Bringing my Novamill back to life

[minimad30]

I'm fairly sure its OK but worst case I have another black box with all new drivers etc. I'll check out what I can when I get back tor the house.

[Alastair]

Hi Minimad,

Can you post some photos and /or a circuit diagram of what you have done? Also tell us a little more about what you are trying to achieve and how you are going about it...that should help us to help you more easily.

Cheers
Alastair

[minimad30]

Hi alistair,

I will take some pics and an image of the wiring when I get back into the garage. I'm fairly certain everything is the same as you had in your post. Can you confirm if the 180v is live on the spindle 12-24v input terminals? All I want now is to control the spindle speeds from mach3, everything else is working (apart from the motor tuning) I'm not sure if my machine has imperial ballscrews... This is easy to sort with some measurements.

Thanks again!

[moray]

I've just had a look at the wiring on Alistair's photos, and noticed he has the spindle control voltage tied to the 'gnd' input on the BOB.

Now, either he has a different spindle control that doesn't have the control terminals at high voltage (unlikely as nearly all common SCR type spindle drives don't have any isolation on the control circuit), or his 0V is totally isolated from Earth which would mean all his control wiring is sitting at high voltage relative to earth (I'm pretty sure Denford don't connect the 0V to Earth, as it reduces the risk of creating ground loops).
The easy way to check, is to use a multimeter and measure the voltage between earth and 0V. If it's near zero, then they're connected somewhere, if it's high, then it's not good. EU regulations limit any operator control/switch to a maximum of 48V, so if it's floating at ~180V, then you would have a lot of explaining to do if it was being used commercially and somebody got injured as a result.

[Alastair]

Hi Moray,

I don't use my mill commercially, but I'm am concerned that it is safe. Concerned by your post, I went and made some measurements. with the machine off and isolated I measured the resistance between 0v and earth and it is effectively zero...so they must be connected somewhere. This is not something I have [deliberately] done.

I have the Sprint Electric spindle motor controller which I believe is pretty common on Denford machines. I measured the voltage across the 0-10v input which varied, as you'd expect, between about 0 and 10v across the speed range. Since the Gnd appears tied to earth, that side of the electronics is not exposed to more than 10v. I have the "Product Manual" for the Sprint drive but not the schematic so can't be sure how/if the 0-10v feed is isolated from the rest of the high voltage side, although a glance at the circuit board doesn't give me confidence. Photo attached.

2015-12-27 20.03.47.jpg (520.75 KiB) Viewed 22945 times

Anyway, it all works fine but I do need to think this through...

[moray]

Try measuring the voltage between the earth and 0V with the machine powered up.

Chances are there will be components linking the two, which can affect resistance measurements, and the only real test is with it powered up.
Also try measuring between Earth and the 0-10V input to the Sprint board.

[Alastair]

Thanks Moray.

Measured voltage between earth and 0v sprint input with machine running...measures at a few mV. Between earth and the 0-10v line I get a few volts (as you'd expect).

I notice that the stepper board is earthed (not by me) I wonder if this is connected to the gnd plane on that board.

Alastair

[moray]

You're spindle controller input must be at low voltage, which certainly isn't that common.

As long as everything works how it should, I wouldn't worry about the gnd/0v connection. I'd have to go and look at the wiring diagrams, but I'm aware that original wiring has all the Earth/GNDs separate from the 0V, although they may be connected at some point. Machine earthing/grounding can be quite a complex subject, but the main jist is you avoid anything having more than one ground return, otherwise you end up with a ground loop which can be a major source of interference.
However, as Denford use 12/24v controls, it's a much lesser issue than machines that use TTL/5V controls.

[minimad30]

After some testing using a dedicated spindle board from diycnc I have spindle control. Still need to figure out the spindle motor tuning in mach3 tho as I'm using step/dir to generate the 0-10v.

I am buying an additional cheap bob with the the 0-10v output to check if my board was faulty. going to post some pics later to check my wiring against yours Alastair.

Everything appears to be working as it should following my grounding incident. I'm not sure that anything within the black box was exposed as the dedicated supply was the only thing connected on that side.

[njlwilliamson]

Hi,

I have a converted to Mach3 Novamill. I'm currently in the process of switching over to a Smoothstepper but I'm having issues controlling the Sprint spindle board.

Did anyone get the Smoothstepper to control the Sprint board?
Would you be able to tell me your settings?

Ta,

Nick

[Alastair]

Minimad, Angel-tech, Moray,

As a kind of postscript....it's been a few months, but I've been thinking about your comments around grounding and high voltages etc. from the Sprint board. My mill still seems to work fine and I haven't had any shocks yet (at lease electric ones!) but even so....I want things to be right.

Now, I took the BOB board off and gave it a really close look over (bearing in mind it's a cheap chinese unit and the documentation available is pretty sketchy) I think I have worked out a few important points. On really close inspection I'm now fairly convinced that the board is in two electrically separate parts - one side opto-isolates all the inputs from switches and lines from the parallel port and delivers them on to the steppers, the other takes the PWM spindle control in opto-isolates it then passes it through a dual op-amp before presenting the 0-10v output on a couple of pins. Crucially, this part of the board has separate terminals for Gnd and +12-24v (from where the 0-10v is presumably derived). I believe the ground plane and power supplies for the two "halves" of the board are entirely separate.

This is all good....but...

