Power supply cable

[Nova2000]

Hi sgl

As most of you'll will be knowing most mounts come with the cigarette lighter cable . But I will do imaging in my sea facing backyard and want power from the plug 

I saw that I need a 12v ac to DC adapter. 

I'm thinking of the AVX mount 

Should the adapter be from celestron or will any with adapter which fits for the avx work? 

[jambouk]

As long as it fits, and the voltage is correct, it can supply sufficient current and the polarity is correct then it doesn't matter who manufactures it. If you get the polarity wrong you'll fry the board unless the mount in question has polarity protection.

I power my mount with a laptop charger I got from ebay and modified to fit my mount.

[Cornelius Varley]

Assuming voltage and amps are correct, the main thing to check with the PSU is that it has a regulated output. Unregulated PSUs may cause damage to the electronics of the mount.

[RayD]

1 minute ago, Cornelius Varley said:

Assuming voltage and amps are correct, the main thing to check with the PSU is that it has a regulated output. Unregulated PSUs may cause damage to the electronics of the mount.

+1

Your mount is a very expensive and sensitive piece of kit.  No mileage at all in even a small risk of damage it due to saving £20 on a power supply.  The Nevada regulated supplies from Flo are a very good and cost effective solution, and will give you some leeway to power a bit more than just your mount.

Don't forget to protect any power supply from the elements if it's outside though, unless you get an externally rated one, and make sure you power it from an RCD protected socket outlet.

[Geoff Lister]

I have used "plug top" 12V 2A supplies with my Skywatcher Skymax 127 MCT and 10" Dob. The Dob takes about 800mA when slewing both axes at max rate, but drops to about 300mA when aligned and tracking. It is worth extending the 12V lead with stout "figure of 8 cross-section" bell flex, and if it has white insulation it is easier to see, and avoid, in the dark.

The RCD advice, above, is sound. I use an extension lead, plugged inside my shed, with the socket end, and power supply, in a closed cardboard box. This seems to avoid any dew problems on the high-voltage bits.

Geoff

[Relpet]

I just bought one of these for a second-hand Skywatcher EQ3-2

https://www.firstlightoptics.com/power-accessories/baader-outdoor-telescope-power-supply-128v-15a.html

albeit from my local astro shop.  This is what Baader say about it.

  "This 12.8 volt /1.5 Amp switching power supply with protective-disconnect plug serves all Celestron telescopes up to the CGEM-DX series. At little higher price it offers enormous benefits compared to common department store indoor units.

Conventional power supplies having a 12V nominal voltage are made for use in your "living room". When used outside in the cold the voltage will reduce with temperature. Already at -10°C the remaining voltage output may have gone down to only 10.5 V. The motors of many telescope mounts will behave erratic at such low voltage. Especially the motor driver electronics then tries to replace the missing voltage by draining ever more Amps until both - power supply and mount electronics - will stall or become damaged. Many users then blame the mount and it´s messy electronics - instead of checking wether an inadaequate power supply may be the culprit.

The Baader Outdoor Telescope Power supply offers continuous 1.5 Amp/ < 12 volt DC voltage all accross the AC voltage range from 90 to 260volt. Even at extreme cold the voltage can not go down as far as to damage the electronic components or motors of your telescope mount.

19 Watt/ 1.5 Amp permanent power ensure ample reserve for smooth tracking even at full photographic instrument load and high torque variations due to changing telescope balance. In addition to the outdoor voltage of 12.8V also the thermal working temperature has been designed for -25°C to +40°C.

The connecting cord measures 2.5m in length. This is longer than usual to ensure that the wall plug portion of the power supply can be safely stored down the tripod legs so that the power cord will not become a trip-wire."

 

Hope this helps

[Geoff Lister]

Replet's information, above, is valid, but I think it is a little pessimistic in the real world. The power supply should be of reasonable quality, but it is difficult to judge the real quality without opening the case.

The power supply should be of the switch-mode type. Any supply that just uses a step-down transformer, bridge rectifier and reservoir capacitor, is not going to have adequate regulation. Off-load, a nominal 12V supply could easily go to over 16V. The output jack should be 2.1mm internal diameter and 5.5mm external diameter, and the input plug type should be suitable for your local mains socket (I believe that an "EU" 2-pin plug should work in India, but check first before buying). Plug-style 12V supplies with 1.5 or 2A capacity, and 2.1mm ID plugs, are often sold to power the 300 LED flexible strips, and I have used these to drive my 'scopes.

A supply that drops to 10.5V when cool would be a poor design. If the supply is protected from dew in a cardboard (or similar) box, self-heating is going to lift the internal temperature to close to domestic ambient.

As a check, I rounded up a few of my plug-top supplies and made a few measurements off-load and with a resistive load of about 1.25A

Details:-                                                          Off-load           loaded

Philips 1.5A, with about a 1m lead                      12.41V             12.13V

Another as above                                             12.31V             12.00V

Fairway 2A, with lead extended to just over 3m   12.15V             11.88V   (This is the one I use in my back garden)

 

If you are likely to need more power, for optics and camera cooling and/or dew-shield heating, then it may be sensible to look at the range of 40W plus "power bricks" similar to those supplied with laptop computers (but checking on voltage and output plug size).

 

I hope this helps.

Geoff