While I have to openly admit I have no idea without a ton of investigation how to fix the code on the Duet side of it there is a simple analog solution for this. If 0.4V is enough voltage to trigger your relay then simply add a resistor in line between the Duet and the relay to drop the voltage enough that when the output is low the relay doesn’t trigger. It shouldn’t take that much extra resistance drop the voltage to it where the relay doesn’t trigger and also would not be sinking any significant amount of energy when the pin is high to have a heat issue.
Sorry Tony. Once I realized it was going to be more than a reply or two that could be related to using the fan outputs I realized this probably wasn’t the right venue and moved it to email. Feel free to remove any unrelated posts as we are in contact via email.
I got your email so I’m guessing you sorted out whatever the issue was. I’ll be doing some research today after work for you.
Ahhh the fun of lasers from the east. And also the scary part as a 15W laser diode is nothing to be trifled with. I have a good bit of experience myself and a very good friend that has a ton of experience with various laser diodes in that 15W class. Feel free to email me: sales at DinkyMods dot com with what info you have on the laser diode and driver and I’ll be happy to do a little research and reach out to my friend as well to see what we can find for documentation.
Aside from the normal fan assignment process above with setting the tool to use the PWM fan output that you connect the ground to with the M563 above the only thing I can possibly think of would be if the laser is looking for a specific PWM frequency you can set that with M106 just like above when correcting PWM frequency for 4 wire fans. I have never had to do that on any machine for laser PWM control though. However there are some picky drivers out there so I would skim through laser driver’s documentation just to make sure if doesn’t have a specific requirement. This also got me thinking a lot of the laser driver’s have a pretty wide voltage range for the PWM/TTL control input. I would assume you have probably already read the docs to see if it can handle 12V letting you can skip this extra process.. but if any others are looking to do something similar I thought I would mention checking the voltage range as a lot of the diode lasers especially the lower power ones will allow control using 12V PWM/TTL
Here are the easiest usable 5V pins. V FAN JUMPER SELECT 5V is probably the best choice as it will be unused always if the rest of your rams are set to 12V. You can see it circled in green as are two other backup choices. Then like I mentioned before run the ground to the cooling fan or your choice’s ground.
Sorry for the delay I had something come up with my family. I should be able to go over the pinout and circle pins you could use later today.
No problem happy to help out. I’m out running a few errands but when I get back to the shop I’ll mark on the wiring diagram where you can get +5V safely. A couple pieces of information that will help ensure nothing gets damaged are: What version of the duet do you have. And what is the current draw of the laser that you are trying to use or just its wattage if you don’t know it’s peak current consumption.
That should be no problem at all. I’m assuming you still need 12 V for the other fan outputs. All you have to do in order to use the laser at 5 V is to run the ground from one of the PWM fan outputs and then run the positive lead from the laser to a +5 V output pin. The PWM signal is on the ground side so it would still be fully controlled by the fan output.
That’s fantastic. I’ve had a batch of 4 wire fans sitting next to the printer waiting for this. It’s going to be so satisfying having RPM displayed for each fan. Thank you very much for your work on this (and everything else you do) While it seems like it should be trivial to figure out the implementation as I assume it’s simply a matter of assigning an unused expansion header pin. However, I figured it wouldn’t hurt to ask if there is any documentation on how to setup the multiple tachometer lines. If not is there anything I can do to contribute when I set mine up by taking pictures, documenting the process, etc?
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