RE: [CAD_CAM_EDM_DRO] Re: Xylotex Pwr Sup replacement

A regulator is not necessary. A bridge rectifier, and a properly-sized filter cap(not too large OR too small) are all that's needed, in addition the transformer.


Andy Wander


-----Original Message-----
From: CAD_CAM_EDM_DRO@yahoogroups.com [mailto:CAD_CAM_EDM_DRO@yahoogroups.com] On Behalf Of Danny Miller
Sent: Monday, November 14, 2011 2:48 AM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: Re: [CAD_CAM_EDM_DRO] Re: Xylotex Pwr Sup replacement

It's hardly a complete system though. The bridge rectifier is no sweat,
but you'll need some large, low ESR- and quite likely a large regulator
and heatsink.

With variations due to line voltage, output loading bringing down the
voltage, and the high ripple of a 60Hz rectification, there will need to
be a large max difference between Vin and Vout to guarantee that the reg
will have enough voltage during the lowest-case input voltage. So, you
may have 10v or more even on a 24v circuit, which means a lot of
regulator heat, which makes for a large heatsinking requirement and
increases risk of failure.

But these components are quite expensive and a 24v switching power
supply's only in the $20 range.

Danny

On 11/13/2011 11:07 PM, Dave Halliday wrote:
> Absolutely agree with you but the "feel" that I picked up on Chuck's
> original post was that he wanted something fast and also cheap and was not
> dis-inclined to roll his own.
>
> Switchers are the way to go if you can get them but for cheap brute force, a
> microwave oven xformer is right in the sweet spot.
>
> Dave
>
>> -----Original Message-----
>> From: CAD_CAM_EDM_DRO@yahoogroups.com
>> [mailto:CAD_CAM_EDM_DRO@yahoogroups.com] On Behalf Of Danny Miller
>> Sent: Sunday, November 13, 2011 2:58 PM
>> To: CAD_CAM_EDM_DRO@yahoogroups.com
>> Subject: Re: [CAD_CAM_EDM_DRO] Re: Xylotex Pwr Sup replacement
>>
>> I don't recommend this at all. Line-freq transformers and
>> rectifiers/caps are just absurdly bad for CNC use.
>> I'm not saying it won't work. But the voltage is poorly
>> regulated and
>> it'll take a large, unnecessary amount of $ to even try to get the
>> regulation and safety features "proper". 60Hz requires very large
>> filter caps, variations in line voltage cause variations in
>> the output,
>> and it draws very dirty power on the input with a leading
>> current. The
>> industry dropped line-freq transformers like 10 years ago for
>> this and
>> many other reasons.
>>
>> It's an unjustifiable risk, considering what overvoltage will do to a
>> driver.
>>
>> There's a 48v 7.3A power supply all over eBay for<$40, and they're
>> GREAT. Geckodrive recommends a guideline that the supply current be
>> rated for 0.6x the sum of the phase currents; this could do
>> 4x 3A NEMA23's.
>>
>> If you require MORE current, you can go totally over-the-top
>> with a Sun
>> rack supply:
>> Sun Sunfire V480 Server 300-1490 Hot swap Power supply 48v 24.5A
>> Sun V880 AC Power Supply P/N 300-1353 48v 15.6A
>>
>> Either one of those can be had for under $40 on eBay. Yup, 1176W of
>> top-quality regulated 48v for $33.
>>
>> Danny
>>
>> On 11/13/2011 4:35 PM, Dave Halliday wrote:
>>> I have mentioned a few times before but a microwave oven
>> has an excellent
>>> transformer for this purpose.
>>>
>>> #1) - do not play with it (plug it in) while the high
>> voltage winding is
>>> still in place. The voltages and currents developed can be
>> instantly lethal.
>>> #2) - because the high voltage winding is so high (around
>> 2,500 volts), the
>>> primary and the secondary windings are separate. Most
>> transformers have
>>> these wound on top of each other. This allows you to
>> remove the high
>>> voltage winding with a hammer and cold chisel. There will also be a
>>> filament winding -- two or three turns of thick wire; this
>> can just be
>>> unwound.
>>>
>>> #3) - wind ten turns of insulated wire around where the
>> high voltage winding
>>> used to be, power it up and measure the resultant voltage
>> on your new
>>> secondary. Divide by ten and this will be your turns/volt.
>>>
>>> You can then figure out from there how many turns are needed.
>>>
>>> The advantage of these is that dead microwave ovens are free and the
>>> transformer is good for 500-800 watts continuous power.
>> Excellent for
>>> projects like this.
>>>
>>> Dave
>>>
>>>> -----Original Message-----
>>>> From: CAD_CAM_EDM_DRO@yahoogroups.com
>>>> [mailto:CAD_CAM_EDM_DRO@yahoogroups.com] On Behalf Of
>> turbulatordude
>>>> Sent: Sunday, November 13, 2011 9:08 AM
>>>> To: CAD_CAM_EDM_DRO@yahoogroups.com
>>>> Subject: [CAD_CAM_EDM_DRO] Re: Xylotex Pwr Sup replacement
>>>>
>>>> you really need to keep the voltage lower.
>>>> remember that the decel of a drive will spike the power
>>>> supply. fast decel times can make the voltage jump.
>>>>
>>>> if you can put your hands on a computer battery back-up, you
>>>> can get some high amps from the transformer.
>>>>
>>>> also, a car charger will have a large transformer.
>>>>
>>>> you will still need capacitors and diodes to get DC from
>>>> these AC units.
>>>>
>>>> you can lower the amp rating of the drive temporarally while
>>>> waiting for the perfect fix.
>>>>
>>>> all electronics offers power supplies that are DC, you should
>>>> be able to get one in a few days.
>>>>
>>>> Dave
>>>>
>>>> --- In CAD_CAM_EDM_DRO@yahoogroups.com,
>> "ebiz_59"<chuckm@...> wrote:
>>>>> Murphy bit the Xylotex box on our minimill tonight. It
>>>> appears as though the 24V 6A power supply gave up the ghost -
>>>> just when we were FINALLY making our first part for our FTC robot.
>>>>> So I need some ideas for replacing this power supply
>>>> quickly. I think I saw a 30V power supply on an HP printer
>>>> the other day, but I'm thinking it was only a couple amps.
>>>> And I think I might have a 15-20V 4ish amp laptop supply
>> lying around.
>>>>> Any other thots? And what are the odds that the Xylotex
>>>> drives are OK if this power supply board is only putting out
>>>> like 1.5V? Should I be looking for another set of stepper
>>>> drivers too?
>>>>> Ugh! Chuck
>>>>>
>>>>
>>>>
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> http://groups.yahoo.com/group/jobshophomeshop I consider this to be a sister site to the CCED group, as many of the same members are there, for OT subjects, that are not allowed on the CCED list.
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