Laser Tutorial Question

Maybe I was just dense last night but do I plug the 40mm fan into the fan port on the laser driver? It seems by the tutorial I plug the fan directly into the power supply. Is the little 40mm fan enough to clear the fumes away as it cuts?

It is best to plug the fan directly into the power supply, but I have done it both ways.

I think the fan is technically just to cool the diode in the heatsink, It does okay at keeping the fumes away if it is aimed like my little laser holder. To keep your optics clean you should run more airflow somehow.

Ok… So if its plugged into the board when does it turn on and off?

Yes I printed your holder… Nice work on that one. I have 120mm like 250cfm fan which I will use to blow fumes.(Bitcoin miner type fan)

The cooling fan always stays on, like an extruder cooling fan. We actually use the fan control pins to control the laser so easy fan control is kinda out.

Ok so if it is always on when plugged into the driver board what would be the point of running a while all the way back to the PSU?

Run less power through the little PCB. If you are using a small fan no big deal at least on the driver I have.

It would just be the 40mm fan that is inside the holder. Do I need to keep a separate version of firmware for the laser and cnc?

My oppinion it is easiest to just use two versions, flashing only takes 2 minutes.

ok so i modified the firmware to remap pin 9 to 44. I measure the voltage across after setting the fan to 100% it was 4.47v, then turn it off 4.29v… There is always almost full voltage across pin 44 all the time regardless if the fan is set to on or off…

Whats going on?

I should also add it seemed to work the first time. But when I connected my laser driver the power wires got so hot with in seconds they started to melt then after that pin 44 was always at about 4.5 volts. I had a 10k resistor soldered between the pin 44 and ground as well as per the tutorial.

@Jason Are the wires you’re using for laser power thick enough to handle the 3 current, or at least 2 amps? Was the laser driver “tuned” before connecting it to the Ramps board and applying power? And finally, double-check the polarity on the driver’s power inputs. I noticed that on some of the newer driver variants out there, the JST connector goes into the power connection with the positive lead connected to the negative output on the board and vise-versa. If this is what happened with yours then you most likely toasted your Ramps and possibly your mega board too. See the link below for details.

See this post

The wires were pretty thin. The driver was not tuned I had not gotten that far yet, i was just applying power the first time to tune the led light to turn on. How do I check the polarity on the board? The board and arduino still work fine i can move the x y and z axis just the output voltage on pin 44 is not working. it is stuck at 4.47v.

The board should be silk screened on the back side and you’ll see the + and - markings by the power terminals. Note which side is closest to the edge of the board per the board markings(+ or -). Now flip the board over and see if the red + lead on the jst connector is actually on the correct side. I’ve seen some boards where the connector leads are backwards and in every case the markings on the board indicated the correct polarity, the problem was always the connector.

You are right… The jst plug was opposite of the silk screened polarity

If you want to troubleshoot the 44 pin then you can try flashing a basic sketch to the board that just does an analogwrite to the 44 pin with a value of 127, lots of examples of analogwrite command on arduino site. That should get you a reading of about 2.5 volts on the pin. If that doesn’t work then your 44 pin may be damaged. At that point I’d try switching to 42 pin instead. Same instructions, just use pin42 instead of 44 in the pin assignments and connect ttl to that pin instead.

I will try pin 42. If that does not work I will try the voltage divider on D9. To confirm there is a 7k resistor between the + and - and a 10k on the + side as well?

In that case, there was likely damage to the ttl pin when you powered up the driver. Try switching over to pin 42 and cross your fingers:) Worst case is you’ll be out 10 bucks for a new mega board. The driver i used for the tutorial can’t be found anymore. It was much easier to work with and the power input was not polarity sensitive and could be connected either way. The board you’re using should be tuned with a diode test load as explained In the guide.

It would have fried the mega and not the ramps? I built the test load with 1 resistor and 3 diodes as per the instructions.

I’m pretty sure the auxilliary pin blocks on the ramps board are just breakout pins going directly to mega but I’m not positive. I’m curious about this now. I’ve tried a resistor voltage divider on D9 but didn’t have much luck with it.

Shoot ok. I thought the voltage divider was a safe option.

So to clarify the procedure I should follow is

  1. Flash to pin 42
  2. Test for variable voltage ~5v at 100% fan at pin 42.
  3. Connect 12v to driver (possibly where i made a mistake… I connected ttl at the same time)
  4. Turn on Current LED then adjust voltage to 5.5v turn off current led.
  5. Attach load to laser + -, connect 12v and ttl.
  6. adjust voltage to 1.7