Overvolting SkyWatcher mounts?

[ofranzen]

I just saw Astrobiscuit's latest video and it featured Dave Woods from Dark Frame Optics saying to overvolt SkyWatcher mounts by 1-2 Volts. He's really a guy who should know this stuff but I've never heard elsewhere about overvolting the mount. Has anyone here tried it? Could you notice a difference?

 

[Dr_Ju_ju]

At home my mounts are usually power by the 12 volt output from a computer power supply, with no issues.....   When at Star Parties, I use a Maplin linear supply, which has an indent on the voltage control, that sets the output to 13.8 volts, and once again I've never seen any issues..... 

[johninderby]

Think it requires 11v to 15v

[Jamgood]

I use to run my HEQ5 via a 30ft 12v extension cable, it only received 11 volts and it never skipped a beat. I've since change a lot around and now it gets a steady, regulated 12v and still doesn't skip a beat.

I can't see how increasing to 13v+ will make much of a difference. There will be a min/max power for the mount to work sufficiently and as long as your supply is within the boundaries, it should work fine.

[Alien 13]

The problem with most commercial power supplies is that they "sense" the voltage at the output terminals so you often need 13.8V to get anywhere near to 12V at the mount due to cable losses, proper lab supplies allow you to run separate power and sense wires to the mount so that the indicated voltage is the real one.

Alan

Edited June 14, 2021 by Alien 13

[Padraic M]

I run mine at 13.8V from a Nevada Radio power supply. Previous 12V power blocks always caused problems, even a 10A rated block. Based on what's showing on the handset, if the supply drops below ~11.5V you can expect issues especially when you're slewing both axes.

[johninderby]

The hand control  in particular will act up if it doesn't get enough voltage. 

[Padraic M]

Just now, johninderby said:

The hand control  in particular will act up if it doesn't get enough voltage. 

May well be true John, but I only connected the hand controller to diagnose the issues experienced with EQDIR through the laptop!

[Robindonne]

How its explained to me on other machines using steppermotors is that its better to have too much voltage running through the drivers. They wont allow to send more than needed to the motors.  A lower voltage can cause the motors to not work as they should and probably slow down, mis steps, get noisy and maybe even get damaged.  

Edited June 14, 2021 by Robindonne

[pete_l]

5 hours ago, ofranzen said:

I've never heard elsewhere about overvolting the mount.

Overvolting usually means running a device with a voltage above the recommended maximum.

The EQ6-R manual states that the supply voltage should be in the range 11 - 16 Volts. Running the mount at 16 Volts is not overvolting it. However to try to overvolt (i.e. above 16 Volts)it does not seem to me to be a good idea.

Edited June 14, 2021 by pete_l

[ofranzen]

11 hours ago, pete_l said:

Overvolting usually means running a device with a voltage above the recommended maximum.

The EQ6-R manual states that the supply voltage should be in the range 11 - 16 Volts. Running the mount at 16 Volts is not overvolting it. However to try to overvolt (i.e. above 16 Volts)it does not seem to me to be a good idea.

That's a fair point. I had no idea that upwards of 16V is still within spec. It does sound like several have had good experience with upping the voltage from the 12V stated on the mount itself. I was planning on changing the power supply and will definitely look into something at 14-15V.

Thanks for taking the time to share.

/O

[tonyowens_uk]

Most pro-sumer mounts use stepper motors driven in microstepping mode. In the case of the older Skywatcher models, e.g. EQ8, there is a definite motor torque benefit to using the highest drive voltage possible. For safety, a regulated power supply set to 15Vdc maximum with at least 5A capacity and preferably 10A is my recommendation. Use sensibly short cabling from the supply to the mount, with 16AWG stranded wire, or more. That will hold cable loss to 0.3V or so.

The reason for maximising torque is that in tracking mode when microstepping is active, significant friction arises in properly set up worm gear drives. This causes a 'following error' to arise - a lag beween the commanded stepper motor shaft position and the actual position, to the detriment of tracking accuracy. Fortunately the effect is small, but it is there. Boosting torque reduces following error.

 

Tony Owens

[jambouk]

I use an old laptop power supply and it delivers 15.5v I think.

