Help i need to convert 12v dc to 12v ac....

[Wildsupra]

Hey guys chasing some electrical info and or circuit diagram or somewhere someone who could supply me with this.

I need to convert 12v dc (car battery) to 12vac at 32hertz, only needs to supply 400ua of power.

i realise i can buy 12vdc to 240vac ac inverters but im after something much smaller and i require much less than the average 150w upwards output.

Can anyone help? Either with a circuit diagram of how to build one with locally available components or can you supply them or know where to buy them etc?

Cheers
Matty

[RA35GT]

Matty didn't you post this a little while ago ?!?

[MWP]

Thats one weird power supply. Only 400uA (micro!) amps?
As always, the first question is... what is it for?

[RT40Corona4AGTE]

yeah I too want to know what it is for?

you sure it is 400 micro-amps and not 400 milli-amps?

[Cuzzo]

Bridge Rectifier?

[oldcorollas]

depends if you want a "clean" supply, a square wave AC, or sine wave AC etc etc..

[Hen]

Bridge Rectifier?

That's for going the other way (AC -> DC)

Maybe check what you're powering and see if the first part of the circuit is a rectifier or other power supply thingy. Maybe you could skip that part and feed it DC.

Or just find one that runs off 12VDC.

[Wildsupra]

square wave will suffice, output can be between 12vac and 15vac.
its directly powering an lcd display box which means i dont need all the other circuitry and processors hence the direct supply of voltage.
It draws very little current and unless i was provided with the incorrect specs from the manufacturer then yep just 400ua (400millionths of an amp)
I have powered it up from a dc source to check it works but i dont want to run the risk of polarising the crystals hence needing the ac supply.

Cheers
Matty

[oldcorollas]

third link from this search.. the "basic theory" one has a link to document from somewhere.. might help

[wilbo666]

Sounds like a H Birdge will sort you out

http://en.wikipedia.org/wiki/H_bridge

Cheers
Wilbo

[23T-GTE]

could you try using a 12vdc->230vac inverter(readily available) and then use a tiny 230vac->12vac step-down trannie..?
not sure if you can buy inverters with adjustable output frequency to get your 32hz.. otherwise the inverter would probably make ~50hz.

[23T-GTE]

or could you rip the power supply elements that produce the 12vac32hz out of the other equipment? or replicate what they use to make it?

[TERRA Operative]

Get a cheap, simple inverter, and remove everything from the transformer onwards, so you just have the AC supply to the now removed transformer.
Smooth the AC as required and trim the voltage.

Otherwise a basic astable multivibrator sort of setup may work for those currents. I would be thinking it would be millivolts though, how big is the panel?

Or you could google it...
http://www.google.com.au/images?q=inverter%20schematic
Second image, swap the transformer to a 1:1 type and adjust R1/R2 and C3/C4 to get the correct frequency. Make sure the resistors and capacitors are the same respectively to ensure a symmetrical waveform.

[Wildsupra]

There was no transformer, power supply or any electrical stuff provided with the screens. im starting from scratch as i was initially led to believe they would run on 12vdc.
This of course is true but can anyone tell me how long it would take for the liquid crystals to actually polarise?? Does anyone know if we are talking minutes, hours, days or weeks of use?

That H Bridge is looking like the easiest and cheapest option so far, only thing is that it seems to use a very low input voltage for the logic drivers. The 12v outputs at approx 100ma is perfect though. Im thinking the actual hertz rating is not so important as the screen doesnt actually display any charactors or keep time so its possibly not so crutial.
Basically i think i need to switch the current just so it avoid the polarising problem.

Any more thoughts?

Cheers
Matty

[wilbo666]

Do you need one of these, a hundred or multiple thousands?!

Would be good to know what sort of scope you have

Cheers
Wilbo