I need some help connecting a diode laser to a PWM control board, and a hi/low signal from my Mach3 parallel port Break Out Board.
None of these cheap Chinese components come with good documentation. None for the BOB, none for the laser, and none for the PWM board.
Lets start with the laser control board. It uses a 12vdc power supply, and has a third pin labeled “s ttl + ,9Khz”. The laser runs at 100% when the 12vdc power is connected, and the ttl pin is left open. I can measure 2.7 vdc across the ttl pin and the 12vdc neg. pin. The laser will turn off when the ttl pin is connected to the 12vdc ground pin. There are some Mach3 user sites that say this method works for turning the laser on and off with the “z” axis up and down direction signal from the breakout board. The BOB signal is high for the z down, and low for the z up. Connecting this signal to the laser will turn it on (hi signal on the ttl pin) when the z travel goes down, and turns the laser off (ttl signal held low) when the z axis goes up. This works well allowing for the g-code generators to turn on and off the laser for simple engraving. That’s all I need , for now, I do not need to get into rastering control for photo etching.
I have tried to use a typical digital volt-ohm meter to measure the ma current on the ttl circuit. The only current I can measure with this tool is the current coming from the laser 12vdc neg. pin. Its 76 to 78 micro-amps when the ttl pin is grounded to the 12vdc neg. pin, and its also 76 to 78 micro-amps when I connect the same two pins to my BOB direction control pins, and then the BOB is flowing this current. If I try to put my meter in series with the signal from the BOB to the Gecko drive for the Z axis, I cannot get any current flow reading, and the in series meter prevents the Gecko from getting the Hi signal to make the z axis go down.
It IS SUCCESSFUL to run both the laser ttl and the z axis from the same signal source on the BOB. This gives the ability to turn the laser on and off with the z commands, and also move the z axis up and down.
So, the challenge is PWM control, when the laser is on, as controlled by the hi/low direction command from the BOB. Sure, it would be great to have Mach3 do it all, but for now, all I want is to run a cheap Chinese PWM board to set the laser strength. My PWM board uses a USB power cable, at 5vdc. It runs the laser just fine when just it is connected, but I cannot measure any signal current with my in line amp meter. It will block the signal.
My plan would be to connect the PWM board to the laser (on the + ttl pin and the 12-), ( connect the BOB COM+ pin to laser ttl pin and BOB DIR pin to laser 12v-), and leave the BOB connected to the Z axis Gecko Drive Board.
So…..what problems might I get (smoke) if I let the BOB pull the PWM signal low, which will shut of the laser when the z axis command is pulled low by the BOB. And, could the 9Khz signal cause any harm or performance issues to the Gecko Servo Motor Drive board? The z axis commands in the g-code are usually there (briefly like "move down .001", "or move up .001") to turn on and off the laser. (the state of the DIR command stays until another command is issued) However, there are some occasions where the z axis is needed to actually travel when engraving with the laser, for curved surfaces or cutting thru thicker materials in multiple passes. (That might project might best be done with g-code and spindle speed to PWM setup, in Mach3.)
If there is an issue trying to pull the PWM signal low, what might a couple of logic gates or transistors/resistor/diodes, do to make it happen? Some way to open the PWM when the laser is held low, and also isolate the Gecko from the 9Khz signal, if that is an issue. If someone with ttl background has a quick answer, I would greatly appreciate it!
Thanks for looking.
None of these cheap Chinese components come with good documentation. None for the BOB, none for the laser, and none for the PWM board.
Lets start with the laser control board. It uses a 12vdc power supply, and has a third pin labeled “s ttl + ,9Khz”. The laser runs at 100% when the 12vdc power is connected, and the ttl pin is left open. I can measure 2.7 vdc across the ttl pin and the 12vdc neg. pin. The laser will turn off when the ttl pin is connected to the 12vdc ground pin. There are some Mach3 user sites that say this method works for turning the laser on and off with the “z” axis up and down direction signal from the breakout board. The BOB signal is high for the z down, and low for the z up. Connecting this signal to the laser will turn it on (hi signal on the ttl pin) when the z travel goes down, and turns the laser off (ttl signal held low) when the z axis goes up. This works well allowing for the g-code generators to turn on and off the laser for simple engraving. That’s all I need , for now, I do not need to get into rastering control for photo etching.
I have tried to use a typical digital volt-ohm meter to measure the ma current on the ttl circuit. The only current I can measure with this tool is the current coming from the laser 12vdc neg. pin. Its 76 to 78 micro-amps when the ttl pin is grounded to the 12vdc neg. pin, and its also 76 to 78 micro-amps when I connect the same two pins to my BOB direction control pins, and then the BOB is flowing this current. If I try to put my meter in series with the signal from the BOB to the Gecko drive for the Z axis, I cannot get any current flow reading, and the in series meter prevents the Gecko from getting the Hi signal to make the z axis go down.
It IS SUCCESSFUL to run both the laser ttl and the z axis from the same signal source on the BOB. This gives the ability to turn the laser on and off with the z commands, and also move the z axis up and down.
So, the challenge is PWM control, when the laser is on, as controlled by the hi/low direction command from the BOB. Sure, it would be great to have Mach3 do it all, but for now, all I want is to run a cheap Chinese PWM board to set the laser strength. My PWM board uses a USB power cable, at 5vdc. It runs the laser just fine when just it is connected, but I cannot measure any signal current with my in line amp meter. It will block the signal.
My plan would be to connect the PWM board to the laser (on the + ttl pin and the 12-), ( connect the BOB COM+ pin to laser ttl pin and BOB DIR pin to laser 12v-), and leave the BOB connected to the Z axis Gecko Drive Board.
So…..what problems might I get (smoke) if I let the BOB pull the PWM signal low, which will shut of the laser when the z axis command is pulled low by the BOB. And, could the 9Khz signal cause any harm or performance issues to the Gecko Servo Motor Drive board? The z axis commands in the g-code are usually there (briefly like "move down .001", "or move up .001") to turn on and off the laser. (the state of the DIR command stays until another command is issued) However, there are some occasions where the z axis is needed to actually travel when engraving with the laser, for curved surfaces or cutting thru thicker materials in multiple passes. (That might project might best be done with g-code and spindle speed to PWM setup, in Mach3.)
If there is an issue trying to pull the PWM signal low, what might a couple of logic gates or transistors/resistor/diodes, do to make it happen? Some way to open the PWM when the laser is held low, and also isolate the Gecko from the 9Khz signal, if that is an issue. If someone with ttl background has a quick answer, I would greatly appreciate it!
Thanks for looking.
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