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Simple Dual Pulse Arduino Based Generator

A useful test source for bench testing

I have a current project on the go for a clock synchroniser. This takes two pulses, one from a GPS reference source and one from a secondary variable source and calculates the time difference between them to correct the clock. The system is Arduino based and I needed to be able to test my software logic without having to manually initiate the two pulses. The result is this simple but very useful pulse generator.

The generator is based on my favourite Xiao SAMD21, a SSD1327 OLED display and an Adafruit rotary encoder. The PCB layout was designed in the Fusion Electronic module and uses through hole components. There are only two top side links so it is easy to mill the artwork using the Fusion manufacturing data in association with FlatCAM. Production boards will be run via PCBWay.

The software provides two output signals that can individually have their rep rate and pulse width defined via the OLED screen and the rotary encode. The two streams can be independent or locked together. If locked together then a delta phase shift can be programmed in. Here is the working unit built onto the CNC milled PCB. The enclosure is a simple 3D printed trough.

The missing BNC placement is a possible external sync input enhancement ( a rainy day job …). The unit is powered from an external source with a 5V on board regulator to feed the logic. There is a 3V3 to 5V buffer driving each pulse output (two digital transistors, two resistors and a LED indicator).

This development had been put on hold. Using a discrete rotary encoder I could not get a stable response on the OLED display and there was poor interaction with the encoder – lots of jitter and missed steps. The Adafruit module uses the same encoder but mounted on a small pcb that has an I2C encoder built in. The SSD1327 has the option for a SPI bus and an I2C interface. The new configuration using the combination of the encoder on I2C and the OLED on SPI completely cured the all earlier problems I was having.

Let me know if you would like a production PCB.

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Fusion 2026 Update Furor

The natives are restless

Autodesk has released an updated version of Fusion in January 2026 that has caused quite a few ripples.

The gist is that the new version now offers both a traditional top down methodology as well as a new bottom up based process.   This is not radically new as both methods were always available but this now hits you in the face via an opening dialogue box that offers various options on how you might want to proceed.  The dialogue box is not optional and cannot be blocked.  This has caused some heavy criticism on the Autodesk forum.

Top down is where you give a file a top level name and all the constituent parts are built under this title as components.   One file holding lots of parts.

Bottom up starts with lots of individual parts in separate files all brought together in one assembly file.  Lots of files with one holding file.  This way of working suits large organisations where multiple operators are all simultaneously working on a large project.

Top down was always Fusion’s ace in the hole as it bucked the trend of other packages that stuck to the more standard bottom up way of working.  Top down is still an option but will be known hence forth as Hybrid working.

For hobby licencees the Hybrid way of working more efficiently supports the 10 active files limit.

Here are some good YouTube videos giving an overview of this change.  

Autodesk has inferred that this is a starting point in a planned new way of working.  Time will tell. It might be a bumpy ride.

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Confusion over the 10 files limit in Fusion hobby licence

A misunderstanding of the Fusion design process ?

I regularly see comments on forums from people who don’t want to use the free hobby licence for Fusion because of the ’10 open file restriction’. This suggests that perhaps they are used to conventional bottom-up CAD design whereas Fusion creates a powerful top-down architecture. (You can still use the bottom-up approach and this is probably why the confusion arises).

A bottom-up approach has each part of an intended assembly created in its own file and the individual parts are then brought together in an assembly file. This creates a 1+N count of files needed for an assembly where N is the number of parts involved. It also places a high demand on the creator to monitor and check linkages between the individual files.

A top-down approach starts with the assembly file and all the components are contained within that file. The file count is just 1. Clearly a top-down file could become enormous if there are lots of components but it is still one file. Unlike the bottom-up method, the linkages between the components are automatically updated.

One of the more helpful descriptions of the differences in the two techniques is the first 5 minutes of this video by Product Design Online.

The other big advantage of a top-down approach is the ability to have parametric modelling of the file. This uses a look up table of all the key parameters in a design. These parameters can be just a value or can be equation linked. They are represented in the design dimension values as text and equations. Once again Product Design Online has a good tutorial.

Although I have a paid licence to use Fusion I have never had an issue of needing anywhere near 10 projects open at anyone time but I might have had well in excess of 10 components active.

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DXF import to Fusion

Doesn’t work with hobby licence

I recently had an article printed in the BHI monthly Journal where I detailed using Gearwheel Designer to create a clock wheel and how the resulting design could be imported into Fusion using a DXF import. This would allow manipulation of the file for creating the CAM machining code.

I have a friend who uses the hobby ‘free use’ of Fusion and he was struggling to import a DXF by this method. After some exploration we decided that DXF import on Fusion was not allowed for the free hobby version. This is not clearly obvious when you look at the Autodesk site.

With this in mind we collectively investigated the differences involved using the licenced and licence free version of Fusion. This resulted in a workaround solution whereby the STL export from Gearwheel Designer can be used instead. This can create a solid model in Fusion for onward processing for 3D printing and for CAM programming.

Rather than have a long post I have detailed the process in the attached PDF write up.

Gearwheel Designer and FusionDownload

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Hybrid 3D brass threaded insert tool

Why didn’t I think of this before ?

I have attempted various standalone soldering iron mounts for inserting brass threaded inserts into 3D prints. None of these ended up being something that I would rush to use with all their various shortcomings.

My brief for a design was that it had to clamp hold my Lytool solder iron (this takes the Hako 900 series bits), ensures the the action on the insert was perpendicular to the workpiece, had a return spring and a depth stop. Most of the designs I had seen were standalone devices.

My outline brief matches a standard drill press action – perpendicular action, return spring and depth stop. Why not use these attributes ?

The result end up being quite simple. A soldering iron mounted on an arm that has an arbor for mounting in the drill press chuck. Here is a garishly coloured Fusion graphic image.

The arbor is a length of M8 studding held firmly in the mounting arm with a top and bottom nut. The soldering iron clamp holds an adapter sleeve to match the soldering iron profile. The clamp is tightened with a 3D printed knob which has a retained M4 nut and thread and this mates with a retained nut in the 3D printed arm.

Here is the real thing.

It clearly doesn’t have much appeal if your 3D printing is in the back bedroom and your drill press is out in the cold damp garage….

If you want the STEP files let me know.

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