Re:Power supply questions

Andrew,

A good price for suuplies over 200W is around 30-35 cents a Watt. Try
www.transformertechnology.com as a representative example.

Regards to bench or "lab supplies" The premier name here Sorenson.
It's who we use for all of our high power supplies. They are like
Tektronix is for "scopes; which is all use as well.

The adage is you get what you pay for. The best is more expensive but
in the long run it's cheaper than what's cheaper.

Mariss

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Andrew Werby" <drewid@a...>
wrote:

> [While we're on the subject of power supplies, are there any
> reasonably-priced power supplies appropriate for this purpose that

are

> available for purchase all set up and ready to go? I'd really like

to find

> one in a box, with a fan installed, and (preferably) with a UL

sticker

> attached. Ideally it would take 110v AC input and convert it to

about 60vDC

> at 20 amps or so. The rest of the circuitry would be at a

(relatively) low

> voltage, which doesn't seem all that dangerous to play with (and

probably

> won't require a UL sticker), but power supplies can bite you if

you're not

> careful.
>
> I can find "wall warts" that put out (nearly) enough voltage but

not enough

> amps (or vice versa), and also switching power supplies built for
> computers, but apparently the switching function, while it reduces

the

> amount of wire necessary and thus the expense, can interfere with

the pulse

> train. (The Gecko site indicates they can be used, though, if one

fits the

> drives with capacitors to filter the current.) The other problem

with

> computer supplies is that they are meant to be mounted to the DIN

rails

> inside a computer, and not to be free-standing.
>
> A third class of supplies I've looked at- bench-type laboratory

power

> supplies- seem ideal: they come mounted in a box, and they can be

found with

> sufficient voltage and amp capacity, but they're hideously

expensive, and

> seem fancier that what's needed, with multiple outputs and

extraneous meters

> and knobs, etc. Has anybody out there powered a Gecko-based servo

setup

> (like the one Thomas wants to build) with an off-the-shelf unit? It

seems

> like a major stumbling block would be removed if we didn't have

to "roll our

> own".]
>
> Andrew Werby
> www.computersculpture.com
>
> "Tom Murray <thomasm923@a...>" <thomasm923@a...>
> Subject: Power supply questions
>
> I hate repost my recent questions, but I really need some help in
> building a power supply.
>
> Questions below:
>
> My Taig mill is ordered, and one of the things that I have to do
> while I wait the 6 to 8 weeks for delivery is make a power supply.
>
> There's a few things that I'd like to ask the group to get me
> started...
>
> First, I am wondering if my choice of caps is correct. I will be
> using a 30 volt transformer to supply power to three 24 volt servos
> rated at 6 amps peak. I doubt that it will ever need to supply more
> than 12 amps at once, if that much, but let's assume that the

maximum

> current is 15 amps. I am looking at some surplus capacitors rated at
> 17,000 MFD, 75 VDC. Would a pair of these in parallel be sufficient?
>
> Second, I wonder if it is ok to attach a smaller transformer to the
> same AC input that is hooked up to the main transformer to supply 5
> volts to the Geckos?
>
> [I thought the new edition of the G-320s didn't need the extra 5v

input. Am

> I wrong here?]
>
> Third, how does one calculate the rating of the fuse that is needed?
> I assume that it should be a slow-blow type, but what would the
> correct amperage rating be? A little over the maximum current, a
> little under, or dead on?
>
> Thanks,
> Tom Murray