J-TECH 3.8W laser assistance


I have a J_TECH 3.8W laser and your V1 mini Rambo 1.3 board. Can you tell me if these will work together on my MPCNC or do I need another board. Also, if so, do you have a “How To” set up the laser for best use and wiring instructions. I’ve noticed, I do not always keep up with you all on how much you know about electronics and building your MPCNCs.

Attached are photos of both items.

Thank you for any info and lessons learned.


That is great news.

I have a J-Tech 2.8W on a mini RAMBo and enjoy what I can do with it.

I will be glad to share more details when I get a chance (aka after work)

I used the original z-min S pin to provide the PWM signal for the JTech driver. I went ahead and redefined the original z-max (digital) pin to provide the z-min function. I also moved the x-min & y-min functions to the original x-max & original y-max pin locations on the mini RAMBO (this is just to stay with all of the min endstops on the same set of connectors). Doing this is strictly to make a PWM pin available.

Lastly, you need to identify the fan pin as the z-min pin.

The only two files that had to be modified are the configuration.h and the pins_MINIRAMBO.h

FROM MY configuration.h

//============================== Endstop Settings ===========================

// @section homing

// Specify here all the endstop connectors that are connected to any endstop or probe.
// Almost all printers will be using one per axis. Probes will use one or more of the
// extra connectors. Leave undefined any used for non-endstop and non-probe purposes.
//#define USE_XMAX_PLUG
//#define USE_YMAX_PLUG
//#define USE_ZMAX_PLUG

// coarse Endstop Settings
#define ENDSTOPPULLUPS // Comment this out (using // at the start of the line) to disable the endstop pullup resistors

// fine endstop settings: Individual pullups. will be ignored if ENDSTOPPULLUPS is defined

// Mechanical endstop with COM to ground and NC to Signal uses “false” here (most common setup).
#define X_MIN_ENDSTOP_INVERTING false // set to true to invert the logic of the endstop. MPCNC
#define Y_MIN_ENDSTOP_INVERTING false // set to true to invert the logic of the endstop. MPCNC
#define Z_MIN_ENDSTOP_INVERTING true // set to true to invert the logic of the endstop. MPCNC //RTM
#define X_MAX_ENDSTOP_INVERTING true // set to true to invert the logic of the endstop. MPCNC
#define Y_MAX_ENDSTOP_INVERTING true // set to true to invert the logic of the endstop. MPCNC
#define Z_MAX_ENDSTOP_INVERTING true // set to true to invert the logic of the endstop. MPCNC
#define Z_MIN_PROBE_ENDSTOP_INVERTING true // set to true to invert the logic of the probe. // RTM

// Enable this feature if all enabled endstop pins are interrupt-capable.
// This will remove the need to poll the interrupt pins, saving many CPU cycles.




  • Mini-Rambo pin assignments

#ifndef AVR_ATmega2560
#error “Oops! Make sure you have ‘Arduino Mega 2560 or Rambo’ selected from the ‘Tools -> Boards’ menu.”

#define BOARD_NAME “Mini Rambo”
#define LARGE_FLASH true

// Limit Switches
#define X_MIN_PIN 30 //12
#define X_MAX_PIN -1 //30
#define Y_MIN_PIN 24 //11
#define Y_MAX_PIN -1 //24
#define Z_MIN_PIN 23 //10
#define Z_MAX_PIN -1 //23

// Z Probe (when not Z_MIN_PIN)
#define Z_MIN_PROBE_PIN 23

// Heaters / Fans
#define HEATER_0_PIN 3
#define HEATER_1_PIN 7
#define HEATER_2_PIN 6
#define HEATER_BED_PIN 4

#define FAN_PIN 10 //8
#define FAN1_PIN 6

I will be glad to go over any other questions you might have

[attachment file=51955]


Doesn’t the Jtech run directly off of the fan PWN port? I thought they had a special driver so a 5v pwm pin wasn’t necessary.

Ryan…I’m not sure. To be honest I didn’t know there is a difference between a PWM pin and a 5V PWM pin. I always thought they were the same thing.

I have struggled to find a clear mini RAMBo and regular RAMBo pin list along with their physical location on the board. I stumbled across the z-min being a PWM pin last year and ran with it. I also use the same pin to drive a SuperPID for router speed control.

They run it off the Fan port of the Ramps, which is 12V PWM (there control pin specs up to 36V). They outlined it here, https://jtechphotonics.com/?page_id=3819.

I do not own one but it should be no different on the Mini and regular rambo’s. The reason for the remapping on the import lasers is they can only handle 5V on the TTL pin.

Hope this makes it easier.

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Thanks guys for the quick responses. I looked at the J-Tech link Ryan and it looks like they are working off a mini RAMBO 1.4 board. Does that matter much.

JD- Good stuff and tomorrow I think I will work on the connections, but possibly try the fan hook up to see how things go. I may need to reach out again if stuck, so thanks again, both of you for helping out. I can’t wait to get this up and running.


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