Thread: Gecko G540 or?
Think you've got to really experience the difference by using cheap drives to appreciate how much more performance good digital drives give. It's not just the speed it's the smoothness and motor heating, or lack of it.!
Combine this with decent motion control card and like you know it takes the machine to all new levels of performance.
Thank you for the input. Im still trying to figure out what procucts i should use.
The Gecko 540 solution felt like a pretty solid turn-key solution but of course limited compared to JAZZCNC´s setup above.
What do i need? I dont want to spend more more money than necessary right now but i dont want to spend it on junk either.
Tumblebeer, what did you start with?
The "what do i need" question was me thinking out loud btw
I'll start with reiterating the same advice pretty much everyone that has built something gives others: Buying cheap stuff usually ends up costing more than buying more expensive stuff. I know, you've heard it before. Yet everyone, including me, think themselves above this one fundamental rule. I'm not. You're not. No one is.
I started buying http://www.ebay.com/itm/2-4-phase-Ne...item3f1fba0066 together with mid range inductance 3nm steppers. I used a 36V powersupply.
When I built a new machine, I added another stepper, for the dual x-axis setup. This time (putting the new stepper on the y-axis), I went for a http://www.cnc4you.co.uk/index.php?r...product_id=362 together with an am882 from aliexpress.
Right now, I'm about to throw the old drivers in the trash and get 3 more am882's. The difference is huge between them. I mean really huge.
I haven't tried the geckos, but from what I've heard people are quite pleased with them. However, I haven't heard of anyone driving a slightly binding, quite heavy carriage at 15000mm/min at only 36 volts. My leadshine driver can do that. Also, I've seen a version called am882h, that takes ac input. No idea if it's any good, but it should make the power supply slightly cheaper and simpler.
As for using a motion controller, I'd recommend getting one. It'll make everything so much easier. You get smoother and faster motors from the clean pulses, you can use a modern computer (even a laptop) to run the machine, you can use a 100m long ethernet cable instead of a 1.8m parallell cable. Less than an hour ago, I added a crosshair laser to my machine, took me 30 seconds to hook it up to one of the relays on my plcm-e4 and I could control it from mach3. Doing that from a printer port would require an expensive bob, and you'd still be limited in the amount of pins on your db25.
I realise I'm rambling a bit here, but perhaps I got my point across. Get a motion controller, get digital drives. If you want to go my route, I'd say buy
1x plcm-e4 http://www.purelogic.ru/shop/elektro...i_ethernetusb/
and either build a toroidal linear psu (should be slightly better) or buy a 70-72vdc switched psu with some overhead (should be good enough, cheaper and easier).
Last edited by Tumblebeer; 23-10-2014 at 02:31 PM.
Ok i can see your point.
About the plmc-e4. How much is it and where can i get one? Is it russian?
Im a bit afraid that ill get in the Electronics part over my head with a "russian" plc.
Im still a bit confused about BB, motion controllers and so on.
Is it right that the plmc-e4 is a more advanced bb and motion controller in one? Whats the difference if you compare that one with the G540 bb for instance? If you got the time i would appreciate the "CNC Electronics for dummies "version of it all. I got the driver and motor part thats no problem.
I just found the PLCM-E3 at Zapps site. Price was ok to.
It all starts at the PC.? We need some way to communicate with the electrical components that make up the machine ie: Drives. The Machine Control software ie: Mach3, linux CnC etc all do the same thing in they convert G-code files into electrical output pulse signals. They also monitor incoming signals for things like Limit switches, E-stop etc. They also control External devices like Vacuum, coolant etc using general Outputs.
Now how these signals are produced and recieved can be done in a few ways. Most common is the Parallel port because it's free and part of most PC's.
Because the Drives are controlled with electrical pulses the quality and frequency of these pulses plays an important role in how the machine performs. If the pulse signals generated are poor quality then the drives don't ilke this and because the drives control the motors this passes down the line so poor performance.
Equaly the frequency of the signal plays a important role in the performance. The Frequency or number of pulses over certain time period dictates the overall speed that can be gained from the drives/motors for a certain amount of micro stepping set in the drives.
This all gets deep quickly so Without getting too deep now this all means that what ever produces the physical pulses has a big affect on the machine.
