I think the Perkin Elmer part is either a transformer or an isolated high-voltage generator. It's just a guess but I would suspect that part may be failing. It could be that the potting has developed a leak which is allowing air into some place where it isn't supposed to be, making it possible for it to sometimes arc-over internally instead of producing a proper output pulse. If this is just on the edge of arcing, then it could indeed display the random behavior you mention because there are so many variables involved in whether an arc happens (air pressure, temperature, humidity, presence of ionizing radiation/variation in the natural background radiation) I think your idea of looking for the proper input trigger pulse to the entire unit is a good idea. If that turns out to be OK, then the next steps depend on your confidence and ability. Maybe take a photo of the innards of the whole unit and let us have a look to judge the probability of whether something else other than the Perkin Elmer unit could be at fault. On Wed, Jan 24, 2018 at 3:49 PM, Darron Black wrote: > It is quite odd how it's failing. It's not consistent, apart from > starting off good early in the day and getting progressively worse until > it's skipping one out of every 3-5 flashes or so. (Temperature?) When > it is failing, it is quite random and not something like "every 3rd of a > sequence of flashes". It will fail even on the very first flash of a > sequence after a 3 second wait, for example... and then get the > subsequent flashes just fine. It's weird. > > The box says it's designed for 20Hz flashes... the actual rate when the > head passes is more like 4Hz. The head will have anywhere from 1-7 > parts to image, and then there's probably 2-5 seconds between head passes= .. > > In fact, the workaround when it gets really bad (and I get tired of > losing money in trashed parts) is to turn off all but one nozzle at a > time... which dramatically slows things down but at least the "3 tries > until parts are trashed" logic lets it keep going. The actual "parts > are trashed" event occurs if a single flash out of a head pass is missed > 3 times in a row (if there's a miss, the head will back up and retry the > pass twice then trash the parts and pause the job). With 5-7 > parts/flashes per pass, it starts to get pretty likely to occur. > > > Darron > > darron@griffin.net > > > On 1/24/2018 2:05 PM, Van Horn, David wrote: > > Sounds to me like the trigger transformer or associated parts are > failing. > > The tube will wear out eventually but it should be slow and failing bul= k > caps should give you flashes at lower light output before they completely > fail, plus they wouldn't come back from the dead. > > Recharge time might be an issue if the caps can't get charged between > shots, but that should give you pretty consistent misses at given positio= ns > but good shots at other positions, based on the time available to recharg= e. > > Recharge time could be pretty minimal on a line powered system though, > as opposed to seconds on a common camera strobe. > > > > > > -----Original Message----- > > From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On > Behalf Of Sean Breheny > > Sent: Wednesday, January 24, 2018 12:16 PM > > To: Microcontroller discussion list - Public. > > Subject: Re: [EE] Xenon flash bulb system missing strobes > > > > Hi Darron, > > > > If I recall correctly, these systems work by having a medium voltage > supply connected across the bulb and then EITHER a separate trigger > electrode OR a some kind of coupling (like a transformer) in series with > the medium voltage supply to be able to introduce a firing pulse. My gues= s > would be that this trigger pulse is not happening or is not being coupled > properly. > > Does the bulb have two or three terminals? > > > > Sean > > > > > > On Wed, Jan 24, 2018 at 1:56 PM, Darron Black > wrote: > > > >> I've got a xenon flash system providing the light for a flying image > >> capture of components on a pick and place machine. Here's the > >> datasheet > >> (MVS-7020-04) http://www.visionlighttech.com/sap/datasheets/302-7020- > >> 10.pdf > >> > >> Lately, it's taken to missing strobes. The pick and place was not > >> designed to handle missed strobes, and when that happens it throws > >> away ALL the parts on the head at the time. > >> > >> I figured it was the bulb at first, and a brand new bulb appeared to > >> help for a bit... but it's back to failing again. I've replaced the > >> bulb a second time with very little improvement. > >> > >> Since the xenon flash system is about ~16 years old... I figure some > >> capacitors may need replacing. > >> > >> > >> So far, I've really only got as far as the big capacitor attached to > >> the bulb itself. It's 12uF +/- 10% nominal, and two different meter > >> readings put it at 13.4 and 13.6 uF. It's of this type: > >> https://chicagocondenser.com/cmp/ > >> > >> It uses "polyester resin film and the finest grade Kraft paper > >> impregnated with mineral oil" (or silicone dielectric fluid, it's not > >> clear which) > >> > >> Can this capacitor actually GAIN capacitance as it ages? > >> > >> > >> I don't really see a safe way to measure this system while active to > >> see what's going on. It's pretty high voltage, and then there's the > >> blinding levels of light output. It's got a door interlock to make > >> sure you don't do something stupid like try to run it open... so I > haven't. > >> > >> > >> Any other suggestions? Does anyone else know of another common failu= re > >> mode for flash systems? The system is difficult to disassemble (or > >> reassemble, rather), so I'm starting with this cap. > >> > >> > >> Darron > >> > >> darron@griffin.net > >> > >> > >> -- > >> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > >> View/change your membership options at > >> http://mailman.mit.edu/mailman/listinfo/piclist > >> > > -- > > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at http://mailman.mit.edu/ > mailman/listinfo/piclist > > > > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > -- http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .