J Tech Laser and the X Controller

Has anyone tried installing the J Tech laser with the new X Controller? The instructions at J Tech are very good when it comes to the stock electronics that come with the X Carve. But they do not address the X Controller.

Should be straightforward. PWM and Earth on X controller to signal input on laser driver.

Please forgive my ignorance, but PWM?

Pulse Width Modulation. Since a laser (unlike a motor) doesn’t get regulated by voltage, we modulate the intensity by pulsing it. If you either have more pulses or longer pulses in a given time period (i.e. more “on” time) you get more power, versus shorter or fewer pulses means more off time = less power.

I have had several conversations with Jay Johnson at JTech regarding their laser and the Xcontroller. They have not gotten a X Controller to test yet but he did send a pic showing the laser going to the spindle PWM and ground to ground.

That is not completely true. There is an analog modulation method to control a laser diode’s intensity also.

We have 3 laser engraving machine builds here that the laser diodes are modulated by an analog voltage range between 0-5v for varied intensity control. The laser diode stays on, not pulsed on/off.

Our Shapeoko 2 is setup with a 6W 450nm laser diode it can be modulated three different ways using either TTL, PWM or analog modulation with it’s Flexmod P3 laser diode driver. The J-Tech driver can only be modulated with a TTL signal on (5v) or off (0v) or PWM to turn the laser diode on/off with 5v or 0v at a very high variable pulsing rate to control the laser diode’s intensity.

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Peter, can you post that pic?

The V/I curve for most laser diodes is pretty flat with very little change in power over their operating voltages.

“There is an analog modulation method to control a laser diode’s intensity also.”

Separate how your controller accepts control signals for output power (voltage range, PWM, TTL, etc) which are techniques to transmit your desired output to the controller, versus the diode itself needing modulation. While there is a little variance in the output based on voltage since laser diodes have negative resistance. You can vary the current, with a clamped voltage supply (which you must have anyway) and then pulse it. More problematic is you also need temperature compensation (more due to self-heating than environmental) as you whale more current through the laser.

These control techniques also are available on the X-Carve itself if you use an external speed controller (such as the SuperPID) which will accept a voltage range in 0-5vdc, TTL or PWM which clearly won’t drive a 110v AC motor, they are just control signals to the motor controller.

It sounds like your not familiar with how the Flexmod P3 laser diode driver works, or misunderstood my statement of us using analog modulation, so here is the manual.


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Even in the link you shared (thanks, makes it clearer) that device does not vary the voltage to the diode (it has negative resistance, it makes no sense to do so). In the words of the text: “[it is] considered a sophisticated voltage to current converter”.

So the voltage is simply an input to the current clamp (it doesn’t say if it is a buck limiter or what other clamp they use). The reason you can’t vary voltage very much to the diode (not the converter, the diode) is because laser diodes have a threshold voltage, below which they don’t lase, but with negative resistance raising the voltage doesn’t do a lot of anything beyond that since voltage wants to go to 0 and current to infinity (V=IR). You will note the output voltage is quite low (1.5v) while the current varies massively (4000%).

So either the TTL (sending the output current desired as a number) or voltage input (sending the desired output current as an analog voltage range 0-24v). So yes they aren’t pulsing for output variance, they are using current modulation (which works equally well, although without temperature sensing from the diode can result in large diode thermal variance in output power), but it has nothing to do with your input voltage (since you can drive this as TTL it’s obvious they aren’t connected).

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This is what we use to output the varied linear analog voltage to the analog modulation input on the Flexmod P3 driver. It’s driven by a stepper motor with timing belt and pulleys and controlled with Z axis commands in the gcode file for TTL/analog laser engraving images or cutting. Of course with our Shapeoko 2 we can use the PWM from D11 & ground with S commands to modulate the laser too.

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Now gents, I didn’t mean to start an argument. I merely asked if anyone has tried the J Tech laser with the X Controller.


There was no argument. It was just an informative conversation. Did you learn anything?

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Actually, I learned quite a bit. Thanks to all for the education.

Same wiring I use to the SuperPID which also accepts 0-5v (I wish the x-controller had variable output?) , PWM and TTL…

This thread has given me motivation to hook up my laser to a PWM signal and see what happens :smile:

BONUS: Non Scientific Current measurements will be included!

I made my own controller. Certainly no where near the quality of the X-controller. The one thing I did do was find an authentic Arduino and found it made the difference in getting the jtech 0.9g hex work. I now have two controllers - one which was the original parts from the X-carve purchase and the second with duplicate parts/pieces. The original set utilizes the latest 0.9j grbl and the other with 0.9g grbl. I just use the quick disconnects for the X, Y, and Z, as well as the USB cable. Works pretty well so far.


