single point grounding scheme and flexmod p3

[kl79]

one important point mentioned in the document is :

For example, this would happen if the metal housing of a DPSS laser is connected to the laser diode driver’s ground connection. A phantom ground connection would be made by screwing the metal DPSS laser housing down to the metal base-plate in the laser projector. Therefore, when assembling the laser projector, you will need to use an ohm-meter, to identify which components have metal parts connected to the electrical ground, and which might come in contact with the base-plate, or other conductive projector parts. Once such parts have been identified, they should be isolated from the projector base-plate.

I always recommend using nylon spacers under any laser, to provide a physical and electrical separation between the laser and the base-plate. The metal case of scanners, and thus, the X-Y mount of the scanners are another notorious place to generate a phantom ground connection, and this should be isolated where possible.

I'm not sure my red for example is isolated from the base, that's why I'm afraid by a bad light or another problem.

I need to check that

[sbk]

If you connect only the ILDA 25 to the central grounding point, it won't happen anything bad to the projector's components.

You should look at your scanners too. Most of mine have their alu head block connected to at least a galvo case, which one is connected through the scanner cables to the Gnd of the driver board... resulting in a phantom ground

[taggalucci]

To prevent this, all my laser housings and galvo blocks have a layer of silicon insulation under them. I have insulated mounting bolts as well.

[LaserGuy216]

so the best way to wire up would be ac power in is grounded to case & db25 ground is grounded to central ground.... but in the way do I need to isolate the metal dpss parts & scanners from the case ?

[taggalucci]

In order to keep AC ground and DC ground isolated, a number of things need to generally be isolated. It depends on whether the powered item is encased in a conductive housing and if that housing is connected to one of the grounds. Use a continuity test meter to find out.

My CNI DPSS lasers do not have DC ground connected to their casing. My SMPSs and galvos do, so I've had to isolate those with nylon bolts and spacers (SMPSs) and silcone pad (galvo block).

[dnar]

I too followed Bill's excellent guide, providing a star ground point for my grounds, inc. mains ground but excluding IDLA pin 25. Works well with no jumpiness.

[LaserGuy216]

so all power supplies, metal case, & ac power in are grounded to the same ground.. and ilda pin 25 will be left alone...

[Steve Milani]

......The major thing to take care of is where you will attach this central grouding point : to the ILDA pin 25 (Gnd) coming from the laser controller, or to the projector earth point (the metallic parts of the case). You just need to choose only one and NOT both.

I agree.
For my personal experience, inside all my five projectors the central ground point is attached at the metallic part of case. ILDA pin 25 is connected to galvos amp "ground" (not to its AC power ground) only.
Up today I had any problem with Laservawe or Kvant modules and ScanPro 40 or Laserword 50k scanners. Everything works fine.

[swamidog]

that's the same configuration i use and everything is rock steady.

I agree.
For my personal experience, inside all my five projectors the central ground point is attached at the metallic part of case. ILDA pin 25 is connected to galvos amp "ground" (not to its AC power ground) only.
Up today I had any problem with Laservawe or Kvant modules and ScanPro 40 or Laserword 50k scanners. Everything works fine.

[taggalucci]

so all power supplies, metal case, & ac power in are grounded to the same ground.. and ilda pin 25 will be left alone...

There appear to be two choices:

Two separate grounds: one for AC, one for DC with pin 25 connected, full isolation required.
Shared ground: both for AC and DC, no pin 25 connected, no full isolation required.

I prefer the first as there is no risk of AC ground noise affecting my DC signals.