5W Laser – Mini-Rambo – Assembly Pics

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This topic contains 47 replies, has 11 voices, and was last updated by  Ryan 2 months, 3 weeks ago.

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  • #62164

    Cap
    Participant

    Hardware:  mini-rambo

    Software: Marlin

    Laser:  450nm 5W Laser Engraving Module Blue Light Marking Engraver With TTL Modulation Link (https://www.banggood.com/450nm-5W-Laser-Engraving-Module-Blue-Light-Marking-Engraver-With-TTL-Modulation-p-1218494.html?rmmds=search&cur_warehouse=CN)

    Thanks – Leo, David, Ryan, Ted G, Jeff, etc…  I read all of your comments and posts about lasers and I learned a lot.  It gave me the confidence to go ahead and give this a shot as a non-engineer, coding type guy.  In the vein of, “I’d rather be lucky than good”, it all worked – the very first time, thanks to the team on this forum.

    Pics of the laser and setup first then a breakdown of a few things I learned along the way.

    Packaging
    Contents of the box
    Came with Power Supply (12V), Laser, Driver
    Mounting holes on back of Laser (33mm x 33mm)

    Things I learned:

    Power.  I thought this was going to be a bigger issue than it ended up being.  Because my laser is 12v it was pretty much ‘plug and play’ into the Fan 1 connection on the mini-rambo.  NO ADJUSTMENTS were needed to the firmware or pins…which was awesome.

    gcode.  The J Tech plug-in for inkscape works.  I was quickly able to get text and simple outlines into executable gcode.  Still working images and raster…but that’s what the forums are for!

    Laser mount.  There wasn’t a mount that fit a 33mm x 33mm laser on Thingiverse so I had to dive into Fusion 360 to make my own.  It took a minute but it was a great learning experience  The new ‘Mesh’ feature in Fusion 360 allowed me to take the DW 660 Lower Mount designed by Ryan and remix it to make it work for my laser.  Its simple and it just works – which I like!  It takes advantage of the machine screw holes on the back.

    Laser Mount

    Initial Burn:

    Giving a friend a hard time - he's a UNC Tarheel fan

    This was really fun  and I learned a lot.  I continue to be appreciative of this site and everything that Ryan is doing to help others do awesome things.

    Have a good one!

    3 users thanked author for this post.
    #62174

    Cap
    Participant

    Ran out of room for photos on the first post.  Here are pics of the laser mounted.  I used the DW660 mount to zip tie the driver.

     

    1 user thanked author for this post.
    #62177

    Ryan
    Keymaster

    Great post!

    12v ttl!? $116 +$5 shipping already in the US. Great find, I think the $21 is worth not having to alter the firmware, not setting drivers, ordering from multiple places, and getting more power than the previous recommended laser. I am going to go broke buying attachments!

    One huge advantage when you go from etching to trying to cut something is compressed air, or similar right at the cut site. I have a pump from the Berd Air that I am not using, I think that would be pretty good for this.

    1 user thanked author for this post.
    Cap
    #62178

    Ryan
    Keymaster

    Are you sure it is 12v ttl? Have you used it at full power, it say 5V ttl? So you might have issues above 41% power (s106).

    #62180

    Cap
    Participant

    Are you sure it is 12v ttl? Have you used it at full power, it say 5V ttl? So you might have issues above 41% power (s106).

    I’m not 100% sure…still new to this.  I have run it at S 10, at S125,  and S255…with no issues.  I don’t have the right gear to check the output to the laser from the driver…it’s probably 5V, not 12V but I’m running it straight from the Fan 1 output and am able to control the power.  The power supply to the driver is 12V 5Amp.

    Definitely interested in the pump

    Thanks!

    #62181

    Ryan
    Keymaster

    Interesting. I can’t find any info. One of there other lasers says 5vttl 12v pwm, since you are using PWM that must be the case. I want to grab one but I hate going in blind on a $120 part.

    How do you have it wired, power and the positive side of the fan port? Any idea what the other port is for. I am getting the feeling the one you are using is PWM, and the other one is ttl. Sorry for a million questions I just think a lot of people would be interested in this or some of there other lasers as well.

