Shielded cable or not

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Auarhau
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Shielded cable or not

Post by Auarhau » Sun Mar 30, 2014 4:58 pm

The lengthof cable I got from Inventables is not enough for my setup. I fitted the shielded cable on three of the motors. The last one will get a normal unshielded wire (it's also a bit thinner..) for now.
How important is the shielded cable? Can I just leave it like this permanently, or should I buy the last bit of shielded wire for the last motor too?

Since it's sunday and I want to see this thing move, I will hook it up with the unshielded one for now (unless I get some loud protests here). But I can't do the complete wiring before I know if this should be swapped out or not.
ShapeOko 2. Nema 17 74 oz·in. GAUPS shield on Arduino Uno. DRV8825 Drivers x4 . Kress 1050 FME-1. Z Acme Screw. Threaded inserts table.

RobCee
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Re: Shielded cable or not

Post by RobCee » Sun Mar 30, 2014 5:37 pm

Shielded cable will be helpful in the future if you add limit/home switches. It's not super critical in the early days though, just helpful.
ShapeOko2 #3400 - Chinese 800W AC Spindle - Stiffened X-Axis - TR10 Z-Axis - Inverted Z Motor - Hall Effect Limits - Drag Chains & Custom Brackets

awesomename
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Re: Shielded cable or not

Post by awesomename » Sat Apr 05, 2014 9:21 pm

How critical is this?

Amazon totally f'd me over and send me 100ft of unshielded 4conductor 18g wire instead of the shielded one i ordered.

cvoinescu
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Re: Shielded cable or not

Post by cvoinescu » Sun Apr 06, 2014 2:42 am

If it's Amazon themselves, they'll put it right very painlessly. Contact them. If it's a Marketplace seller, they should put it right too (and most would).
Proud owner of ShapeOko #709, eShapeOko #0, and of store.amberspyglass.co.uk

awesomename
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Re: Shielded cable or not

Post by awesomename » Sun Apr 06, 2014 7:17 am

Is there softer/more flexible alternative or a place to get better shielded cable besides inventables? this unshielded cable is much softer but Im concerned with power interference

cvoinescu
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Re: Shielded cable or not

Post by cvoinescu » Sun Apr 06, 2014 8:40 pm

Proper shielded cable for machines (with extra-flexible plastic or rubber, and many strands of copper in each conductor -- typically 30 or more) is frightfully expensive. Places like Farnell/Newark, Mouser and Digi-Key may stock a small selection, if you're willing to pay $10 per meter or more. We have to compromise. Inventables chose the shielded alarm cable, which is cheap and easily available in the US, but fairly stiff and has only seven strands in each conductor (so not made for continuous flexing). I found a more expensive cable with thicker conductors with more strands (I think 16 each -- still not made for continuous flexing, but less of a problem), but it's not bendy either. The specialty cable manufacturers I found so far are Alpha Wire in the US, and Lapp Cable in Europe.
Proud owner of ShapeOko #709, eShapeOko #0, and of store.amberspyglass.co.uk

veng1
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Re: Shielded cable or not

Post by veng1 » Mon Apr 07, 2014 9:49 am

Home Depot in the States carries the shielded alarm cable for about $.33/ft.

As it is not too flexible, to the largest extent possible, mount the switches and thus the wires so they are stationary. For example, fixed Hall effect sensors and moving magnets or fixed mechanical switches and a moving closure mechanism. This is really best practice for any type wire to reduce flex.

If a wire flexes, put a connector on each end and clamp the connector so it can't move so when the wire breaks (not if) it is easily replaced.

The highest probability of failure is an unsupported wire that flexes soldered to a fixed point. Really bad idea.

It worth remembering that except for phenomena like semiconductor junction wear out,essentially all major failures in electronic equipment can be traced down to a conductor failure, even in an integrated circuit it is usually a bond wire failure or migration. Obviously, circuits that are dependent on element values like a specific resistance or capacitance are a different problem.

cvoinescu
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Re: Shielded cable or not

Post by cvoinescu » Mon Apr 07, 2014 6:16 pm

veng1 wrote:It worth remembering that except for phenomena like semiconductor junction wear out,essentially all major failures in electronic equipment can be traced down to a conductor failure, even in an integrated circuit it is usually a bond wire failure or migration. Obviously, circuits that are dependent on element values like a specific resistance or capacitance are a different problem.
That is true to some extent; however, thinking of what died on me over the last ten years or so, I find three other causes quite frequent, if not more frequent: aluminum electrolytic capacitors (especially low-ESR units subject to high ripple current in power supplies); X2-rated "self healing" polypropylene capacitors when used, with a Zener diode, to power low-voltage circuitry from the mains; and triacs (i.e. in light dimmers) that become shorts.
Proud owner of ShapeOko #709, eShapeOko #0, and of store.amberspyglass.co.uk

ALuomala
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Re: Shielded cable or not

Post by ALuomala » Fri May 23, 2014 3:50 pm

I made the bonehead mistake of not ordering enough cable for my upgraded/extended SO2, and figured "How hard can it be to find this cable where I live [Edmonton, Alberta, Canada, which is a fairly large city, with many industrial parks]?!?". None of the big box store here (Lowes, HomeDepot, Rona) carry shielded cable, and all of the specialty shops I have contacted only sell shielded cable by the spool.

I found this cable (unshielded 4 strand 22 ga cable) at Lee Valley (used for LED light strips). For some reason I didn't even clue in that they carried 18 ga wire. Regardless, I used this cable for the connection from my electronics to the machine, on which I used the supplied shielded cable. So far, so good. When I was hooking everything up, I was quite concerned about using a smaller gauge wire, but then reasoned that since it is a relatively short distance (~5 ft), and the wiring to the stepper motors is thinner yet, I should be good-to-go. Am I correct in this assumption? Everything works (for now) but I still have a lingering doubt about the wiring I used. I am likely going to order some from Inventables in the near future (I forgot to order some things that I can't source (cheaply) locally (such as 30mm M3 cap screws for the 24V fan for the electronics enclosure.... I made a temporary fix by purchasing 1 1/4" machine screws that were slightly larger than 3mm and using a M3 tap to get the first 1/2" down to M3) so I will order then... I have this irrational hatred of ordering things on the internet if I am fairly certain I can buy them locally, but the time and gas I have wasted for these two things (shielded wiring and metric screws) is really starting to add up :evil:
ShapeOko2, serial ??
DW660 spindle;
Upgrades: 900mm X axis and 1000mm Y axis; ACME Z Axis; modified MDF wasteboard with t-slot
Primary usage: wood crafting (signs, plaques, and ultimately a CNC-made electric guitar)

ALuomala
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Re: Shielded cable or not

Post by ALuomala » Fri May 23, 2014 3:57 pm

I just realized something that never occurred to me when I was looking at the above Lee Valley catalogue page: I could have purchased 3 strands of the 48" cable with connector (item G) and 3 of the terminal blocks (item H) for my connection from electronics to machine. I had a hell of a time with all of the wiring on my SO2 due to a table-saw injury to my good hand (don't ask....), so those cables/connectors would have saved me a considerable amount of time/discomfort!! Live and learn!
ShapeOko2, serial ??
DW660 spindle;
Upgrades: 900mm X axis and 1000mm Y axis; ACME Z Axis; modified MDF wasteboard with t-slot
Primary usage: wood crafting (signs, plaques, and ultimately a CNC-made electric guitar)

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