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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
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.
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
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.
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.
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.!Quote:
Originally Posted by Gary
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)
Not really need a soldering Iron if you don't want.? . . . It's so easy you won't belive how simple the wiring is.!Quote:
Originally Posted by jonbabbz
Couldn't find it either, so just drew this:Quote:
Originally Posted by jonbabbz
Attachment 6345
(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.
Thanks guys, appreciate the advice
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
That's precisely the reason I said '24V or 25V transformer (preferable)' in the previous post. Wondered if someone would pick up on that :)Quote:
Originally Posted by Iwant1
If they're not equal then more current will flow in the secondary windings, but I don't think it's likely to be a big enough difference to cause failure.
Quote:
Originally Posted by Iwant1
I remember that one, to which I replied saying I'd checked the actual voltage at the MOSFETs and the spikes on switching were well below their rated 100V so I was happy to do it. That was with a 25+25V transformer from rapid, with the same PM752 drives from Zapp.
70.7V is correct, but the diode will drop about 1.1V, so more like 69.6V. However the mains voltage does have a fairly wide tolerance. It looks like those transformers output 50V with 230V on the primary, however the mains voltage could be 240V (depends on numerous factors). That would make the output voltage 240/230*50*√2=72.7V... still less than mine which has been fine for a long time now. You could always add a couple of turns of thick wire out of phase to reduce the output voltage, but crude but it works...
Sent you a pm Jonathan regarding a build if you're up for it?
Think I should say that if you choose the top pic Jonathan drew you will be getting double the voltage of the 2 secondery ouput ratings IE: 2x24=48V but only half the rated Amps of both seconderys but if you wire have 48V seconderys and wire parallel you get the same 48V but double the amps.
No difference really has lower voltage seconderys have higher amps, roughly double, if the higher seconderys are double the voltage.!! . . . So 2 x 24Vac 12A seconderys can either give 48V @ 12A wired series or 24V @ 24A wired parallel. . . . So obviously 2 x 48Vac 6A seconderys wired parallel will give 48Vac @ 12A.
The 48Vac when rectified to DC will give roughly 68V IE: 48Vac x 1.4 = 67.2Vdc
Heres a pic of one (Big one) wired in parallel using 4 x 4700uf caps.!! ( Ignore the chocy block on the input that was a temp bodge.!) Attachment 6346
Has you can see nothing too it. . Simplizzzzz.
Didn't see the point of that...In short, the power has to stays the same, hence why I specified what power transformer to get as then so long as you wire it for the right voltage, the current will be correct by default.Quote:
Originally Posted by JAZZCNC
Yes I am. I'll sort it tomorrow - need to check what bits I have as I might already have everything you need.Quote:
Originally Posted by jonbabbz
I've always wired mine parallel and never had a failure or problem yet.!Quote:
Originally Posted by Jonathan
Yep but I find folks under stand better when it's spelled out and the difference known.? He could have been wondering why or how 24V could give him 65+V.?Quote:
Originally Posted by Jonathan
Just me being OTT maybe.?
Don't need much change for that :)Quote:
Originally Posted by JAZZCNC
http://www.ebay.co.uk/itm/UK-DC-5V-1A-Switching-Power-Supply-adapter-100-240V-AC-Promotion-/200791372447?pt=UK_Sound_Vision_Other&hash=item2ec 019329f#ht_3691wt_1037
I guess.Quote:
Originally Posted by JAZZCNC
Jazz where did you get your transformer from? Is it this one?
http://www.rapidonline.com/Electrical-Power/Toroidal-Transformer-1000va-0-50v-0-50v-88-3852
Was thinking something a bit easier and neater than that.!!Quote:
Originally Posted by Jonathan
http://www.ebay.co.uk/itm/DC-5V-5A-R...item2a1fbcca51
Edit: I've had 2A version of these for £5 before this was just an example.
Nope got it here I think.? http://www.airlinktransformers.com/c...ard_range.htmlQuote:
Originally Posted by jonbabbz
You don't need or want 1000Va for 68V-ish @ 12A 625Va will do fine.
With toroidal setup You only really need about 68% of total motor amps so 12A will be fine for 4x4.2A motors.!
Oh right ok. Nice one, I'll just buy the setup Jonathan suggested then and have a bash. Thanks mate
What is said was the PS806 is a far better solution to the PS705, not just because of the size difference but also because its linear and linear power supplies are far better suited for stepper and servo applications.
The advantage is that the PS806 can handle quick changes in current draw a lot better than the PS705.
Looking at the spec, the PS806 is cutting it very close and ideally you would need about 8-10A of peak current, however I have run 3 X 6.2A motor from one of these with no problem at all and the voltage is still in 60V range.
Next week i will power one up with 4 AM882 and SY60 motors and monitor the current and voltage and report back to you.