    #62183

    Cap
    Participant

    That is how I have it wired.  On the Driver I’m going into the ‘Power In’ connection, and on the mini-rambo I’m matching the +/- on the Fan 1 Output.  Here are a few pics:

    IMG_1329
    IMG_1328

    I’m not using the ‘Yellow’ wire coming out of the driver, and that isn’t impacting my ability to control laser power.   I will try a grayscale pic to see how that goes and let you know.

    #62188

    Cap
    Participant

    quick results on some 1/4″ plywood.  To your earlier question – I’m not sure what the other output (PWM/TTL) is for.

    The circle was max 90%, min 20% power in lightburn (free trial) Power was too high, went pretty deep.

    The box was max 70%, min 20% power in lightburn.

    grayscale-test

     

    Attachments:
    #62197

    dkj4linux
    Participant

    Can’t argue with the results — which look good — but you are modulating (PWM) the *power* (12v) to the laser with the D9 fan output. This is the way lasers without TTL (or other) input are usually controlled. I have an LCheapo laser — the one in the ruler engraving video — that is controlled that way.

    Yours is actually designed for constant 12v power application and a separate TTL (5v) PWM to control the intensity. You’ve inadvertently discovered that the unconnected TTL input “floats” high — interpreted as ON — and then the 12v power modulation achieves the desired result… just like the LCheapo and with only 2 wires!

    Since yours appears to work nicely, I’d probably leave it that way… the floating TTL input probably isn’t best but it appears to work.  Mine is the same controller and I tap constant 12v from the RAMPS power and then pick the remapped D9 fan output from pin 44 on the RAMPS for TTL compatibility. Since it’s still the fan control signal, M106/M107 is used to control the laser intensity.

    Good work, Cap! — David

     

     

     

     

     

    2 users thanked author for this post.
    #62198

    Steve
    Participant

    iu-1

    Attachments:
    #62205

    Jeffeb3
    Participant

    Yeah, it’s like you’ve got the knob set to 100% and you’re turning it on and off fast.

    The results do look good.

    #62213

    Cap
    Participant

    Dave – I knew that you’d have the answer!  I don’t know that I fully understand it – I’m with Steve, mind blown – but it does make sense.  In your experience what would be the benefit of utilizing TTL vice working the PWM route I’m currently using?  I thought hard about buying a RAMPs setup to do what you described with pin 44 because it was a proven method but decided to give the mini-rambo a shot before I did so.

    Have a good one

    #62214

    Ryan
    Keymaster

    I thought hard about buying a RAMPs setup to do what you described with pin 44 because it was a proven method but decided to give the mini-rambo a shot before I did so.

    It works on every board, it is just a pin change. There might even be a way to do it without flashing the firmware. I will try and find it but I think you can specify what pin with the M106 command somehow.

     

    I don’t know that I fully understand it – I’m with Steve, mind blown – but it does make sense. In your experience what would be the benefit of utilizing TTL vice working the PWM route I’m currently using?

    I did a lot of searching last night about this. The advantage of ttl is you will get 255 levels of power very accurately. With PWM you will get a lot of levels but it is driver and laser dependent most start at level 20-30 and do not ramp up linearly in power. The way you are doing it isn’t really even PWM (yes and no), but you will get even less range than real PWM.

    They way you are using it you can dither your art to get a better range but you can see in the wheel you don’t actually have any gradual fade out, it is basically just off and on.

     

    I believe the instructions are there for changing the mini-rambo pin, and if you look into m106 commands I think that is an option as well. You should get that ttl pin hooked up and you will be amazed at what that laser can really do.

    2 users thanked author for this post.
    #62216

    Ryan
    Keymaster

    Heck, I forgot Marlin now has Laser control built in….Maybe it is time for some firmware updates.

    #62218

    Jeffeb3
    Participant

    Heck, I forgot Marlin now has Laser control built in….Maybe it is time for some firmware updates.

    Pew pew pew (sorry, I’m just a big kid).

    The laser stuff is a little muddled with spindle stuff too, so you’d be killing two birds with one stone if you can get a set up for lasers and your PID controller in one version.

