Re: [CAD_CAM_EDM_DRO] Re: Question on Power Supply

>
>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...
>
>
>