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I need someone to ID a doohickey.

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Yes, PS --> CONTROLLER --> DPDT --> MOTOR is right  :thumbup:

Like Dave says, some sort of load is often needed to wake an ATX up. A high wattage resistor from +12v to 0v would do it, but you seem to have amps to spare with your ATX, so how about 12v halogen illumination permanently on while the PSU is plugged into the mains? A 12v, 50 watt lamp pulls about 4A, giving you somewhere to warm your hands in winter. And burn your forehead  :doh: if you put the lampholder in the wrong place.

BTW, you may find your PCB marked "+" to show where the +ve terminal of the capacitor should go. But the caps themselves usually indicate which is the -ve leg, often by an arrow-shape down the side, with a thick minus sign inside it.



That's OK ..

The point that was made is that the controller must be correctly polarised.
If the Switch was before the controller, it would almost certainly go Pop.

If you want to use a PC PSU, I wouldn't bother replacing the blown cap. Plenty of smoothing in the PSU.

Edit, Sorry Andy posted this when your post was on Page2  ::)

PC PSU's have quirks, don't I B****y know. Some like the 5V loaded min. about 200mA, otherwise no go.
Some I have met have more than 1 12V o/p. If you just parallel the things, the PSU won't come up.
But, if you put a 0R1 10W resistor on each 12V o/p, then parallel them after the resistors, they will.
10W is overkill, but I've got a lot of the screw down sort, easy to fit. :D
Just the same as putting LM317T's etc. in parallel, 'cos the price of LM338K? ( the TO3 5A jobbies ) is beyond belief  :(

Dave BC

Thanks for all your help guys! I salvaged a 50v 47uF cap off of an old blown power supply board I had out in the scrap box  :dremel: I transplanted it and wired in the modded PC power supply. Smoooooooth! I have much more low end control now. I'm going to learn this electronics stuff whether I want to or not I guess.  :proj: I'll try and get a video of the power feed in operation later today...right now it's time for breakfast.  :thumbup:

Bluechip --- hopefully I am reading this right.  Yeah a LM338K is exxy.  What I have done in the past is put a TO3 PNP pass transistor in when I need more current than a LM7812 can handle.

I only needed 1 PNP.  Here is a more extreme case with multiples used, but u get the general idea.

Hopefully this helps those in need of more O/P grunt.


Thanks for posting that cct. I was aware of the general idea, used it myself. Boost circuits are often on the data sheets, there is also, usually, a cct. for npn bypass transistors.

As you say, quite right to post the info. it may well help others who are into this stuff.

As an aside, apart from data sheets, quite a few manufacturers of devices also do 'Application Notes'.
Worth while doing a search on these, far more eg. type circuits that the (few) on the data sheets.
Not always successful, but sometimes a lot of good stuff.

Try this for my favourite reg. chip ..

Dave BC


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