Can anyone make a device that I can attach a laser to so I can turn it on and off. I want to attach it to my Rose Engine to make designs in wood.
Hi Bill, do you already have a laser module? Iâm assuming we are talking a diode laser setup.
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Basic clarification; what is a Rose Engine? Itâs not familiar to me.
There are lots of ways to switch a laser, ranging from a simple mechanical switch and a power supply, through to sophisticated high speed 32bit laser controllers. It really depends on your needs.
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I think he wants to do something like this.
It depends on if he wants to control power as well as off and on. He could get a diode module with a driver and just use the TTL with a basic switch to do off and on at full power. Controlling power via PWM is a bit more than my experience.
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Since the pattern is created by moving the spindle in front of a stationary laser I donât think any modulation of the laser is necessary. Simply turn the lasers power on/off with a switch controlling lasers DC power.
To use a PWM control of power, some form of intelligence that is in sync with the spindle movement would be necessary. This could be a variable resistance that rubs on the cams (rosettte) driving the spindle. Alternatively, add another cam that is dedicated to power adjustment.
Power control doesnât seem to be a useful feature.
BTW, the lack of an enclosure and interlocks makes this a dangerous setup.
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If all you need is an on/off control, and you have Alexis or Google Gemini available, the easiest way would be a smart plug. Just plug the laser into the smart plug and that into the wall outlet. Pair the plug to the assistant you use and then you can turn it on and off by voice, and in most cases even program a scheduled off time.
Iâm thinking youâd want a DC power supply in the middle of the smart plug and the diode laser module unless youâre looking to let the magic smoke out of the diode laser module.
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I forgot my audience. I should have been more specific. I was suggesting putting a smart plug on the wall socket that supplies your DC power supply.
ya, youâve got to watch it or someone will try it as stated and wonder why there were sparks and flames instead of laser light. 
I donât think a simple on/off switch will do. The laser cuts in a rotating surface. In the center the laser intensity should be less than the outer circle. When you do not modulate the laser the pattern will be dark in the middle and light on the outside.
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Hi Bill,
Do not toddle the power on the main DC supply, the PSU on the laser module does not handle voltage spikes well, you need to let the capacitors discharge in between power cycles.
The laser module that you use to drive the laser will have a connector for PWM, depending on the the module it will be TTL (5v) or Line (12v) most modern modules are TTL it will also have a switch to enable PWM. Basically you apply >3.3v to the PWM + pin and the laser turns on full power, < than 3.3v and the laser turns off, so all you need to do is enable PWM mode, it will look like the laser is not working its ok, now using the 5v from the laser module connect a wire via a switch to the PWM + pin, closing the switch will turn the laser on.
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Hi Bill,
I just watched the video @NedMan posted, I was not familiar with a rose engine, looks very nice.
Note the warning on the side of the laser power module âDo not unplug the DC power while the laser is turned on otherwise it will destroy the laserâ, basically the capacitors and inductors on the laser module psu sends a voltage spike to the laser that can destroy the laser diode.
Iâm not sure what you are using to drive the stepper motor, if it is a simple Arduino CPU you have a very good source of PWM (TTL) that is synchronized with the stepper motor / position of the laser, so you can do a lot more than geometric patterns
Also if your laser power module is not TTL, no problem you can make a simple FET switch to modulate the line pwm from a TTL pwm source.
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From what I see it says âavoid direct exposure to skin and keep away from childrenâ. Good advice.
It would need to have be an exceptionally poorly designed DC supply to generate any kind of output voltage spike when the input supply is removed. If this were generally true then all the LED strips in my apartment would pop when I switch them off at the wall.. I could go on about the design of current-regulating dc power driver circuits used for LEDâs but suffice to say that the capacitors on the output are only at the output voltage, and just collapse down from that.
However; all laser modules contain active cooling; the diodes run very hot and need strong cooling. All have a big heatsink and powerful, loud, fans. Some even have internal heat pipes, peltier coolers etc.
Switching the cooling off while the diode is still hot can cause a damaging thermal shock in the diode, which expects to be able to dissipate heat from the body at a certain rate, and follow heat curves defined by the diode manufacturer.
One of my diode modules (the only one that came with a real data sheet) explicitly warns that the fan must be left on for a minimum of 5 minutes after the laser has fired.
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I am looking at this setup from China,
https://www.aliexpress.us/item/3256808843457115.html
It has TTL but what I donât understand is how do you control the board to make things work as I dont see a connection for a computer. Iâm only looking at this because if I take the board off of the CNC I have a worthless bunch of metal. I can connect the board of the one on the CNC with a computer. Ineed to apologise to everyone who has tried to help for not being up on this stuff.
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You do not need to connect it to a computer if you just want to turn it on and off, a simple switch will work. However if you want to control it by the computer the easiest way is to get a USB relay e.g âUSB Relay 1 Channel | 102056 | Other by www.smart-prototyping.comâ.
For example this is my 15w module you can see it has 2 connectors (PWM connection is duplicated).
The default mode is laser off, I need to connect the + pin on the 3 pin connector to the PWM pin on the left of the 3 pin connector to turn on the laser.
I actually drive the PWM from my CNC controller so I can cut wood.
This is the 1W laser same as you are looking at (note 1W is very low power you are better purchasing a higher power so you can adjust the engraving strength)
This module has a single 3 pin connector and a switch, the switch just bridges the power pin to the PWM pin so if the PWM pin is not connected the switch acts like an on/off switch.
Hi easytarget,
Unfortunately the PSUâs are about as basic as they can be, you have a good point about thermal however from experience and putting an oscilloscope on the lasers power lines, it is clear that the output stage has no filtering it is just a simple constant current design. The problem being is the non linearity of laser diodes, so the circuit can produce very high voltages via the output inductor.
Regarding home lighting I have high voltage LED strip lighting in my lounge and family rooms, the controllers that are supplied by the same company as the LED strips explode roughly every 9 months (yes I do meen big bang and smoke), the LEDâs last about 2 years (for some reason red always seems to burn out first). I pulled the supplied controller apart only to find a simple 240v bridge rectifier and a IR controller via a resistors controlling the gate of 3 tiny FETS.
The explosion is caused when an LED burns and causes the FET to overload, the resulting burn burns the PCB.
Bill, I should have said the USB relay is not PWM, it is just a switch so it can only turn on/off the laser. Yes you could turn it on/off fast and simulate PWM but not advisable with these simple relay modules.
However if you want to drive the laser with PWM the best way is to use a simple USB CNC controller e.g. https://www.amazon.com.be/-/en/Engraving-Machine-Control-Controller-Regulation/dp/B0D549QBFD
It can drive the stepper motor and control the PWM all from a simple app on the PC via the USB port.
This link explains how to wire up the board.. itâs under specification tab in your supplied link.
Looks like @Les_Smith has already figured it out.
