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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.