Laser not firing on a new build.

[Jeffrey Aley]

I am really stumped here. My next thought is to borrow an oscsiliscope and see if the controller really is providing a PWM output. Likewise if there was simple way of generating an appropriate PWM output I could hook that to the PSU and see if it works. That way I guess I could identify which bit of kit is faulty. I'll have to let you know how I get on with that.

Meanwhile, if you or anyone has further thoughts I am ready to hear them.

Thanks for being a shoulder to lean on

Well, you should be able to see the value of L-ON1 using a voltmeter. Set up a job to cut a 10mm line at 5mm/sec. Power is irrelevant. You should be able to see L-ON1 change voltage when you start the job, and change back when the job stops (2 seconds later).

You could probably dummy-up a crude PWM signal using a 555 timer if you have that capability.

Try Russ' video #112 and 113, and possibly #97 for o-scope pictures.

Chris Medcalf also gave some advice - I have no knowledge of that, so I can't comment.

[Jeffrey Aley]

I haven't seen you mention the WP input on the PSU, I don't think. It needs to be pulled low, I think, if you're using the controller's water circuitry.

The more I think about this, the more convinced I am that this must be the case. I imagine that the input has an internal pull-up, which would signal "there's no water!" if the input is not connected.

[Les Brown]

Hi Chris and Jeff.

Thanks for your inputs. Really appreciated.

First off, thanks Chris for the explanation about the power supply info on the display. I've turned that off now so at least that is good.

I had originally included the water protection wired directly into the Ruida controller on WP1 as this is an option instead of wiring directly to the PSU and allows for it to be disabled in the controller software. I have tried it with and without it disabled to no avail.

I have also checked other things: I drew a series of simple lines and allocated different laser power to each. I ran it and used a multimeter to read the output from the controller pin 3, LPWM1. I got voltage outputs that approximately related to power defined in the lines, including around 5v at 100% power. From that I deduce that the PWM output from the controller is functioning.

I’ve just checked the voltage on pin 2, L-ON1. It starts in the region of 4.6v and drops to about 1.5v when the laser would be running, returning to the higher value as it heads back to home after finishing the ‘job’. So that looks right I think.

Earlier I tried something else. I disconnected the PSU from the controller and , after making sure it was safe, applied 5v to the ‘IN’ connection on the PSU to simulate a 5v PWM at 100%. (I took the 5v from the adjacent 5v supply of the PSU itself). Nothing happened. But I realise in reading your replies here that when I did that I hadn’t made the WP connection so it wouldn’t have worked anyway. I may try again.

Meanwhile, I am still mystified. I had made the WP connection via the controller in accordance with their diagram. When it didn’t work I disabled the WP in the software and in desperation even disconnected the switch too. This wasn’t intended to permanently ignore WP but just while I chased this problem. Maybe if it's disabled in software it assumes it exists on the PSU itself so I was shooting myself in the foot.

Something now occurs to me. Maybe the polarity of my water switch is wrong. One thing I never tried was firing the laser (just a pulse) with the water pump off. Or at least simulating the alternate switch polarity.

Just to clarify, to allow firing, should the water protect switch be closed or open? Seems obvious but I’m losing attachment with reality!

Thanks again, again.

[Les Brown]

Another update;
I checked the wiring - again. All ok. I also realised that of course the water protect switch needs to make contact to allow the laser to fire. I checked that the switch contacts do in fact make when the water flows and indeed they do. The switch is (was) connected to the Ruida as detailed in the schematic i.e. between WP1 and GND.

In desperation I disconnected that and put a link across WP and G on the power supply and it immediately worked. Hallelujah!!!!!!! So, having read an article on similar problems with a Chinese K40 machine where the fault was diagnosed to an inadequate flow switch I wondered if that were my case. But in actual fact my switch closure is not made by the flow switch but rather by a decent sized relay. (I used a DPDT relay as it also controls lighting of my flow indicator to backlight it red when no water and white when there is water). Anyway, I digress.

I couldn't leave the machine without water protection so I tried transferring the relay connections to replace the link I added to the PSU. In fact now replicating the PSU diagram but with the exact same contacts. I tried it and it works.

So, I'm now wondering why the Ruida controller didn't like the water protect connection.

Any ideas on that one?

By the way, I'm feling a little elated to have got this far; it's been painful. I wouldn't have managed it without your input to keep me going.

[Chris Medcalf]

The water protection on controller and PSU are independent, both need to be 'safe' to fire the laser. If the sensor is connected to the controller, WP on the PSU needs to be pulled low. If the sensor is connected to the PSU you can disable the water protection in the controller settings, or pull the pin on the controller low, if you prefer.

[Jeffrey Aley]

The water protection on controller and PSU are independent, both need to be 'safe' to fire the laser. If the sensor is connected to the controller, WP on the PSU needs to be pulled low. If the sensor is connected to the PSU you can disable the water protection in the controller settings, or pull the pin on the controller low, if you prefer.

After giving it some thought, I'd connect the WP to BOTH the RuiDa and to the PSU. This gives proper protection to the tube (can't use the "Test" on the PSU) while also showing WP Error on the control panel if the WP sensor fails or if the water isn't flowing.

[Toon Van Cauwenberg]

After giving it some thought, I'd connect the WP to BOTH the RuiDa and to the PSU. This gives proper protection to the tube (can't use the "Test" on the PSU) while also showing WP Error on the control panel if the WP sensor fails or if the water isn't flowing.

Does this work? I tried the same, but in my setup I found out that the PSU input is pulling down the input of the Ruida thus always saying that there is water flowing. Only disconnecting the signal from the PSU resoloves this.