start-up behaviour related to which half of the AC signal (positive-going or negative-going) the motor terminals are first powered by at turn-on/when the fan is plugged in and starts?

--- Updated Apr 4, 2021 ---

CMitra , Klaus , The OP states that motor turns different direction each time he starts. This sounds to me that it is a synchronous motor which doesn’t make since for a pump. If so how do you make it start in same direction every time. Or could there be another reason.

An obvious reason why the erratic and consequently useless start-up behaviour is that of a sub-quality-control product only fit for poverty penny stores and online marketplaces is what anyone (such as myself) forced to buy 'buy-today-cheap, broken-by-tomorrow-quality' is one we are bitterly aware of...

 

[Kajunbee]

From the reviews nearly everyone says they start backwards. The motors in microwaves behave the same way. As the saying goes, you get what you pay for. I don’t have a money tree in my backyard so I’m forced to buy cheap also.

 

[c_mitra]

From the reviews nearly everyone says they start backwards.

It is not easy to guess the type of motors being used in any given application. But shaded pole induction motors are cheap and efficient.

They can be run (low power types) from the mains and are simple in construction. But I do not know how they can start running in random directions.

Like many other items you can buy in the market, the quality has only a very remote connection with the cost and sales price. The motor in the CD-ROM drive (how many motors are there in the CD-ROM drive? I have dissected a few) are definitely cheap but certainly not low quality. Modern motors are very rugged too.

I am not sure but most likely some coils (it is certainly not a shaded pole induction motor) have gone bad and is making poor contact. However, it is not possible to say much more without seeing the physical device.

 

[BradtheRad]

A few AC motors I worked on (usually from a disassembled clock) made a single knock at power-up. While holding the motor I got the idea an internal part hit a notch and shifted position. At the same time I seem to recall the output gear changing direction. It only happened part of the time so I believe it's to guarantee the motor runs in the right direction.

 

[kamlesh barot]

Thank you so much each one of you, for your detailed analysis and comments. What has scared me is the word shock & death ☠.

Searching all over amazon only shows me (https://www.amazon.in/s?k=10+watt+10+k+potentiometer&ref=nb_sb_noss) these 10k potmeters without any, showing 10 watts. These resistor pages are equally as confusing for us laymen: https://www.amazon.in/s?k=1W+6.8K+resistor+4.7K+8.2K&page=2&qid=1617618663&ref=sr_pg_1.

Is this such a complicated thing, I thought like a fan regulator, there should be something very easily available to turn down the speed of the motor, forget the wrong direction starting. That can be dealt with.

As you pals have said fixing the potmeter or the resistor both, will have life-threatening issues, am now more confused than ever!

I can buy the resistors from the Lamington road shops, but soldering them on both ends of the 2 pin plug, meaning shorting the positive and negative wires or cutting the red live wire and soldering the resistor in between, don't have any idea now, how to reduce this 6W power to 1-2 watts, thereby the speed of the water, pushing all of the hard-work in making plants setup!

 

[c_mitra]

A few AC motors I worked on (usually from a disassembled clock) made a single knock at power-up.

Most common wall clock movements use Lavet type stepper motors: see for details https://en.wikipedia.org/wiki/Lavet-type_stepping_motor

These motors turn only in one direction and this is fixed by the stator geometry. Yes, it looks more like black magic!!

These stepper motors with a PM rotor are usually very reliable (losing time only if the battery is low) but there are versions that appear to move almost continuously. So the second hand moves almost continuously rather than in fits and starts.

The rotation direction is fixed in the stator geometry and I shall love to call them a kind of variable reluctance motor.

There may be other types but my knowledge is limited.

 

[d123]

Hi,

What is the reason for the wavemaker fan? Is it the same reason as for freshwater tanks with goldfish - to keep the water moving so it doesn't stagnate? Or, is it for the plants?

I've seen photos of those/similar fans where the fan is clipped onto the top of the tank, out of the water. MUCH safer. Not sure if yours has to be submersed or can be out of the water too... Outside the tank could get rid of need for the potentiometer as presumably more force would be needed for the same amount of water circulation, and a big plus would be that the erratic start-up polarity/motor direction would no longer matter. Also, that way you would expect that the plants wouldn't get blasted around the tank.

I think you have a bubble machine or two (aerator) in the tank from what I see and you must have a filter there... When I had goldfish in a 240l tank (~ 200l of water), I used two aerators at either end of the tank and a filter output pipe with holes all along it that could be positioned to return the water to the tank at or above the surface - it was (very) good and good enough to keep most of the fish I had alive for years (one lived for nine years, 'Shark' , big orange carp, sad to see him/her go after so long together...).

Me, I'd re-think this solution if it could be KISSed instead.

--- Updated Apr 5, 2021 ---

Just remembered: I absolutely hated cleaning the tank or water change or tidying plants in winter when the heater was in there - insanely dangerous devices IMO... I'm sure you'll know what I'm referring to: thin-looking tube made of glass containing 30 or 50 Watts of electricity + water + your hands... Unplug first or what?!

 

[Kajunbee]

If you want to give it a shot you could try reducing the prop size like in video.

 

[c_mitra]

cutting the red live wire and soldering the resistor in between,

This is the correct way.

Safety precautions are a must. Cover the resistor and the soldered region with a generous amount of insulating tape.