Who is using ILDA pin 12 return and/or ILDA pin 13 shutter?

[weartronics]

Hi Ihor, thanks for this info, it is very useful. Best regards, Nic

[buffo]

How does the software drive pin 13? Is it always driven high when the software is running?

It's only supposed to be high when there is an active cue. That is, you have a laser frame active on the timeline. It could be zoomed out of the frame or faded to black, but as long as there is at least one active element on the timeline, the shutter is open.

If you ever have a portion in your show where you have no active cue in the timeline, then the shutter will close. My old shutter (an STP8) used to clank shut a couple times during some shows because of this. It always opened in time for the next cue, but the noise bothered me. Since it also didn't have a spring return, I decided to get rid of it in favor of a GM-20.

Isn't that a problem if the shutter moves every time there are blanking points?

No - see above. You can have a frame faded to black and zoomed off screen (thus no output) and still have the shutter open.

Finally, to answer your first question, here's my schematic for the interlock and shutter lines. (Note that I have a separate isolation switch on the line going to the shutter so I can manually close the shutter it even if the software wants it open. This is not shown in the schematic, nor is the shutter driver circuit shown.)



There is a larger version of this schematic available in the gallery.

Adam

[mccarrot]

Interesting schematic Buffo.

I use the shutter, but I have wired it directly to my emergency button, and my keyswitch to my interlock (power down complete projecotr)

[mccarrot]

I use pin 12 in my new safety over Ethernet design

[Stoney3K]

There is a larger version of this schematic available in the gallery.

Adam

How are your lasers responding to the power being hard-switched by a relay? I'd imagine some lasers would not be very happy with that... of course, in ideal situations, the relays would only disengage when the projector is already off.

Since I've got the remote kill/key switch inside my DAC, I can use the standard ILDA loop to switch laser emission, and I don't need extra cables for a remote kill box.

I still got to figure out a use for pin 12 (projector return), I might even abuse that as a TTL digital feedback signal to display some data (like actual output power, status, scan speed, etc...) on a display inside the DAC.

Shutters are on my wishlist, for now, I'm just shorting the modulation lines to ground. Does that also count?

[mixedgas]

[QUOTE=Stoney3K;125616]How are your lasers responding to the power being hard-switched by a relay? I'd imagine some lasers would not be very happy with that... of course, in ideal situations, the relays would only disengage when the projector is already off.

How is that different from any other line power inrush when the lasers are first turned on? I'd like to hear your reasoning on why their would be a difference?

Steve

[sugeek]

Pin 12: In RIYA PCI\USB\Ethernet controllers we use this pin as "Safety input" :
- if user connected this pin to GROUND ("emergency button") - controller make shut down all color channels, intensity and shutter, and move beam to center of coordinates.


Pin 13: some manufacturers (Neo-Neon for example) use mechanic shutter in their projectors; without high-level signal on this pin beam will closed.

In RIYA PCI\USB\Ethernet controllers we have command for control level on this pin;
in Multibus controllers we make high-level within translation show and low level when translation is finished.

Thank you Ihor,

I need to get the new firmware upgrade for the multibus basic sometime in the future. The micro was quite useful for testing projectors at PaCoLEM 2. I will be building my projector soon so this information is very relevant.

Best Regards,
Adam

[mccarrot]

This is a "software" solution. I had this discussion before with some safety experts and they say your safety must never rely on grounding or disconnecting the modulation input!

If you do you could still get laser output if :
1. DAC fails or
2. Your laser driver fails.

Some people have seen laserdrivers die and the laser started to output light, in your solution you will not be able to switch off the laser.

You would be able to do this if you had a shutter but this depends on the communication of you DAC.

[Stoney3K]

This is a "software" solution. I had this discussion before with some safety experts and they say your safety must never rely on grounding or disconnecting the modulation input!

If you do you could still get laser output if :
1. DAC fails or
2. Your laser driver fails.

Some people have seen laserdrivers die and the laser started to output light, in your solution you will not be able to switch off the laser.

