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Hey all after blowing my leadshine drivers (my fault)
Ive finally save up for the gecko g203v's
and the Pdmx motherboard for them along with the Pdmx 26
4x geckos cost me £567 from charter controls
Pdmx boards cost like £200 posted from us
now here's my next problem
my power supply
motors are rated at 3.78v
current is 4.2a/phase
inductance is 3.8mh/phase
any recommendations for a psu to drive 4 motors ?
Thanks in advance
Have you bought the Gecko drives, if not why not stick with Leadshine drives (are you sure you have blown them up).
Re the power supply the Gecko drive with take up to 80V but I would keep it down to around 70V. Something like http://www.zappautomation.co.uk/elec...er-supply.html or find one with a little more amps .
Have you got two motors on one of the axis if so will the Pdmx board support slaving?
I couldn't fault the leadshines to be fair I just thought I'd get the geckos as there is so much info on them so I now have 4
the leadshine may come in handy for another project, just wanna get the plasma working
the Psu from zapp only has 3 outputs
yes I have two motors on 1 axis and yes I'm sure the pdmx supports slaving
doing some research and it looks like for these motors 62v is the right Psu
is this correct?
I think you will find that all the outputs are connected together so you can just connect two to one of the outputs.Quote:
Originally Posted by Lewywri89
If you read the Gecko manual it says that the motor voltage can be up to 20 time the rated voltage on the motor ie. 75.6V
I found this calculation online saying
take the square root of the motor inductance which is 3.8mh
times it by 32 and this is the voltage
is this the wrong way to calculate?
thanks again for the help
the pmdx 126 can only be slaved if used with pmdx 134 I think
Well you are using Gecko drives so why not take their figures? I take it you are using nema 23's motors, It will run fine with 62V but you will get better performance with a little extra.Quote:
Originally Posted by Lewywri89
I don't see in the manual re the 134 slaving it just looks like a breakout board for the gecko.
An axis can be cloned but the direction of the clone is the opposite directionso phases need switching Attachment 18510
Ok if you are happy BUT can you home them individually to square the gantry!!!Quote:
Originally Posted by Lewywri89
The 20 times motor voltage is a very rough guide for maximum voltage. If the motor inductance is known, the sqrt of the inductance times 32 is a more accurate voltage.Quote:
Originally Posted by Clive S
Gecko cover it in the power supply section of their stepper motor basics guide - http://www.geckodrive.com/support.html
So 60v - 62v would be the correct size psu? If I use 68v I assume I would have unwanted motor heat?
is anyone in the north west able to make a psu for me for a fee
cant find enough info to buy the parts and build myself
would like a linear psu to minimize electrical noise
Also what amp psu would be sufficient
thanks again
lewis
Asked pmdx direct And got Instant replies as I wasn't 100% on slaving and squaringQuote:
Originally Posted by Clive S
Attachment 18511Attachment 18512
It is not that hard to build your PSU. you only need a toroidal transformer, a bridge rectifier, a capacitor and fuse(s) if you want to be on the safer side.Quote:
Originally Posted by Lewywri89
I would go with a 45V 500VA toroid (or 625VA max.) but here you may find different answers as there is not a generally accepted formula to calculate the power you need.
I think you have it spot on and they can all be purchased here http://www.rapidonline.com/electronic-componentsQuote:
Originally Posted by paulus.v
I'd probably err on the side of caution and go for a 40V toroid.
Theoretically, 40VAC should give 57VDC, and 45VAC give 63.6VDC, however that's assuming perfect mains voltage of 230VAC, however it will more than likely will be higher.
Allowing 10% gives a reasonably safety margin.
Typical current guidelines IIRC are 50% of the total of maximum motor current for all motors (that gecko guide I linked to previously covers it), however it's always good to go slightly bigger, and from what I remember there's not much price difference between a 500VA and 625VA toroid.
Rapid Online should have everything you'd need. I normally use RS, but I've got an account with them so I get free postage. Airlink Transformers can be cheaper for the transformers.
Thank you
If I go for the 45v 625va from rapid online (new shop to me so thanks)
could anyone tell me the values of the other components needed
The bridge rectifier values should be higher than your output. 50A 600V is a common value, for example. You need aluminium electrolytic capacitor. One or more wired in parallel to the DC output of the rectifier. The voltage should exceed your output values, 80V or the more common 100V. Regarding the capacitance, the larger the better, but they are not cheap. I recommend at least 20.000 uF. You may find these large capacitors also with screw terminals that are easier to wire, without the need of soldering. On the toroid mains input I would put a simple glass fuse, T4A (time delay fuse). Not sure about the output fuse, probably a circuit breaker will be more robust. Personally I have only the fuse on the mains.
Don't worry about running higher than 32x Inductance rule because the motors won't be damaged or wear out from heat. You'll find they will happily run at 70Vdc without any issues from heat. The extra voltage is welcome because it gives more speed and to lesser degree torque.
All machines I build get fitted with 2 x 25V 500 or 625Va depending on number of motors. 625Va for 4 motors with Seconderys wired in series. This gives approx 68Vdc output. Don't go higher than 625Va else you'll suffer with In-rush current tripping fuses etc.
Regards Capacitors then you don't need one large Cap. You can use several wired in parallel. Infact your better doing this because it lowers ripple and is much cheaper.
3 or 4 x 4700uf 100v is what I use.
This is what I fit given your motors etc.
Toroid = 625Va 2 x 25V
Caps = 4 x 4700uf 100V
Bridge = 35A 300v or higher.
The wiring is simple as it gets. See pic to give an idea of how simple.
Attachment 18519
Should I buy the one from zapp automation for simplicity
68v 6amp linear psu
is 6amp enough for my system?