Power Transistor / Mosfet Suggestion?

[exelanoz]

So after listening (or is it reading?) the suggestions offered by the helpful members here, I have settled to use the IRF3205 mosfet. Seems to work well, as sayzer mentioned, you must use a resistor in the gate to pull it down, otherwise it is a bit eratic on the scope. In driving the LED strips, i have changed the strips to 5V type instead of the 12V.
I tested it with a small strip, seems ok.

The TOTAL powersupply requirement I need is whopping 18Amps @ 5VDC.
I am ready to connect ALL the strips and before I blow anything up (again), I have a question.

I have 2 switchmode powersupplies, <a href="http://jaycar.com.au/productView.asp?ID=MP3123&CATID=27&keywords=&SPECI AL=&form=CAT&ProdCodeOnly=&Keyword1=&Keyword2=&pag eNumber=&priceMin=&priceMax=&SUBCATID=647">Powersu pply</a>

On the casing they are rated 10Amps for the 5V. Can also do 24V @4.5amps (but not needed)
Is it possible (and safe) to connect the outputs in parallel to achieve a 20Amp capacity?
My other idea was to use a computer PSU where normally the +5V DC rail can deliver up to 30Amps.
Not quite sure how else I can achieve a high output PSU.

[BrianT]

Your mileage may vary but I have come to grief several times when trying to switch high currents in LED star cloths (1000+ white LEDs for a theatre backdrop), heaters, and high brightness LED strings. Screw terminals get hot if not perfectly terminated, board currents give ground bounce, a single short takes out the entire display, etc, etc.

What I found is much more fault tolerant is to divide the load into several parallel strings each about 2 -3 amps. The Philips (NXP) PMV31XN will switch a whopping 5.9 amps in a tiny SOT-23 package so several handling smaller currrents means you don't end up with hot spots in connectors handling 15 amps. The inputs can be driven in parallel with a small series R to each gate and the source pins can be paralled into a very large all copper fill area on the PCB. Each output goes via its own fuse and screw terminal block. Multiple strings can be individually fused so most of the show goes on even if some clown has sliced one of your display lines.

HTH
Brian

[exelanoz]

Hello Brian,

Many thanks for your suggestion, I now realise that I should have split the load.
This won't be for any commercial setup. It is going on my verendah outside.
Sort of a party light RGB led type effect.

So if any clown is going to slice the wire, it will be me(and probably will)....and if the verendah burns down......., - well... that will also be me and if that is the case, I will be running for the hills so that my other half doesn't kill me. (She can be threatening at times)

At this stage I have already etched the PCBs and the best that I can do is split the 18A load in 2 parts which would suit the PSU I have (9Amps to each).

I am using screw terminals, (18Amps spread over 30 screw terminals) all decent size and I made the board with heavy duty tracks.
And your fuse is not a bad idea either. I think I can include that on all screw terminals.
Alu box is also fan assisted (120mm) cooling with lots of heatsinking.

I guess my primary concern was whether it is an acceptable practice to parallel independant power supplies to get more amperage.

Many thanks. Hopefully I can post some success pictures of the project, - and not the verendah burning.

[Archangel]

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