Re: [CAD_CAM_EDM_DRO] ribbon cable ampacity

On Tuesday 28 February 2006 06:43 pm, Denis Casserly wrote:

> Hi Everyone,
> I need a flexible cable assembly between the base and the gantry on my 3
> axis router and am considering ribbon cable. The bend radius is 1 inch. Is
> it a good idea to use 28 AWG gage ribbon cable for carrying the power and
> control? The stepper drivers will be mounted next to the motors to reduce
> the noise, and they are rated at 3 amp/24 VDC. The rest the conductors
> would be low current step/direction and limit switch wiring. I've tried to
> find out how much current 28 gage will handle - would anyone know.

How much current a wire will handle depends on a couple of factors. One is
the allowable voltage drop in that wire (and the connections to it, as
connectors and terminations and whatnot will contribute to the resistance
here) and the other is the allowable temperature rise given the environment
and the materials of the insulation.

I've seen people use guidelines intended for house wiring when figuring what
wire was okay to use for low-voltage stuff, and that just doesn't work...

What else would concern me in this application is the amount of flexing that
the wire would be seeing over time. Ribbon cable is *not* normally a real
good candidate for continued flexing, nor are the connectors normally used
with it. Take a look at what sorts of things were used for print heads in
older printers to get an idea of what I'm looking at here. Maybe some of
those flat mylar bits can be salvaged, along with their connection hardware.
Or, if you're not looking at using a whole lot of wires, maybe some "test
lead wire" (which has a LOT of strands compared to normal wire) might be
used, too, though your selection of colors seems to be limited to red and
black. In any case, multiple strands of wire for one given signal might not
be a bad idea.

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