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  1. #1
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    Question 12V DC Battery Power to 12V AC Power Conversion



    ok i'm a bit stumped. I have an inverter which can convert from 12V to AC (modified sine wave) but I want a portable power source for 12V AC for the 1 rpm motors.

    I found several methods to do this some very easily converting to AC quite cheaply.

    The cheapest source seem to be electroluminescent inverters which convert either USB power to AC (although quite high Hz)

    USB 5V DC to AC inverter EL Lamp Foil Wire electroluminescent | eBay

    or AA Battery packs to AC (although quite high Hz)

    12V battery to AC Power inverter EL electroluminescent | eBay

    I have read you can use cycloconverters to change 700-1000Hz to 50/60hz but despite thyristors and such talk I can't find any product that can do this cheaply and is portable. I just found Frequency converters may do the trick but this guy may fit the bill lol but does not for portability:

    http://www.ebay.com/itm/Mitsubishi-f...item3a6bf7846d

    Any ideas (maybe something more safe too? ) here I'm close to getting something I hope to save my AC motors.
    Name: Gus OTAs: ED 100 PRO refractor, Orion ST80 (not the CF), 8" Dob stuck in Canada Mounts:HEQ5PRO Synscan mount, Manfrotto Tripod CAMS: Guidecam Philips SPC900 webcams (4), Canon unmodded-450D DSLR

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    Seems like the EL converters make a square wave and not a sine wave... I heard this is ok. If you dump the electrons into a transformer like this:

    http://www.ebay.com/itm/50Hz-60-Watt...item2569e112b1

    will this get the Hz down to 50hz?
    Name: Gus OTAs: ED 100 PRO refractor, Orion ST80 (not the CF), 8" Dob stuck in Canada Mounts:HEQ5PRO Synscan mount, Manfrotto Tripod CAMS: Guidecam Philips SPC900 webcams (4), Canon unmodded-450D DSLR

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  3. #3
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    Default

    Quote Originally Posted by admin View Post
    Seems like the EL converters make a square wave and not a sine wave... I heard this is ok. If you dump the electrons into a transformer like this:

    50Hz 60 Watt Voltage Converter Electronic Transformer | eBay

    will this get the Hz down to 50hz?
    That won't work.

    That's a AC to DC step down transformer. It's taking 220/230V AC and converting it to 12V DC. It won't work backwards.

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    Default

    Gus, why not simply use a small UPS and a 120vac to 12vac transformer?
    SXINIAS

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    Just let me get this straight quickly.

    You've got 12V AC motors that you want to run off a DC (Battery) source, correct?

    Something like this: Mos-Fet Power Inverter might be helpful, but it seems like a lot of effort to convert DC to AC, much more than going AC to DC.

    Honestly, if I were you (and I'm planning on doing something similar as per your other thread) I'd cut my losses, sell the motors you've got now on eBay and order 3-12V DC motors and gear them to 1rpm.

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  9. #6
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    Default

    What about a 12v dc to 120 v ac power inverter ,then a 10 to 1 step down transformer.. ?

    good luck
    kev
    day sleeper since 5/22/2010
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    Default

    Hi Kev and Joe, yes I have a 12V DC to 240V AC inverter and also a 12V AC power supply but I hoped not to go this route carrying all these and a big 12V battery but I could still get a few hours running of the motor out on the balcony with this setup.

    I will also try the MosFet Inverter I found that during my searches but was not sure how to build it exactly, will try it as a project. thanks!
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    Default

    I'm not sure what your application is, but I will assume the 12 VAC motors are driving a scope. If so, your problem may be much more difficult than you have discussed so far. The rpm depends on the sine wave being stable in time and exactly the right frequency.

    Common inverters chop the dc at high frequency. A simple relaxation oscilator will give you what ever low frequency you want. But it may not be stable.

    Getting the right sine wave is a lot more effort than just any old 12 VAC.

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    First of all, are you sure you need 12 volts AC ? If there is a controller that the motor uses, many times the controller is taking AC and convertering to DC and motor and controller are actually running on 12 DC.
    If that is case it doesn't matter, with in reason what the frequency or voltage is. So for example the frequency can be 65 Hz at 15 volts since this will all get converted to DC.
    Now if the motor is really running on AC then the frequency is critical since that determines the rpm. Since your down in Australia, the frequency should be 50Hz. So the simpliest thing is to take your 240 VAC inverter which should be also putting out a modified Sine wave at 50 hz and use a wall transformer which goes from 240 to 12 VAC. Now you have the correct AC voltage and the correct frequency.

    - Dave

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    I would agree with cutting your losses and going down the DC route. Apart from all the wires and plugs you will have, remember 120 or 240 vAC is dangerous dew on equipment and on hands only makes it worse, add in tiredness and darkness Bob

 

 
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