Re: CP4 is definitely NOT water tight - VERY suseptible to DEW flooding


Joe Zeglinski
 

Chris,
 
    We are both professional electrical engineers, and your points here,  are so waaaaay off.
 
    An expensive and professional level electronics product like the CP4 ... should NOT require a paper or plastic bag on it,  to operate properly.
Putting a bag over the CP4 – while that would be an appropriate look for its present state –  would be difficult with all the attached cables in the way. A “dew heater patch” under it, if there actually were enough space between its backside and its cradle to still lock it down, might work – I doubt there is. There is probably enough heat given off by the enclosed electronics, to be equivalent to using a dew heater patch.
 
    However, I was thinking about integrating a “Liquid level sensor” inside the CP4, based on its present case design status.
 
    All that AP had to do was simply to put some RTV around just that ONE leaky RJ-45 connector, or use a proper water proof Ethernet connector, similar to ALL the others on the panel, or even just stipulate that it NOT be attached  on top of the RA axle of old model mounts,  and the CP4 would be “water proofed” – but they DID NOT, couldn’t be bothered to make the effort, and AP’s  “legal disclaimer” on water resistance was an easier out, for the company.
 
    Don’t know why you assumed my CP4 and telescope is installed inside an “observatory” – I thought I made it perfectly clear,  it was NOT. You must be skim-reading,  or confusing the post with some other case.
    The site is a backyard, 20 feet from the house, in the middle of a major city of 4 million people on Lake Ontario – not out in the deep woods or farmer’s field. We don’t have “corrosive air pollution” like many places in the US or China. People in the US, and most of the world consider Toronto as one of the cleanest cities, air, streets, etc. on the planet,  and we don’t wear medical face masks when walking outdoors.  – Ever been here? – Try again, Chris.
 
     The only way it would be corrosion,  from (distilled) water “dew”, is if the circuit board wasn’t PROPERLY RINSED during manufacture,   to neutralize solder paste acid, etc. and THAT acidic water solution would definitely make the incoming dew water,  corrosive. So, perhaps it is a case of poor AP manufacturing practices? But, I wouldn’t expect that.
 
     Mainly,  it is simply a case of plain drowning, and the circuits were blowing from a string of “orange rust”, obvious in the photo, between several pins along the bottom of the PCB. That is also evidenced by a huge wide swath of  “rust stain” along the case inside bottom ledge, at the base of the circuit board, about 2 inches long – that’s REALLY significant rusting. Would you care to see Marj’s photo of the first damaged board, and mine of the second drowning?
 
   It was just normal average city dew, perhaps a bit heavier on one night,  than  average. Good grief Chris, it “wasn’t raining” from  dew at the time – the skies were pristine, since I was imaging without problems.  It also happened to TWO CP4 boards – and by the way, NEVER happened to my original two CP3 boards, after over a decade of use, in the exact same spot. But then ... CP3’s don’t leak – CP4’s can easily leak, if facing skyward, rather than being vertical.
 
    And yes, the 14.5 inch primary mirror is doing just fine, no corrosion or dulling, nice and shiny, even after more than 7 years since re-coating, and the ASUS laptop sitting right beside it,  exposed to the same environmental dew conditions, (covered by a LAPDOME, but not closed up)  didn’t short out ...  so please don’t go spinning cobwebs about corrosive air around here.
 
    Don’t know why you think the circuit board is “dip sealed”, it certainly isn’t “Potted” which would be overkill.   Perhaps you actually mean “Conformal Coated PCB Traces” -  but obviously the solder joints  are NOT – they,  and all IC’ pins are bare solder, fully exposed to water and being short circuited by water and the iron in the rust, even if the PCB circuit traces themselves,  are (green) conformal coated.
 
    The CP4 needs proper water proofing, more than your suggestion of just relying on its  “PCB conformal coating”,  since Astronomical Telescope electronics are ACTUALLY MEANT to be exposed and used outdoors, at night, even in winter conditions of wind blown snow dusting. Even some  lowly porch and garage lamps are especially required to be UL/CSA rated for water penetration, before allowed to be sold to the public.
  What makes “astronomy accessories like the CP4” ... UL/CSA exempt?
 
    I would surprised if the CP4 could have passed UL or CSA certification – didn’t find it stated in the documentation – only the  FCC radio emission standards.
 
Joe
 

From: 'Christopher Erickson' christopher.k.erickson@... [ap-gto]
Sent: Sunday, October 7, 2018 7:00 PM
To: ap-gto@...
Subject: RE: [ap-gto] CP4 is definitely NOT water tight - VERY suseptible to DEW flooding
 


If you have a condensation problem with your CP4, simply put a plastic, paper or cloth bag over it. Or put a dew heater patch on the back of the CP4.
 
