12AC variable voltage

[Harpz]

Hi
We brought our youngest one of them bubble lamps for Xmas, the ones that you fill with water drop in the unicorns and rainbows, turn on and a little pump in the base blows bubbles and the bits bob up and down.

This thing was going to replace her ageing night light but as soon as we plugged it in we found out how loud it was, no way it can be used as a night light.

I’ve opened up the base inside is the LED board and a small 12v ac pump, both there are soldered directly to the barrel jack on the side of the thing.

The power brick outputs 12v ac, 300mA, 3.6W according to the tag on the brick, looking online I can see there are versions out there that have a knob on back that adjusts the output of the pump thus making it quieter.

My question, how simple would it be make something or buy something that would give me control over the voltage to the pump, thus making it quieter, Is it as simple as soldering in a potentiometer in line with the pump, it’s been many years since I did anything remotely like this.

looking online I see plenty on 12v dc control boards that would allow me to achieve this but none for 12ac.

Thanks in advance.

 

[Martaine2005]

You could put a diode in series with the ‘brick’ power supply. Then use a DC controller.

Martin

 

[Harpz]

You could put a diode in series with the ‘brick’ power supply. Then use a DC controller.

Martin

Would that affect the pump though as that says it need 12v ac input?

 

[Harpz]

You could put a diode in series with the ‘brick’ power supply. Then use a DC controller.

Martin

You got me thinking, may of solved my own problem, just want to check that this should work,

I could use something like this to convert the incoming AC to DC
AC-DC Converter 6/12/24V to 12V Full-bridge Rectifier Filter Power Supply Module: https://ebay.us/q2nfwQ

Replace the AC pump with a 12 DC version
KOGE DC 5V-12V 6V 9V Small 370 Air Pump Oxygen Pump for Water Aquarium Fish Tank: https://ebay.us/rqYTpb

Then finally control the pump with
Low Voltage DC PWM Motor Speed Controller Module 1.8V 3V-5V-6V 12V 2A R8L6: https://ebay.us/EUKArW

Do you thing this would work?

Thanks again for getting the old brain going

 

[Martaine2005]

Yes, that would work, but the motor you have may run from DC.
Try it, it will either hum and not move or work perfectly.

Martin

 

[Harpz]

Yes, that would work, but the motor you have may run from DC.
Try it, it will either hum and not move or work perfectly.

Martin

Don’t think it will work as it’s not a motor as such, its a transformer that attracts and repels a magnet on an arm connected to a diaphragm, its nothing like the pump / motor I linked above.

Thanks for confirming the bits I linked should play nice with each other.

 

[Martaine2005]

Ah ok, a diaphragm rather than a motor with impeller.


Martin