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ramps 1.4 + a4988 polulu drivers + grbl || can't feed the motors

Posted by okuzster 
ramps 1.4 + a4988 polulu drivers + grbl || can't feed the motors
November 19, 2017 11:20AM
hi all, i have arduino mega, ramps 1.4 a4988 polulu drivers and some stepper motors. i make them work with marlin software before (more then a year ago) as a delta.

i wanna make a laser engraver now and as i have all this parts, i am thinking use them. i connected all but when it powers on, motors not lock them self, also not responding any command from pc. i am thinking it's from drivers but i have 5 drivers, 3 used and 2 never used, i tried them all, no change. (i need only 2 for now) this can be wrong wiring, but as i remember they worked that way before, still changed wiring orders from drivers to motors, no change.

what can be the problem here?

thanks in adv.
o─čuz
Re: ramps 1.4 + a4988 polulu drivers + grbl || can't feed the motors
November 20, 2017 01:12AM
Which grbl version did you use? Was it rewritten to match Atmega2560 pin assignment?

You can run a laser engraver with Marlin, too. There are many ways to switch the laser driver ( fan output, extruder step pin, any other PWM-capable I/O pin ) and also some tools to generate gcode in "inkscape".
Here's a grayscale example I made:

Re: ramps 1.4 + a4988 polulu drivers + grbl || can't feed the motors
November 20, 2017 09:21AM
i used this, it's mega version of grbl. i think it's updated enough for me.

i did run laser with marlin before from fan output, but there were problems with controlling it from pc, i had to move g-codes with sd card. i am thinking grbl would fit better for me this time.

edit: i have no problem with connecting grbl softwares to ramps, they can connect but motors are not moving or locking themselves when plugged.

Edited 1 time(s). Last edit at 11/20/2017 09:24AM by okuzster.
Re: ramps 1.4 + a4988 polulu drivers + grbl || can't feed the motors
November 23, 2017 10:15AM
i installed marlin this time to see if it's the firmware or hardware, it's firmware. so it's wrong topic, sorry.
Re: ramps 1.4 + a4988 polulu drivers + grbl || can't feed the motors
November 23, 2017 10:56AM
It might only be something simple like wrong signal-level on the enable pins....you said, they were locking themselves. ( right from the start? )
That would mean, they would idle when they should actually move.
Re: ramps 1.4 + a4988 polulu drivers + grbl || can't feed the motors
December 01, 2017 01:14AM
Quote
o_lampe
There are many ways to switch the laser driver ( fan output, extruder step pin, any other PWM-capable I/O pin )

Hello,
I have a big question mark: if I have a laser capable of 3.5 Watts aprox. 4 Amps, and I'll use the fan output on the Ramps board doesn't this burn down the circuit?? The fan output is capable for this much current?
The laser diode I'm talking about is found over here:
NUBM06 445nm Laser Diode
In 20mm Copper Module
W/Driver

Thank you in advance!
Re: ramps 1.4 + a4988 polulu drivers + grbl || can't feed the motors
December 02, 2017 12:16AM
I'm not familiar with DTR's laser driver boards, but mine has a"TTL" trigger input.
I made a voltage divider, that reduces the fan output voltage to TTL-level.

If this sounds like chinese to you, better look for a different hobby. Lasers are dangerous for non-educated people. Sorry to sound harsh, but I'm really concerned....
VDX
Re: ramps 1.4 + a4988 polulu drivers + grbl || can't feed the motors
December 02, 2017 01:26PM
... my 3.5Watt-diodes are driven with 2.3Amps max. and will wreck with more than 3Amps! - 4Amps sounds more like 6Watt-diodes ... so read better twice (or more), before attaching power.

Your driver should have two inputs - one with 4Amps (or less) for the power, another with a voltage level of mostly 5V max. for controlling/modulating the laser.

If you're not familiar with this sort of electronics and controlling, then find someone to help/inform/educate and read/learn for the basics ...


Viktor
Re: ramps 1.4 + a4988 polulu drivers + grbl || can't feed the motors
December 03, 2017 09:10AM
I really appreciate your concern and with all my respect let me tell you the same thig I say to all those who answer the same way: IF you are not willing to give an answer then don't answer at all... just ignore the topic, really, no problem at all! But just writing something and not answering is... not right! My simple question was if the fan output on the Ramps can handle 3-4 amps? As you can see on the page with the diodes they have only two (2) wires and if I'll need something else between the ramps and the laser please be kind and tell me what exactly or point me to somewhere else where I must learn "the basics" and only after that I should come back here to this forum to continue my journey...
Sorry to sound harsh...
VDX
Re: ramps 1.4 + a4988 polulu drivers + grbl || can't feed the motors
December 03, 2017 09:51AM
... your 3.5W-diode with 4A-driver sounds like a hard overdriven diode with a simple constant current driver, not suited for modulation (fast switching).

Better search a datasheet for the diode and check the recommended max. current and common working current, before you blow the diode after some minutes use.

DTR itself recommends other drivers for modulated applications ...


Viktor
Re: ramps 1.4 + a4988 polulu drivers + grbl || can't feed the motors
December 03, 2017 01:44PM
I've found this:
NUBM06
So... with the integrated driver is a No-No for Ramps...
What about such driver? ebay
VDX
Re: ramps 1.4 + a4988 polulu drivers + grbl || can't feed the motors
December 03, 2017 02:18PM
... your diode is specced with roughly 4Watts power @2,5Amps current @4,5Volts - so a slightly overdriven 3,5W-diode, which are normally driven with 2,3Amps max.

The internal "driver" is only a current limiter - if it's set for 4Amps, then it will kill the diode instantly! - Better remove this internal driver and attach the diode to a "common" LD-driver - maybe the type from your ebay-link.

But then again - adjust the current for max. 2,5A and clamp the diode into a good thermal heat sink (the bigger, the better) - normal coolers won't be enough!


Viktor
Re: ramps 1.4 + a4988 polulu drivers + grbl || can't feed the motors
December 04, 2017 02:40AM
Hi,
My friend, your help is much appreciate it! Thank you very much!
Maybe one last question... looking for a good driver on internet I observed that on many link it is specified: "driver for 445nm or for 800nm" and so on... is this really matter? All I have to check is the rated voltage an amperage, no? So even if my diode has 445nm wavelength I can use a driver "for 800nm"... right? (as long as the input/output V/A are correct)
VDX
Re: ramps 1.4 + a4988 polulu drivers + grbl || can't feed the motors
December 04, 2017 03:01AM
... the diode wavelength is irrelevant - only the needed current is of interest.

I'm developing my own drivers with higher currents of up to some ten Amps -- and use the same types for 405nm-LED's (up to 21Amps!) or 445nm-, 652nm-, 808nm- or 975nm-laserdiodes (up to 35Amps!) winking smiley

One essential point when driving laserdiodes near to max. rated currents is te "quality" of the driver.
Many (even comercial/proffessional) drivers generates short high-current spikes of up to some Amps when switching ON and OFF - the spikes are pretty short (some ten nanoseconds to microseconds), so the "positive" spikes will only reduce the life-time of the diodes ... but caution, when the driver too generates high "negative" spikes, when switching OFF (or modulating) -- this can kill the diode pretty fast !!


Viktor
Re: ramps 1.4 + a4988 polulu drivers + grbl || can't feed the motors
December 04, 2017 03:27AM
I see... can you recommend a good schematic for such driver or maybe a link for purchasing? I do not have an oscilloscope to verify this spikes, one of my good friends had one but unfortunately cancer took him a couple of months ago...
Again, thank you for your time and help!
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