Lightobject.com Support Forum

Well, I am making good progress with my 40W laser upgrade. I have a problem though with the red dot pointer and the digital ammeter. I have both running independently. They are powered by a 5V regulated power supply. Up until yesterday I had the ammeter (digital, from Marco) hooked up to the 5V supply but not connected to the negative pin of the tube and the tube power supply. The digits lit up showing 00.0 and the red dot pointer was doing it's thing nicely. I then wanted to test the tube so I connected the tube's negative pin to the ammeter and the remaining lead from the ammeter to the negative connection on the tube power supply. Now both the ammeter and the red dot pointer fail. If I remove the red dot pointer from it's aluminium bracket both run again. It seems that somehow the red dot pointer is shorting the 5V supply.
The outer casing of the red dot pointer is aluminium but I cannot see how it would cause a short. I have looked inside and there don't appear to be any loose wires touching the case. The pointer was already in the machine before I started the upgrade but it is similar to the one that Marco is selling. It is 10mm outside diameter and has an adjustable focus. It was only after I completed the ammeter circuit that the problem started. Everything else works normally. The tube fires and all the stepper motors work and communicate with lasercad. Am I missing something????

Regards,

Preso

Unless it is overload (means that not enough current to drive both devices), otherwise I don't see the possility of not working. Check your connection see if somehow you ground the +/- by mistake


Marco

In the end I got lazy and just insulated the red dot pointer mount.

Preso

I was doing some reading on another forum and found out that the laser pointer of the type that I am using is case negative. This would explain why the laser pointer shorted out the 5V supply. Strange though that it only happened after I connected the digital ammeter. As it turns out I abandoned the idea of using a beam combiner lens. I will instead mount the laser directly to the air assist shroud. I have 3D printed some fittings in ABS plastic which angle the red laser beam at an angle of around 40 degrees to the vertical. This system also assists with focussing the main beam.

Preso

Hi Preso
I'd be interested to see what your 3D print looks like. If it works will you be willing to share the files?
Nick

I too am curious of your 3D print of this.

I thought of doing something similar to avoid having a beam combiner lens but didn't get to figure out what I was going to do for a angled mount.

The first Chinese laser we had at my former school had a pointer setup like the one I have replicated. Initially I thought it was a fairly cheap and simplistic idea however it does have the advantage that it can be aimed so that when your focus distance is correct, the spot made by the pointer will be directly under the centre of the cutting beam. When I set mine up I set the focus distance with a piece of 8mm acrylic (that is my correct focus distance) and then burned a spot in a piece of wood. Then you only have to angle the red dot pointer to coincide with that spot. Tighten up the M3 screw to set the angle and the M4 screw can be used to rotate the collar around the air shroud so it is in a convenient position. The only down side is that the power supply to the pointer has to be threaded through the X and Y cable chains and then back to the electronics bay. No problem if you are building from scratch but a pain if you are retrofitting like I was.
Evidently, STL files and other CAD formats cannot be attached to this message but I will put the files for both parts up on Thingyverse if anyone wants to have a go. Here is the link http://www.thingiverse.com/thing:472793/#files

Regards,

Preso