billy bobinski Posted August 25, 2009 Share Posted August 25, 2009 Hi Guys, This is a bit of a different one, because it's not manufacturer specific. Has anyone had problems with movers (any manufacturer) suffering from pan/tilt drift, wandering off by several degrees or even losing the preset position completely? If so what was the problem? Was it mechanical or was it software based in the head itself? As I say this isn't about any particular kit, more for my own interest. As always, any info would be greatly appreciated. Cheers,Billy Link to comment Share on other sites More sharing options...
Guest lightnix Posted August 25, 2009 Share Posted August 25, 2009 There used to be a problem with early V*L Series 200 luminaires, which caused them to slowly nod (or shake) their heads; they'd gradually drift a couple of degrees off position, then snap back. IIRC it was caused by a 0V line drifting off cal. The heads used 0V as a reference for centre pan and tilt postions. The fix was to get the oscilloscope out, measure some (now forgotten) point on one of the cards and adjust a trimpot on the low voltage board, until it sat back at 0V. AFAIK the problem was (mostly) cured with software updates; so it was a rare thing, by the time 2C's appeared. Link to comment Share on other sites More sharing options...
Ben Posted August 25, 2009 Share Posted August 25, 2009 This can happen with some old control desks, the DMX can drift slightly and it is most noticeable on pan and tilt. This can often be fixed with either software updates or sometimes replacement of DMX chips. Link to comment Share on other sites More sharing options...
niclights Posted August 25, 2009 Share Posted August 25, 2009 This will be an encoder reading problem. Simplest reason is dirt partially blocking one or more notches. As head moves the optical sensors don't see these notches and so it will move a few more degrees than it should. Each time this repeats the head drifts more out of position. Clean both encoder and sensor. Another possibility is the encoder wheel has come loose on the motor spindle. Remove belt, check and tighten if necessary. Finally you could have a faulty sensor/cableset. Link to comment Share on other sites More sharing options...
Tomo Posted August 25, 2009 Share Posted August 25, 2009 Many 'scans' use an open-loop design for mirror position, thus vibration or being knocked would cause them to lose position. On Cyberlights, this could be compounded during reset as they forced the mirror against an endstop with a rubber cap - if that cap was missing, they'd calibrate several degrees out of position. I've also seen these occasionally 'bounce' off the endstop during reset calibration. A concurrent post has been automatically merged from this point on. This can happen with some old control desks, the DMX can drift slightly and it is most noticeable on pan and tilt. This can often be fixed with either software updates or sometimes replacement of DMX chips.This does not happen. Seriously. *Faders* can drift, but DMX does not. Link to comment Share on other sites More sharing options...
J Pearce Posted August 25, 2009 Share Posted August 25, 2009 Some older desks, such as the Zero88 sirius (as far as I have been told) worked 0-10V internally then muxed up to DMX, so could be unreliable in recalling the correct DMX value. Link to comment Share on other sites More sharing options...
Ben Posted August 25, 2009 Share Posted August 25, 2009 This can happen with some old control desks, the DMX can drift slightly and it is most noticeable on pan and tilt. This can often be fixed with either software updates or sometimes replacement of DMX chips.This does not happen. Seriously. *Faders* can drift, but DMX does not. Yes it does, having spent a long time in service I can tell you that DMX can drift on old desks, this tends to be as said above when it is muxed up to DMX (hence older desks not new ones) but older desks often had less reliable DMX that on new units can be seen as drifting where the refresh rate and reliability are not great. I work with an old masterpiece regularly that has unreliable DMX and this can be seen as drifting on some units if left on one one value for long enough. I took the OP to be asking if units can drift not if they can calibrate out of position, there are many reasons units will not calibrate properly but drifting is a very different problem as it implies that the unit did calibrate properly but over time is losing its position. End stop calibration is unlikely to cause this, encoder reading however can. Link to comment Share on other sites More sharing options...
martinw Posted August 25, 2009 Share Posted August 25, 2009 DMX can drift slightlyIt really doesn't, honestly. The values of analog components like resistors, trimmer pots, capacitors and timing crystals will change over time (and also with temperature), but a microcontroller with some software will just continue to do what its always done. If the software is unreliable now, then it was unreliable to begin with. M Link to comment Share on other sites More sharing options...
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