You would be able to do this if you had a shutter but this depends on the communication of you DAC.

I was intending to use the 'ground modulation' trick as a makeshift shutter, not as a safety measure (the projector interlocks are for that, and I designed those to trip in case of DAC failure)

My thought is that a shutter is only useful to prevent any light leakage when you don't want the laser to be in-show, not as a safety measure. Therefore it might be more useful with gas/PCAOM projectors than with diode rigs which can be switched off completely without much hassle. I've seen a gas rig (fiber coupled into 5 separate heads) leak a beam at the Jarre World Arena Tour, my seat was right underneath it.

Killing the laser power does more than enough of a safety job in emergencies, since power cycling DPSS or diode lasers is way less cumbersome than gas or other solid state lasers. Just throw the switch, and watch the beams fly. In case of a (seriously) faulty driver which is outputting laser power clamped way up, you can always power down everything with a turn of the key on your remote box. I intend to add a 'mushroom' style kill switch to the DAC box for situations like that.

[buffo]

How are your lasers responding to the power being hard-switched by a relay? I'd imagine some lasers would not be very happy with that.

What do you mean, hard switched? The relay is in-between the regulated 5V DC power supply and the laser driver. When the relay closes, there is no surge, as the DC power supply is already powered up (it has to be on before you can press the run button, as the DC supply also generates the +12 volt power that runs the interlock circuit).

As Steve mentioned, it's no different than using the AC to DC power supply that originally came with the laser, as that unit would send power to the driver as soon as you plugged it in. (It's actually safer in my case, since the DC power supply is always on for a short period before the laser gets any power.)

of course, in ideal situations, the relays would only disengage when the projector is already off.

Are you worried about killing the power to the lasers while the modulation signal is still at some positive value? Because that happens all the time when you yank the power cord on a TTL laser. Most TTL drivers will float high with no input, so they are on until you remove power. This doesn't cause any harm, and I'm not sure why you think it would.

Since I've got the remote kill/key switch inside my DAC, I can use the standard ILDA loop to switch laser emission, and I don't need extra cables for a remote kill box.

The problem with this arrangement is that you don't have a remote "run" switch. In my opinion (which is also reflected in the CDRH rules), *any* condition that causes the projector to interlock should be a hard, latched shut-down. That is, once the projector is shut down, it must only re-start after being commanded to do so by the operator.

In your case, if you remove the ILDA cable, the projector stops. But when the cable is re-connected, your projector starts up all on it's own, doesn't it? That's not kosher. (Think about the case where you have an intermittent connection because someone stands on your cable...)

With my design, once any interlock condition trips that main relay, the projector is dead. The shutter is closed and all lasers have no power. It will stay in that condition until all interlock conditions are cleared *and* someone presses one of the two run buttons to re-start it.

Shutters are on my wishlist, for now, I'm just shorting the modulation lines to ground. Does that also count?

No. You need to turn off the power to the drivers, or else you need a hard shutter. It's recommended to have both, but technically if the lasers have no power, you are always in the clear.

Note that having a hard shutter is OK for emission control, but that won't help you if you need a case-intrusion interlock. (Granted, this is not required if the guy that built the projector is the one operating it, since you'd be protecting yourself from, well, yourself!)

I was intending to use the 'ground modulation' trick as a makeshift shutter

If by this, you mean emission control for safety reasons, then grounding the modulation leads is really iffy. I don't think you'll get an approval on your product report that way. The appropriate way is to remove power to the drivers.

My thought is that a shutter is only useful to prevent any light leakage when you don't want the laser to be in-show, not as a safety measure.

A shutter is the primary emission safety device when dealing with ion laser projectors. It has a secondary benefit in that you can block all light output while you continue to run the laser (to prevent re-starting it several times). However, it is still recommended for solid state projectors as well, as a secondary safety device.

Therefore it might be more useful with gas/PCAOM projectors than with diode rigs which can be switched off completely without much hassle.

True, they are absolutely required for ion laser projectors, but they are highly encouraged even with solid state ones.

Adam