Zap…zap…Boom!

[Dennis]

Hello,

Most of my astro gear and accessories uses mains adapters that have the centre conductor positive and the (outer) barrel negative, but some, mainly my Vixen stuff, has the opposite; that is, the centre pin is negative and the (outer) barrel is positive.

To avoid costly mistakes, all my mains adapters and devices are labeled, but I also have one of these Jaycar Polarity Checkers (http://www1.jaycar.com.au/productView.asp?ID=QP2214), just in case I am unsure one dark night! Cheap insurance at $11.95, even cheaper at $9.00 when I purchased mine and they do not require a battery.

Cheers

Dennis

[Karls48]

Dennis, fortunately all my scopes use centre positive power inputs. If I had one mount or scope that uses opposite polarity power input, I would build small adaptor that plugs into mount and have a socked for power input. Inside would be diode in series between power in and power to the mount. That way plugging wrong plug to it would not result in any damage, it just would not work. I would find the way to make this adaptor permanently attached to the mount. Knowing myself I’m sure that sooner or later I would plug wrong power plug to such a mount regardless if marked or not.
There would be about 0.6V voltage drop across the diode and if used with battery it would shorten time it can be used, before battery appeared to be discharged..

[Dennis]

Hi Karl

Thanks for the DIY tip. From what I have read, some manufacturers of astronomy equipment do design and build reverse polarity protection into their units, but I know that my (old) Vixen DMD-1 controller does not have this, a real oversight given that we do tend to use multiple adapters and in the dark!

Cheers

Dennis