Motor box cable


Jay Murphy
 

I'm looking for recommendations for cable to connect the Onstep controller to the motor boxes. I need 9 wires and the motor wires need to carry about 1.5 amps. I've got 9 pin aircraft connectors. I'm just looking for nice looking, flexible, ready made cables. I tried HDMI but it's a bit messy in there with all the extra shielding and grounds.


Chad Gray
 

I am using CAT7 right now with each pair twisted together.

I also decided on these connectors.  I am not sure how many pins they come in, but 6 is good for me for right now.
https://www.amazon.com/dp/B07D3CKYTM?psc=1&ref=ppx_yo2_dt_b_product_details

I still haven't found a nice flexible cable though.  I want something rubbery or silicon like.  Also Orange if possible to go with the Celestron colors.

I will be watching the thread if one starts. 



On Mon, Sep 13, 2021 at 8:58 AM Jay Murphy <stercust@...> wrote:
I'm looking for recommendations for cable to connect the Onstep controller to the motor boxes. I need 9 wires and the motor wires need to carry about 1.5 amps. I've got 9 pin aircraft connectors. I'm just looking for nice looking, flexible, ready made cables. I tried HDMI but it's a bit messy in there with all the extra shielding and grounds.


Corey Mooney
 

I use industrial cable from IGUS.

I shoot for "continuous flex" or "robotics" grade, with a TPU, PUR, or TPE jacket for flexibility. 

Some of the High tier stuff is eye-wateringly expensive, but the "lower" tier stuff Is great, and reasonably priced for the impressive quality.

On Mon, Sep 13, 2021 at 9:07 AM Chad Gray <rchadgray@...> wrote:
I am using CAT7 right now with each pair twisted together.

I also decided on these connectors.  I am not sure how many pins they come in, but 6 is good for me for right now.
https://www.amazon.com/dp/B07D3CKYTM?psc=1&ref=ppx_yo2_dt_b_product_details

I still haven't found a nice flexible cable though.  I want something rubbery or silicon like.  Also Orange if possible to go with the Celestron colors.

I will be watching the thread if one starts. 



On Mon, Sep 13, 2021 at 8:58 AM Jay Murphy <stercust@...> wrote:
I'm looking for recommendations for cable to connect the Onstep controller to the motor boxes. I need 9 wires and the motor wires need to carry about 1.5 amps. I've got 9 pin aircraft connectors. I'm just looking for nice looking, flexible, ready made cables. I tried HDMI but it's a bit messy in there with all the extra shielding and grounds.


Chad Gray
 

That stuff is pretty cool... $8 a foot on this 8conductor 24awg one!  :)  Pretty expensive stuff.  


Where are their leftover scrap pile cables that I can pick through?  :)



On Mon, Sep 13, 2021 at 1:39 PM Corey Mooney <coreydmooney@...> wrote:
I use industrial cable from IGUS.

I shoot for "continuous flex" or "robotics" grade, with a TPU, PUR, or TPE jacket for flexibility. 

Some of the High tier stuff is eye-wateringly expensive, but the "lower" tier stuff Is great, and reasonably priced for the impressive quality.

On Mon, Sep 13, 2021 at 9:07 AM Chad Gray <rchadgray@...> wrote:
I am using CAT7 right now with each pair twisted together.

I also decided on these connectors.  I am not sure how many pins they come in, but 6 is good for me for right now.
https://www.amazon.com/dp/B07D3CKYTM?psc=1&ref=ppx_yo2_dt_b_product_details

I still haven't found a nice flexible cable though.  I want something rubbery or silicon like.  Also Orange if possible to go with the Celestron colors.

I will be watching the thread if one starts. 



On Mon, Sep 13, 2021 at 8:58 AM Jay Murphy <stercust@...> wrote:
I'm looking for recommendations for cable to connect the Onstep controller to the motor boxes. I need 9 wires and the motor wires need to carry about 1.5 amps. I've got 9 pin aircraft connectors. I'm just looking for nice looking, flexible, ready made cables. I tried HDMI but it's a bit messy in there with all the extra shielding and grounds.


