I’m looking at possibly running a servo on my MPCNC for pen plotting. I’ve got a Jackpot 1 board and ESP32 for wifi connectivity, so as far as I can tell I cannot run a signal pin for the servo unless I want to solder it to a top in on the ESP32.
Is there some way to accomplish this with the servo? I’ve got the C plug open and another TMC2209, would there be some way for me to use that setup for the servo?
Use the expansion header?
Are you wanting to us a RC servo? If so, yes you can use it with the JP1. This is what I have in my config:
z:
steps_per_mm: 100
max_rate_mm_per_min: 5000
acceleration_mm_per_sec2: 100
max_travel_mm: 5
soft_limits: false
homing:
cycle: 0
allow_single_axis: true
positive_direction: true
mpos_mm: 0
feed_mm_per_min: 100.000000
seek_mm_per_min: 200.000000
settle_ms: 500
seek_scaler: 1.100000
feed_scaler: 1.100000
motor0:
limit_neg_pin: NO_PIN
limit_pos_pin: NO_PIN
limit_all_pin: NO_PIN
hard_limits: false
pulloff_mm: 1.000000
rc_servo:
pwm_hz: 50
output_pin: gpio.27
min_pulse_us: 1000
max_pulse_us: 2000
I’m going to reveal my levels of noob here but the wiki didn’t really call it out - is this the expansion header?
Yes.
Thank you for clarifying - I am that new to this.
Should I be using gpio.12 instead of 27 if I use that pin in the expansion header?
Also, is it possible to switch the config between regular MPCNC Primo Z stepper and the expansion header servo without rewriting the config every time? I was hoping to just switch tools in Estlcam for pen plotting but if it’s one config or the other, so be it.
You still want gpio 27 because that is 5v. The ones in the expansion header are 3.3v. You would still use the 5v and GND from the header.
It’s probably easiest to have 2 configs. You can switch configs with $Config/Filename
Gotcha, so I solder the signal pin to gpio27 on the ESP?
Nope. I use the connector in the top left for signal. Then I use the 5v and ground from the connector.
This is how I have the servo connected on my pen plotter. I made a little board to try and make it cleaner.
Awesome - thanks tons! Any suggestions on printable servo mount pen holders? I was going to kludge one together since I couldn’t find one specific to the MPCNC.
I already have a few pen holders available on printables.com, and frequently use them at RepRap fests to do plotting all day long. We use the Z axis of the machine. Why are you wanting to use a servo, is it just to learn?
I’ve found the Z axis doesn’t lift pens fast enough with any of the mounts I’ve tried. It’s a quick of white ink - it’s heavily pigmented and needs to get a fast lift off, otherwise it leaves blobs. If I get Z+ fast enough in Estlcam to lift effectively, it doesn’t plunge Z easily enough to blob on landing.
A servo + light rubber band has done pretty well on a repurposed Atomstack laser engraver, it just doesn’t have the jog setup controls like an MPCNC does, so it involves a lot of guesswork. I was hoping to add a servo in an MPCNC mount to get that rapid lift/lower speed.
Interesting. When I use gel pens I use less than 1mm of spring contact, and there are no visible blobs, but I have not used a white pen. Me and Jeff even ran gel pens on drink coasters for open sauce last year and they were flawless.
With a very small lift <= 1mm the speed is less of a factor than acceleration is.
Have you seen the printed spring pens mounts of mine. The print width dictates pressure, so you can dial in pressure and travel.
