Woody's Workshop – Page 38 – Keeping the Grey Matter active

May 13, 2020

Making a Brocot Escape Wheel using Fusion 360 and Tormach PCNC440 CNC milling machine

A Steep Learning Curve

My wife has presented me with a sign that has just got JSN written on it. It is to remind me when I answer the phone to a ‘can you just do’ enquiry…… to Just Say No.

I try my best to live up to her expectations but sometimes something comes along that should really be a JSN job but which scratches an itch. You know what I mean. You think about it and you do all the right mental arithmetic in your head and the answer keeps coming back to the same – don’t even think about it. But the the other side of my brain is screaming at me … what a challenge, what a learning experience, what fun to have a go at it. Providing the asking party is aware of your thought process or lack of it and accepts that it might just go belly up and never come to fruition then why not ?

Back to the story – 10 days or so ago I had a call from David Pawley who is a turret clock expert extraordinaire to say someone he knew was after an escape wheel for a turret clock and was desperate. David passed on the details and a couple of days later the potential customer arrived on our driveway. After a suitably socially distant conversation and a rubber gloves inspection of the old damaged wheel …. I got sucked in and turned the JSN sign over to face the wall.

The original Brocot 30 tooth escape wheel that needed a new one making

As you can see it is not an ordinary escape wheel and I had to delve into one of my favourite books ‘Wheel and Pinion Cutting in Horology’ by J Malcolm Wild FBHI in order to learn about Brocot Escape wheels. Malcolm is a great guy and his book should be on any clock experimenters bookcase.

The Brocot is no ordinary escape wheel. In fact it is a real challenge. Not a simple fly cutter job. Traditionally it would be cut in an indexing device such as a lathe with two different cutters, one for the curve and one for the notch. I didn’t have these so I thought I would probably upset the traditionalists and try to use CNC.

Read all about the adventure and see the result in this pdf download …….

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May 5, 2020February 26, 2021

Experiences and understanding FlatCAM PCB milling program

FlatCAM Write Up – Experiences and Procedures

After a lot of editing I think the attached document will give an in depth understanding of how to use FlatCAM based on Version 8.5. The document is based on our experiences and a steep learning curve. We now have a repeatable process for milling PCBs from Gerber and Excellon files exported from a PCB design package.

The document may well have mistakes and we would appreciate feedback good or bad.

Latest version is now based on FlatCAM v8.991

FlatCAM v8.991 and milling pcbs 2021

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May 5, 2020

Supply, IC2 and USB connections over CAT5 connection

CAT5 Breakout Board

One of our group of ‘silver experimenters’ is building an Arduino based celestial camera tracker. This will be deployed in the garden and he needed all control to be routed back inside the house. The garden installation consists of a USB webcam mounted on a servo controlled platform all powered by 12V DC.

We pondered long on how we might remotely connect to the garden. The crucial thought was that the Arduino servo board was a two wire interface using the I2C format data exchange. Given that the USB needed four wires and the DC supply two wires we had a need for an eight core cable connection. It seemed like a length of CAT5 cable would do the job and we could elegantly use standard CAT5 sockets.

The PCB was designed in Design Spark and milled on the Tormach PCNC440 using FlatCAM.

There is a problem with running USB over more than 5m but I did some tests at 10m and all seemed fine which should be adequate for the application.

The breakout boards had a male and female USB connector fitted and the connections had to ‘cross over’ on one of the breakout boards to maintain continuity. We also paired the Data + and Data – connections with the +5 and Ground twisted pairs in the CAT5 so the Data + and Data – were not twinned together.

Nothing technically magic but a simple solution to a project need.

CAT5 breakout board for USB, I2C and DC supply — CAT5 breakout boards for USB, I2C and DC supply

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April 29, 2020April 30, 2020

Arc and Circle I and J code calculator for GCode cutting paths

I & J Arc Code Calculator (with updated spreadsheet)

I had a need to hard code a circular PCB cut out CNC code that would cut four arcs around a milled PCB and leave four breakout tabs to retain the board in place in the blank until the job was finished.

To create I & J codes you need to know the start point, end point and radius of the arc. The end point becomes the X and Y. The delta X and Y location relative to the radius centre point X and Y becomes the I and J values. You can also add a depth of cut value for Z as part of the block. Note that the Arc is assumed to run anticlockwise when using a G3 code running from start point to finish point. Use G2 if you want a clockwise motion. The principle is the same with both rotations.

You end up with a block code of the format G3 (G2) Xa Yb Zc Id Je where a,b,c,d,e are the coordinate values. I found that working with positive and negative values when trying to find the I and J values relative to the centre was hurting my brain. A spreadsheet was needed …..

Screen shot of I and J calculator spreadsheet for G2 and G3 coding with examples based on CW and ACW arcs around quarters of a circle with small gaps between each arc.

You can download the sheet as a ZIP file from the link below.

Arc and Circle Calculation Sheet for GCode

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April 27, 2020April 27, 2020

How to Register Velux radio controlled windows

Velux Window Registration of Window to Controller

An Off Piste rant ….having just had a few hours of my life dribble through my fingers I thought others might want to avoid having the same misery.

We have two Velux centre hinge windows in our ‘Summer Room’. They have been temperamental about behaving to the handheld controller over the years and at the weekend they both went AWOL to the controller while open.

The handbook is a bit disjointed and has a circular path if you have a problem that does not get you anywhere apart from very frustrated.

First thing is that if you end up with the window open and not responding there is a tiny white button on the electronics box inside of the window frame which if you press once will cause the window to close. This assumes that the window has failed fully open and you can get at the button….

Now to the main problem, getting the remote control to ‘see’ and register the window(s). I got the spectrum analyser out and checked what was happening. When you take the batteries out of the controller and give it a hard bounce it takes you into a primary screen asking for the language option you want. This is followed by a Register menu option. When I selected this I could see a polling signal at 868MHz (European short range devices frequency allocation) so the controller looked to be working OK.

To activate the window to listen for a poll from the controller you have to switch off the power to the window and then switch back on. For the next 10 minutes it should be listening for the controller polling request.

Well I followed all this but the controller was not seeing the windows to register them. I could not see the ACK on the analyser coming back from the window so something was wrong.

Digging in the handbook there is mention of a ‘window reset’. The same white button that allows you to close an open window also acts as a reset button for the window. If the window is closed you can manually open it to get at this button. You hold the button down for 10 seconds and this causes the mechanism in the frame to cycle back and forth and make noises.

When all stopped and it went quiet I turned the windows off and on and re-tried the controller and immediately both windows registered.

Magic. I can now get on with something more important or at least more interesting.

In summary : –

Remove the batteries from the remote controller.
Manually open the window and press the white button on the black electrical unit on the frame for ~8 secs. The white T shaped part of the mechanism will go into an ‘in and out’ process for 6 or more times and then stop.
Close the window manually and switch off the power to the window.
Put the batteries back in the controller.
Switch on the window. You now have 10 minutes to register the window.
The controller will ask for the language to be selected and will then give an option to Register. Cross all your fingers, hold your breath and then press Register and wait for registration to happen.

Hope that helps someone lose a little less of their life trying to get this to work.

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