ZWO - externally powered cooled cameras - PSU requirements confusion re, 2A, 3A or up

[g__day]

Hi Folks,

Interesting situation developing today from me reading the ZWO ASI1600MM-c and ASI071-MC cameras manuals and asking questions on Cloudy Nights and on ZWO's Facebook page about what size power supply is required.

You see on there are varying views stated by ZWO:


on back of both these cameras is printed 12V 2 amp
in the manual it clearly states use 12V 3 amp
On Facebook ZWO just said use 12V and over 3 amp and
On Cloudly Nights ZWO replied use a big enough one but only 2 amp is consumed.

To me that is a recipe for confusion and possibly voiding of warranty from supplying excess power. Have folks come across this sort of thing in the past - would folk here advise wait and see if the Vendor finally picks one number and sticks with it. I explicitly asked will using over 2 amps void my warranty - given that is what is printed on the back of your cameras yet your manuals say use 3 amp - they didn't answer that question.


I wonder what final number they will stick with and if they will confirm it won't consume more than 2 amps - especially given folk on Cloudy Nights alread state they supply over 2 amps (3 - 6) as they believe it will draw what it needs and their potential over supply won't void their warranties...


It is lack of quality control across all information channels that is frustrating!

[billdan]

Matthew the camera draws 2A from the power supply, that power supply must be able to supply at least 2A or it will not work.

So you can use any power supply that can supply greater than 2A, so you could use a power supply that can deliver 25A and it will not damage the camera (just make sure its a 12V supply).

That is what I use in the Observatory a 25A 12V supply that delivers power to everything, camera, mount, dew heaters etc.

Cheers
Bill

[g__day]

Hi Bill,

I have Lab power supplies to (bit smaller than yours) I don't like supplying more power to gear than their makers specify - unless they tell me such parts have the smarts to not kill themselves.

Imagine if I hooked up one of my 12V 10 amp Lab power supplies then in the camera's ascom driver told the camera to shoot for -60 celcius - wonder if it would try drawing all 10 amps to get then fry itself? I imagine the manufacturer would then say oh you shouldn't have tried that and I didn't enfore and hard saftey limits in my gear or the drivers - oops, my bad but you are out of warranty.

At what point do we expect the gear won't be able to handly the power available to it?

BTW - didn't realise if you connect multiple items to a lab power supply at a set voltage - most gear will only consume the part of the overall that it needs - that is clever! I use two variable power lab supplies in my astrolab - one set to the voltages required by my mount and only powering it and one to a Digitech / peltier combination running a cool box holding a Canon 40D I purchased from a nice chap here!

[billdan]

That's true, if the camera developed a fault (short circuit) then the full 10A of your 10A supply will go into the camera until it either burnt out or the power supply gave up.

I would like to think that these manufacturers would have a fuse or some type of overload protection incorporated into their products.

You could install a 2.5A fuse in the camera 12V positive lead for insurance (maybe I should do it as well).

[glend]

The 12V socket on the ASI1600MM-C is strictly for TEC power, and camera electronics run just fine off the USB connection power. The TEC used is rated at 2 amps. If you wish to fuse the TEC power go ahead, but most 12V supply leads like the cigar type have a 10amp fuse in them already. My camera runs fine at 100% cooling settings for hours at a time, and it will only draw what the TEC can use, even if connected to a 100 AH battery, just like the small unfused 12v fan i use as an exhaust fan in my observatory. As long as you never reverse polarity to your TEC ( which turns it into a heater) it will be fine.

[Camelopardalis]

You can't supply excess power...any device will draw what it draws, unless it's got a leak or a short in which case it's fried regardless of whether it's being fed 3A or 10A...

[OICURMT]

Electrical power requirements are governed by the device drawing the current, not the device supplying the current.

Your device will state what its requirements are and will only draw (up to) that current, barring a problem with the electronics.

The only problems that can arise to disable or break your device is if the supplied voltage is higher than required or if the supplied amperage is lower than required.

[g__day]

Thanks folk - that is good to know. Folks on CN also warned me that a device that can't supply enough current could cause the voltage to go over or under. Bintel said under voltage is more serious than over voltage with ZWO cameras.

Given I have a a spare Lab power supply in the AstroLab already - I think I will just set its voltage to 12V and let just let supply all the ZWO cooled cameras I plan to get whatever current they need. That means I just need the adapters to hook the 12V plugs out of the Lab to the central pin in on the ZWOs! Jaycar should be able to provide something!

[The_bluester]

A device that can't supply enough current will fall out of regulation and go under voltage rather than over.

What people have posted here is correct, the consuming device will draw the current it requires, a device requiring 3A at 12V will draw 3A from the power supply even if the supply is rated at 50A, it just means that the supply could be connected to more things at once.

There is such a thing as a constant current power supply but they are a sepcialised device and you won't see them normally, I am sure there would be an application for them in the lab but I can't think of it at the moment. They are used in things like car MAF (Mass Airflow) sensors where they apply a fixed current to a wire with a large temperature coefficient (A large resistance change with temperature) The current is fixed so the voltage across the hotwire will change with the amount of air flowing across it (Resistance in ohms multiplied by current in amps giving the voltage, the constant current heating the wire to a known temperature and the airflow cooling it)

[g__day]

Well about $20 of equipment from Jaycar and I can now power both ZWO cool cameras from my Digitech variable Lab powersupply set to 12V. Just took a few banana-plug terminators, a breakout box, some crimp ends, and two power leads fitted to variable end power supply adapters and a tiny bit of soldier. The breakout box is so smally it can fit snuggly between the carry handle of the SCT so all the cables runs will be rather neat and tidy.

Given the lab powersupply has both a voltage and ampage readout - will be interesting to see what the various cameras pull when they target -20!