Building my Oskitone Poly555

This isn’t really a post like my usual blog posts. This isn’t a project of mine as such or a build guide or anything. It is simply a few comments and photos of my building my Oskitone Poly555.

I’ve always liked the idea of the Oskitone. I’ve used it as the inspiration for some of my own projects and event split up the oscillators into a block of individual circuits for some experiments.

I’ve wanted one for a while, but they aren’t shipped to the UK and actually at the moment there is a waiting list anyway. But all the design information is published – so why not build my own?

I was able to follow the “Poly 555 from Scratch” page for all the design information required.

A massive congratulations and thanks to Tommy from Oskitone for such a fun build and a very well thought out and documented design!

The PCB

I had a PCB made and populated it, following the build guide. The only thing to watch out for is the fact that the PCB also includes the Oskitone APC in the cut-out so you might get charged for it being two designs, depending on how your PCB manufacture charges for boards.

I seem the recall the build being quite straight forward – it was a little while ago now. The only things to watch out for are the couple of components that are mounted on the underside of the board (the regulator and the power switch).

I didn’t do the step-by-step suggested (test one circuit, power first, etc) – but I did test each of my 555 timers before soldering them in.

I was sure I had a photo of the completed PCB but I can’t find it now! If it surfaces, I’ll add it in and if not, I might take it apart at some point and grab a photo anyway.

For now, basically, well, it looks like the photos in the build guide!

Two problems I had:

First, I mis-read the BOM for the 6mm switches. I thought they were the switches with a 6mm high button, not a 6mm high /in total/. This means that when I finally built my case, the buttons were too big. I had to desolder and clean all 20 buttons so I could replace them (I tried trimming them down, but that basically just trashed the buttons!). That was quite a pain.

Coming back to the design information, I notice there is a comment about “BUTTON_HEIGHT” – so I might have been able to build a variant with an alternative button… but I’d already printed my case by the time I found the problem…

The switch I used first of all was quite poor, so I had to desolder that and use a new one. Then I ended up with a bit of a solder bridge between the switch contacts and the switch casing which meant it wouldn’t turn off. The pads for the switch are very close together, so watch out for that.

The only other thing I did that was slightly different was to solder on header pins for the speaker. This was because I didn’t have the correct speaker at first, but I could plug in any old speaker for initial testing.

Eventually I bought the specified speaker from an online site. It was actually quite expensive, but it was the exact make, so I just went for it to be sure it would fit.

I think everything else was as stated or obvious.

The Case

When I started building my Oskitone, I didn’t own a 3D printer, so I was going to attempt to find someone who could build it for me.

But I finally took the plunge over the holidays and ended up with a Creality Ender 3 V3 SE and for a complete novice like me this has been great so far. In particular, I found the following massively useful for me:

• Auto bed-levelling. Alas I will never know the joys of manual bed-levelling of a 3D printer!
• The “pre-printing” routine – auto homing, centering, printing a couple of test lines on the edge of the print area to get the nozzle working, etc.
• The magnetic bed making it easier to pick the finished print up and slowly peel it away.
• The Creality Print slicer. I know many seem to find it simplistic (from the online comments I’ve seen) but for me, it is basic, simple, and just works fine as it knows about my printer.

One thing that was a slight concern – the keyboard section requires a colour change at a height of 16.8mm according to the build guide. Was that a step too far for a novice? There was no information about how to do that…

For my printer, it turns out that whilst there is an option in Creality Print to support a colour change, it isn’t actually implemented yet.

But the M600 gcode instruction does appear to be recognised by the printer firmware itself and from some small test prints, results in the following:

• The print head gets moved over to the edge of the print bed.
• The filament is unspooled.
• The printer pauses.

This allows time to change the filament and then simply un-pause to restart the print.

Here is my test print and the SCAD code that produced it.

cube([14, 10, 2], center=true);

translate([0,0,1.999])

    cube([10, 10, 2], center=true);

My initial attempts seemed to cause a bit of “spaghetti” on filament change, so I experimented with additional gcode instructions to attempt to replicate the pre-print routines from Creality Print to get the filament flowing again – but I don’t know enough about gcode and couldn’t get anything to work successfully.

In the end I stuck with the single M600 instruction and just manually made sure the new colour was flowing through the filament and that the nozzle was clean, using some tweezers, before resuming the print.

I don’t know if it was beginner’s luck, but that seemed to work and I was really pleased with the final result!

By the way, the M600 instruction has to go between layers 83 and 84 as per the gcode, i.e.

; COLOUR CHANGE

M600

;LAYER:84

;MESH:0_0

G0 X30.26 Y131.25 Z17.4

M204 S1000

;TYPE:WALL-OUTER

G1 F600 Z17

Layer 83 has a G1 F600 Z16.8 instruction – layer 84 has the same instruction referencing Z17.0.

Note, when running the slicer, I was getting warnings about additional structural supports being required, but I figured that as these are sold as kits, I trusted that Tommy from Oskitone knew what he was doing with the designs and ignored them!

Here are some photos of the parts being printed.

And here are some of the finished pieces.

I’m sure someone who knows what they are doing could get better print quality out of it, but for my first real attempt at printing, I was quite pleased with this.

Assembly

The complete build also requires the following:

• The speaker – as already mentioned I searched out the exact part number.
• The clear plexiglass/perspex cover – I found someone who did custom sizes online and just ordered what I needed.
• The hardware. Note the imperial sizes listed in the BOM translate as follows:
  • 4-40 1″ screw: M3 x 25mm
  • 4-40 1/4″ screw: M3 x 6mm
  • 4-40 square nut: M3 x 0.5mm square nut

I tuned the circuits prior to assembly. I just used a guitar tuner and ear and quite like the fact that each note isn’t perfectly in tune. When playing a chord or octaves there is a nice chorus/detune effect. Apart from the low G – on reflection, that sounds a little flat!

Issues:

• The volume wheel didn’t easily push onto the trim pot without bending the trim pot leads.
• The PCB was a little hard to get oriented correctly as it took a bit of pressure to get the switch located correctly in the hole in the base for it.
• On final assembly, the top note was continually playing. It turns out the button wasn’t soldered flush to the PCB – largely as a result of me having to desolder the original buttons and replace them with the correct ones.
• All six nuts are a bit of a pain to keep in place when attempting to put everything together, so eventually I just stuck a blob of hot glue on them all to hold them in place.
• The plexiglass was a bit fiddly to get in and I was worried about breaking the 3D printed parts… but it was all ok in the end. Note there were some residue 3D printing supports left in the “slot” in the case where the plexiglass goes, so this needed gently cutting out.

Closing Thoughts

This build has been a long time in coming, but it was worth the wait. I love it 🙂

I’m also really impressed with how the Creality Ender 3 V3 SE has allowed me to actually print the case – me, a complete novice in 3D printing, managing a larger build like this including a colour change. As I say, someone who knows what they are doing might get a better finish, but for me, this is totally fine.

I expect at some point I’ll outgrow the Ender, but as an entry level printer for a complete novice, who just wants to get on and get things done, so far I have nothing but praise for it.

Of course a lot of that is also due to Tommy’s design, which I can’t fault.

I was also very impressed with OpenSCAD, which I used for my test print object. I’ve only really installed it and just done that one thing, but I think I’ll like that kind of scripting approach to 3D model generation.

Kevin