Power supply

[itsme]

Hi there,

I think I know how to wire up a power supply, but can someone please just check it for me. I have included an awesome schematic that I drew up. It took me hours to get the shading right...

The supply is for a Xylotex 4-axis unipolar board that will be driving four 2.5A 4.5V stepper motors.

I'm also unsure of the earth connections. I was thinking about putting all the electronics into a case (metal???) and then earthing the whole case as well as an earth connection to the machine itself. Does this sound OK? Any other suggestions here? I'd rather not get it wrong when I'm playing with the mains...

Thanks
Warren

[Al_The_Man]

Personally, I always ground the DC common, the incoming ground, the chassis, shields and DC commons all go to a common ground point.
Al.

[DieGuy]

Really that will burn up a Xylotex. The very max it can handle its 35 vdc with BEMF. And that transformer is way over kill on the amperage side. You might want to step back a bit on the VAC and shoot for about 30 VDC on the output side. The boards do well if not pushed to the MAX spec. I am running mine on a taig mill with 270 oz-in steppers @ 28.7 vdc and 8 amps and it is just about unstopable.

# Three axis bipolar drive # ±2.5 Amp/Phase PWM controlled drives # up to 35 Volt (w/BEMF) # FULL, HALF, QUARTER, & EIGHTH step/Full Step # Built-in DC-DC Converter for 5 Volt Logic # Filtered and Buffered STEP & DIR Signals # Built-in Break-out:Screw Terminals for Unused Parallel Port I/O # Synchronous Rectification # Internal UVLO and Thermal Shutdown circuitry ...

Edit:
that is a 28.7 VDC 8 amp Power supply!

[dberndt]

8 amps on a xylotex? Hows that work, i thought they were rated for 2.5

[DieGuy]

Originally Posted by dberndt 8 amps on a xylotex? Hows that work, i thought they were rated for 2.5

An 8 amp powersupply for 4 axis board that supplies 2.5 amps per channel. Sorry should have made that more clear.

[bkukowski]

also, when deciding on the right transformer (I think that rectified current is higher than the original ac...or it's the other way around) place an appropriate fuse between the transformer and mains, just in case something crazy happens. You should probably put a 2k ohm @ 1 watt resistor across the terminals of the cap to discharge it. If you can't find one, you can use an equivalent 2x 4K @.5 watt instead.

sometimes I see the fuse on the other side of the transformer but I dont think it matters. Please anyone correct me if I'm wrong.

[Al_The_Man]

Originally Posted by bkukowski place an appropriate fuse between the transformer and mains, just in case something crazy happens.

In the UK they have a fuse in the wall plug.
Al.

[itsme]

Hi there,

Thanks for the replies. The board that I am talking about is the unipolar board. This board is rated up to 44VDC and it has 3 amps per phase. It is NOT the same as the bipolar board.

Al, could you possibly go into a bit more detail on your grounding method? I'm not too good with all the terminology. Do you basically just connect all the 'negative' wires to a common ground? Do you use the 'earth' connection from the plug at all?

Thanks
Warren

[Al_The_Man]

Warren, If you do a forum search for 'grounding' it has been covered quite a bit in the past like this http://cnczone.com/forums/showthread...ight=grounding
The earh connection from the plug would go to the grounding plate.
Al.

[itsme]

Hi,

Thanks for the replies. In the next week or two I'll start working on the power supply - I just need to get the mechanical side of the machine finished now.

I'm pretty clear now on how to wire up the all the electrical things, so hopefully it will all work properly. If I suddenly disappear from the forum, you can assume that it all went horribly wrong...

Thanks again.

Warren

[JavaDog]

Originally Posted by itsme If I suddenly disappear from the forum, you can assume that it all went horribly wrong...

I'm building my PSU this weekend...I was thinking that same thing!