Re: Stepper Power Supply. Question about Voltage

Hi all

Guess, what? I hooked up the cap, and the reading was 39.1 VDC. You
guys were bang on ! Well done.

Thanks a lot for the replies, and no doubt, there will be more
questions as time goes by. It will be interesting to see how much the
voltage drops, when I apply the load (the stepper motor). I
discharged the cap each time I unplugged the unit, by shorting it
with a pair of pliers, and ZAP ! I think I will add a bleed resistor
just to be kinder and gentler, but I'll have to figure out what
resistance and wattage.

Cheers all, this group is great. Tom Kay, Ottawa Canada.

--- In CAD_CAM_EDM_DRO@y..., "kaynrc" <tom.kay@n...> wrote:
> Hello
>
> I am just getting around to selecting some transformers to build
> sparate little power supplies for Dan Mauch's 5 amp boards, and
each
> transformer is rated at 26 VAC, 5 amps. I plugged one in, and read
it
> at 29.2 VAC, which is fine by me.
>
> Then I connected the bridge rectifier and got a surprise, which is
a
> reading of 26 VDC. I had not yet hooked up the 10,000uf, 50 VDC
> capacitor. Because the VAC is supposed to be higher than the VAC
(by
> a factor of 1.41) I expected the DC voltage to be higher, around 35
> to 39 VDC. Again, it might be important that I did not attach the
big
> cap yet.
>
> So, what's going on? Will I notice a voltage increase when I add
the
> capacitor? Why is my DC voltage so low just taken right off the
> rectifier, since it's only suppose to consume around 1.7V? Is the
> transformer perhaps too small to supply proper voltage? And last,
> these 521 oz-in motors that I got from Camtronics (and the circuit
> boards) can run up to 40VDC, so am I simply going to operating
slower
> with somewhere around 25 to 30 VDC? Noticably slower?
>
> Thanks, Tom.