SmartJointer: introductory article

Important note

SmartJointer is a project suitable for those familiar with assembling electronic components and messing about with software.

It is not a project for those whose primary interest is woodwork and we cannot provide support for anyone building one.

We supply SmartMini boards but we do not supply kits for SmartJointer.

Additional information

SmartJointer provides an example of QUS SmartMini boards in action.

SmartJointer video

Matthias Wandel has a lot to answer for!

It's all Matthias' fault!

SmartJointer started life as a virtual reality model in SketchUp.

Three of us retired from business at about the same time and, naturally, we wanted to keep our brains busy. I had a workshop built onto my house a few years ago and I felt the time had come to do some serious woodwork.

My business had been software so I decided to investigate CNC and, at the same time, I got the plans from Matthias for his screw advance box jig. That worked out well because the plans arrived at the same time as I was installing my Heiz/CNC-Step CNC router on to its custom cabinet.

The black drain pipe on the right is filled with concrete and serves to hold a rotating platform for a PC. On the work surface you can see my very first cuts - designed with Matthias' gear template generator.

So, the jig got built, used and was excellent - though it did take up rather a lot of room in the workshop.

Then the trouble started

Showing off the jig to my friends led to: "how could we use our expertise here?"

Between us we have over 120 years in software and electronics development and we had been "playing" with various Arduino projects. We are particularly fond of the Arduino Pro Mini - which is extremely small, extremely powerful and very low cost - Chinese versions are under one pound English, under two dollars American and goodness knows what in Canadian!

The Arduino Pro Mini in all its glory

Serious stuff in a very small package!

Atmega328p processor running at 16 million cycles per second, 32K flash, 2K RAM, 1K EEPROM, 19 digital date lines of which 6 can handle analog input and 6 can output PWM. Built-in Arduino bootloader to enable it to be programmed from a PC.

Now, you either find this a thing of rare beauty or you don't! We computer people are a funny lot.

The downside of the Pro Mini is that it is not very flexibly for development purposes and has to be fitted to a breadboard or custom PCB to use it.

We decided to have a crack at designing a family of boards that would make the Pro Mini easy to use in real world projects and enable multiple Pro Minis to be used together for distributed or parallel processing.

Enter Quite Useful Stuff

So, we (Brian, Pete and me!) have called ourselves "Quite Useful Stuff" (just for the hell of it and because we want to develop quite useful things!) and the SmartMini family of electronics boards came into being.

The first project was SmartJointer - using a SmartMini-SA (Single Axis) board to control a stepper motor to move a work holder while cutting finger joints. Initially this was linked to a laptop where you entered the timber width, the saw blade kerf and the number of pins required. SmartMini-SA does the maths and SmartJointer moves to the first cutting position for you to you push it through the saw blade and back again - just as you do with Matthias' jig. This is repeated until all pins or tails have been cut.

As with all such projects it went through several iterations, each one making it simpler to build and more flexible to use.

In theory the width could be extended to whatever you like just by changing the length of the two support rods and the drive belt. This version uses 300mm rods and can cut up to 200mm (8" for those still quaintly Imperial) or 400mm if you cut from one side then from the other - assuming you want symmetrical finger joints. Given we are using a small but powerful processor to do the sums, symmetry is not necessary - you can have pins and tails of whatever mixture of sizes you want.

This view from the back also shows SmartMini-SA (not connected!) which, as you can see, it is pretty darn small (50mm x 55mm). In use it fits on the back of SmartJointer along with small 12V lead battery - I don't like mains wires close to my saw blade!

Here SmartMini-PS (power supply) and SmartMini-SA (single axis) are joined together with the EPort ready to drive the manual version of SmartJointer.

Now to go over the top

Not being one to think a project is ever finished, and being a great believer that "if a project is worth doing, it is worth going over the top" (and being lazy), I felt all this pushing and pulling was too much so I came up with a second axis to do the job.

Fully automatic SmartJointer was born!

The principle is really simple. The pusher part is bolted to the track in the saw bench while SmartJointer is free to move forwards and backwards with a runner in the same track. A single bolt dropped into the back of SmartJointer joins them together - rigid connections have to be avoided or everything locks up (as I discovered when I made the first one!)

The pusher shares the same mechanical components as SmartJointer and is very quick to make.

The combination of the two is controlled by SmartMini-MA (multi axis) and connected to a SmartMini-EB (expansion board) on the back of a 20 character x 4 row LCD display. The SmartMini-EB also supports local or remote keypads (I am using a remote one), SD Card reader and 32K of additional EEPROM - for storing all sorts of stuff like messages, cutting files etc. I mounted the lot to a simple acrylic plate but it could be boxed up to look nice and professional.

To the left of the SmartMini-MA board you can see the tiny SmartMini-PS (power supply). This converts the 12v from the battery into 5v for the Pro Mini and passes the 12v to the motor drivers via the Edmundson Port or EPort (designed by, and named after, Brian!) For those wanting more power (!) it is possible to connect motor power of up to 35v to SmartMini-PS.

The laptop is no longer required - everything can be set up and run from the keypad and display with data stored in EEPROM memory between sessions.

You can see the 12V lead battery on the right.

The SmartMini-MA board supports up to three stepper motors while the SmartMini-SA supports one. Both can be seen in this next photo.

The setup used for the automatic version of SmartJointer is shown below.

SmartMini-PS is on the left linked to SmartMini-MA with the EPort bridge board. SmartMini-EB is hidden on the back of the the 2004 LCD display.

Distributed processing

The Arduino Pro Mini has a limited amount of programming space (32K bytes) and this quickly becomes full if you are controlling a lot of devices and doing a lot of clever stuff. For example, storing files on an SD card is a great idea but the code to do it uses up almost half of the programming space.

We designed the SmartMini family so they can be daisy chained together and they can talk to one another.

So, one can handle the human interface (display, keypad, SD card etc.) while another moves things or senses things - or whatever!

The boards are linked with the "Edmundson Port" or EPort and the number that can be linked together is limited only by your imagination!

The photo below shows three boards linked in this way: SmartMini-HI (Human Interface), SmartMini-SA and SmartMini-MA. (The slight curve in the photo is because of the wide angle used to take it - the board are straight!)

So, thanks Matthias, you have started something we haven't yet finished - it's all your fault!