Jay Murphy
 

This place looks like just the ticket. Thank you


George Cushing
 

Well, 30AWG will carry 2A without trouble and 28AWG is good for 3A, but finding stranded un-grounded/twisted lightly insulated wire today is difficult. Everything is made for a specific application. 

As an inveterate hoarder I generally make up cables from old systems cables. A favorite are Centronics printer/teletype cables. They are usually stranded 22-24AWG and contain over 20 conductors. A ten footer will keep you in wire for quite a while. 

Braided cable sleeve is available in all the fashionable colors.



Chad Gray
 

I probably have some old parallel printer cables.

I also found 5pin XLR microphone cables.  That is the kind of jacket i am thinking of.  Guitar patch cables or microphone cords.



On Tue, Sep 14, 2021 at 9:43 AM George Cushing <stm32bluepill@...> wrote:
Well, 30AWG will carry 2A without trouble and 28AWG is good for 3A, but finding stranded un-grounded/twisted lightly insulated wire today is difficult. Everything is made for a specific application. 

As an inveterate hoarder I generally make up cables from old systems cables. A favorite are Centronics printer/teletype cables. They are usually stranded 22-24AWG and contain over 20 conductors. A ten footer will keep you in wire for quite a while. 

Braided cable sleeve is available in all the fashionable colors.



Drew 🔭📷🚴‍♂️
 

Your solution is the one I prefer also. Since I go back to before the beginning, (I built one of the first home computer kits) I have lots of obsolete around.

If they are flexible enough I use old serial cables. I have used old video, printer, SCSI and other assorted connection cables. What I avoid is Ethernet cables. These are made for high frequency and the conductors have different impedance and capacitance values that can be problematic.

I have not stripped conductors out and put them in braided sleeve. What method do you use to remove them from there existing sheath? How do you pull them thru the sleeve?


Prasad
 

Geo

Do you know any cable that does not harden (insulation) when used in winter weather? Long ago I had a Losmandy G11 and it came with its Losmandy control. The coiled cables for it remained flexible at least till 20 deg F. I have not found such stuff in the market. Every cable works fine but slowly becomes like a rock when temps go down. 

Prasad


On Tuesday, September 14, 2021, 09:43:13 AM EDT, George Cushing <stm32bluepill@...> wrote:


Well, 30AWG will carry 2A without trouble and 28AWG is good for 3A, but finding stranded un-grounded/twisted lightly insulated wire today is difficult. Everything is made for a specific application. 

As an inveterate hoarder I generally make up cables from old systems cables. A favorite are Centronics printer/teletype cables. They are usually stranded 22-24AWG and contain over 20 conductors. A ten footer will keep you in wire for quite a while. 

Braided cable sleeve is available in all the fashionable colors.



Ken Hunter
 

For a more modern cable source check out the HDMI cables at the local GOODWILL store.
A lot of wires, twisted, paired, flexible...


Ken Hunter
 

While you are there, pick up all the Laptop and Printer power supplies they have.
18-19V @ 3-4 Amp usually around $9.49


Mark Christensen
 

Drew,

I have to disagree: I use flat spiral modular cables from DigiKey - they are more flexible than a lot of other options, esp. things like old printer cables which are awfully stiff - I use those as a source of hookup wire and have a lifetime supply of it for that application collected since the 1970s. I would not use them for a mount swinging around doing GOTOs - at least the ones I have are just too mechanically stiff and heavy.

If you buy the RJ45 8P8C models you have eight conductors, so pairing them up into four lines give plenty of current handling capacity. I've had zero problems with them running my mount with 1 amp drive levels. Maybe you've had actual problems (as opposed to caution) with inductive and capacitive reactance. I haven't seen any myself. Since my mount runs fine I haven't bother to put a probe on the lines. What me worry?

If you use the RJ45 connectors on the various Mini and Maxi OnStep PCBs this happens automatically on the PCB end so you only need to cut of the RJ45s at the motor end and make up your own connectors, which is what I do at both ends using four pin avionics connectors - I've had too much bad experience with modular connectors on field equipment. But heh, if you like that option, use it.

Depending on the length you want they go for between $5 and $12 each. They seem reasonably flexible in the cold (it gets to -10F here pretty often in the winter). Much more flexible and lighter than the cables used by Celestron and Meade for their handsets, if that point of reference helps.

