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DC-DC Buck Convertor - 12V To 3.3V 5V 9V

I'm have looked around and can find individual schematics for making a fixed switching regulator 12v to 3.3v or 12v to 5v.. or an adjustable switching regulator that I can use to make a 12v to 9v convertor, but I can't find a schematic for a simple circuit that will take 12v from a battery and convert it to 3.3v, 5v and 9v. Anyone done this already?

I have found a 12v to 3.3v and 5v convertor, premade. It has two seperate regulators, but they share an inductor and other componants, making a cleaner unit. If this unit also supplied 9v, it would be perfect.

I am looking for either a schematic or affordable premade unit. I would like switching and not linear, and I would like to output 3.3v, 5v & 9v DC from one 12v DC input

Advise or suggestions welcome. Thank you.

Rick

 

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Bajdi's picture

BTW Sisco, 58.39$ for 5 LM2596 boards is super expensive. I pay 1.5$ a piece, from Chinese sellers.

Sisco's picture

I think it's a typo. The price was $8.39 for 5. I see the ad was edited yesterday and now the price is changed. I ended up ordering 10 from the same guy for $15.00 shipped, but thanks for the heads up.

Dan M's picture

They must have fixed it, because for me it says they are $1.78 each with free shipping.

Bajdi's picture

Yes output will drift (+-0,2V) as the mini PCB heats up (I'm talking after 1 hour or so with a +1A load). It is a 3A regulator but I would not recommend drawing more then 1.5-2A from it since the PCB can not dissipate the heat. Adding a heatsink would of course help. I have done extensive testing with lots of different switch mode regulators the last months. An LM2576 or LM2596 outputting 5V works best (most efficient/less heat) with an input voltage of 12V. Still I love these boards, you can't beat them at that price. You can not buy the parts for the prices they are selling them on Ebay. The great thing is the enormous benefit in efficiency compared to a linear voltage regulator.

Sisco's picture

Thanks for the info. I do have some 1/2 square copper heatsinks kicking around here, so that should not be an issue.

The price point is great. Like you said, you can't build one for that price. These should work great. :)

Rick

OddBot's picture

Although I could not find a schematic to support my theory, looking at the PCB you linked to, the regulators do not share the inductor. You have a 12V - 5V switchmode regulator with a 3A output and then an LDO regulator that drops 5V down to 3V.

It is unlikely you will be able to just buy an "off the shelf" regulator that has 9V as well as 5V and 3.3V.  You could build your own using a hand made inductor to give you the different voltages but it will cost a lot more than you can by two seperate modules for.

What do you need 9V for? If you want to power an Arduino then just bypass the Arduino's built in regulator and feed the 5V directly to the logic.

 

Sisco's picture

Thank you for the reply. I will probably just grab these...

http://www.ebay.com/itm/5PCS-LM2596-Step-Down-Adjustable-Power-Supply-Module-Output-DC-1-5V-35V-/160933911452

and mount a few on a backboard and mount that in my case.

 

Sisco's picture

I was hoping to find a unit that had multiple outputs, like the one I linked. It outputs both 3.3v and 5v, but I suppose I can just mount a few of them together and mount that. Thank you.

Rick

Chris the Carpenter's picture

You are about 98% to where you need to go on this one. 

Hit the Ebay again and look for the same thing, "buck regulator" or "switching regulator" --whatever you searched to get you to this current model. From there, you are looking for basically the same thing, but look for one that is A) adjustable and B) has a LED display. Some of the fancy ones ("fancy"=$7 instead of $5) have 7-segment LED displays on them to show the output voltage. Sure, you would have to adjust the little pot for different voltages, but hey, we're talking about 4 or 5 bucks here. (HA!  "bucks"!!)

 

 

Bajdi's picture

Search on Ebay for LM2596. You will find a massive amount of boards with an adjustable LM2596 voltage regulator. This is a 150kHz switch mode voltage regulator. It's an old design but still pretty good. Best of all they are dirt cheap.