Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: ostie01 on June 29, 2008, 09:55:37 AM
-
Hi, My power supply for my router table is a switching power supply at 24v 6.5A. Look like it is not powerful enough for this purpose. I have two, can I connect both in parallel to increase current for the motors without damaging my board or power supply themself. Thanks for any advices, Jeff
-
When you say it is not powerful enough, what do you mean.
What are you trying to power.
If your main axis need, say 4 amps each, then power each axis from it's own supply - it makes no difference to the driver cards where the power comes from. As long as the leads to each motor are not interconnected, then you will be fine.
If say your Z axis needs another 2.5 amps, then use one of the supplies to power this as well.
I am thinking of powering my x and y axis from 36 volts (Gecko drives) and the Z axis from 24 volts (Routout drive) to see if I can increase speed and reliability on my X and Y.
-
Hi, thanks for the reply.
My router table have 4 stepper motor, two nema23 425 ounces of torque for the X axis, one nema23 425 ounces for the Z axis and one nema34 1200 ounces torque for the Y axis. When they move all at the same time, I think my power supply is not powerful enough since it can deliver only 6.5 amp and all motors together would need more then that.
This is my board. :
http://cgi.ebay.com/4-AXIS-CNC-ROUTER-OR-MILL-STEPPER-MOTOR-DRIVER-BOARD_W0QQitemZ230266327652QQihZ013QQcategoryZ78197QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
This is my power supply.: S82J-15024A1 ( this mean, 150 watts, 24 volts)
http://pdf1.alldatasheet.co.kr/datasheet-pdf/view/152773/OMRON/S82J-15024.html
I have two of these power supply but only one input on my board for the power. I'm just wondering if I could hook up two power supply in parallel in only one input to have more current deliver to my motor. Sometime when the move all together, one or two loose steps but this never happen when only one or two are moving.
-
Yes - well, just fasten them in parrallel - pos to pos and neg to neg.
I would, however, include a fuse in line wtih each supply.
-
i would agree your power supply is not capable , given the limited information you have supplyed ,
i would have liked to see a voltage around 35 - 48 v and a current rating of 10 - 15A , although you do not give the model numbers or ratings of your stepper motors , so it is difficult to comment further .
but as a very crude and quick way , add the current ratings of all the motor windings together and add 20% and that will give you a good starting point for the current capability requirements of your power supply , it's better to have an over rated supply than one to low , it's also usuall to supply them with a voltage of about 5 times the motor voltage rating , then adjust your stepper motor driver current resistors as per the manual
also simple transformer type power supplys are better suited than switched mode for our uses , and tend to be more reliable long term
Dave
-
Hmm....
Should the parrallel supplies feed a common capacitor before feeding the board?
RICH
-
Hi, my board have a maximum voltage rating of 32 volts.
This is my nema34 motor for the Y axis. http://www.kelinginc.net/kl34H2120-42-8B.pdf (1200 ounces)
These are my motors for the Z axis and X axis. (X axis have 2 motors for the gantry for a total of 3 Nema23) http://www.kelinginc.net/KL23H286-20-08B.pdf (425 ounces)
All are connected in series.
I'm just asking since I have 2 similar power supply at 6.5 amp instead of buying one at 12 amp.
-
Yes - we understand - BUT - what is the rating of your motors - mine for instance are - forget the name, because it doesn't matter - 220Ncm, rated at 2.5 amps at 7.5 volts - this is the important bit - and it enables you to work out what power you are likely to need as per da21's post
-
Click on the link for the PDF file I have posted, everything you need is there, rating, volts, ect. Thanks
-
your motors are rated at an average of 3A per phase , with bipolar windings ( 2 phases ) that means each motor requires 3A x 2 , so thats an average of 6A per motor
so 4 motors @ 6A each , have a maximum rating together of 24A , if they happen to be at a worse case situation of requiring maximum current on all motors ( ok it's not going to happen often , but you need to be able to handle this ) .
so your options are a single power supply that can supply 24 A or split your motor supplys between more than one power supply , but allowing each supply to cover the current needed for what ever it is connected to i.e 6A for each motor in your case .
in this case current capacity is more important than voltage , as the controller supplying the motor can be current limited by onboard resistors on a per motor basis , and therfore the voltage is also limited to .
your voltage requirement needs to be as i said before , as a crude guide 5 times the rating but it's not critical so 24v - 30v will be fine
just keep it below the maximum requirement of your controller by say 5v
as i said this is a quick crude way of finding power supply ratings, without going into all the mathmatics and formulas , so yes everyone will find their own disagreements
if they wish to look for them , however it works in oractice.
i am just trying to keep it simple for the electronicly challenged amongst the community .
Dave
-
ostie01,
Your driver board max power supply rating is 32VDC@7A, with a recomended supply of 24VDC@7A.
Now if you were to use two power supplies wired in parallel you could get 24VDC@12A which is over the driver board rating.
This is not good.
Should the filtering quality of the power supplies be inferior, a properly rated capacitor may be desired. My preference would be to provide the additional filtering and some surge capacity via the capacitor if they were parallel connected ( but that's only my opinion).
I only glanced thru the 20 pages of the power supply manual and noticed there is info on series and parallel wiring.
Pay attention to it.
With no motor curve info, which relates wiring confirguration to speed, torque @ some voltage, you can not forecast motor preformance ( it will be trial and error in finding it via tuning). The driver board info shows max individual drive fusing to be 2.5A. This says any individaul stepper current draw will be limited to 2.5A MAX which futher defines how you would wire the steppers.
Also as a total ( three steppers with a total current draw should not exceed the 7A rating of the board ).
RICH
-
as quite rightly picked out by Ostie01 , which i missed , your driver board is under rated for the current requirement your motors need
i'd suggest you look for a better matched drivers such as Geko's for these motors
Dave
-
Thanks for your help guys, really appreciated.
Will try to find a better board for my motors.
-
I might argue a little bit with Dave about the current required wiring these in parrllel, but - yes - in the scheme of things your power supply is not adequate even to supply two of these motors when running at full chat.
I would get Gecko 201 drives. These are rated at up to 7 amps, but are fully adjustable up to that - e.g. mine are set at 4 amps, but they are also capable of running up to 70 volts (or so). You will find that your motors as they are will run better on the power supply you have, but when you can afford to uprate the power supply to say 36 volts at 20 - 24 amps, they are sturdy enough to cope with that as well._
As a stop gap limit the Geckos to match the pwoer suppy you have to avoid any problems.