Search on modular cable assemblies at DigiKey.

Mark Christensen


George Cushing
 

I just score the sleeved with a box knife and it will usually tear when pulled against the core. The braided sleeve works like a Chinese finger trap. I just push it back the cable to loosen a foot or so then move down beyond the loosened section and loosen another foot. Lastly just push it all off the end. Recycle or use to desolder. The foil strips away fairly easily.


George Cushing
 

Probably Polyurethane


Mark Christensen
 

Prasad,

The modular flat, coiled, cables at DigiKey are exactly what Losmandy uses on the 492 Digital Drive. You can get them in 8 conductor models and pair the wires up to get more current with 4 conductors if you need it. If you don't then all eight wires are available. The old 492 drive used 6P6C connectors with flat coiled modular cables for the old Hurst/SAIA unipolar motors since those have six wires to the motors.

For our friends with CGEs and other mounts, alas, they do not make 9 wire versions, so for something like the CGE Pro you're kind of stuck unless you're willing to run a separate wire for either the RA limit or RA home switches. Or just give up on one (like the Home) and use the Park function. Since the RA housing doesn't move that is not a big deal (in fact you really don't need a flex cable for that one). The DEC really does need a flexible cable but isn't a problem since it only needs 4 for the motor, 1 for Signal Ground and 1 for Home and, again, the Home is expendable in my opinion since the Park function give more flexibility. The other 3 pins (in the original Celestron cable) aren't needed. Unless you spend a lot of time adjusting the Home microswitches by hand you won't get close to polar home anyway.

The older, original, CGE (modified to use circular connectors by TPI-Astro previous to me working on it) got around the problem by using the housing as signal ground for the RA. Not a good practice in my opinion. I've mod'ed both CGEs and CGE Pros but the original cables were available. I sure didn't worry about the color! If anything, for visibility at night, I wouldn't use black, red, or orange.

By the way, while ethernet signals are high frequency (in terms of bit rate), it is high frequency digital (as opposed to an analog sine wave) and hence has a very broad spectrum going all the way down to DC. Just ask C. Fourier and J.W. Gibbs. So ethernet cables have to be able to pass low frequencies without excessive loss and the spec requires them to be tested down to nearly DC (0 Mhz). Take a look at:

"Why Not Test at the Frequency of the Ethernet Signal?" -- Blue Jeans Cable

Best regards,

Mark Christensen


Khalid Baheyeldin
 

As someone from a cold climate, I did face the stiff cable problem.

To solve it, I found the flat Ethernet RJ45 cables work well. They are stock eBay ones,
so nothing special at all.

Like others have said: I solder each adjacent pair together, so the current is split in
have for each of the 8 wires.

Working well for close to two years now, with my 675mA tracking and 850mA slewing.

You can see them in my videos, e.g. this one.


Howard Dutton
 

On Tue, Sep 14, 2021 at 10:38 AM, Mark Christensen wrote:
The old 492 drive used 6P6C connectors with flat coiled modular cables for the old Hurst/SAIA unipolar motors since those have six wires to the motors.
Many years ago I had a Mega2560/OnStep with DRV8825's to 0.9A NEMA17 motors for my G11.  I tested everything on the bench and it worked nicely.  Took that and installed with those cables and was confused/surprised at just how awful the motors worked.  No fast slew speeds, micro-stepping was a mess, lots of noise.  Switching to 20 AWG (what I had) returned things to how it should work.  Not doubled up as an 8C would be, but just as a point of reference.


GuitsBoy
 

I also use ethernet cables, and double up the twisted pair for redundancy / current capacity.  I stick with the 26 AWG for fear the 30 AWG might be too thin, however Ive found the monoprice cables to have a fairly soft outer cover.  My cables are left as long loops, and I regularly image all winter long, many nights well below freezing (15º to 20º F).  Ive found no ill effects from the cold cables.  The cold grease is a bigger issue IMO.

Rather than soldering or otherwise splicing the wires together, you can simply loop the wire around and punch down in two places on the RJ45 jack.   A little difficult to see since I've glued them in place, but you can make out how the same wire from the motor is looped around to both terminals in the RJ45.  Simple, clean, and reliable so far.

