Dew heater cables

[redeye64 (Paul)]

Have just received 2 dew heater strips for my refractor and guidescope. They have very long cables which l'd like to cut to a suitable length and fit new jacks (also doing away for adapters for the ASIAIR) .....wondering if there is any reason not to do so and if polarity matters?

[Leo.G (Leo)]

Generally a heater polarity isn't of much concern if it's just straight 2 core wire. Though if you have a multimeter available you could check the polarity. If it's only using barrel jacks convention is centre positive on output jacks though I do have a few I ordered which I'd tested before use and found reversed connections one end (small extensions with 90 degree plug one end). Though they come in handy at times playing with small DC motors, switch extension cable in to reverse motor.
The resistance for the element should be within the element (nichrome wire or resistor band (maybe that's just my home made thing) not in the cable and cutting it should make no difference to supply.



In saying this I'm not familiar with the ASIair and what it has.

[Startrek (Martin)]

Like Leo I don’t use these little red boxes but when you look online at the specs , the 12V outputs are 3amp rated each and assuming they are centre positive ( ASIAIR don’t provide data on polarity so you would have to assume centre positive like the majority of 12V power ports )
So maximum wattage of your heater strip can’t exceed say 30watts at 3 amps
Most popular heater strips like Kendrick ( which I use are 12V 5amp rated , but more robust )

Some heater strip cables from the heater band use an insulated conductor for centre core positive and a braided shield type conductor for negative. So shortening / splicing or fitting new plugs as a result of shortening them is a pain in the butt unless your an electronics buff and have all the right gear ( mini soldering iron and so on … )

Personally I’d just go and buy some decent quality RCA plugs ( eg Jaycar or Startech brand ) at the correct length. Cheaper and simpler
That’s what I use for my Kendrick heaters as they are too damn short for my 8” and 10” Carbon fibre Newtonians , so I extended them with standard RCA leads and they work fine and dandy.

Cheers
Martin

[ChrisV (Chris)]

No polarity issues with a simple resistor type heater which doesn't have a ground.
If possible, I wouldn't even cut them. Just wrap round twice - no harm and no damage to your straps. If you cut you'll have to keep the wire intact (as Martin says) to maintain the resistance and keep the current at a suitable level.

I assume there's no sensor inside for feedback control, just a simple heater?