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Why some 5.5x2.0mm power plugs don't fit iOptron mounts

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#1 Michael Covington

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Posted 30 June 2020 - 07:38 PM

The strangest thing I've discovered so far about my new GEM45 is that although the power plug is indeed 5.5 mm o.d., 2.0 mm i.d., positive center, exactly as specified, some plugs of this size won't go into it, and others will.

 

I got out my calipers and figured out why.  The hole in the iOptron mount's housing is exactly 5.50 mm in diameter.  

 

But American-made power plugs normally run large.  Switchcraft and at least one other manufacturer round the size up to 0.218 inch, which is 5.54 mm, and then have a tolerance allowing them to be slightly bigger.  And judging by the ones in my parts bin, they always run large, not small.

 

Asian-made ones, on the other hand, run small, about 5.47 or 5.48 mm.  This includes the ones sold by Radio Shack.  I think it reflects clearer thinking about how the connector works; it can be a good bit smaller and still make good contact in the socket, but if it's too big, it might not fit through the outer hole (as happened to me).

 

Now we know.  When my mount is out of warranty, I may ream out the hole a tiny bit.  In the meantime I know why the plugs I use in my Celestron will not fit my iOptron even though the specified size is the same.

20200630-plugs.jpg


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#2 Michael Covington

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Posted 30 June 2020 - 07:39 PM

You could probably use a 5.0x2.0mm plug, though it would be loose.



#3 biz

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Posted 30 June 2020 - 08:00 PM

Actually the true size of these plugs you are referring to is 5.5mm outer and 2.1mm inner. most companies use this size but a few , namely Meade use 5.5 x 2.5.

cheers

Graham


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#4 Michael Covington

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Posted 30 June 2020 - 08:24 PM

Actually the true size of these plugs you are referring to is 5.5mm outer and 2.1mm inner. most companies use this size but a few , namely Meade use 5.5 x 2.5.

cheers

Graham

Some manufacturers say 2.0 mm in the center and some say 2.1 mm.  The main thing is to know that 5.5 x 2.5 is not going to make a good connection, as you point out.



#5 Devonshire

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Posted 01 July 2020 - 04:58 PM

Ahhh... Thank you!   

 

That may explain why I had a power plug issue with my Anker hub, as well ! 

I ended up cutting their plug off its power brick and splicing up what I needed...  


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#6 Michael Covington

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Posted 01 July 2020 - 06:25 PM

The essence of it is, if you are making a part that has to fit into a hole, you should treat the specified diameter as the maximum.

That is the point that Switchcraft missed.

 

 



#7 RandallK

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Posted 01 July 2020 - 07:07 PM

Hi Michael,

 

I ordered two right angled DC connectors off Amazon

 

https://www.amazon.c...394800_TE_dp_i1

 

These fit my iOptron CEM-40 perfectly. I also ordered 2 - 10' DC connecting cables to connect to the above. Saved $20.00 over getting the stock DC Cable.

 

I found the AC-DC OEM cable very loose on the AC plug end..it disconnected twice on my while imaging....very P O'd!!. Much happier running everything in my

back yard off 12 VDC.

 

Randy


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#8 eblanken

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Posted 01 July 2020 - 09:07 PM

Hi Michael,

 

I ordered two right angled DC connectors off Amazon

 

https://www.amazon.c...394800_TE_dp_i1

 

These fit my iOptron CEM-40 perfectly. I also ordered 2 - 10' DC connecting cables to connect to the above. Saved $20.00 over getting the stock DC Cable.

 

I found the AC-DC OEM cable very loose on the AC plug end..it disconnected twice on my while imaging....very P O'd!!. Much happier running everything in my

back yard off 12 VDC.

 

Randy

Hi Michael & All,

 

I have been using the iOptron mounts for many years. I found the best solution for the DC on these mounts is to use a right angle to pigtail tinned leads which I solder to an external, 12 Volt Lead-Acid, Deep-Cycle battery. I use a fuse between the battery positive and the pigtail. I purchased these pigtails in a quantity of ten from a company where I knew they would come from China. Alternate sources are go to iOptron and buy the long Cigarette Plug on one end and the "correct" connector for the mount you own. You can cut and solder the two ends as a pigtail if you want, so you get two cables for the price of one.

 

It is a sad commentary that buying from USA doesn't work in this instance. I would NOT MODIFY YOUR MOUNT.

 

Very Best Regards,

 

Ed (aka eblanken)



#9 eblanken

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Posted 01 July 2020 - 09:12 PM

Actually the true size of these plugs you are referring to is 5.5mm outer and 2.1mm inner. most companies use this size but a few , namely Meade use 5.5 x 2.5.

cheers

Graham

Graham is EXACTLY right on this matter.


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#10 dapalmer

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Posted Yesterday, 11:34 AM

Instead of reaming out the port, why not sand down the plug? Hold a piece of sand paper around it and spin it in circles. .04 mm is only 1.5 mil. That is less than half the thickness of a piece of paper. It shouldn't take much and you won't void your warranty. Either that or return the oversized plug.

 

Also, if you actually did buy 5.5mmx2.0mm power plugs, that is your problem. They are available but not standard. The iOptron uses the 5.5mm x 2.1mm plug. The first number is the o.d. of the plug, the second number is the i.d. of the hole the pin of the mount plugs into. A 2.1 mm pin will not plug into a 2.0mm plug.


Edited by dapalmer, Yesterday, 11:52 AM.


#11 Michael Covington

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Posted Yesterday, 11:39 AM

The oversized plugs have the retaining ring for my Celestron mounts and I use them with those.  I've found plenty of plugs that do fit.  I posted because I was surprised that not all plugs specified to be this size actually fit.

These fit and are what I am using:  https://www.amazon.c...uct/B0851CBH87/

 

But I like your idea of sanding down a plug.  I have several of them.  I may chuck one into a drill to do the sanding.

 

I don't think the pin diameter is the problem -- I don't think it's going in far enough to engage the pin -- but I'll keep looking into that.  The one that doesn't fit is Switchcraft S761K, and they do specify it as 2.0 mm i.d.

 

https://www.digikey....C240-ND/1289494

 

Thanks very much for your insight.


Edited by Michael Covington, Yesterday, 12:00 PM.



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