Advice on best interface to buy

[Arjan]

I'll probably pick up a Chauvette Xpress 512 tomorrow.

Welcome to the party

Thanks! I did get it yesterday and tested it for a short while, seems to work fine.

Is there anyway to see how many updates per second are actually being transmitted? I'm pretty sure that the problem is with my ancient Martin 805 RoboScan fixtures but their movement is extremely choppy unless the mirror is moving at it's maximum speed. Yes, channel/step is set to Fade, not Step in the software.

I know the 805 has only 8 bit pan&tilt but I've seen a video of the (infinitely more recent) ADJ X-Scan Led Plus that is also 8 bit but it seems to be much, much better at slow moves. I know there is no comparison in terms of technology but these RoboScans did cost a small fortune back then (I've been told US$3000). Effectively anything below maximum speed appears to be completely unusable with these Martins but I'd like to make sure it's the Martins and not something I'm doing wrong with the software. The movement in the 3d visualizer is perfect.

[support]

Does the fixture might have a pan/tilt speed channel ? If yes, you have to adjust it (3DView does not consider this channel).
If the movement is ok in 3DView, it should be ok for dmx data as well.

[Arjan]

Does the fixture might have a pan/tilt speed channel ?

No, it only has Lamp, Color, Gobo, Pan and Tilt.

If the movement is ok in 3DView, it should be ok for dmx data as well.

So 3DView does not interpolate between positions inbetween DMX updates, ie it only displays the beam in the exact direction of each DMX value that it receives?

I'll see if I can make a video showing how the panning/tilting looks, I have no idea if this is how it's supposed to be with this particular fixture. I'm told this used to be a fairly expensive fixture (US$ 3000) back in the day (not expensive for that time probably, I doubt there existed (m)any budget scanners back then). As such the mediocre performance is somewhat surprising.

I did notice that some slightly more recent Martin 812 scanners (still pretty old) have a vector and tracking mode:

The RoboScan 812 supports tracking and vector mode. In tracking mode, speed is determined
by the controller’s fade time. In vector mode, speed is determined by a value programmed
on a separate DMX channel. For smooth movement in vector mode, the
controller’s fade time must be set to 0, i.e., the position must bump from the current value to
the next. If the RoboScan 812 is set to run vector mode, tracking mode can be enabled by
programming the speed channels to 0.

The 805 doesn't have this.

Update: I just read the following

The draw back with the martin 812 is the stepper motor, when moving slowly the mirror will jitter, this happens less on newer lights due to new stepper motor technology.

I was planning on perhaps renting some 812's (I can get a very good deal on a set of 8) but I guess I should keep my expectations of these scanners low and at least I should try them first to see if the improvement, if any, is worth renting them instead of using the 805's.

Thanks,
Arjan

[support]

So 3DView does not interpolate between positions inbetween DMX updates, ie it only displays the beam in the exact direction of each DMX value that it receives?

Exactly.

[Arjan]

So 3DView does not interpolate between positions inbetween DMX updates, ie it only displays the beam in the exact direction of each DMX value that it receives?

Exactly.

That's good.

I found out why the scan movement is so choppy: these scanners only respond to a new DMX pan or tilt value if it is at least 5 levels higher (or lower) than the previous value. So effectively these are something like 5.5 bit scanners, not 8 bit. They do respond to all intermediate values but only if you jump to them from at least 5 levels away.

I tried all sorts of things to try and get them to break out of this hysteresis loop but to no avail. There is simply no way to get these things to move smoothly except if you let them move at full speed by jumping to a much higher or lower DMX value

Thanks for all your support.

[support]

Thank you for this report.