On 9/14/2021 1:58 PM, Khalid Baheyeldin wrote:
As someone from a cold climate, I did face the stiff cable problem.

To solve it, I found the flat Ethernet RJ45 cables work well. They are stock eBay ones,
so nothing special at all.

Like others have said: I solder each adjacent pair together, so the current is split in
have for each of the 8 wires.

Working well for close to two years now, with my 675mA tracking and 850mA slewing.

You can see them in my videos, e.g. this one.


adraasch
 

All,

For cold climates, and flexible cables, consider silicone insulated wires.

Hope this helps,

Arlen

On Tue, Sep 14, 2021 at 2:14 PM GuitsBoy <guitsboy@...> wrote:

I also use ethernet cables, and double up the twisted pair for redundancy / current capacity.  I stick with the 26 AWG for fear the 30 AWG might be too thin, however Ive found the monoprice cables to have a fairly soft outer cover.  My cables are left as long loops, and I regularly image all winter long, many nights well below freezing (15º to 20º F).  Ive found no ill effects from the cold cables.  The cold grease is a bigger issue IMO.

Rather than soldering or otherwise splicing the wires together, you can simply loop the wire around and punch down in two places on the RJ45 jack.   A little difficult to see since I've glued them in place, but you can make out how the same wire from the motor is looped around to both terminals in the RJ45.  Simple, clean, and reliable so far.

On 9/14/2021 1:58 PM, Khalid Baheyeldin wrote:
As someone from a cold climate, I did face the stiff cable problem.

To solve it, I found the flat Ethernet RJ45 cables work well. They are stock eBay ones,
so nothing special at all.

Like others have said: I solder each adjacent pair together, so the current is split in
have for each of the 8 wires.

Working well for close to two years now, with my 675mA tracking and 850mA slewing.

You can see them in my videos, e.g. this one.


Prasad
 

Thanks, Mark, 

I found them on Digikey. They have several of them and are a bit confusing too. Still looking at specs in detail. 

Prasad




On Tuesday, September 14, 2021, 01:38:16 PM EDT, Mark Christensen <mjcw500@...> wrote:


Prasad,

The modular flat, coiled, cables at DigiKey are exactly what Losmandy uses on the 492 Digital Drive. You can get them in 8 conductor models and pair the wires up to get more current with 4 conductors if you need it. If you don't then all eight wires are available. The old 492 drive used 6P6C connectors with flat coiled modular cables for the old Hurst/SAIA unipolar motors since those have six wires to the motors.

For our friends with CGEs and other mounts, alas, they do not make 9 wire versions, so for something like the CGE Pro you're kind of stuck unless you're willing to run a separate wire for either the RA limit or RA home switches. Or just give up on one (like the Home) and use the Park function. Since the RA housing doesn't move that is not a big deal (in fact you really don't need a flex cable for that one). The DEC really does need a flexible cable but isn't a problem since it only needs 4 for the motor, 1 for Signal Ground and 1 for Home and, again, the Home is expendable in my opinion since the Park function give more flexibility. The other 3 pins (in the original Celestron cable) aren't needed. Unless you spend a lot of time adjusting the Home microswitches by hand you won't get close to polar home anyway.

The older, original, CGE (modified to use circular connectors by TPI-Astro previous to me working on it) got around the problem by using the housing as signal ground for the RA. Not a good practice in my opinion. I've mod'ed both CGEs and CGE Pros but the original cables were available. I sure didn't worry about the color! If anything, for visibility at night, I wouldn't use black, red, or orange.

By the way, while ethernet signals are high frequency (in terms of bit rate), it is high frequency digital (as opposed to an analog sine wave) and hence has a very broad spectrum going all the way down to DC. Just ask C. Fourier and J.W. Gibbs. So ethernet cables have to be able to pass low frequencies without excessive loss and the spec requires them to be tested down to nearly DC (0 Mhz). Take a look at:

"Why Not Test at the Frequency of the Ethernet Signal?" -- Blue Jeans Cable

Best regards,

Mark Christensen