Small electric question regarding mounts and overvoltage

[Robindonne]

A question about protecting the mount and other electronics. I hope someone can advice me on this.   In a recent thread here someone adviced to better go for 2 or 3 power supplies, each 12v 5a, instead of 1 bigger one, a 12 v 8a for example.   While trying to find out the best supply for a mount i read a lot about fried boards/mounts and their solutions to protect the board.    Im planning on placing a dc buck converter between all the power supplies and the equipment.   I have some boost buck converters that can be set to output always a given voltage (whatever the input voltage may be), protect reversed polarity and other possible problems.  i would like to get a steady 12-13 volts from the buck converter with as high as possible amps.    

What powersupply is the best to give juice through the buck converter to my equipment?

is it better to start with, 12v 5a or for example a 18v 3a?    How can one achieve a steady 12v with high amps?   
 

Oh and in that same little project box i want to add a fuse or other sort of protection. I just dont know if the fuse will protect the overvoltage that can occur because most of the time fuses protect against high amps instead of high voltages   That questionmark made me opt for a buck converter to have at least one device that checks the overvoltage.  But i prefer adding a fuse in between

Have to ask this because while checking on of my 12v supplies i measured a 19v peak at the start.  
 

very much thanks if someone can give a view om his or her solution.   
 

its for an heq5, a eq5 and in the near future a eq6r 

and the equipment isnt really special also.  Just basic and cheap stuff.  Dslr, some dewprotection and an asiair.    The mount And the chance to end up with fried electronic in it is what concerns me the most

Edited June 20, 2020 by Robindonne

[Robindonne]

Planning to install it in these small boxes. The buck converter uses about half the box.  Its ventilated and the room for a fuse is like 25x20x10 mm.   They make longer boxes, so if a fuse needs more then i have to order longer ones.  
With some velcro or dual-lock they can be placed everywhere on the mount.  

[Dr_Ju_ju]

First of all, before buying anything, try and work out the total current you'll need for all your equipment, at the nominal 12v. If it comes to approx. 3A, I would then recommend at least doubling that to 6a, to ensure you have enough headroom.... 

Personally I wouldn't use any step-up converters, as the basis on which they operate, may cause unforeseen issues by inducing high frequency crosstalk into 'delicate' systems, but I do use step-down regulators...

For my garden pier system, I run everything off a standard 500 Watt PC power supply, this not only drives the local PC, but mount, cameras, focusers etc....

Then at Star Parties I use standard power bricks like these https://www.amazon.co.uk/JnDeeTM-ADAPTER-Transformer-Monitors-Powering/dp/B071VW5R3P/ref=sr_1_29?crid=2L1AY0W5B061F

  

[Robindonne]

35 minutes ago, Dr_Ju_ju said:

Personally I wouldn't use any step-up converters, as the basis on which they operate, may cause unforeseen issues by inducing high frequency crosstalk into 'delicate' systems, but I do use step-down regulators...

Oke thx.  That i didnt know.   I have to say i wasnt planning to start with a lower voltage then needen but somehow i thought that only the boost step up converter have all the protections I mentioned in my first post.  The reversed polarity etc.   But the main reason was thinking that a step down converter always needs more voltage input then the desired output.   So much of the 12 volt power supplies become useless.  I added a description of my boost step up/down.  Is the noise that can interfere with the delicate electronics in our mounts the noise they try to cancel With the described filters? Or is it not possible to have a stable and clean output?   

Edited June 20, 2020 by Robindonne

[Robindonne]

28 minutes ago, Dr_Ju_ju said:

, I run everything off a standard 500 Watt PC power supply

That sounds like it must work.  But im trying to find a solution thats light, sticks to my tripod legs ( so room for 3 power supplies) and because i dont use a laptop/pc and have to set everyting up at around 10 meters from the house i dont prefer a pc power supply or a nevada 8a sort of supply 

[Dr_Ju_ju]

 

7 hours ago, Robindonne said:

But im trying to find a solution thats light, sticks to my tripod legs

that's why I linked to the power supply off Amazon... 

They are small enough to be ty-wrapped to tripod legs etc. then together with some step-down regulators, to power the lower voltage requirements e.g. DSLR\micro computers etc... The one thing I would recommend is that you replace the output connector with a more robust, lockable solution, that is part of your power distribution system.

 

Edited June 21, 2020 by Dr_Ju_ju

[Robindonne]

No correct.  The power brick from your link is what I prefer also.  I use them as my only form of power supply.   But even whet those you can burn your equipment.  It happens almost every week a couple of times.   And thats only astro related frying,  and only members at this forum. So in reality it happens very often.  Good working powersupplies who lose Or dont have the ability to keep the voltage as set, even at startup of the psu.   
I think it can be easily protected but im not sure.   Do you use the stepdowns in your astro setup?   And for what reason?

