Running 4 axis from a ps806 or sps705 psu

[jonbabbz]

Im shopping for a 68v power supply and am deliberating the ps806 or sps705. Is it possible to run 4 axis from these? The following website says 1-4 axis while zapp says 1-3 axis, I know they have 3 main outputs but can they be used for 4 axis, i.e using one output for a master and slaved axis, or will I have to buy 2 psu's. Also what are the differences between the 2 as the price difference is quite significant? Thanks

http://www.leetro.com/english/sale/73.html

[Jonathan]

Presumably you're using the 3Nm stepper motors which draw 4.2A? I've found them to be OK on one 500VA transformer, but more is more stable.

The PS806 is 500W (500VA strictly) and a linear PSU which for this application is generally considered better than a switching PSU which is what the SPS705 is. In addition the SPS705 is only rated for 340W.

I wouldn't consider either. All you need to find is a suitable transformer, then buy a bridge rectifier, capacitor(s) and solder it all together which is easy enough. If you got the 625VA transformer here that would be good for 4 motors. Shop around, that may not be the cheapest. Anything with that VA rating or above is fine, 24V with two secondary windings in series will get you 48V which is fine, similarly 25V/48V/50V transformers are fine. If you decide to do this I can post the circuit etc.. or you can probably find it as I've posted about this many times before.

[jonbabbz]

i am indeed running the 4.2A motors. If you could post the circuit that would be great, I've searched for it but couldn't find it. Thankyou

[Gary]

The PS806 is by far a better solution.
Linear power supplies are much better in handling inrush currents and also the PS806 has a regulated 5V output to power your breakout board.

[jonbabbz]

I'm fine with building one, but would much rather buy an 'off the shelf' supply than break out the soldering iron tbh. I just wanted to be sure that it would be sufficient to power 4 motors.

[JAZZCNC]

The PS806 is by far a better solution.

Not really Gary.!! . . . . To run 4 x 4.2A motors he'll need 2 x PS806 thats £204 plus del For less than 1 PS806 he can build a supply that will easily give what he needs and still have change to buy a small 5V 1A reg supply.!

Inrush is not a problem @ 600Va and easy enough to build an inrush circuit if really needed.! ( Which it won't be in most case's)

[JAZZCNC]

I'm fine with building one, but would much rather buy an 'off the shelf' supply than break out the soldering iron tbh.

Not really need a soldering Iron if you don't want.? . . . It's so easy you won't belive how simple the wiring is.!

[Jonathan]

If you could post the circuit that would be great

Couldn't find it either, so just drew this:


(next time I'll find the mouse..)

Top one if you get 24V or 25V transformer (preferable), lower one if it's 48V or 50V. The capacitor needs to be 10000uF minimum, ideally a bit more so three of these in parallel is good (assuming you get transformer from Rapid, otherwise might be cheaper elsewhere, eBay, Farnell etc). This bridge rectifier is good as it wont need a heatsink. So about £60 in total...

If you got the bits posted to me I'd feel guilty charging more than a fiver to wire it up as it's less than 10 minutes work.

As Jazz just implied, you could use terminal block and crimp connectors instead of soldering.

[jonbabbz]

Thanks guys, appreciate the advice

[Iwant1]

I am also thinking of making my own power supply and have no problem building the circuit, but a few questions about design. How accurate are the secondaries in a transformer? I'm asking to see if there will be any premature failure if they are not equal, from one coil working harder than the other. Which is better to connect the secondaries in?, series or parallel as both 25v and 50v are available from many suppliers.

I will be using pm752 drivers which I've had lying around for 2 years. Their datasheet says typical voltage is 48v and max voltage is 75v. In another post I read Gary saying to Jonathan that 72v from a toroidal supply is bit on the high side for the pm-752 driver. When I do the calculation 50 X √2 I get 70.7v. Is this the output I will be getting or are there other factors which bring it down by a few volts.

I don't fancy messing around with windings.

Adil