car lighter 12v dc cable - how to get the right one?

[cmr]

hello , my ioptron minitower came with a *very* long dc cable to connect to a car lighter socket. As i'm using a portable powee source just under the tripod, the cable is way longer than needed - thought id just go and buy anothe afaoter cable with a short cord, but know from past experience things like tip positibe, sleeve size etc all need considering. anyone got advice on what plug size, tip polarity etc i need? manual no help, neither has google been much help... exoect to find an "ioptron 12v dc cale for the princely sum of $49.95 ! from an online telescope shop! thanks :)

[GlassHammer]

"Gererally" speaking cigar lighter sockets in cars are tip positive.
But to make sure you could hook up the current socket you have to a battery and hook a test light to the same battery's negative terminal and touch the end of the test light into the socket. If the test light lights up then the tip is positive.
You should be able to pick up a shorter socket from Repco as I got one for my Celestron CPC for around $15.
If you take the current one you have they should be able to match it up size-for-size.

I hope this helps.

[traveller]

Hi Chris, you have quite a few options:
1. Is there a label on the minitower near the plug input showing the polarity? Is there a AC/mains adpater to the minitower as well? There is usually a label on the AC adapter showing the output current and polarity.
2. You can plug it into an outlet and test the polarity with a multimeter. If in doubt, you can always take the cable to Dick Smith or Jay Car and they can hook it up to test it for you (if you ask very nicely).
3. If you don't have a multimeter, Jay Car acutally sell a polarity sensing 2.1mm plug http://www.jaycar.com.au/productView.asp?ID=WQ7288&keywords=2%2E1mm&form=KEYWORD so you can buy this plug and use the bare wires on your existing plug to determine polarity.
HTH
Bo

[cmr]

Thanks everyone - Yes good idea - I should have thought to look at the ac adapter - it has the usual little diagram that indicates tip positive!

Cheers!

Chris:thumbsup: