Cable

[wookie1965]

OK people can someone help me I have found out all my mount problems were down to my power supply. 

I have 3 power packs like these a 5amp, 7amp, and 10 amp just plugged them all in one by one to the handset and box for the EQ5. 

5amp had 12.2v 7aml had 12.3v and 10 amp had 12.2v that is before I tried to slew a scope around. So I am going to purchase this bench supply but can anyone point me in the right direction for a cable that will go from it to the mount please. 

They are 5.5mm x 2.1mm and needs to go to separate positive and negative rings maybe. 

Thanks 

Paul 

[malc-c]

Paul, why are you powering the handset and the synscan box ?

All you need is a 12 - 14v (so the bench supply is more than enough) with a cable terminated in a 2.1 x 5.5mm  plug.  The ring of the connector is negative, with positive being the inner ring.

[teoria_del_big_bang]

That is a great power supply I use one (in a weatherproof box that is big enough to allow plenty of air around the supply as they do get hot).
But I cannot believe all three power supplies are faulty.
I do use this power supply but to run many bits of kit not just the mount but at times I have also used nominal 12V supplies on both my HEQ5 and IOptron CEM60 and even at 12v I have never had an issue with them, they should run fine at 12V, even down to 11.5 they should run okay, unless using some really long or thin cables to the mount.
Yes the voltage will drop slightly when slewing but unless the mount has a fault it should not drop over 0.5V from 12,2V as they should have some regulation.

But if you do go this route and want a cable with colour coded ring terminals drop me a PM I can make you one up as not sure there are any available off the peg so to speak, I have the ring terminals, crimper and 5.5/2.1 plugs, I might have some cable or may have to buy that.

Steve

Edited March 19, 2022 by teoria_del_big_bang

[wookie1965]

I will tell you what`s happened,  I had the 5amp power supply and ran the scope off that, plugged into the control box with the din cables and handset. I am having issues with alignment and accuracy at first I thought it was the mount so sent it to RVO to have a strip down and regreased, when it came back it still was out once I had done 1, 2 or 3 star alignment objects where either on the edge of the FOV or not even in it. I thought well I need more amps and got the 7amp no luck there either but I was running my dew strips off it so then I thought well obviously got to be a power issue I will get a 10amp that will run the scope and the dew strips. 

I have not had the mount out for a while due to bad weather and health issues but I got it out a couple of nights ago 3 star alignment  now I have read the 3rd star will be there or there abouts not in mine over 5° out past the outer circle of my Telrad.

Got everything centered then used the handset to polar align just to make things more accurate did that punched in M42 looked through eyepiece nothing a star on very bottom of FOV  looked through the Telrad it was high on the top star of the sword.

I used PAE to drag it into the centre (press escape then press and hold escape until says centre object) went to Sirius over 5° again out.

I went backwards and forwards to M42 and Sirius until both were dead centre then punched in NGC 2264 (Christmas tree cluster) unmistakeable and in the FOV nothing so I packed up.  

I talked to a friend who said it sounds like a power issue if the mount doesn't get enough power or if the power is not regulated it wont work. the power packs I have are probably Chinese jobs that send the power as a pulse on-off-on-off which wont work.

After all this I have come to the conclusion it is a power issue and I need to buy the power supply in my first post.

Edited March 21, 2022 by wookie1965

[wookie1965]

8 hours ago, malc-c said:

Paul, why are you powering the handset and the synscan box ?

All you need is a 12 - 14v (so the bench supply is more than enough) with a cable terminated in a 2.1 x 5.5mm  plug.  The ring of the connector is negative, with positive being the inner ring.

I am not I just plugged the power into the control box then plugged my handset in to see what power I had  12.2v  which is low.  I know it needs a 5.5mm x 2.1mm to go into the power box but I need the cable to be split at the other end to hook up to the power supply.

[Padraic M]

I don't know about the EQ5 but I had similar problems with a HEQ5 - with a generic power brick rated 12V 10A, voltage dropped close to 11V under load and mount behaved erratically. It didn't fail as gracefully as yours - it could stop moving or take a random slew at any stage. It's been perfect since I upgraded the PSU to 13.8V.

That Nevada Radio PSU will be fine. The cigarette output at 5A will give you plenty of juice so just get a cigarette male connector to 5.5mm x 2.1mm. Forget about the ring connectors.

Edited March 20, 2022 by Padraic M

[Carbon Brush]

The problems reported using standard desktop type power supplies are not unusual.
They are built down to a price and the China manufacturers often regard specifications as general guidelines, rather than a guarantee of performance.
Some years back at work we wanted some 5V supplies and despite generously over rating, an oscilloscope told the truth about voltage dips on pulse current loading.

The Nevada bench supply will do the job for you.
Starting with >12V is a big help to cope with voltage drops on cables and (in my opinion unsuitable for the application) DC connectors.
Using the cigar plug you are limited by the quality of the plug on (built down to a price) cable assembly. OK some are good, some are not
The ring terminals will be more relaible - but only if you correctly terminate the wires with crimp lugs.

