I made this gramophone in four weeks. It looks and feels like a gramophone but obviously doesn’t function exactly like one. It has a turntable and (fake) vinyl records, but it is actually a laptop in disguise. There is a webcam on top of the screen, and the electronics inside include a Mac Mini and Arduino as seen below.
This is what it looks like when using it:-
The final product is pretty faithful to the original design in SketchUp:-
How it works is that you place lego blocks on the rotating turntable and the webcam will pick up the colours and position of the blocks. A custom software will translate this data into sound based on a virtual scan-line on the turntable. My other team mate for this project did the software. I worked on the hardware and as such, this blog post will only cover the hardware portion.
I spent the first week planning and sketching the design in SketchUp and spent the other three weeks full-time at the new maker space at the National Design Centre. I had the opportunity to use most of their facilities, such as the laser cutter, 3D printers, computer numeric controlled (CNC) machine and vinyl cutter. This post will be structured around how I used each of these machines.
CNC machine and laser cutter
I used the CNC machine to cut most of the wood. I used thicker 12mm plywood for most of the frame as mechanical support and 6mm for some parts which needed finer cutting and could be laser cut. Both the CNC machine and laser cutter accept .dxf files which could be created in DraftSight based on my SketchUp drawing dimensions.
Here is a component breakdown when disassembled in SketchUp:-
This is an example of what a .dxf file looks like in DraftSight:-
This is what the CNC machine in action looks like:-
The result which has to be cut out and sanded:-
Bunch of cut wood:-
A lot of cutting involves taking accurate measurements. For wood, an error of a few mm is acceptable, and inevitable.
When sanding, I made the mistake of using the sanding belt with too much strength. As a result, my design was off by a few millimeters and I had to make up by paper sanding other parts. Fortunately, everything worked out in the end. This is the belt sanding machine:-
I also used the CNC machine to cut out the shape of the turntable. As you can see, the CNC machine is not good at accuracy and at cutting curves. I had to further cut out the parts I don’t need using this cutting machine.
A mistake was made using the CNC machine and a gash is there where it shouldn’t be. I used wood filler to cover it up. After painting over the entire surface, the mistake becomes less obvious.
While assembling the wood, I learnt how to properly glue wood together using clamps and nails to hold the surfaces tightly together while the glue dries overnight:-
Oh, and I learnt how to properly nail a nail. I was quite proud that after a few tries, I can nail the nail straight down into the wood instead of going in an angle. The trick is to score a hole first with a few light knocks, and then forcefully hammer it down thereafter. Hammering a nail should be a basic lifeskill.
Me hammering a nail:-
Another basic lifeskill I learnt was how to use a power drill. I had to use it to drill some holes when using the CNC machine:-
This is what the laser cutter looks like:-
The laser cutter is an amazingly accurate tool. You don’t have to account for the width of the laser itself when cutting. What you design is what you get, unlike the CNC machine which has a 6mm width drill bit. This 6mm has to be taken into consideration when designing your drawing. The laser cutter can produce extremely intricate drawings on wood. The laser cuts on wood have a beautifully charred and distinctive brown edges that has to be wiped with a damp cloth to remove the soot. I also used the laser machine to cut out the discs for the fake vinyl records from 3mm acrylic, achieving a perfectly round circle.
After the wood was assembled, I used mahogany wood stain to colour the plywood dark brown and then lacquered the exterior to give it a glossy finish and to protect the wood.
This is what the original plywood looks like, which is raw and uneven in colour:-
3D Printing
I used SketchUp’s 3D printing template to draw the parts that I needed to 3D print. I had to print out hinges for the lid, the stepper motor gear mount, the webcam mount and gramophone stylus. Because the free version of SketchUp can only export in Collada file or .dae file formats, I had to use a 3D printer software (Cura) to slice the file into .stl format. I used another free software called Nettfab Basic to verify the file to check for any missing surfaces or holes in the drawing.
To take measurements, I used electronic vernier callipers because the measurement has to be in the order of 0.1mm. The SketchUp template for 3D printing has measurements in mm with up to 10 decimal places. I had to reprint a few times because some hollow tube was too big or small. The 3D printer also has an error of 0.2mm due to the width of the filament when printing. So you have to take this error into account in your drawing. Hollow parts have to be designed slightly larger by 0.2mm in radius and solid tubes designed slightly smaller.
Here is the Ultimaker printer in action:-
Here is a drawing of the stylus and the 3D printed result-
Here is the webcam mount:-
And here is the stepper motor gear mount. The turntable sits on this.
The hinges and bolts. I used epoxy glue (resin + hardener) to glue the bolt and nut together:-
Electronics
The stepper motor’s speed is controlled by the position of the stylus. I used a potentiometer to keep track of the stylus’s position and a A4988 stepper motor driver which is able to give a step resolution of 1/16 a step of 1.8 degrees. The code is very simple. The mapping is because I only want the stepper motor to move for a small range of the potentiometer knob movement, like 45 degrees, out of a possible 270 degrees. :-
The wiring was not so simple. I had to draw all the connections on paper to keep track of the wires:-
Here is the prototyping on breadboard:-
And the final soldered version. I was amazed everything worked on the first attempt, because there were about 50 solder points:-
This is what the back of the soldered board looks like:-
Crimping is very useful when you want to modularise your wire connections:-
Compare the above with the bad example below which was my first version of this circuit. There is no modularity and the use of hot glue which is unreliable and messy. The K179 driver used below also does not allow micro-stepping which the A4988 does.
Vinyl cutting
I had to make the “vinyl record” discs matt because the acrylic itself is glossy. The surface has to be read by a webcam and a glossy surface would give distorted colour readings. Compare the surfaces side by side:-
Here is the vinyl cutter in action. You have to stick the vinyl on a sticky mat and feed it to the machine. The software to operate the machine is called Silhouette Studio. Here, the cutting is for the colour coded disc centres.
Sticking a large piece of vinyl on any surface is not so straightforward because it will stick together and crumple easily and you have to throw away the entire piece. So the trick is to use soapy water to prepare the vinyl sticker so it wouldn’t stick together and you can adjust its position on the surface you are sticking it to:-
You then use a squeegee to squeeze out all the soapy water so that the two surfaces will properly stick together:-
The power accuracy of an artknife to trim edges:-
The finished disc:-
I also used the vinyl cutter for the labels:-
The labels:-
Credits
The people in the lab have been incredibly supportive and I would like to thank them for their help and advice.
In particular,
I have to thank the electronics lead, Sim Joo Khai, for helping me troubleshoot the breadboard connections and teaching me how to crimp a wire. He also helped me rush 3D printing jobs and taught me how to use the vinyl cutter.
Sathi, for helping me with the CNC machine and laser cutter.
Poh Hong for tips on how to to use the various tools in the lab.
Robin and Veera for helping me with tips and laser cutting.
Hidaya for her administrative advice and moral support.
lohjianhui 