1. OCAU Merchandise now available! Check out our 20th Anniversary Mugs, Classic Logo Shirts and much more! Discussion here.
    Dismiss Notice

Trying to power a 12VAC pump with 12VDC

Discussion in 'Electronics & Electrics' started by Thraxeh, Dec 27, 2019.

  1. Thraxeh

    Thraxeh Member

    Joined:
    Nov 23, 2003
    Messages:
    4,348
    Location:
    Sydney Australia NSW
    I have setup up a 12vdc battery and solar panel charging system to power a 12v pump once each day for a balcony plant irrigation setup.

    Its all coming together. I was ready to connect the battery to the pump etc, however I discovered the water pump actually runs off 12VAC.

    I have tested the pump on DC and it doesn't work. The only solution I have at the moment is source a DC pump, or try a circuit to invert 12VDC to 12VAC

    The problem I find is that all the circuits out there require a transformer, and you can't find 1:1 12v transformers. Its all step up/down etc. Is there another simple way to do this?

    edit: I did find this - are points A and B the AC output?

    https://electronics-project-hub.com/wp-content/uploads/2018/07/multi-vib-1.png
     
    Last edited: Dec 27, 2019
  2. Jazper

    Jazper Member

    Joined:
    Jul 28, 2001
    Messages:
    2,667
    Location:
    Melbourne Australia
    Last edited: Dec 27, 2019
  3. OP
    OP
    Thraxeh

    Thraxeh Member

    Joined:
    Nov 23, 2003
    Messages:
    4,348
    Location:
    Sydney Australia NSW
    Thanks for that. So I played around with this today and it has become clear that finding a DC pump/s will be best...

    So I now have 2 windscreen washer pumps and it looks like I can get the pressure/flow rate I need from them.
     
    grrrr likes this.
  4. Jazper

    Jazper Member

    Joined:
    Jul 28, 2001
    Messages:
    2,667
    Location:
    Melbourne Australia
    Be careful with those, they are not rated to continuous flow/on, short bursts are better than full on. DC motor driver may help here.
     
  5. OP
    OP
    Thraxeh

    Thraxeh Member

    Joined:
    Nov 23, 2003
    Messages:
    4,348
    Location:
    Sydney Australia NSW
    Yep, have that in mind too, they wouldn't last long going at full draw.

    I'm controlling both with a PWM controller, and as I have 2, each pump has to do even less of the work.
     
  6. koss

    koss Member

    Joined:
    Mar 6, 2009
    Messages:
    8,014
    Location:
    Vic
    Never heard of a 12v AC pump. What's the brand and model?
     
  7. OP
    OP
    Thraxeh

    Thraxeh Member

    Joined:
    Nov 23, 2003
    Messages:
    4,348
    Location:
    Sydney Australia NSW
  8. merlin13

    merlin13 Member

    Joined:
    Apr 12, 2003
    Messages:
    2,057
    Location:
    back in BrizVegas
    Short Answer? Suggest take that pump back to Bummings and go buy a suitable 12 volt DC one.

    Not a bad concept.

    But check how much noise they put out when running (because "balcony"), how long they'll continuously cheerfully run for before dying (saying that because I'm assuming "balcony" also involves "fountain/waterfall", yes/no?) and verify how much power they'll need to run.

    Oh, as an aside - that multivibrator circuit. Outputs will be a 12 volt (ish) square wave, not a sinusoidal one. Not a good idea feeding domestic AC powered devices with a square wave...

    But if you need to turn the output level of your washer pumps down, rather than choking or limiting the water input then feeding the pump(s) with a suitable square wave isn't a bad idea - that's called PWM control.
     
    mmBax likes this.
  9. oculi

    oculi Member

    Joined:
    Aug 18, 2004
    Messages:
    11,702
    I had a 12 volt AC pump in a fountain, got it running with the transformer out of a halogen desk lamp (that I always thought was DC) 12volt AC power wall warts are gettable but if you have DC supply then you should get a DC pump.
     