The way it is today, to power this part of the BOB I have used the +12v and ground from the Denstep board, the ground is then shared in turn with the ground from the Sprint board, which I can now see is not a clever solution! I don't think this has been particularly dangerous but I could have risked frying (at the very least) the BOB.

You live and learn.

I will now rewire, isolating the grounds and supplying the 12v for the 0-10v part of the BOB from either a stand-alone supply or I think I can take off 12v from pad 61 of the Sprint board. I prefer the second solution as it's more self-contained and should mean the stepper electronics are properly isolated from the evil Sprint board.

I hope all this is of interest and makes some sense. I'll report back with results and perhaps post photos or a wiring diagram.

[bpmsl]

Hi Folks,
This is definitely a timely thread for me. I'm "upgrading" my novamill to run on a Chinese USB CNC controller card and finally got round to testing the spindle yesterday. Everything except 24v supply and the spindle drive signal is opto-isolated and interfaced via the 96 way header. This has been running well for a year or so just driving the steppers as I've been using the mill as a 3D printer.

My view is that the sprint spindle control board is definitely running on a high AC voltage and the speed demand pins are coupled to it in some way. Whilst my USB CNC 0-10v spindle output has survived the ordeal I'm getting the board crashing at greater than half speed, I suspect because of 50hz noise feeding back up the sprint demand line and an associated relay on the USB cnc is ticking nicely at about 50hz when the spindle is running.

There are a pair of axes demand pins on the 96 way header according to the denstep card manual, does anyone know if these are for sending the signal from the control card via the back plane (with some filtering / isolation hopefully) out of the normal back plane to sprint connections?

Otherwise does anyone know of a way to isolate a variable 10v signal line between the two cards? I'm an electronics hacker so no in depth knowledge here unfortunately.

Any help would be gratefully received.

Cheers
Barry M

[DavidJ]

Barry,

See this thread viewtopic.php?f=54&t=5051- post of 31st Jan and the link provided on how to re-use the optically isolated 0-10V (actually 0-11V) out from the Denstep board.

The PWM doesn't go via the 96 way header - you can do what is shown in the link, I soldered my current limiting resistor into a through hole on the Denstep board (follow the track from R29). See image - but note the resistor shown is incorrect value, and I hadn't yet removed R29 (surface mount) from the Denstep board.

Re-use Opto.jpg (396.12 KiB) Viewed 22741 times

[bpmsl]

OK that looks great and the linked information has sent me in an equivalent direction.

I have a few more of the opto-isolating boards left (I bought a job lot from China) so will isolate digitally from a PWM spindle signal (the controller can do 0-10v or Radio Control PWM) then use the +10v and ground on the sprint to drive that side of the isolating board and add in some signal conditioning to get the full 0-10v range. Think I finally need an oscilloscope...

I got started with USB CNC with my hot wire cutter and an all in one 4 axis board a while ago and really like the interface and the fact that it's a controller rather than just a BoB, so I want to go common across my workshop. My plan is to try and make a fully plug and play control card assembly as I effectively have two novamills (one original, and one set of electrical components going into a larger home built router) and a novaturn to convert and wanted to have a common set-up to cater for component failures etc.

I've included a pic of my set-up for interest sake, it's not the latest wiring standard (pre spindle control) but you can see the isolating daughter boards mounted on the bottom of my 3d printed bracket which holds the 96way header and the Chinese controller card. Hopefully I'll just have connections via the 96way connector, flylead to the spindle card, and a 24v power supply, when finished.

Thanks for the pointers,

All the best
Barry M

[JohnShep]

FAO Angel-Tech

Tom, I think I have found the correct isolated spindle controller https://diycnc.co.uk/cnc-boards-v5-spindle-board/ but it comes in 12 and 24 volt options, which one do I need ?

thanks, John

[Andy_b1986]

Hi All,

Many thanks for your thoughts and replies. It took a long time (not a complaint) between posting my original questions and there being any kind of response here so I continued reading and went ahead anyway based on what I'd learned from around the web.

As Pete noticed, I have access to a slightly tatty but perfectly serviceable laptop, It doesn't have a parallel or RS232 port. I found that I could either spend £50-£100 on a second-hand and somewhat out of date old desktop computer, or I could go down the Ethernet route with a Smooth Stepper card. I chose the Smooth Stepper which cost quite a bit at £107, thinking that I'm future-proofing myself to some extent. It's a lovely piece of kit and was very easy to set up.

To go with this I bought a cheap Chinese parallel breakout board on eBay for £5.50 which seems to do the job well and includes 0-10v support for the variable speed spindle drive. I considered many (more expensive) Break out Boards but found it hard to see why it was necessary to spend more than a few quid.

I then took off the original controller board and mated my new kit with the existing stepper controller board through a 96-way DIN connector (£3.50).

After a lot of reading-up and measuring and head-scratching it all seems to work well with Mach 3. To be honest I'm feeling quite pleased with myself.

I still need to spend a bit more time getting friendly with Mach and I'm not 100% sure I've got all the settings optimised yet but I'm learning a lot as I go.

Next steps...start machining. Can't wait!

I'll post a couple of photos too to help anyone going through the same agony. Any questions? Please ask.

Alastair

I know that this was a long time ago - but it would be really great if you could provide the connections pinout you used - specifically for controlling the spindle and also the mach3 setup to make this work

Many thanks