Switching Cold Cathodes

PhillyDee · 23 Apr 2008 at 19:56

Long story. I have 2 s light sets of cold cathodes for inside my car boot. 2x Red and 2xwhite. This is for when ive got my telescope out on a night time near the car. The plan is to have a red and white on either side of the boot and have it switchable. I tried to lengthen the cables for one side, and got nowhere, looks like the current drain is too much at the 1.5m distance i need. Even at a 0.5m extension it became very dim. Does anyone know what voltage and current the inverters run at on the AC end? My multimeter doesnt seem to like measuring AC. I plan on sticking a switch on the cathode end, but need to know what rating of switch i need.

WillSpengler · 23 Apr 2008 at 21:30

They are only dimming because of the extra cable length?

Over a distance of 1.5m you should be fine with 16 or 18 AWG if that is what you are meaning?

Otherwise, I dont know what the problem would be.

PhillyDee · 23 Apr 2008 at 22:36

Nope, tried thin and thick cable, they dont like it at all. I think it was 18AWG i used, not sure. The same stuff used for car electrics. The plan is to attatch the dual inverter and switch on/off the cathodes individually. Not sure what rating of switch i need though. Dont want it to set fire to my scope!

WillSpengler · 23 Apr 2008 at 22:49

Wierd, possibly a problem with the connections? As on a short run like that you should be fine.

Could always up to 12 AWG, but, that's a little overkill

Day03 · 24 Apr 2008 at 00:02

Extend the cable from the power source to inverter and not from inverter to cathode. Can't see why it shouldn't work that way.

PhillyDee · 24 Apr 2008 at 01:14

Yes, but im after a red light on either side of the boot, and a white light on either side of the boot switchable between red and white. With that way i will need to buy another 2 inverters. Which im trying to avoid. Being more expensive.

I thought i would be fine on a 2 metre run too! Hmm. Ding! Think ill try mains cable

. Even so, the existing wire on the cathodes is only thin.

jackassuk56 · 24 Apr 2008 at 08:59

i tried extending the cables on cathodes before, and nope never worked.

You have to extend the power cables going to the inverters.

Tis very anoying but it did work for myself.

Day03 · 24 Apr 2008 at 21:00

If you have 2 inverters, each one supplying 2 cathodes then cut one cathode from each, swap them round and without extending the cable just solder the loose ends together. Just make sure that you cut the wire in exactly the same place on both cathodes. Then just extend the power cable.

killersheep34 · 24 Apr 2008 at 21:43

I would have thought a good throw switch with the pins fairly far apart would be ok. You're talking thausands of volts at miliamps. That ain't gonna catch alight.

I know what you mean bye the cathodes not working when you extend cables. I tried it myself and extending the cables even half a metre had the same effect.

PhillyDee · 24 Apr 2008 at 22:21

The boxes are dual cathode boxes, but I cant have a white and red on one box as Its to either light the boot up Red or White. One inverter will supply 2 cathodes, which is fine, but I want one white and red at either side of the boot. Hence the problem. Think ill get some mains switches. They tend to be pretty well isolated.