I’m looking here: http://reprap.org/wiki/Rambo_firmware#Motor_Current
If that’s what you’re doing, then I agree with your math. If 255 sets Vref to 1.66V, then that would be equal to 2A. I’m suspicious of 255 = 1.66A. is there somewhere you can measure it? That will get rid of this guessing game. It seems like 255 should be 100% duty cycle, so I would guess that’s 3.3V…
Yeah There are test points but there is just something off about they way these are set. I am guessing it is this way in case you are using a 24 or 36V power supply and it would change everything?
I have to set the value in pins-minirambo.h, but there is a section in config adv.h for the pwm but it is commented out. I have them set now to 900 which gives .78v on the xy ref pin, .76v on the z and E ref pin (why are they different?).
At this setting the drivers are hot but I can touch them, the steppers feel warmer than the 8825’s at .7v (1.4A).
The board is working great, I just don’t like this guessing thing and none of the formula’s seem to fit what is happening, even if the stepper rating is off I am trying to compare it to the 8825 settings and it seems off.
Nevermind, sorry, solid brain fart on my end.
The steppers I am using are rated at 1.5A per coil…I kept thinking 2A.
The equations in case someone needs them in the future (most likely me).
ITripMAX=(As stated Setting the drivers to 70%-90% of max rated amps is a good idea, 70% seems pretty good to me.)
VRef = ITripMAX * 0.8 (this gives you the ideal test point voltage)
Wv = (VRef / 1.66) * 255 (Wv=the pwm value needed (if you are using a rambo stop here I believe))
// Motor current PWM conversion, PWM value = MotorCurrentSetting * 255 / range
#define MOTOR_CURRENT_PWM_RANGE 2000
#define DEFAULT_PWM_MOTOR_CURRENT {900, 900, 900}
So Wv/255*2000=DEFAULT_PWM_MOTOR_CURRENT (Values are XY, Z, E)
When do you think theyll be up for sale?
This evening I hope. I have been beating up this one little board and it seems to be a great alternative to the ramps.
Its pretty much the same thing right. Same drivers and all, but just a much better design?
Well once it is up and running there is no difference.
This is the from the same designer of the Ramps stack, but with all the improvements he learned over the years and ramps iterations, and US components.
They are different drivers, and set in the firmware instead of the little pots. The connections are better and all plugs. There are more safety features built in so it should last longer, and be much harder to mess up. I have seen them take some serious back voltage from the steppers (please don’t try it on purpose), and embarrassingly I set the board down on my metal bracket while powered up and it rebooted and has had no issues.
I will still offer the ramps but I am going to offer these as well I feel they are a better option and worth the money especially for the newcomer who is more likely to make a ramps killing mistake and this board should not die.
The down side to the Mini is only one extruder port, whereas the full rambo has dual. But I have only seen a few dual extruding MPCNC’s but maybe I will get a few full rambo’s as well.
Thinking of ordering a board and a LCD display. Is there any reason I shouldn’t go with minirambo board? Does this board work well with ESTLCAM. Also will the wiring harness include the needed plugs or can I order them seperatly? I’m very experienced 3D printing but no CNC time yet. I do not care that there is no second extruder port. Thanks a lot.
Bob
Hi Bob. You have a few questions in there so in list format.
1)Is there any reason I shouldn’t go with minirambo board?Nope Mini Rambo looks like an all around improvement to me. I am a cheapo with the board cost so much more I really needed a reason to carry it, I put my stamp of approval on there.
2)Does this board work well with ESTLCAM. It works perfect with ESTLCAM, but it does not work with ESTLCAM Firmware. I don’t use estlcam firmware but if you wanted to there are other boards that are more supported. The basic workflow is shown on the getting started pages.
3)Also will the wiring harness in the kit include the needed plugs or can I order them seperatly? Not to sure what you are asking here so here is all of it. My wiring kit from the shop plugs into the mini-Rambo. The mini rambo does not come with the wires they are separate. The hardware bundle does come with the wiring kit.
You clarified everything very well. I ordered the minirambo board. Can’t wait to get it. Thanks,
Bob
I am fairly certain this is the same board that is on my Prusa i3 MK2. Been a bit since I’ve looked at it. It has served me well.
Some answers to your firmware questions may be answered by reviewing the MK2’s firmware, and there are thousands of people running this printer. Some are very savvy when it comes to firmware. MK2 owners groups on FB are good resources.
Yeah it should be the same board.
I think I have a firm grasp on all if it now. The new batch should be here tomorrow, and we can get a few more of these out into the wild. I am really confident now that this board is a major step in the right direction. A more robust set of electronics is just as good as a more rigid machine, but are much appreciated updates.
Has anyone found a good enclosure for the mini rambo board? I see a few meant to mount on a printer, just wondering what others are using. Thanks,
Bob
I actually haven’t even looked. I need to make one though at least for the lowRider.
Are there any that catch your eye a little or some specific design features you want?
I like my ramps case but it is too big. I like the open part of my ramps case so the wires don’t have to be super carefully arranged and that it has plenty of circulation. I have both the open ports facing down so no dirt can get it, a place to clip[ in the wires, a cover so you can get at it but don’t actually have to move it, if that makes sense.
Maybe something like that or?
Exactly like that. Just something to cover it up to protect it and maybe mount a fan in if needed. I don’t like to have to carefully arrange the wires either so extra room is a plus.
Bob
Sweet, No promises on time frame but I will move it up the todo list.
Maybe two versions, or two lids. one with the lcd and one without. Both with a fan somehow, and bonus points if I can make some of the parts cnc-able.
Thanks. No rush I’m still building the machine. An all in one solution which also holds the display would really be nice. I definitely will use it if you create one.
Bob
Hi,
I hooked up my mini rambo today. The board lights up green but the LCD display shows nothing. If I turn the knob it beeps and the light on the board changes to orange and flashed when the dial is turned. Sometimes the LCD starts flashing and beeping. This stops for a little while then starts again. This happens when the LCD is plugged in the same as your diagram. If I reverse where the two LCD wires plug in the LCD does nothing at all. Can you please let me know if you have any ideas what may be wrong.
I did turn the potentiometer to make sure the brightness wasn’t turned down.
I took a video of this behavior which I attached.
Thanks a lot,
Bob
In that video you have them wrong. You have to be careful with this the plugs fit in each other and in both facing directions. If you compare it to my picture you will see the red strip is on the wrong side so I am guessing you have the plugs facing the other way to fit in the box, meaning you need to turn the rambo ones around the wire will naturally go towards the middle of the board.