[Carbon Brush]

Sorry (before I start) to be controversial.

If you look back in time, rather than just what is offered today, the mount manufacturers were reluctant to specify a voltage range for mount operation.
In other words if you complained a mount would not work at 11.9V they could say - you need 12V sir.
Similarly if you claimed it blew at 12.1V - well you know their response.

Off topic. But take a look at historically how few mounts have an operating temperature range specified.
Just how could we buy very expensive electronic mounts when we had no assurance of operating under field conditions?

The next problem is the general lack of understanding in the (not just astro) community about reliable connectors, and low resistance cables.
Yes I realise there are some knowledgeable people contributing to this and other threads.
But a look at past posts on this sort of subject demonstrate there are a lot who should not try to 'mix and match' power supplies and electronics.
I think that this is the biggest problem by far.

If you need a 13.8V supply to get 12V at the mount, you need to sort out your power cables and connectors.
The DC connectors (fitted by many mount manufacturers) and their thin cables are fine for a demonstration. But not for long term reliable operation.

A battery (whatever type it is) might produce 12V with low load. A handset on an idle mount is OK. But start slewing and pull more current, the battery drops to (say) 11V. What happens in the cold?
If you don't understand about how a battery internal resistance varies during discharge, and with temperature, you risk problems.

If you have a grasp of Ohms law. Understand about cables and connectors, have a bit of battery knowledge, then you can make your own choices.

But if you don't have the electrical knowledge, then you should buy 'what the man in the astro shop says'.
If you start mix and match the Skkwatcher/Celestron/whatever mount, the Amazon Chinese 12V battery and a seperate charger or a power supply given by a mate............

Hope this helps, David.

 

 

 

 

[StuartJPP]

As mentioned, the Skywatcher EQ6-R manual states that the power requirements is DC 11~16V.

Running the mount at 16V is not "over-volting" the mount, it is running it (just barely) in specification. The term "over-volting" is disingenuous as that implies running it out of specification which it asking for trouble. A term that is both nebulous and dangerous.

Running the mount at its maximum rating will more than likely provide more torque to the motors but will also impact the life of the electronics and since consumer electronics devices are almost always designed to the lowest cost, "over-volting" is definitely not recommended.

Think of it like "over-revving" your car to get you to the shops faster, just keeping it in the red the whole time 😉

 

 

[Paul M]

If a mount is provided with a car cigarette lighter type plug on the power cable then it should be assumed that the mount could/will be exposed to a cars alternator voltage circa 13.8v. 

In my view any mobile 12v equipment should be expected to fine with 13.8v, indeed some of it is going to be optimised for 13.8v. Stories abound of Skywatcher mounts getting flaky at more than a few 10ths below 12v . I have my Nevada PSU set to 13.8 and run my DC distribution off that.

 

[Merlin66]

I’ve been running my HEQ5 and NEQ6 mounts at 15v for the past 15 years or so.

A car convertor 120w, 12v to 15v does the job. No issues, no drama.

 

[ONIKKINEN]

I am running an EQM-35PRO quite near its maximum payload capability and can confirm that small differences in voltage are a big deal. My RA stepper motor can start slipping at below 12.5V while it never happens above this. Under 12V is a complete no-go especially anywhere near the meridian.

 

Switching to a car plug (with the engine running and producing over 14 volts) and/or a proper 13.6v output powerbank pretty much eliminated all slewing problems.

[gaz81]

Interestingly, tonight I hooked an in line DC meter to see what my EQ5 Pro pulls. 
 

The video is tracking to full speed. My generic 12v supply dips under 12v and draws 2 amps. 

[malc-c]

Most of the SW motor boards use the MC2171 buck converter / regulator to provide the 5v line for the PIC micros (which in turn is further regulated by a 7805).  This buck converter generates the 33v that is used to drive the steppers, and has a wide operating voltage of 3 - 40v DC.  However the filter arrangement for incoming voltage has been designed to accept 12-16v DC.  

Voltage is not the issue with these mounts, its current.  The supply needs to be able to supply 3amp at 12-16v without any voltage drop.  9/10 time when people report poor communications between handset or PC and mount is down to the fact their supply struggles to provide the amps at the voltage, so you get voltage drop.