Again, no where near the quality of the X-controller but it was a fun build. In this case, I made two boxes as noted above- 1 for 09j grbl (spindle operations) and 1 for 09g grbl (jtech laser operations). I drew a lot of the inputs for this from this forum and I am thankful for those that posted the details. Having the two boxes works well for me. Unfortunately I spent more time on the sourcing the parts and setting up the electrical/electronics than I did in actually creating the boxes around them.

List of materials (the wood and acrylic actual boxes were left over pieces but basic 1/8" material bought at Home Depot and Amazon- 12"X12" pieces)

Uxcell Universal Panel Mount 16mm Aviation Connectors Plugs 5 Set (Qty 2) (http://www.amazon.com/gp/product/B00G9KLU72?psc=1&redirect=true&ref_=oh_aui_detailpage_o08_s00)
StarTech.com 3-Feet Panel Mount B to B Female to Male Adapter Cable (USBPNLBFBM3) (Qty 2) http://www.amazon.com/gp/product/B00FSYBKPM?psc=1&redirect=true&ref_=oh_aui_detailpage_o08_s01
Kalevel® 120pcs Multicolored 40pin Male to Female, 40pin Male to Male, 40pin Female to Female Breadboard Jumper Wires Ribbon Cables Kit (Qty 1) http://www.amazon.com/gp/product/B00M5WLZDW?psc=1&redirect=true&ref_=oh_aui_detailpage_o08_s01
Uxcell 3Pcs NO NC Momentary Square Push Button Switch DC 24V (Qty 2) http://www.amazon.com/gp/product/B00GLQVQ1Y?psc=1&redirect=true&ref_=oh_aui_detailpage_o08_s02
60mm x 25mm 24V DC Ball Bearing PC Case CPU Cooler Cooling Fan (Qty 2) http://www.amazon.com/gp/product/B00PZM2NJY?psc=1&redirect=true&ref_=oh_aui_detailpage_o01_s00
Inlet Module Plug Fuse Switch Male Power Socket 10A 250V 3 Pin IEC320 C14 (Qty 2) http://www.amazon.com/gp/product/B00F4MFMXE?psc=1&redirect=true&ref_=oh_aui_detailpage_o02_s00
Silver Aviation Plug 4-Pin 16mm GX16-4 Metal Male Female Panel Connector Pack Of 5 (Qty 2) http://www.amazon.com/gp/product/B00IJ673ZW?psc=1&redirect=true&ref_=oh_aui_detailpage_o03_s00
CNC Z-Axis Tool Setting Touch Plate Probe Compatible With Mach3 and Other Router Mill (Qty 1) http://www.amazon.com/gp/product/B00UNXXZAG?psc=1&redirect=true&ref_=oh_aui_detailpage_o04_s00
Switching Power Supply 400W 24V 16.7A for CNC Router Kits 115V/230V S-400-24 (Qty 1)
Bonus: Craftsman 089140301162 Drill Press Laser Assembly (Qty 1) (added this, after cutting in in half and being careful with the wires inside, to the end of my dust collector to add another way to verify I am in the right location during bit change out) http://www.amazon.com/gp/product/B009YERZQA?psc=1&redirect=true&ref_=oh_aui_detailpage_o07_s01
5pcs 2.54mm 8-Pin Plug-in Screw Terminal Block Connector Panel PCB Mount (Qty 1) (used on the gshield) http://www.amazon.com/gp/product/B00JM4RHQA?psc=1&redirect=true&ref_=oh_aui_detailpage_o01_s00
Bayite DC 6.5-100V 0-100A LCD Display Digital Current Voltage Power Energy Meter Multimeter Ammeter Voltmeter with 100A Current Shunt (Qty 1) – (I purchased different elements previously which was a clock in one display and an ammeter/voltmeter in another- not sure if I really like it or not) http://www.amazon.com/gp/product/B013PKYILS?psc=1&redirect=true&ref_=oh_aui_detailpage_o03_s00
“Authentic” Arduino Uno http://www.mouser.com/ProductDetail/Arduino/A000073/?qs=%2Fha2pyFaduiWnARry29OWyRv1Njr02QaYRfUvXA%2bq%2FxOo6yQwTCR1g%3D%3D
Gshield –https://www.inventables.com/technologies/gshield


Back to the OP topic… I have the X Controller and a Jtech laser on the way. Seems straight forward enough to connect to the spindle PWM. Anyone else using this yet? Anything else I should look out for?