Power Supply Help

[scitmon]

I'm in the process moving some of my equipment from AC adapters to a DC power supply and doing the calcutions:

• AZEQ6 mount 3A
• 2 x DSLR cameras - no idea!? 2-3A wild guess
• 3 x dew heater strips - 2-3A
• MiniPC - 2A

I'm looking at around 10A if everything was max load.  This is beyond my current https://www.firstlightoptics.com/batteries-powerpacks/nevada-ps-08-6a-8a-regulated-linear-power-supply.html.  Buying a additional one is the most cost effective solution (£35) but there is also https://www.firstlightoptics.com/batteries-powerpacks/nevada-psw-30-25-30a-switch-mode-power-supply.html.  

 

Any help deciding which one to get?  Is the low noise output something worth having?

[Adreneline]

I run all my gear from an old (1980's) Trio 12V, 30A psu originally intended to run a Trio HF amateur radio transceiver. When I sold the transceiver I decided to hang onto the psu because it might come in handy one day; at the time I had no thoughts of getting into this hobby as my amateur radio interests long pre-date digital cameras, etc.

It might well be possible to find a second hand Trio psu as amateur radio is still a hobby that demands stable voltage (13.8V), high current, low noise power supply units; the likes of here will provide you with lots of choice / food for thought - including the unit offered by FLO.

HTH

Adrian

[Carbon Brush]

The low noise (electrical) should not be an issue. Whenever a piece of equipment is designed, methods of removing noise from the incoming supply, or preventing it from affecting operation, are always high up the list of priorities.

If going for linear power supplies, then I would run dew heaters from one supply and cameras/scopes from another.
Dew heaters average the current by turning on and off at intervals. The large almost instantaneous changes in current can cause the supply output to overshoot, then undershoot.
This is not an issue for for dew heaters, usually, but can be an issue for a mount.
Cameras, mounts and the like tend not to change current rapidly. Only over microseconds to milliseconds! Then by smaller amounts.

A benefit of linear supplies is that the simpler circuits (compared to switched mode) mean repair is more likely in the event of a failure.
Then again, at £35 a go, if you have to pay someone?

By running any power supply well under rated load you reduce internal heating and therefore improve life expectancy.

Running at less than full load means the supply is going to tolerate component degradation with time.
In particular large electrolytic capacitors degrade and reduce their value. If you ask for only 50% load, then only 50% capacitor remaining will suffice.

When the dew heaters switch on/off a switched mode supply will usually adjust output in less time than a linear supply.

Linear power supplies are heavier than equivalent power switched mode.

Linear power supplies are significantly less efficient than switched mode.
But using outdoors there is convection and the power supply has an inbuilt dew heater.

With any of the supplies, I would connect using the 4mm terminals/binding posts.
Cigar lighter sockets are for lighting cigars.

You can see that there are arguments for both options.

If it was me trying make the choice, it might well come down to fixed or portable use.

In an observatory the extra mains connections and cabling associated with two supplies is easily tidied away and forgotten.
In the garden it is more to setup, trip over, then put away every session.

Sorry for the long winded response.

David.

 

 

[haitch]

I've just bought a bench PSU which I haven't run the whol set up from yet but testing it out my mini pc barely causes a flicker on the Ampmeter and even with a dew heater for an 80mm scope running full blast it doesn't reach 1 amp so I suspect you could be wildly overestimating your requirements.

[haitch]

PS My PSU is the same as the FLO one

[almcl]

My Maplin supplied PSU bit the dust recently and was replaced with this one link

It happily runs the AzEQ6, Canon camera mains adatper, two dew heaters and the camera cooler.  The 13.8 volts doesn't 'sag' at all.

[Carbon Brush]

Just to clarify.

Output voltage undershoot, or overshoot, on a changing load is a transient effect. It lasts at most tens of milliseconds.
You won't see it on a panel meter or a digital multimeter.
If you want to see it, you need an oscilloscope.

The other way to experience undershoot is to have a mount suddenly shut down, requiring a power off/on cycle to recover.
This is despite you having what appears to be a good 12V supply.
The power fail detection in a mount (or computer or anything) is intended to respond quickly to a voltage dip below a threshold.
This ensures that things can be tidied away - like finish a memory write - before the power fails completely.

Then a power dip with some older mounts/handsets can just make them forget what they are supposed to be doing, or where they are pointing.

There was an old Meade handset (I forget the number) that was well known for scrambling memory on power dip.
It required the right equipment to reflash the memory, or just buy another 2nd hand handset.

The power supply is the heart pumping the blood of your scope associated electronics.

David.

[haitch]

That’d be the Meade 497 - I know those only too well!