  10. koss

    koss Member

    Joined:
    Mar 6, 2009
    Messages:
    8,014
    Location:
    Vic
    Ok thel
    That sure says AC 12v on the power pack. Did you try the DC both polarities? eg. the pump may have a rectifier.

    I can't think of what motor would be in it that uses single phase AC at such a low voltage.
     
  11. oculi

    oculi Member

    Joined:
    Aug 18, 2004
    Messages:
    11,702
    Supplying an AC powerpack with a DC motor seems more likely to you than a motor running on 12 volt AC?

    I tried both polarities on the pump I later found out was AC, it just went "bzzzt" and make sparks.
     
  12. Privatteer

    Privatteer Member

    Joined:
    Mar 19, 2006
    Messages:
    863
    Two winding and a magnetic armature with a small cap on one winding is one way.

    There is plenty of 12V dc pumps used for caravan water etc available that can be used.
     
  13. Idafe007

    Idafe007 Member

    Joined:
    Feb 22, 2008
    Messages:
    162
    Location:
    Florida - USA
  14. grrrr

    grrrr Member

    Joined:
    Jun 30, 2001
    Messages:
    1,037
    Location:
    Cornubia
    Don't forget 12VAC is +12V to -12V (has a 24V swing) and rectifies back out to something like 18VDC not 12VDC. I know you have this sorted a different way, but to help explain the DC to AC conversion there are 2 starting options (and then tricky modifiers on how you actually do it):
    1. Convert the 12VDC to 24VDC(or more), then chop that up to make 12VAC
    2. Chop the 12VDC to make 6VAC, then use a transformer to step that up 12VAC.
     
  15. merlin13

    merlin13 Member

    Joined:
    Apr 12, 2003
    Messages:
    2,057
    Location:
    back in BrizVegas
    Seen small outdoor fountain pumps run low-level AC like that. Even seen some of those small indoor water features having AC pumps as well.

    Uh-oh. THAT might make any return policy somewhat invalid...

    Ummm, no. Sorry, but just... No.

    Unless otherwise specified AC voltage levels are usually deemed to be as RMS, not Peak-to-Peak like you posted there. Ask Uncle Google or any sane electrician/electronics engineer...
     
  16. oculi

    oculi Member

    Joined:
    Aug 18, 2004
    Messages:
    11,702
    The fountain was free, think I ended up giving it away with the transformer.
     
  17. Symon

    Symon Castigat ridendo mores

    Joined:
    Apr 17, 2002
    Messages:
    4,764
    Location:
    Brisbane QLD
    I've seen 6V AC shaded pole motors before that drive the turntable in microwaves. Old school mechanical clocks sometimes had a plug pack that dropped the 240 down to 12V AC and then a shaded pole motor for the movement.

    12V AC is 12*1.414 = ~17V peak, or 34V peak to peak.
     
  18. koss

    koss Member

    Joined:
    Mar 6, 2009
    Messages:
    8,014
    Location:
    Vic
    I have seen lots, typically in fan heaters and other domestic appliances, but they have always been 240v. I would have thought not cost effective for a pond pump, but I guess if they designed it a long time ago. If it were me, I would be pulling the pump apart to see what was in it.

    The easiest way to run it would be just get a DC to 240v AC inverter like you run in a car or truck, and run the pump plug pack with that.
     
    Last edited: Jan 1, 2020
  19. Symon

    Symon Castigat ridendo mores

    Joined:
    Apr 17, 2002
    Messages:
    4,764
    Location:
    Brisbane QLD
    A shaded pole motor is about the cheapest type of motor you can make.

    It's a $50 item, just get a DC one. Getting an inverter just for this is nuts.
     
  20. mAJORD

    mAJORD Member

    Joined:
    Jun 4, 2002
    Messages:
    11,227
    Location:
    Griffin , Brisbane
    An AC pump is more cost effective to build than any DC.

    It would look exactly like a 240 pump inside , but it'd be potted so you won't see it
     
    Symon likes this.

Share This Page

Advertisement: