+2 for the separate drivers.
By all means read 500 posts, hopefully it will persuade you not to waste time and money buying one of those drivers when you'll almost certainly want to change it to something better later on.
hi thanks all,
should i start another thread. feel like im hijacking.
machine will be a 6x2 or 4x4 not sure yet. its gonna be a work in progress. should be getting the workshop built in the summer. so doing the research etc now..
and its mainly gonna cut mdf... or perspex
Last edited by crossleymarko; 22-03-2012 at 08:56 PM. Reason: missed
Hi to everybody,
I am using two off these boards on my cnc machines for two years and have no problems whit these,but Iam a hobbyist no a pro.
Thes boards are very cheap instead they are sold for 140 Euros in Germay.I bought them in China for minus of 50 Euros.
At this price you can budget a reserve one in case off!
I've got one of these boards running my CNC3040.
I'm curious because it is running on 24V and gets nothing like hot, but it sounds like most here find they get rather warm. I think I could even run mine without the fan!
It also doesn't go very fast - I can get a reliable 1200mm/min from it. I did run it at 1900mm/min but found it occasionally skipped steps.
Is this normal? Have I got something set-up wrong?
The stepper motor shows about 2 Ohms across each of the connections to the board. I don't know if this means it is in parallel or series as the connections at the motor end are covered by heat-shrink.
The big resistors near the output (I assume current sense) are 0.4 Ohms.
Measuring across one of these I get 200mV on idle and 280mV at full speed. That is about 0.7A, so does this means the motor is drawing 1.4A because it is each phase? You can see the measurements below.
This is at idle. The time base is 50us/Div
This is at full speed, but please note the time base is now 10ms/Div
On the 'idle' graph I make it 12% duty cycle. So since current is 0.5A peak, that makes it:
Can't really find anything useful from the other graph - it just shows how at that speed the current is limited by the inductance of the motor. I guess we could calculate the motor inductance ... T=2.07ms, change in current is 700mA, so dI/dt=700/2.07=1.449A/s (linear approximation).. applied voltage is 24V minus a bit for losses so call it 23V, so the inductance L=24/1.449=15.9mH (roughly, oversimplifying a bit there). That's either a pathetic motor or I've done something wrong! Unless it's wired in bipolar series, that would be reasonable since the same motor in bipolar parallel would be about 3mH which is not bad.
Either way these numbers seem a bit fishy.. please could you link to the motors you are using (datasheet?) and confirm that the resistor you're measuring across is definately 0.4ohms, not two 0.4 ohm resistors in parallel or something like that.
The simple answer is just increase the current and so long as the motors don't get too hot, i.e. above 80°C on the case, it's fine.
The motors don't get hot at all, and neither does the driver board.
I don't know what motors they are, they are no doubt pathetic as they come with the CNC3040 and are small.
I stuck my LCR meter across one of the connection to the board. It tells me 1.93mH at 15KHz and gives 1.4R DC resistance.
I stripped back the wires at the motor end. There are actually 6 wires coming out, 2 of which are not connected at all, and the other 4 go to the board, so it seems I don't have any choice about series or parallel.
The resistors seem to be one per phase and are 0.25R. I thought it was 0.4R because the meter probes have a small series resistance.
Oh and the dip switches are set like this:
Last edited by Tenson; 11-06-2012 at 01:26 PM.
I doesn't seem to be any of those! Body length is 53mm, phase resistance is 1.4R and phase inductance is 1.9mH.
I found that when I set the current limit switch to 100% it ran worse.
I could increase the voltage to the board. The motors nor board run hot. Is it safe to do so, and should I make that mod listed earlier - http://www.mycncuk.com/forums/showth...ll=1#post19305
Did you measure the body length including the boss? If so it should be 51 mm and is probably a 57BYGH51-602A and produces 100 oz.in (about 0.7 N.m) at 2 A. Your resistance and inductance figure aren't a mile off considering the quoted tolerances.
I know the voltage rating is higher than 24 V but, considering the reliability (or lack of it) of these boards I would be nervous of doing so. Some of the mods suggested on various sites are decidedly dodgy!
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