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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.


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#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 02 July 2020 - 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, 02 July 2020 - 11:52 AM.


#11 Michael Covington

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Posted 02 July 2020 - 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, 02 July 2020 - 12:00 PM.


#12 Jose_Salcedo

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Posted 04 February 2021 - 07:39 AM

You can find two types of plugs - and two types only - with 5.5mm outer diameter: (1) with 2.1mm central pin, male or female, and (2) with 2.5mm central pin, male or female. Normally, the 2.5mm central pin variety is used for higher current needs. You should not mix them, as a 2.5mm central pin male plug, for example, will most likely not make electrical contact - or make very poor electrical contact - with a 2.1mm female plug. I suggest to use cables with the proper connectors at all times. If necessary, use plug adaptors from 2.1mm to 2.5mm or 2.5mm to 2.1mm. You can find them on Amazon.



#13 Michael Covington

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Posted 04 February 2021 - 04:23 PM

You can find two types of plugs - and two types only - with 5.5mm outer diameter: (1) with 2.1mm central pin, male or female, and (2) with 2.5mm central pin, male or female. Normally, the 2.5mm central pin variety is used for higher current needs. You should not mix them, as a 2.5mm central pin male plug, for example, will most likely not make electrical contact - or make very poor electrical contact - with a 2.1mm female plug. I suggest to use cables with the proper connectors at all times. If necessary, use plug adaptors from 2.1mm to 2.5mm or 2.5mm to 2.1mm. You can find them on Amazon.

Right, but the problem at the beginning of the thread was something much more subtle than that.


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#14 mphotog

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Posted 10 February 2021 - 09:51 PM

I just received my new GEM 45 yesterday and I can assess that the power plug is 5.5 MM by 2.5 MM.



#15 ryanha

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Posted 10 February 2021 - 11:23 PM

This is such weird timing.  I just today got an adapter plug to convert from 2.5x5.5 to 2.1x5.5 so I could use the port on the back of the RA axis of the CEM70 and the adapter plug would not fit.  I gave it a bit of force (which generally I don't like to do) and it ended up fitting.  

 

Now I know why. 

 

--Ryan



#16 mikerepp

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Posted 12 February 2021 - 08:12 AM

Do not sand down the connector your just asking for trouble down the road.   Sanding will remove the plating and the connector will develop rust over time.  Buy the connector that fits, do it right don't short cut.


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#17 ryanha

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Posted 12 February 2021 - 10:06 AM

I was able to get the adapter plug in my using a bit more force than I was comfortable with. But now that it is in I just will leave it there.

--Ryan

#18 Der_Pit

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Posted 12 February 2021 - 06:06 PM

using a bit more force

Guess that's why you posted it thrice, is it?  grin.gif  and SCNR

 

But good it's solved now waytogo.gif



#19 EmeraldHills

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Posted 24 September 2021 - 09:11 PM

CloudyNights is the best. I have a new iOptron CEM70G. Thanks for helping me with my sizing problem!

I ordered these:

 

https://www.amazon.com/dp/B07D49F3TW

 

I hope that's the right thing!



#20 Woody218

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Posted 25 September 2021 - 08:14 AM

The power input on my CEM70 is 5.5mm x 2.5mm. The power output ports on the saddle are 5.5mm x 2.1mm.


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#21 EmeraldHills

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Posted 27 September 2021 - 06:22 PM

On my CEM70G, Woody218 is exactly right -- the power input on the base will easily and comfortably accommodate any 5.5mm x 2.5mm plug. But the power output ports on the saddle definitely will NOT accept the 5.5mm x 2.1mm plugs I have in my kit (including my favorites: https://www.amazon.c...duct/B07C61434H which fit all Celestron gear) . If I push a bit hard (hard enough that I'd call it "press very firmly," but not hard enough that I'd call it, "press until you feel like you're going to break it"), these "Longdex" adaptor plugs WILL fit into the ports on the saddle:

 

https://www.amazon.com/dp/B07D49F3TW

 

Just in case you decide to experiment, I already tried these:

 

https://www.amazon.com/dp/B0851CBH87

 

and these:

 

https://www.amazon.com/dp/B07L5FB4F5

 

Neither of those (latter two) will work. From my tests so far, only the Longdex adaptors will work on my mount. Thankfully, I can adapt my normal 2.1 plugs now - because my normal (Celestron-style) plugs fit into the LongDex adaptors.

 

Hope this can save someone else the trouble of ordering these -- and point you to something that will work.

 

Doug


Edited by EmeraldHills, 27 September 2021 - 06:25 PM.



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