Re: [CAD_CAM_EDM_DRO] Re: Question on Power Supply

Dave,

Most electronics catalog stores will have capacitors.

I am going to go to a local surplus sale store tomorrow. I can pick up one
and send it to you.

Bob Campbell
Bob@...
www.campbelldesigns.com
Breakout board
THC board sets
CNC router plans
Stepper Motors
VisualMill Basic

----- Original Message -----
From: "Dave Davies" <davegsc@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Wednesday, June 08, 2005 2:51 PM
Subject: RE: [CAD_CAM_EDM_DRO] Re: Question on Power Supply


> This thread on power supplies is excellent. Thanks to everyone. Does
> anyone
> have a source for the capacitors - I've been able to find bridge
> rectifiers
> and transformers, but no caps so far.
>
> Thanks
>
> Dave Davies
>
>
> -----Original Message-----
> From: CAD_CAM_EDM_DRO@yahoogroups.com
> [mailto:CAD_CAM_EDM_DRO@yahoogroups.com] On Behalf Of jymmm
> Sent: Wednesday, June 08, 2005 12:02 PM
> To: CAD_CAM_EDM_DRO@yahoogroups.com
> Subject: [CAD_CAM_EDM_DRO] Re: Question on Power Supply
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, Luke1027 <luke1027@p...> wrote:
>> When you say "Just check for the maximum that you can use."
>> You are talking about the max. voltage that the Driver can handle
>> ... right?
>> Which in my case will be 30 Volts. So I would need a transformer
>> that will put out 30V. I would like to build my own, just for the
>> sake of learning.
>
>
>
> Hi Luke,
>
> Since you said you want to learn, I thought I would toss in my two
> cents. Take it for what it's worth =)
>
>
> A plain old transformer ONLY does AC voltages, NEVER EVER DC voltages.
>
>
> Below are the unregulated voltages. Just using a transformer, bridge
> rectifer (or four diodes) and capacitors.
>
> If you need (for example) 24VDC you can simple divide the desired DC
> voltage by 1.4 to obtain the AC voltage you would need from a transformer:
>
> 24VDC / 1.4 = 17.14 VAC transformer
>
> The same goes if you have a AC transformer already and want to know
> what DC voltage you'll get out of it:
>
> 12VAC * 1.4 = 16.8 VDC
>
>
> You can read up a bit here:
> http://www.sciencelobby.com/general-theory/rms-and-peak-to-peak.html
>
> The difference from 1.414 and 1.400 is the 0.07 (fwd) voltage drop
> across the diodes in the bridge rectifier: 1.414 - (0.07 * 2) = 1.400
>
> Some folks say to use unregulated power supplies mostly to deal with
> back voltages (BEMF) from steppers.
>
> This is the MAIN reason you don't drive steppers to the max potential.
> They HOPE that not all 3 axis are deaccelerating all at the same time.
>
> If you want to try something kinda neat...
>
> Grab a stepper motor (any kind will do, not connected to anything -
> just bare wires and nothing connected to the shafts) and turn the
> shaft with your hand. Then, short out any two wires and try to spin
> the shaft again.
>
> If you feel resistance, then you've shorted two wires from the same
> coil inside the motor. (This is a simple way to find out the wiring
> scheme when no diagram is available).
>
> The 'resistance' you feel is the BEMF that would be sent from the
> stepper motor to the power supply. If the power supply is regulated,
> it'll try to fight this as well (so to speak).
>
> I hope this helps a little in understanding the basic concepts.
>
> Jim...
>
>
>
>
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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.
>
> NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY POSTING THEM.
> DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO EXCEPTIONS........
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