best stepper driver???????

[John S]

Only all in 1 is the Gecko 540

G540 4-Axis Motor Control

Unfortunately what with taxes etc it doesn't come cheap
Gecko will not sell direct to you as they have a UK agent, Charter controls who's web site is down at the moment.
You can but off Ebay.com for about £190 plus £30 shipping but expect to get hit for about £40 duty on top of this.

You can connect a lot of wires for this price plus if it does go wrong you are faced with shipping it back etc.

Separate units are far better

[dudz]

The "all in one" that I had was fine for about 3 months. We have power surges here every week and I think this is what fryed it.http://www.easy-cnc.com/3axisdriver.html

The one that you mentioned.... Is it likely to go wrong if wired correctly ?

I was going to buy this one ; CNC Router DIY Kit 5 Axis Breakout Board + 3x M542H Stepper Motor Driver 1A-4.5A | eBay

If it is compatible with my motors and PSU. Seems simple enough, and in cases

[John S]

I was going to buy this one ; CNC Router DIY Kit 5 Axis Breakout Board + 3x M542H Stepper Motor Driver 1A-4.5A | eBay

If it is compatible with my motors and PSU. Seems simple enough, and in cases

You are just buying what I posted to but you are prepared to pay £149.82 for it.

However if you buy three of the drivers i linked to [ which are exactly the same ] for £24.76 = £ 74.28 and this breakout board and lead

Upgraded 5 Axis CNC Breakout Board Stepper Motor Driver + 5V USB Cable + Mach3 | eBay

Look familiar ?

For £10.99 you will have spent £85.27 to get the same thing.

However if you insist on spending more then send me £140 and I'll bung 3 drivers, a lead and the breakout board in the post first thing tomorrow.

I don't mind and you get to save £9.82

[Lee Roberts]

John i have a question for you if you will.

A member who i dont think is around anymore once said to me that, if a motor is rated at 3a per phase that you only need to make an allowance for this of about 50% because the motor is unlikely to ever require its full amps rating, I think he did say its posable but you would have to be seriously working the motor for that and its just not likely.

Is that true?, also dose a motor draw more current when its doing rapids vs when the machine is cutting into stuff or dose it draw a steady amount consistently through all operations?

Thanks.

[John S]

Lee the accepted figure is 2/3 for a parallel wired motor and 1/3 for a series wired motor.
These are figures that Marriss Fremanis at gecko drive came up with and are repeated as law.

So a 3a motor in parallel take 2a and 1a in series.

However I have had clamp ammeters fitted to power supply leads and running a system under rapids and loads i have never seen these figures, they have always been far less.

In fact in many cases the figures have been very small, far smaller than I would have imagined so the 50% is a far more acceptable figure.

One machine I used to convert I used 650 VA transformers at 50 volt AC, in a cost cutting exercise, due to rising copper costs, I dropped to 500 VA and saw no difference, a drop to 400VA still didn't make a difference but going to 330 VA did,

So the drop from 650 VA to 400 VA halved the transformer cost.

[dudz]

Is there any benifit from having a USB instead of Parallel port ? ...I found this 3 Axis CNC USB Card Mach3 200KHz Breakout Board Interface Speed: 48M Win 7 | eBay
I know it is more expense, but is it better quality ? and are there benifits ?

[John S]

Is there any benifit from parallel port or USB...I found this 3 Axis CNC USB Card Mach3 200KHz Breakout Board Interface Speed: 48M Win 7 | eBay
I know it is more expense, but is it better quality ? and are there benifits ?

Not a lot to choose. More expensive and no better than a decent PP card but has the option of being able to use laptops and any USB interfaced computer.

There is an argument that PP port equiped computers are dying out, it is true but there are still 1,000's about for not much money that the argument isn't valid.
I buy Dell DX260 in bulk.



No mine but this is how they are offered, cost about £20 each with an XP license on them.

However we are trialling a couple of the USB boards, first one will be later this month and I expect that the price will drop.
The one shown is from a different company that the ones that developed them,

[paulus.v]

Lee the accepted figure is 2/3 for a parallel wired motor and 1/3 for a series wired motor.
These are figures that Marriss Fremanis at gecko drive came up with and are repeated as law.

So a 3a motor in parallel take 2a and 1a in series.

However I have had clamp ammeters fitted to power supply leads and running a system under rapids and loads i have never seen these figures, they have always been far less.

In fact in many cases the figures have been very small, far smaller than I would have imagined so the 50% is a far more acceptable figure.

One machine I used to convert I used 650 VA transformers at 50 volt AC, in a cost cutting exercise, due to rising copper costs, I dropped to 500 VA and saw no difference, a drop to 400VA still didn't make a difference but going to 330 VA did,

So the drop from 650 VA to 400 VA halved the transformer cost.

Shouldn't be taken into account the motor amps/torque vs. the machine weight/working material?

If I put 3A motors on a belt driven PCB milling machine it is impossible to use that power assuming to have idle-current reduction.

I think the 60% rule for the power supply works only with toroidal transformers which have an instantaneous power at least 25% higher than the nominal, and with one PSU for all motors because it is unlikely to have all axis under high loads at the same time.

John, what rated current had the motors and drives for your conversion where you used reliably a 400VA transformer?

[Jonathan]

However I have had clamp ammeters fitted to power supply leads and running a system under rapids and loads i have never seen these figures, they have always been far less.

In fact in many cases the figures have been very small, far smaller than I would have imagined so the 50% is a far more acceptable figure.

Part of the reason for your low readings is the sample frequency of the clamp meters is low relative to the frequency of the current the motors are drawing, so it tends to miss the peaks and generally not be reliable, especially if the meter is not true-rms. An oscilloscope reveals a lot more.

However, it is still true to say the rms current, and therefore power drawn, is substantially lower than the 2/3rds 'rule' implies. It's easy to show why - just look at the motor ratings to work out the power. For example the common 3Nm motors require 4.2A and 2.73V. Power is current multiplied by voltage, so P=4.2*2.73=11.466W. That's per phase though, and it's a two phase motor, so 2 times that which gives 23W. You're driving it from about 70V, so the current is pulsed such that the mean power does not exceed this rated power. Same formula again, so the mean current is I=P/V=23/70=0.33A.

That's why you see a low current (about 0.33A) per motor, not 4.2A or some significant fraction of that. The reason it helps to have the power supply rated for quite a lot more (i.e. 2/3*4.2) than this anyway is that the peak currents can be substantially greater, so you need a transformer capable of delivering that. That's not the only way to solve it though.