More importantly, if you are getting this kind of profound volumes of dew inside of your observatory or around and on the rest of your observing site and equipment while observing, you have other problems that urgently need to be dealt with. Serious problems. All of the rest of your electronics will be much-more vulnerable to corrosion than the CP4 electronics. Not to mention OTA parts and delicate optical surfaces.
 
The circuit board in the CP4 is dip-sealed and dew is, by definition, non-corrosive, distilled-water. However if your observing location atmosphere has potentially-corrosive gasses or particulates in it, like car/truck/furnace/propane/butane exhaust, that could be, when mixed with water, the source of your corrosion issues.
 
My suggestion is to stop fixating on the CP4 and start evaluating your entire setup location and see what-all is vulnerable and what can be done about the condensation and corrosive gasses and particulates. Your cameras, optics, computers and everything else are at serious risk, not just the CP4.
 
I have seen people use a big binder clip to wrap a beach towel around the lower half of their mounts and all of the electronics. Not high-tech and it doesn't involve new holes and machine tools, but is very effective.
 
I hope this helps. 
 
 
-Christopher Erickson
Observatory engineer
Summit Kinetics
Waikoloa, HI 96738
www.summitkinetics.com
 
 

From: ap-gto@... [mailto:ap-gto@...]
Sent: Sunday, October 7, 2018 4:50 PM
To: ap-gto@...
Subject: Re: [ap-gto] CP4 is definitely NOT water tight - VERY suseptible to DEW flooding

Hi,
 
    One further note of observation, on my original post on CP4 dew water entry.
 
    I should emphasize that the CP4’s  “Achilles Heel” – the CP4 Ethernet RJ-45 connector – is most prevalent for those who “Upgrade their CP3 on one of their OLD  AP mounts” and choose to continue using the new CP4 still attached,  angled upward on top of their RA axle. This leaves the gaps in the panel around the RJ-45 fully exposed to its own  dew condensation  as well as the excess dripping down off the OTA surface. There would still remain a slight risk of water going straight down the center plug’s hole, to the circuits inside.
 
    The best avoidance is to attach it vertically to the AP-900 or AP-1200 pier or tripod, rather than on the RA axle. This will make the CP4 as well protected as on the current model mounts – (AP-MACH-1, AP-1100 and AP-1600, etc.) ... in their vertically oriented position.
 
    You should still “RTV or Silicone rubber seal” around the Ethernet (and possibly a bit around the Guider) panel connector gaps, and either unplug the corner rubber stoppers from the new CP4 (black) models, or drill the two missing corner DRAIN holes in the first few years released CP4 (white) model versions,  case bottom edge,  backsides.
 
    Upon closer examination, I notice that WHEN the CP4 is mounted “vertically”, there is an...  additional BONUS in dew protection.
The “upper front cover” (the one with the antenna stick), sticks out in front of the connector panel by 3/4 inch, compared to the old CP3 which stuck out slightly less,  (1/2 inch).
 
    Although not likely intended, this acts as an “OVERHANGING ROOF”, protecting the panel of connectors below it, from being hit directly by dripping dew from above, such as dew streaming off the far greater OTA surface. Thus, the Ethernet connector’s oversized hole’s gaps (approx.  0.030 inch), would not endure a direct splash, in this configuration.
   
    Furthermore, if you still wanted a bit more protection, you could even glue a square dowel or piece of wood/plastic,  6-1/4 inches long by whatever extra thickness you like, along the upper cover’s bottom edge, to provide an even further outward diversion of the dew, away from the connector panel. Ideally, you could even locate a triangular prism cross section dowel, or just use a small piece of plastic or metal strip, to angle outward from just slightly above the CP4 top cover’s lower edge, which would divert the water drips even further away,  with a smoother run-off – while presumably still not interfering with the mount’s cabling.
 
    All of the remaining panel connectors, (except for the Ethernet and the Guider), are seen to be bolted VERY securely from beneath their panel surface,  making those connectors very  likely “water tight”,  to begin with.
 
     Along with the YOUR now properly sealing the Ethernet connector, and  “opened” DRAIN holes (for insurance), the CP4 should then be truly “water resistant” ... if not finally ....   “WATER PROOFED” -  ready in its vertical attachment position, to challenge dew,  unexpected rain showers,  and errant sprinkler blasts.
 
Joe Z.

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