    I think M106 has some problem with buffering, like it doesn’t go into the planner, or something. One of those pins was special and it shortcuts the planner and just turns it on, even if it hasn’t finished the moves to get there. Actually, that might be the fan pin? Or maybe the fan is the only one that goes into the planner? I’d have to look at the M106 code.

    1 user thanked author for this post.
    Cap
    #62220

    Ryan
    Keymaster

    Yup, just glanced at it. For the Rambo…two birds, the mini’s current laser pin is on the lcd header, there is another pwm pin on H3 Rx or TX. Better double check if we can actually use that pin.

    That gives us M3 commands instead of m106

    2 users thanked author for this post.
    #62223

    dkj4linux
    Participant

    Cap,

    I don’t use the mini-Rambo board (yet!) so you need to listen to Ryan, etal… and use the pins it provides for this. Please don’t buy a RAMPS board just for this. I think Ryan explained the TTL PWM thing pretty well so let’s hang loose and wait until we get definitive info on which pins to use. Then you can hook it up properly, without fear of breaking something  =8^)

    — David

    1 user thanked author for this post.
    Cap
    #62227

    Cap
    Participant

    Ryan/Jeff – thanks, I’m ready to hook up the TTL wire once we figure out where to plug it in.  Appreciate the info on TTL vs PWM, very helpful.  I ‘dithered’ the circle and ‘grayscaled’ the box for the test last night.  Probably should’ve mentioned that.

    Dave – thanks, appreciate the advice – I’m hopeful the team will find a solution.  The mini-rambo has been a great board, I’ve had zero issues with it.  Now that I know this works though I’m going to have to build a new machine, I gotta have both!

    #62235

    Jeffeb3
    Participant

    It would be nice if the 5V pin would just accept the 12V signal. Seems like a low part count to accommodate that for a high impedance input. Oh well, no one making these control boards is ever going to read this…

    #62236

    Ryan
    Keymaster
    #62238

    Jeffeb3
    Participant

    I’m not sure what you/they mean by TTL in this context. I thought that just meant 5V logic, and you’d still be using a PWM signal at 5V to determine the laser intensity. You would have the laser always powered, so you would get better control at low levels 5%.

    So if the control board added a zener diode to dump voltage over 5V through a resistor, the 12V PWM would look just like a 5V PWM (which I think is the same as pin 44). To use the fan pin, you would also need a pull up resistor (because it really switches between open and ground).

    Fan pin — Rup — 12V
    |
    | — 5V zener |< — ground.
    TTL

    The zener would dump any voltage over 5V to ground, which would have to come through Rup, which would limit it to something that would keep it all cool.

    I wasn’t thinking this would be a separate board, I was thinking they should put the 2-3 more parts on the laser control board. I have no idea why that board has so much on it. There’s probably something I don’t understand about all this.

    #62240

    Ryan
    Keymaster

    Yeah I have no idea why none of them have both voltages. You definitely understand this more than I do. I know at one point early on I tried a voltage divider and it did not work (I could have done it wrong).

    I thought the drivers had some sort of power curve to them, to make the laser function smoother. Most let you set the output, some let you tune the startup/low point. Maybe that is all it is.

    #62244

    Jeffeb3
    Participant

    I know at one point early on I tried a voltage divider and it did not work (I could have done it wrong).

    The D8,9,10 pins are either floating or ground, so you could do something like this:

    12V — R1 — FAN/OUT — R2 — GND

    I would try this with a scope first… I’m just spit balling here. I should probably test some of these crazy ideas myself.

    When the FAN is floating, the output would be R2/(R1+R2)*12V.
    When fan is ground, it will be pulled down (so 0V), and the current it has to sink is 12V*12V/R1. So R1 of 7k and R2 of 5k would be about right (and only sinking 20mA when it’s on). A little bigger R1 would be on the safer side.

    There’s probably something else that I’m oversimplifying. If you did something like this, it wouldn’t work:

    FAN — R1 — OUT — R2 — GND

    When fan was gnd, it would be zero, but when it was on, there’s nothing to pull it up.

    #62246

    Ryan
    Keymaster

    Interesting, I definitely would have done it the second way…figures. It would be cool to try it.