The parallel port is free but limited in both the quality and how many/fast the pulses can be produced over a certain time period or frequency. It's also limited in how many channels(axis) of signals it can output and recieve but will get to this later.
So the next step up is to use an external Motion control card that does the same Job but much better with dedicated circuitry to give much much higher frequencys and higher quality pulses. Often they also give more Channels of outputs and inputs known as I/O.
Now we need some easy way to connect or access these outputs and input signals and this is where the Breakout board comes into the eqation.
Most motion control cards only provide access to it's signals with a connection or multiple connections similair to the parallel port pins and this makes life very hard for connecting wires etc.
So here's where the BOB comes into play and makes wiring easy. They are essentially just distribution or I/O connection devices with some of the better ones providing features like protection for the PC with optoisolated connections and Charge pump in case PC connection is lost so it Stops any signals and the machine. They also provide other features like Spindle control and on-board relays to turn on/off external devices thru outputs.
Now while BOB's appear simple devices they are also very very important and THE largest source of trouble on any machine. Because they are an intermediate for all the signals then if the BOB is of poor quality it doesn't matter how clean or fast the signals recieved they will get distroted or lost before they reach the intended device so not something to skimp on which often happens.
Some motion control cards Like the PLCM-E4 (not the Plcm-e3 which is just a motion control card and needs a BOB) and the much much better CSlabs devices come with inbuilt BOB's. This takes one aspect or area for trouble out of the equation. Also to be considered is the Voltage that I/O can handle.? Better boards will let you use 24V logic which is much better for electrical noise immunity which doea plague some machines with cheaper BOB's which only allow 5v.
Now regards I/O then Motion control cards offer many more Inputs and outputs compared to the Parallel port. With the PP you only have so many inputs and outputs and by the time you have used up those needed for motors etc you'll be left with 5 inputs and 2 outputs.
This for some machines can be limiting and restrictive and if you need more then another parallel port and BOB are required.
Compared to Motion control cards that will offer 16 or 32 inputs along with 10-12 general outputs and 3-4 Analog input/outputs for controlling speed of external devices like VFD's or pumps etc.
So as you can see the concept is easy enough to grasp you have signals along with inputs and outputs which flow like below.
MOTOR OUTPUTS (MOVEMENT): = = CONTROL SOFTWARE - - MOTION CONTROL DEVICE- - DISTRIBUTION DEVICE - - DRIVES - - MOTORS
INPUT SIGNALS = = EXTERNAL SIGNAL(ie:E-STOP) - -DISTRIBUTION DEVICE(motion control)- - CONTROL SOFTWARE
GENERAL OUTPUTS= = CONTROL SOFTWARE (M) COMMAND- - DISTRIBUTION DEVICE(motion control)- - EXTERNAL SOURCE(ie: Vacuum)
That's about all there is too it.!! The tricky part is buying the kit which plays nice together and gives good performance. Unfortunatly the ones which play best often cost more. . .Lol
Last edited by JAZZCNC; 23-10-2014 at 06:33 PM.
Allright, it feels like im getting closer.
After some research i found that the Aliexpress price for the AM882 drivers are really good. I think im gonna go with them...
Stepper motors are not hard to find. Maybe ill take Tumblebeers recommendation-link even there...
How much is the PLCM-E4 and where can i get one?
Are there any alternatives with a good price/performance ratio?
Btw, i really appreciate your help guys!
Cheap motors which you may find on Ebay etc can have very high inductance which affects the speed you'll get from them so check the spec before buying.
I've used most Motion control cards and I can tell you the best by far is the Cslabs products but they do tend to cost more money, thou you get what you pay for.
That said the PLCM cards are OK thou I've not used the plcm-e4 yet only the E3 but suspect it's much the same just with built in I/O board(BOB).
Then there's the ESS Smooth stepper from Warp9 in the US. The ESS just pips the PLCM cards in terms of performance ESP when used with a quality BOB like the PMDX 126.
Again like Digital drives you do to some degree get what you pay for and with pulse and signal handling being very important to performance and reliabilty then IMO it's worth spending that bit more in this area.
Go with the CS labs unit! it has been pretty straight forward and i think a lot less to go wrong if its your first time. Im so glad i did as you can get some great support from people around these parts hay jazz ;)
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