Denford Orac refit

This topic has 18 replies, 5 voices, and was last updated 3 September 2025 at 14:30 by Stuart Smith 5.

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21 August 2025 at 11:50 #813307
Richard Evans 2
Participant
@richardevans2
Morning all,

Having sold the Denford Triac which was discussed on here a while ago, I’m turning my attention to my Orac lathe. This has a very basic Mach 3 control set-up- breakout board, motor drivers and PSU. No limit switches or E-stop.

It’s been giving trouble for a while and now the drivers power up, the motors lock but no movement.

A couple of basic questions:

1. The BoB is the Optoport v3 from diycnc. When powered up, the two red LED indicators for the relays come on (why?) but the power indicator LED does not light up. Is the board broken in some way?

2. I bought a cheap BoB for the Triac on the recommendation of John Haine. This has a 12-24v power input. A friend (not me!) has been trying to sort things out and connected it to the existing 36v supply. I assume this has been fried? Might it have some sort of over-voltage protetction?

I’m guessing the answers are obvious but just thought I’d ask!

Richard
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21 August 2025 at 13:03 #813321
John Haine
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@johnhaine32865
I once had an Optoport which initially worked fine but later I was getting all kinds of problems with it. I also noted that John Stevenson somewhere had a lot of problems with them. I finally ditched it and replaced it with the type I recommended to you.

Those BoBs are pretty basic and are unlikely to have any over-voltage protection. They need a 5V supply for the PP input which comes from the PP itself (or can be external) and a 12V (at least) which is needed for some other purpose I can’t recall right now – something to do with the input opto-isolators. I had to add another regulator to derive 12V from the stepper supply. I have a vague recollection that even with a 24V supply they need extra dropper resistors for the optos, if connected to the 38V I think you should assume it has been fried! I have to say that it works perfectly fine in my lathe with a UC100 motion controller.
21 August 2025 at 14:51 #813345
Stuart Smith 5
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@stuartsmith5
Richard

Just to let you know, I managed to get the Triac working.

As you thought, the small board that converts the pulses to an analogue 0 to 10v signal was faulty.

Luckily, the spindle drive board was ok, but it is not isolated and the inputs are at high voltage.

The first converter board I bought wasn’t fully isolated so I bought a different one which has an opto-isolated input. I have powered it from a separate 24v power supply to keep it isolated from the bob.

I have kept the veroboard bob for now as it is working ok.

Your problem with the Orac could be the same issue with non isolated output.

Stuart
21 August 2025 at 14:56 #813347
Richard Evans 2
Participant
@richardevans2
Thanks John. I’ve ordered a replacement board of the same type. I managed to track down a manual for the board, it says the 12-24v input is optional and the board will take 5v from the USB connection.

We’ll see when it arrives.
24 August 2025 at 16:59 #813710
Richard Evans 2
Participant
@richardevans2
The replacement BoB arrived, but I’m tearing my hair out over this! If I connect the X axis driver to the BoB, the X axis will move but only in one direction. It responds to the Z axis jog buttons on the keyboard. If I connect both X and Z, the X axis works correctly (still with the Z axis jog buttons) but the Z axis doesn’t work at all. The power light is on on both drivers.

The BoB has no dedicated ground connectors for the axis outputs so I’m using a ground terminal associated with the limit switch inputs- the board has several ground terminals and I’m assuming they are common?

Any thoughts please?

The Mach3 profile has been used with this machine for years, but I loaned the lathe out and it might have been messed with? I don’t find the relevant part of the manual much use, unfortunately.
2 September 2025 at 16:35 #814930
Richard Evans 2
Participant
@richardevans2
More problems. I’ve just got a new BoB out of the packet in case the old one is blown, but there’s no change in behaviour.

I only have one axis connected, for testing. When I connect the power to the board, the stepper starts a slow grinding movement. This is without a connection to the PC. It’s the same with either axis, any combination of motors and drivers, and two different BoBs. If I remove the Direction output, the movement continues. If I remove the Step output, the movement stops.

Any thoughts, please??
2 September 2025 at 20:08 #814946
Richard Evans 2
Participant
@richardevans2
I think it’s some kind of earth loop problem. I’m getting 15v (as per the board PSU) between the board 15v input terminal and the 35v PSU (for the drivers) earth/case, with the computer switched off but the USB cable plugged in. With the PC or USB cable unplugged this drops to zero. If I switch the PC on and have the USB inserted, it’s 19v (the sum of the two inputs to the board??).

I’m running this lot from two piggy-backed four way extension cables, using sockets on both blocks at random. I’ll have to take another look in the morning. Ho hum…
2 September 2025 at 21:20 #814958
John Haine
Participant
@johnhaine32865
Hum being the operative word perhaps…
2 September 2025 at 21:33 #814961
Stuart Smith 5
Participant
@stuartsmith5
Richard

This manual may be useful.

https://www.vallder.com/images/product_details

It may not be for the exact board, but looks the same.

Stuart
2 September 2025 at 21:52 #814966
Stuart Smith 5
Participant
@stuartsmith5
Richard

I have just measured on the board I bought and the ground terminal you are using is not connected to the ground terminal on the output strip.

I think you need to use this ground connection instead. It is the third terminal from the right on the bottom terminal strip if you look at the board with the parallel port at the top.