     

    I just started digging and the only available pwm pins are min endstops, Fine don’t need XY on the mini, Z maybe a probe. Or they can be flipped max to min then the…anyway rather not use these. The others are on p3 TX and RX, I’ll try these now.

    #62247

    Jeffeb3
    Participant

    Or, even easier:

    5V — Rpullup — FAN/OUT.

    10k pullup, pulls it to 5V when floating.

    1 user thanked author for this post.
    Cap
    #62248

    Ryan
    Keymaster

    That wouldn’t pop anything, 5v and 12v circuit mixing?

    Well crap, the list was wrong schematic was right, the only PWM pins are endstop min. I think it would cause some waves if I flipped the min’s to max’s. So the best way to go about using the laser 5v ttl/pwm is the way described here and on the mini page, bummer. This is going to come back up with some PID users. That is going to take two free pins, I am going to have to flip X and Y…..shoot, should I just do it, or make a whole new firmware? How many people actually use endstops on a mini?

    #62250

    Ryan
    Keymaster

    Cap, there are some instructions here on using the min pins. I am not sure I am ready to flip endstop pins yet for everyone, that could cause some irritation.

    1 user thanked author for this post.
    Cap
    #62259

    Cap
    Participant

    Ryan/Jeff – you guys never cease to impress me, good stuff.  I don’t quite understand the lingo yet…but I’m working hard to get there.  It’s like learning a second language!

    I’ve been messing around with lightburn today and the gcode it generates.  After tinkering with the settings a bit and talking with their customer service reps via email I was able to figure out how to drop the power below 20%, which allowed me to actually burn a grayscale image (I think!).  Pic below of some of the test burns I did today.  The difference between Red Oak, Pine, and 1/4 plywood were pretty distinct…Red Oak burned much better than the others for me.

    Test-Burn

    Thanks again for all the great advice.

    Attachments:
    #62261

    Jeffeb3
    Participant

    That looks great. The difference between dithering and grayscale on the pinwheel is pretty obvious. Maybe try etching a rectangle at the lowest setting where you can still see something. That would give you a good starting place for the min. I don’t use a laser, so that’s just a guess. If I were you, I would definitely make a bunch of stuff before I changed anything. Might as well, in case you break it later :).

    For anyone interested in the 5V fan pin discussion, I did some experimenting tonight too.

    Turns out… I was WRONG. That won’t work. Because they wired in an LED to show when the fan is on. So if you put a resistor between FAN1(-) and 5V, you get this (when the fan is off):

    12V — 1.8kOhm resistor — LED3 — FAN1(-) — 10kOhm — 5V

    Schematic here (I love open source): https://reprap.org/mediawiki/images/4/41/MiniRambo1.3a-schematic-pg4.svg

    So the pin ends up at 10V or so.

    What I did instead is connect a smaller resistor between FAN1(-) and ground and tada (that’s 5V).

    IMG_20180624_214735

    This looks like this:

    12V — 1.8kOhm — LED3 — FAN1(-)/OUT — R2 — GND

    The voltage at that pin is:

    (12V – LED) * (R2/(1.8kOhm + R2))

    With an R2 of 1.5kOhm, I get 4.7V. The LED voltage must be between 1.5-2V.

    It has it’s problems though:
    – M106 S255 turns OUT to ground, M106 S0 turns OUT to 4.7V. That’s inverted for most people (and maybe most CAM).
    – The resistor value needs to be kinda close. Bigger resistors and you’ll get a higher max voltage. Lower values and you’ll get a lower max (and it might not trip). It’s a balance between that 1.8kOhm resistor. You could get 3.3V out of this too though.
    – It’s mini-rambo specific. There are different setups for different boards. If they replaced the 1.8kOhm with something else, you’d need to find a different resistor.
    – It has to be the (-) terminal. The (-) is farther from the USB plug.

    It is a simple fix though.

    1 user thanked author for this post.
    Cap
    #62269

    Ryan
    Keymaster

    The things we do for fun… To skip all that is there some sort of logic translator, kind of like with the PID, read the 12v PWM output 5v? I suppose this might have some sort of lag though.  Just looking for a more universal solution.

    What about grabbing the signal right at the mosfet leg, isn’t that 5v and the mosfet directly changes it to 12v?

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