Edited June 21, 2020 by Robindonne

[Cosmic Geoff]

I used to work in the electronics industry.  I do not recall encountering any power supplies that failed by giving an over-voltage, though I am sure it is possible. I dimly recollect that some designs included a crowbar protection, so that should an over-voltage start to occur, the power supply output would instantly be clamped to 0v. Cheap supplies may omit the protection circuitry...

As for a high voltage appearing at switch-on, was this with the power supply loaded or unloaded? A power supply is supposed to have a load, so it may be possible for a transient to occur with no-load that would not occur if the load was present.

I am not convinced by the idea of using a step up or step down converter. To my mind this just introduces another point of failure.

A battery supply for a mount etc has the advantage that the output cannot rise to a damaging level, and also you can't electrocute yourself with 13 volts dc.

Multiple supplies may have an advantage in that some devices (mounts) are sensitive to over and reverse voltage while others (dew heaters) are not.

Almost all power supplies these days are switchmode, and (especially if poorly designed) could generate some electronic hash.  There are also linear regulated supplies, generally distinguished by their weight and lower efficiency.

[Robindonne]

Great and thx to all.  I just bought 2 switched power Supplies.  Each 12 v and a max of 6,6 amps.  Hope it feels a bit safer.  Havent had any problems with my old psu actually. The reason of course was seeing that “fried” boards are almost getting a common and not even surprising issue.  
a weekly returning thread on forums.  But why they all get cooked?, im not sure if its all overvoltage.  Although it seems like it.   
my amateuristic idea behind those cheap buck converters was starting with a 13 Volt psu, via Dc buck, ending with A double protected 12 volt.  If the psu fails then the buckconverter keeps it at 12 and if the buck fails it lets only 13 v passing through. The step UP was because i thought the step down always lose some percentage in voltage so that should make the 12v psu’s useless. All in a small 30x30 box combined with a fuse sounded pretty safe to me.  But i wasnt aware of all the downsides of these step up or down converters, noice etc.  I use them sometimes in small projects and they never failed on me.   But 12 v and multiple amps... i cant tell.   
But thanks again and hope to see a decreasing number of fried electronics, at least not from me😬

Edited June 22, 2020 by Robindonne
I wrote “an” instead of “a”

[Robindonne]

5 hours ago, Cosmic Geoff said:

As for a high voltage appearing at switch-on, was this with the power supply loaded or unloaded

No in my case it was unloaded.  Only had the multimeter connected.  But while always being aware of the risk to end up with damaged electronics, another member posted the same day about his burned mount, and at his second attempt a fried asi1600 and something else.  So he did suffered overvoltages while having his psu loaded.  And it looked like the “safer” linear psu

Edited June 22, 2020 by Robindonne

[Dr_Ju_ju]

Fried boards, especially where components are wrapped around the output drive stages, are usually caused either in a component failure, or the motor is 'stalled\frozen' so the drive currents are being forced into a resistor not a coil....

[Tenor Viol]

Woudl you mind posting a link to the PS you opted for? Having rad various threads on here, I think I need some decent and separate power supplies for the parts of teh AP rig I'm building. Certainly having the drive on its own.  

[Robindonne]

https://www.conrad.nl/p/mean-well-gsm90b12-p1m-tafelnetvoeding-vaste-spanning-12-vdc-667-a-80-w-1293432

 

just check the connector size to be sure.  

Edited June 22, 2020 by Robindonne

[Robindonne]

25 minutes ago, Tenor Viol said:

Woudl you mind posting a link to the PS you opted for? Having rad various threads on here, I think I need some decent and separate power supplies for the parts of teh AP rig I'm building. Certainly having the drive on its own.  

Added the link of the one i opted for.  But while scrolling through the models there was a lot i have to remember for later.  I guess my next order will include a 5v 5a ps and for my dslr a 7,5v 2a i think.  If its really a reliable product, safe etc., then the costs are surprisingly reasonable.  

[fozzybear]

https://hamradiostore.co.uk/catalog/product/view/id/3834/s/power-supply-30-amps-variable-voltage-analogue-design/category/121/

Being an ex Ham operator never renewed my licence when moving to France  I use one of these for the Mount and Aux with relevant convertors. Just what I had lying around and why not use it. When I bought it I think it cost me around 50 quid 15 years ago... and still works. albeit the model has had a facelift since then but still the same

Edited June 22, 2020 by fozzybear