PSU : prices and differences

[JAZZCNC]

Hi Dean and Thank you!

I'm a little bit confused right now..,
I have Gecko G540, and I decided to use these motors from cncrouterparts
so if you think that the toroidal transformers suit them better, then I'll go with your suggested route

Thank you
Gytis

Ok no need to be confused buddy it's nothing special or difficult to get your head around. I'll explain for the sake of others thou it's all on the forum somewhere else.!

You have G540 which is limited to maximum 50Vdc and provides 3.5A for the motors. Now the Voltage is Fixed and you can't use higher than 50Vdc else you'll damage the G540, in real use you shouldn't actually run at 50Vdc has Steppers are like dynamo's and produce electricity when decelerating, some of this then gets passed back to the drives and if your running at the drives maximum it can easily push the voltage past drives threshold and blow it up.!!

Now the reason why Unregulated and toroidal PSU are better for steppers and much preferred to linear regulated PSU's is because when this excess electricity is produced some of it gets passed back to the PSU. Regulated PSU's tend to be very sensitive to this and have protection built in which trips the PSU and saves it's components. When this happens that's not the end and Electricity still needs to go somewhere so back it goes to Drives which can't handle it and either trip out if protected or BOOM.!! in less capable drives.!!

Now we can't have this has steppers are constantly doing this, esp under hard deceleration from higher speeds. So with Linear regulated PSU we need larger safety margin for the drives so instead of 50Vdc you'll want to run at 40-44Vdc maximum for safety sake.
Now with steppers Voltage makes a big difference to speed and torque you'll get from them so really we don't to waste any if we want peak performance..!!. . . . . Unregulated Toroidal supply works different and it's capacitors act like sponges so easily handle any returning electricity (provided enough spare capacitance is built in.!)
Now Because of these caps sucking up excess juice it also means we can use voltages very close to the Drives Maximum and 48Vdc could safely be used.
They also mean we don't need has high Amp supply because the capacitors hold a reserve of power and because the drives will only pull power during the PWM ON cycle there's plenty juice in reserve so less amps are required for several motors. Roughly 60-70% less. So for your 4 x 3.5A maximum requirements you'll only need Approx 8A not 14A you would with Regulated supply.

One other thing you or others may not know about the G540.? It's not limited to 3.5A motors.?
It can be used with higher currant motors but the drive will only provide 3.5A so you'll get reduced Torque than motors rating. On top of this you'll lose the auto currant reduction the gecko provides when motors are at rest. (There is a easy trick to get this back thou which involves using a resistor.?)

Get in touch if you want to build one.!!

[birchy]

Making your own is quite simple as long as you do your sums first. Just make sure you get the voltage right and have a bit of spare "currant".

[Gytis]

Thank you for the simple explanation Dean!

Get in touch if you want to build one.!!

You think that you have enough patience with me if I choose DIY route?

[birchy]

I'm sure that if you ask nicely, one of the guys on here will make you a PSU for cost price + a couple of beers.

[Jonathan]

one of the guys on here will make you a PSU for cost price + a couple of beers.

Wouldn't be the first time ;)

Get the bits sent to me and I'll solder it up for you - it wont take more than 15 minutes. In fact I think I have a spare new 500VA toroidal transformer... 4 motors at 3.5 amps, so you need about 70% of 4*3.5 which is 9.8 amps. 9.8*50V=490VA ... so the transformer I think I have is perfect.

[birchy]

Jonathon, wouldn't it be easier for you to buy the parts, make the PSU and send him a paypal invoice? There seems to be a serious lack of decent quality PSU's on eBay...

[Gytis]

Wouldn't be the first time ;)

Get the bits sent to me and I'll solder it up for you - it wont take more than 15 minutes. In fact I think I have a spare new 500VA toroidal transformer... 4 motors at 3.5 amps, so you need about 70% of 4*3.5 which is 9.8 amps. 9.8*50V=490VA ... so the transformer I think I have is perfect.

Thank you very much Jonathan for the offer!
But I like to learn new things, so I'll try DIY route., just in case if Dean lose his patience with me, then I'll be back to you with big case of beer and I ask you to do it for me.

Thank you!

[JAZZCNC]

You think that you have enough patience with me if I choose DIY route?

No problem mate I've helped proper thick twats in the past and they got it in the end. . .Lol

[Gytis]

No problem mate I've helped proper thick twats in the past and they got it in the end. . .Lol

Hi Dean,
I'm ready to go DIY route, when you have time can you point me out where I have to look and what I have to buy for the PSU?

Thank you!

[Jonathan]

The mains things are;

Capacitors:
SNAPIN:4700UF/63V Panasonic (ECES1JU472N) 25.5 X 50 | eBay

Transformer (other places have them too):
Toroidal Transformer 500va 0 50v 0 50v

Rectifier (excessive rating, but means you don't need a heatsink so it's easy):
KBPC5006 Bridge Rectifier 50A 600V

Plus you'll probably want a fuse holder and a switch...