An alternative is a large capacitor (a few thousand microfarads) near to the point of load - the mount.
But this is a big component (think size of D battery size) and presents mounting issues.
Pulse currents then get delivered from the capacitor, rather than the PSU.
The resistance in the leads and connections helps the PSU cope wit transient loads.
Did I mention the word bodge?🤔

Another issue with the desktop power supplies is component degradation.
Large electrolytic capacitors inside degrade due to heating. How slowly does heat escape from a thick plastic case?
You can buy longer life at high temperature capaciors. But not if you are trying to sell a PSU for £1 less than a competitor.
When the capacitors degrade, the PSU is OK on light load, but as load current increases, the output voltage gets ripply and the dips can cause mount motor step errors or trigger equipment shutdown.
Again an oscilloscope shows the story quite well. Or just a resistor (car bulb) monitoring PSU voltage on an off load.

HTH, David.

 

[wookie1965]

From your answers both From Padraic and David I am more convinced these cheap power bricks are the issue. 

I am ordering the power supply from FLO tomorrow and a member has kindly offered to make me a cable with colour coded ring connectors on so hopefully I will be sorted and can enjoy this hobby rather than fighting with the mount every time. 

Thank you all I really appreciate your help. 

Paul 

[AstroKeith]

50% of the time I come across this problem - its the cable.

Servo and stepper motors try to draw significant peak amps, but only for milliseconds as they are pulse driven. The resistance of most common cables is enough to drop the volts as the pulse is taken. No regulated supply can overcome that. Using a voltmeter won't show the issue as the pulses are too short.

Often this is overcome by using a 13.5 Volts supply. This will usually work, but its not solving the actual problem.

Thicker copper in the cables. (a lot of 'cheapo' cables are thick but that's the pvc sheath.)

[Ian McCallum]

Here's what I use...

https://www.eham.net/reviews/view-product?id=8459

[teoria_del_big_bang]

1 hour ago, AstroKeith said:

50% of the time I come across this problem - its the cable.

Servo and stepper motors try to draw significant peak amps, but only for milliseconds as they are pulse driven. The resistance of most common cables is enough to drop the volts as the pulse is taken. No regulated supply can overcome that. Using a voltmeter won't show the issue as the pulses are too short.

Often this is overcome by using a 13.5 Volts supply. This will usually work, but its not solving the actual problem.

Thicker copper in the cables. (a lot of 'cheapo' cables are thick but that's the pvc sheath.)

Makes sense and sounds the most plausible explanation of why some people have this issue.
And I agree with using thicker wires but so difficult to get any decent size cables when using these 2.1 / 5.5 mm plugs I have no ide why so much astronomy gear uses them, apart form the confusion of some having 2.1 and 2.5 mm centres which some people do not realise and often force a 2.1 onto a 2.5  connector on as they are sure it is the correct size OR using a 2.5 on a 2,1 and getting poor connection they are just poor connectors for any sort of current applications.
There are far better connectors about.

Also I notice that many of the cables (generally cheapos such as amazon or Ebay) are not even copper strands which will add to the voltage drops.

Steve

[wookie1965]

If it is cables the new lynx astro one should suffice but what do I do about the din cables has anyone got links to a couple of good ones please. 

[adyj1]

10 hours ago, wookie1965 said:

then I thought well obviously got to be a power issue I will get a 10amp that will run the scope and the dew strips

The only thing I'd add is that you seem to have run all three power supplies with your full load, including dew heaters. For diagnostic purposes I would have thought that one of the PSUs would have been good enough to power the mount on its own and therefore run without error, and once you've established a 'known good' configuration you can add more load to show that the psu iss the most likely culprit. I'm not saying it isn't the psu, just that I think that I'd prefer a better indication that it was psu before spending money on it. 

I hope it fixes your problem, though - the nevada is a good bit of kit. 

[wookie1965]

28 minutes ago, adyj1 said:

The only thing I'd add is that you seem to have run all three power supplies with your full load, including dew heaters. For diagnostic purposes I would have thought that one of the PSUs would have been good enough to power the mount on its own and therefore run without error, and once you've established a 'known good' configuration you can add more load to show that the psu iss the most likely culprit. I'm not saying it isn't the psu, just that I think that I'd prefer a better indication that it was psu before spending money on it. 

I hope it fixes your problem, though - the nevada is a good bit of kit. 

I had the scope out two nights ago using the 10amp but I've bought a power tank which I strap to the scope and wind the cables around the ota as before they were hanging down and getting caught on the locking pins on tripod. So I have used it just for the mount. 

[wookie1965]

The 10amp supply must be faulty I have been out tonight using the 7amp and a power tank to power a dew heater, so the 7amp was just powering the mount and after a 2 star alignment using Sirius and Caph went to M42 it was up and to the right so used PAE got it to the centre, next NGC 2301 just a tad out did the same to that next NGC 2264 bang in the middle so was Beta Mon (SAO 1333 17) lovely triple. next M36, M37,M38, NGC 457 all bang in middle I got three doubles in Leo then cloud rolled over but I now know there is nothing wrong with the mount its definitely power. 

As the 7amp is working I am going to use that for a couple of weeks and save up for the power supply and lynx astro cable  then I will be set.