Just an idea, I may be bonkers......

**Voicecoil** · 25-09-2019

Looking at my machine whilst wiring up the closed loop steppers and cursing the Chinese bods who don't use screened cable for the motor wires - WHY??? -there's 48V switching edges on those wires!!!!! - I suddenly thought why not put the driver modules on the machine next to the motors? That way all you have to run from the control box is low powered step/direction/enable lines which could easily live in a a bit of 26 AWG 6 core screened cable (about 4.5mm diameter) connected by M12 connectors and power which could be a few strands of 1mm2 wire twisted together*, or if you're flash some high power flexible coax like the Mogami 3082.

* actually 2 x 2 x 0.5mm2 would be better on reflection.

**m_c** · 25-09-2019

Denford never used shielded wiring to stepper motors, and it's never caused them any problems.

Having the drivers at the motors is nothing new, but it's not something I'd personally want to do unless the step/dir were using differential signals.

**Voicecoil** · 26-09-2019

Originally Posted by m_c

Denford never used shielded wiring to stepper motors, and it's never caused them any problems.

Having the drivers at the motors is nothing new, but it's not something I'd personally want to do unless the step/dir were using differential signals.

I can see that as long as your limit switch wiring is well shielded then it shouldn't be a problem as far as the machine is concerned. However I'm conscious that I have some short lengths of the original unscreened cable of the limit switches in use (WHY don't they cable them with twin screened rather than the pissy miniature 3 core stuff???), and besides which I would like to be able to listen to the radio interference free whilst I'm working!

**m_c** · 26-09-2019

Originally Posted by Voicecoil

I can see that as long as your limit switch wiring is well shielded then it shouldn't be a problem as far as the machine is concerned. However I'm conscious that I have some short lengths of the original unscreened cable of the limit switches in use (WHY don't they cable them with twin screened rather than the pissy miniature 3 core stuff???), and besides which I would like to be able to listen to the radio interference free whilst I'm working!

In my Triac, the only shielded wiring were the original spindle motor tacho wires, and one of the tool carousel sensors. Everything else is unshielded, and runs in the same cable tracks as power wiring.
However, Denford always used 12 or 24V for control wiring, so noise should never be a problem.

Given the amount of effort it takes to properly and reliably shield wiring, I'm surprised more people don't use higher voltage signal wiring.

**Kitwn** · 26-09-2019

Originally Posted by Voicecoil

and besides which I would like to be able to listen to the radio interference free whilst I'm working!

VHF-FM is likely to be more interference free than MW-AM and DAB better again. Having spent 21 years as a BBC Transmitter Engineer before moving down under I'd also like you to be able to listen to the radio interference free whilst you're working.

Kit

**cropwell** · 26-09-2019

Originally Posted by Kitwn

VHF-FM is likely to be more interference free than MW-AM and DAB better again. Having spent 21 years as a BBC Transmitter Engineer before moving down under I'd also like you to be able to listen to the radio interference free whilst you're working.

Kit

After 21 years as a T-E. I'd have thought you had had enough of radio interference and not needed to listen to it at all, even though it is free !

Rob-T

**Kitwn** · 27-09-2019

Originally Posted by cropwell

After 21 years as a T-E. I'd have thought you had had enough of radio interference and not needed to listen to it at all, even though it is free !

Rob-T

One of the problems of being an engineer in that field is you can be more aware of the technical quality than the program content.
I was very much a talk radio man, R4 and the World Service were my favourites, but rarely watched television. I spent the last 16 of those years as a lecturer at the BBC's technical training school and was known for saying of TV "I teach people how it works, I'm not obliged to watch it". I usualy had (still have) no idea who people were talking about when discussing programmes. Unless it was David Attenbourough of course.

Voicecoil,
If you're going to be THAT determined even the power of Auntie will have to give in.

**Voicecoil** · 26-09-2019

Originally Posted by Kitwn

VHF-FM is likely to be more interference free than MW-AM and DAB better again. Having spent 21 years as a BBC Transmitter Engineer before moving down under I'd also like you to be able to listen to the radio interference free whilst you're working.

Kit

That's entirely logical, but it's perfectly possible to knock out VHF-FM. A few years back I was designing a class D (PWM) audio power amplifier which ran on similar power rails to an 80V stepper driver and with a not dissimilar switching frequency (about 300KHz IIRC). In spite of the pretty massive LC output filter, with a lead running to the loudspeaker consisting of a couple of pieces of 1.5mm2 twisted together it completely obliterated VHF reception in the workshop.

**Kitwn** · 25-09-2019

It's a cunning plan. There could be problems with dust and vibration for the drivers mounted on your gantry and don't forget that the power cables feeding the drivers, which will have to come from the control box alongside the control cables, will not have a smooth DC current flow, though you could add some filtering at each driver to reduce that.

The biggest problem I can see is that you are replacing the nice short signal cables between your controller and the drivers by several metres of 'antenna' wiring which will have to run alongside the still noisy stepper driver power cabling and the VERY noisy spindle power cabling from your VFD. It might be case of frying pans and fires in spite of your best efforts at screening. But please don't stop thinking out loud!

In my controller the break-out is mounted inside it's own screening box and has short screened cables running to the drivers leaving only about 20mm of exposed wiring. The output cables are deliberately routed away from the inputs to minimise coupling. I've cut the motor's own wires quite short and use screened cable to connect back to the drivers with all the cable screens connected only at the controller end. Limit switch inputs have 1uF capacitors across them to prevent noise-induced false triggering. I haven't had any problems since upgrading the controller to this design.

Kit

**Voicecoil** · 26-09-2019

Originally Posted by Kitwn

It's a cunning plan. There could be problems with dust and vibration for the drivers mounted on your gantry and don't forget that the power cables feeding the drivers, which will have to come from the control box alongside the control cables, will not have a smooth DC current flow, though you could add some filtering at each driver to reduce that.

Aye, I can see that dust etc. might be a problem and was thinking of a cover to minimise that.With a suitable cable (starquad or high current coaxial) I don't think the current flow in the power line would be too much of an issue.

The biggest problem I can see is that you are replacing the nice short signal cables between your controller and the drivers by several metres of 'antenna' wiring which will have to run alongside the still noisy stepper driver power cabling and the VERY noisy spindle power cabling from your VFD. It might be case of frying pans and fires in spite of your best efforts at screening. But please don't stop thinking out loud!

I was thinking of using a 3 x twisted pair screened cable running to the (Lichuan) drivers with have an iso-optalator input so are effectively floatting diff., so ought to be OK. But I'm not sure I can be arsed to undo all the "conventional" wiring I've already done

In my controller the break-out is mounted inside it's own screening box and has short screened cables running to the drivers leaving only about 20mm of exposed wiring. The output cables are deliberately routed away from the inputs to minimise coupling. I've cut the motor's own wires quite short and use screened cable to connect back to the drivers with all the cable screens connected only at the controller end. Limit switch inputs have 1uF capacitors across them to prevent noise-induced false triggering. I haven't had any problems since upgrading the controller to this design.

Kit

Caps across the inputs are cool, been using them for years with great results.