Labelled ‘PC GND’ on this drawing:

Stuart
2 September 2025 at 22:26 #814968
SillyOldDuffer
Moderator
@sillyoldduffer
On 24 August 2025 at 16:59 Richard Evans 2 Said:

The replacement BoB arrived, but I’m tearing my hair out ….

The BoB has no dedicated ground connectors for the axis outputs so I’m using a ground terminal associated with the limit switch inputs- the board has several ground terminals and I’m assuming they are common?

Any thoughts please?

…

Assuming the grounds are connected together may the mistake. The BoB circuit opto-isolates inputs from outputs: they should not be connected electrically in any way. The diagram uses two different triangle symbols to show the ‘commons’ are different, circled in red and green:

The OUTPUT grounds are all in the DB25 socket, not available on a terminal. They are in the cable.

You may have bypassed the opto-isolation by using the INPUT ground: try disconnecting it.

As the BoB is fairly simple and unlikely to go wrong unless over volted , I suspect the original problem is the cable, not the Bob, Check the cable and the plugs and sockets for continuity. Look for dirt, corrosion, dry joints and bent pins. Metal fatigue causes hard to trace intermittent faults – wires broken inside the cable that make contact or not as the machine vibrates. Replace cable if suspect.

Dave.
3 September 2025 at 07:44 #814983
Stuart Smith 5
Participant
@stuartsmith5
Dave

Have you read my posts?

It turns out that this board is not isolated. Just buffered.

It is powered by the PC via the USB connection (which is not used for data, just power). It is this connection that removes any isolation. If the USB port is supplied from a separate PSU it would be isolated. But the connection diagram shows it taking power from the PC.

What you said in your post would be true for an opto isolated board, but this one isn’t if connected as shown.

It seems to have two sections which are isolated from one another, one for the stepper drives and a separate section for the spindle drive. The spindle drive section uses the higher voltage input to convert pulses from the parallel port to a 0 to 10v analogue output for spindle speed and a relay to switch the spindle on/off. This section might or might not be opto isolated from the parallel port but I haven’t checked.

Stuart
3 September 2025 at 09:29 #815000
Richard Evans 2
Participant
@richardevans2
Thank you for all the comments- I’m off into the workshop shortly with fingers crossed. Stuart- thanks for the link to the manual- I already have it and it’s that which I’m trying to follow. The wiring diagram is ambiguous to be polite, but now that you have suggested it, I can see that the PC ground connection is the one to go for- they have a box drawn round drivers and steppers with a line to that connection.
3 September 2025 at 09:40 #815001
Michael Gilligan
Participant
@michaelgilligan61133
I have taken the liberty of posting a screen-shot, for convenient reference

MichaelG.

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3 September 2025 at 09:43 #815003
Michael Gilligan
Participant
@michaelgilligan61133
… But of course the forum-software has downsized the image
3 September 2025 at 10:09 #815008
Richard Evans 2
Participant
@richardevans2
Success! Both axes moving smoothly. Now I have to work through some settings in Mach, and we’ll be back in business.

Sincere thanks for all the help!

Richard
3 September 2025 at 12:12 #815017
SillyOldDuffer
Moderator
@sillyoldduffer
On 3 September 2025 at 07:44 Stuart Smith 5 Said:

Dave

Have you read my posts?

Not the ones timed at 21:33 and 21:52! Not visible to me when I posted my reply at 22:26 last night. A forum bug causes delayed action images and posts: they don’t appear for some time after being sent. Intermittently. I’ve mentioned the bug elsewhere but I guess you don’t read all my posts! I suspect a cache error.

Whatever the reason the bug causes unnecessary upset! You’re annoyed because it appears I can’t be bothered to read your posts, and I’m annoyed because you assumed I was at fault rather than this being a technical glitch. We are both innocent!

Here’s an example: the drawing is missing from Stuart’s 21:52 as I see it this morning, I only get it’s hexadecimal reference:

It turns out that this board is not isolated. Just buffered.

…

What you said in your post would be true for an opto isolated board, but this one isn’t if connected as shown.

Which board? Can I make a general plea? Always good to clearly identify stuff. I’m easily confused!!! The model, part number, photos, circuit diagram and a link to the manual help reduce confusion and make diagnosis easier. I now think Richard has a “vallder Mach3 5-axis Board“, for which the manual says “All the signals are opto-isolated”. That being the case, was my advice wrong?

Delighted to see Richard has it working!

🙂

Dave
3 September 2025 at 12:25 #815021
Stuart Smith 5
Participant
@stuartsmith5
Sorry, Dave.

The photo was the same as the one that Michael g has posted.

Anyway, I have a similar board, but have not used it.

I did a bit more testing this morning on my board and ( not unexpectedly), the product description is misleading ie wrong!

The pins for the stepper drivers are not opto isolated, they are just buffered via two bus transceivers and are directly powered from the USB port.

There are only 5 opto isolators and these are for estop and limit switches. They share the same gnd connection as the 12 – 24v power input for the spindle drive circuit. The 0 – 10v output for the spindle drive is not opto isolated and shares the same gnd connection as the 12 – 24v power input.

So all round if anyone is using this board they need to be careful!

Stuart
3 September 2025 at 14:30 #815049
Stuart Smith 5
Participant
@stuartsmith5
Just a correction for my previous post. I should have said that the spindle drive circuit IS opto isolated from the parallel port, but the output is not isolated from the 12/24v power supply (ie they have a common ground connection).

Stuart
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