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How to make 230V inverter for small aquarium pump?

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suhasm

New Member
I am making a science fair project in which I'll need to pump water through a small distance. I am using a small submersible aquarium pump (5W) for this purpose. I don't want to meddle with 230V mains since water is involved.

Can anyone give me any ideas for making a low power inverter for this purpose?

Will the pump need a modified sine wave or will it work on a square wave?

I am thinking of using a H bridge made out of TIPS/3055s driven by a 555 to produce 60Hz 12V AC which will be stepped up by a 12-0 transformer.
Will it work?

I want to keep this as simple as possible and don't want to go for readily available circuits from circuits.com ect as i will understand nothing by building them.

Efficiency doesn't matter. I would be happy if it runs for 15 mins when it is powered by a 12V 8 AH battery.
 

Sceadwian

Banned
As long as you take care of your cables properly there's nothing wrong with using mains voltage near water, as long as this isn't a swimming pool just a small project. Simply use fast blow fuses on everything, and if use a ground fault interrupter at the outlet. Then just make sure everything is covered and that you have a vertical u shaped loop in the cables to prevent incidental water drops from traveling down cables into electrical outlets.
 

blueroomelectronics

Well-Known Member
Then it would make sense to try and find a 12V pump. There must be some available if you look and certainly cheaper than a 12V to 220V inverter.
 

Sceadwian

Banned
I'm assuming your pump is 230VAC is that correct? If that's the case at 5 watts an inverter is still going to be able to supply lethal currents at a high enough voltage to get it going, or at least shock you stupid if there's water involved.
 
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tcmtech

Banned
Most Helpful Member
The simplest and crudest inverter design you can get that will work for small loads is this.
Its a free running oscillator of sorts and the capacitor on the output is going to dictate what frequency range it runs at.
All you need for 12 volt opperation is a basic 18 - 20 volt center tapped transformer, two transistors or Mosfets, two resistors and the AC capacitor.

You will need to select the right value for the resistors depending upon what gain your transistors have. This circuit does work with Mosfets and the resistor values are much higher for voltage controlled switching devices so the overall circuit does get a little efficiency boost when using them also.

The AC capacitor needs to be sized for the transformer and the load but the over all circuit does give you a fair sine wave output but the frequency and AC voltage does drift a little depending upon the load.
 

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Hero999

Banned
I'm assuming your pump is 230VAC is that correct? If that's the case at 5 watts an inverter is still going to be able to supply lethal currents at a high enough voltage to get it going, or at least shock you stupid if there's water involved.
If correctly designed it does have the advantage of being isolated from earth so you have to touch both wires to receive a shock.

Also, if the current was limited to a maximum of 25mA, it would be unlikely to give a lethal shock, although it certainly would be a nasty shock.
 

Sceadwian

Banned
If properly fused, ideally with an over current crowbar circuit, straight mains isn't that dangerous.
 
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KMoffett

Well-Known Member
Could you adapt the 12V pump from a auto windshield washer ?
Windshield washer pumps have plastic bearings and are meant to run only a few seconds at a time. The bearings will melt if run more than that. I went through several trying to make an automatic Christmas tree watering system. :( I used the desktop fountain pump in the end. :)

Ken
 

suhasm

New Member
I'm sure that using a low power inverter is much safer than using the mains supply directly.
I don't think i can order things online as my parents wouldn't permit it.:mad:
I tried powering it up with a 12W inverter made for CFL lamps. It didnt work. The CFL lamp inverter is probably a square wave inverter.

No suggestions? :(C'mon ppl. I'm sure you all have loads of ideas. Atleast tell me if the pump will work with a square wave.:confused:
 

mneary

New Member
I have plenty of ideas. But all of them involve getting a $10 (US) 40W inverter made for automotive use. Sold in auto parts stores. I guess I'm not as creative as you would like me to be.
 

arunb

Member
the submersible pump you are talking about is a sealed one. We use this in coolers in India.

Its quite difficult to get a shock with this kind of a pump as they are sealed. But they are quite un-reliable though and tend to fail after a few months of running.

But I suppose they would work well in your aquarium as the water is usually clean.

We used a similar pump for our hydroponics project, it was powered by a UPS (external batteries), as power cuts are frequent in our place.

We never had any problem with the pump. Make sure the UPS is a fairly good one.

How many hours of backup do you need ??

I suppose if you have an inverter in the house, it would work very well.

thanks
a
 
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Hero999

Banned
I tried powering it up with a 12W inverter made for CFL lamps. It didnt work. The CFL lamp inverter is probably a square wave inverter.
That wouldn't work for the following reasons:


  • Incorrect voltage, CFL lamp inverters output a constant current, the pump requires a constant voltage.
  • The frequency is far too high, CFL inverters work at >20kHz, the pump requires 50Hz.
  • Not enough power, the motor requires 25W and the inverter puts out a few Watts at the most.


No suggestions? :(C'mon ppl. I'm sure you all have loads of ideas. Atleast tell me if the pump will work with a square wave.:confused:
We've made plenty of suggestions and someone has actually posted a schematic!

Perhaps you should read the thread.

Windshield washer pumps have plastic bearings and are meant to run only a few seconds at a time. The bearings will melt if run more than that. I went through several trying to make an automatic Christmas tree watering system. :( I used the desktop fountain pump in the end. :)

Ken
Did you try reducing the voltage?
 
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