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Author Topic: ~RECOMMEND A BUCK 12V-5V DC converter?  (Read 1979 times)
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Im looking for a high amp converter to take a solar battery at 12V down to 5V for large LED arrays? any recommendations ? I hope to have at least 10 amps.
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10A @ 5V is a lot of current for one wireon either side 12 or 5. Personally I would use several smaller 2 or 3 amp converters like one of these for $1.59 ea: From Chip Partners on Ebay.
http://www.ebay.com/itm/1pcs-DC-DC-Buck-Converter-Step-Down-Module-LM2596-Power-Supply-Output-1-23V-30V-/251066005460?_trksid=p2045573.m2102&_trkparms=aid%3D555001%26algo%3DPW.CURRENT%26ao%3D1%26asc%3D34%26meid%3D2232964115197841127%26pid%3D100034%26prg%3D1030%26rk%3D1%26sd%3D170880554877%26
The LM2596 is good to 2 A and your best shot for a reasonable and affordable power supply. It is a "reference" design recommended by National Semiconductor for their part and well tested. I did find several 10 to 20 A switchers but they were in the 15 - 20 dollar range.

Doc
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I think you get higher losses at 10A - in the switcher, wiring etc. I would series connect more LED's to up the voltage, or break them up so you can use smaller 2-3A switchers.

Doc, I tried a few of the LM2596 switchers from eBay, I was going to use one for an iPad charger. They just don't have the heatsinking or diode rating to dish out 5V@2A from 12V, so for $1.59 they let me down. They run quite hot.

DX has some "10A" ones but they are potted: http://dx.com/p/dc-12v-24v-to-dc-5v-car-negative-booster-power-converter-silver-149111?item=14

A cheap buck converter will fail and overvoltage your load, so I don't cheap out on them anymore.
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If you read the instructions they are clearly marked... for continuous loads blah, blah , blah... it's the bla, bla that you didn't follow. Most come switchers with a warning about heatsinking and soldering the area under the switcher IC to a heatsink a 12 mm X .5 mm piece of copper about 4 cm long bolted to an aluminum panel or heatsink. It CAN be soldered to (that's why there is no solder mask there). I've used several of them W/'O problems...  as cheap as they are I just use one for every 1 - 1.5 A. A bigger switcher is probably better for you as someone else has done the engineering for you... I do my own, I don't trust others to do my work for me because it is frequently bad... Not so much defective work just that there is mo more work done except the bare minimum... I also used 1,5KE6.8 tranzorbs with my switchers "Just in case". My single point was to be that it is a lot easier to make it modular and distribute the voltage to the switcher than it is to use heavier copper wire to avoid I R losses. much smaller wires that cost less money and are easier to work with... But that's ok. I'm outta here.
If a power supply says 2A did you look to see if that was continuous, did you take a look at the Mfr's data sheet for the device and check to see what would be needed for 100% continuous duty @ max load for the expected heat rise.
I had a specific reason for suggesting the switchers one is that they can be used with higher input voltages where the efficiency is better. The project that "Failed?"... how much homework did you do or are you relying on other advice from the "resident" experts... I'm not here for fame and fortune, I am here to learn the language. I do however know how to do that simple "Due Diligence", making sure what i buy is workable and if not what it takes to make it right... Completely right. It's called experience and for the grief I get here It's frankly not worth my time. that number beneath my name isn't the number of times I have been here... rather it is the time I take away from time I would like to use to do my own work. I rather think in the future I will keep my keyboard quiet.

Doc...
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Im sure glad you did not keep your keyboard quiet Doc. Prairie Mystic thanks for your input too.

The LEDs Im running are the flexible LED strips which have a max. voltage around 5 volts. So I cant put more "in series".

I can figure out how many amps Im going to be pulling and hope to post again soon.
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Unfortunately buck, boost,  and boost buck mode controllers don't series very well. The ground is common from in to out and will short the output if connected in series with a common supply for the input voltage. If you need greater output voltage then there is a pot to adjust the output keep in mind several things.... The input voltage must typically be 2 volts greater  than the output for a buck mode converter.... If you have questions I will try but the data sheet and a little common sense should answer the bulk of your issues.
The devices can get hot so make provisions for that and ALL devices can fail and only a FOOL doesn't take that into account and a BIGGER fool is the one who takes no precautions whatso ever
This was the main reason I suggested using several devices and split the loads up Between the devices...
There was one poster that claimed that the devices fail with over current... I suggest he hasn't a concept of how to use them and I still think i will keep my keyboard quiet.
I am tired of spending time that I could use to do my own work trying to help people who know it all and are apparently just trolling for someone to take on someone...
To try to "Help" someone who can't read the free information provided hare is unforgivable and the Last Expert who shared his ineptitude was the final straw.
To take a switcher and load it to the max without reading the relevant information on the website that sold it to him (free too) is frankly unbelievable. To wire the Arduino to the same power supply as a High Current load is it's own just desserts and to do so with anything but a star ground system is not the smartest either... one ground fails and suddenly... You think Crosstalk...
There are quite enough engineers of good ability and knowledge (or at least there are enough to try to tell me that I have no idea of what I am saying) here to more than Ably take my place.
This whole endeavor is too time consuming for the occaisonal thank you.
The only thing I can figure out is that my knowledge is just out of date and rather than have some "Expert" try to tell me that what works for me is no good and will damage someones project is beyond me. If you or anyone here wants my opinion... PM me. I am here to advise people with what I know and now it's tine for the REAL experts to take up where I am happily leaving off.
Unlike the Experts I WILL back up what I advise and I TEST anything I advise and anything I advise was something that worked over the 40 year period I was actively in this business or is something I am doing today. I am old and tired and quite tired of trying to make a difference here. There is always some sophomore engineer who knows more about everthing except how to keep his mouth shut.

Robert Khayyam Sr
« Last Edit: September 23, 2012, 10:54:34 pm by Docedison » Logged

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Dubuque, Iowa, USA
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When dealing with solar panels there are additional efficiency questions that need to be taken into account: maximum power point tracking. You're going to lose lots of efficiency without a MPPT controller.

This whole endeavor is too time consuming for the occaisonal thank you.
I'm sure I'm not the only one watching your responses and not chiming in a "thank you" just to keep the signal to noise ratio high. Not to be a brown noser but I've always given your posts special attention.
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