Draw me to the moon…

…Led me sweep among the stars

 

So, I have a long therm project that will require a display with some particular needs.

I want it to work with 3V3, retro-looking and curved.

Yup, nothing off the shelf is going to work for me (flexy o-led displays with a big aspect ratio are not going to be a thing in time, and they don’t exactly look the way I want the thing to look anyways.

We could say I want to inspire the display in these:

The gorgeous HDSP-2000’s wich are nigh impossible to obtain nowadays at good pricings (and besides, they are small for my application). But the amber dot matrix look is just too gorgeous to let it pass, so I started drawing my concept:

8×8 groups of leds, using a SN74LVC244 line driver as row selector, and 74HC595’s shift registers to select the columns using a clock signal (and a start pulse). The thing is, when I started this, I was not sure I could program a microcontroller well enough to actually use such a display (for some people it would be awalk in the park, but to me, programming is always a chore I don’t particularly like to do). Of course, since this post doesn’t have a doomed kind of tittle, and I’m actually writing this post, is fairly evident I succeeded.

Oh, sorry, spoiler alert. XD

 

 

Anyways, so I just put myself to Altium the shit out of this thing, one schematic at a time:

Then PCB it:

Damn altium. XD

For a moment, I was also afraid I would have to chase every individual led, however Altium was kind enough to group them in couples of 8 leds:

At first I just put them horizontally, altough I knew I was going to rearrange them to be as compact as possible (1206 led footprint):

90º rotation and compaction afterwards:

The other componentry:

It’s not like it’s a particularly difficult board, but I spent an insane amount of time compacting it for a 2 layer board. (remember, this is a prototype to test my programming skills (and secondarily. that the circuit worked).

8 row input lines, a clock input and traveling pulse input.

And, since I was at it…made it BLACK:

Nope, there was no way of avoiding those three jumpers without heavy board remodelling, and I was tired of it already. Two weeks later:

First, a bit of testing:

Once I was satisfied I assembled the rest, and lo and behold!

Consumption is moderate at 40-ishmA, as per design.

However, not everything was perfect in the land of the led. Previous tests where only lighting one led at a time sequentially, and that is innefficient both because I designed a parallel load, AND because reduced overall light intensity per led. Given that I was already working at very low levels (5/8mA per led) reducing it even more was not going to help with visibility. When I tried to start doing more, this happened:

 

That line was supposed to be one led thick, but somehow, the line was doubling horizontally.
Hummmm…
Quick check with the scope:

LMAOOOOOOOOO, no wonder the leds where doubling, I had made the software in such a way that it put the (blue) led activation, in between column pulses. XDDDD
Some softwareing later:

Nice and cozy!
Beautiful pulse-within-pulse (blue led activation, yellow, column selection).

After some more fiddling with the STM32F103:

BAHAHAHAHAH…Had to be done, sorry-not-sorry. XD

Some more poking:

The software side, in the next post, folks!

See ya!

Ouroboros

If you have a decent mitology background, this will be self explanatory:

For those who dont, Ouroboros is an ancient symbol depicting a serpent or dragon eating its own tail. {Wikipedia}

Also, this is the first post I have ever written via smartphone, and I’m proud of it. XD.

GitS, seriously?

I just saw this in another of the featurettes from Ghost in the shell.
Major’s recharging station:

Seriously, Hollywood, you have a problem of designers not being up to date, or not imaginative…or not techie enough, frankly.

Nothing else to add.

Stimpak, an overkill mechanical paste dispenser.

In the age of internet, some people think it’s weird not looking up if something exists. I myself I’m in the leage of “buy the tools if possible”, because I don’t like spending time creating the tool I need AND then more time to do what I intended to do in the first place.
However, in this case, it didn’t cross my mind that it could be possible that what I needed already existed (not in a egotistical way, I just didn’t thought much about it). Anyways, I wanted a mechanical paste dispenser.

Easy enough, a screw, a syringe, and something in between to hold everything together, right? Well, normal metric screws do not bear well with pressure, they tend to bind, so I figured that, at least as a test, I could go by with a micro fine pitch screw. As I didn’t had such a screw (or tap, for that matter) at hand, I had to make my own:

That’s like half a millimetre or less pitch screw in a 8mm diameter shaft. That would need a keyway guide AND machining the end to accept a standard plunger tip:

Since I had made it at home, I also had to make a tap for the nut/actuator wheel, wich was simply done by putting a cone on a threaded shaft and some relief cuts so a sharp edge with all the threads would engage on the nut material:

The point here, tough, is that the shaft was 8mm, so in order for the tap to work, I had to make an undersize hole, probably in the order of 7.8mm or so in the nut, but I don’t happen to have a drill in such diameters at hand AND they are usually expensive. However, if I freezed a drill bit to -12ºC, I could achieve somewhat the same effect:

Super cold alcohol+water mix to freeze the drill bit.

And there we go!

Shaft threads haven’t been deburred yet on this photo.

So, did it work? Well, more or less it did:

However, the nut bind easily because of the shape of the screw threads AND the friction against the backplate. As expected,  I stripped the nut threads, as acrylic is not the best material to machine high load/friction parts. But the concept was there and somewhat solid, now it needed a real trapezoidal screw, a technic material for the nut and some bearings.

As before, a tap is needed for this screw:

With that I could thread a delrin wheel and machine the leftover screw end to accept the plunger:

Also machined two flats on the screw, as I did not like the keyway idea in the first prototype:

With all that done, a needle bearing (and some acrylic machining I did not photograph) there it was:

The bottom plate captures the syringe in place, and the top bearings both grab and guide the axle so the gear can do it’s job. The needle bearing removes stiction between the top plate and the gear.

It is made to be easily removable/serviceable:

In action:

Note how fast stops the paste extrusion. (nothing exceptional, just that it does XD! )

It will have a ratchett mechanism to actuate the wheel and a small nut on top to make the needle bearing captive, but it sorta works now, wich was the objective.

You know the drill.

Or maybe not…

CNC drill, stahp, you’re broken!

Also note the crappy edges in the central square.

Pen Pineapple Apple Pen.

This post has been moved to a new home:

The Pen Foundry

Dragonfly

Sometimes I wonder if I should change the blog’s name to “The Electromechanical Mercenary”, mostly because I keep doing things like this:

Extras:

Those were developed in just under one and a half weeks, so they should count only as prototype. I am preparing a fancier version with hollow axles on all gears, better pneumatic mechanical advantage and overall higher quality in design, mostly because I can, but also to show-off at Eurosteamcon 2016

Some more shots of the beautiful model that wore it:

This is my wallpaper for the time being:

Lastly, the blue in the wings is high quality automotive reflective tape, so you must avoid taking pictures with flash, or this will happen:

 

WTF?!

Can’t remember on whose computer I saw this, but…I feel insulted:

Silver bracelet and COMPUTER CHIP.

Where? that’s just a PCB! holy mother of all fucks!
I will concede that it is well mounted and properly jeweled (seen the girl’s shop in person, she works well) but still, that’s NOT a chip.

Fairy’s anatomy.

Because I forgot to show the final mechanical wing engine:

Wire guide close up.
Interestingly, it was easier to mechanize the circular wire guides than the square ones.

Aaaand that’s it, for the moment.

Spineless II: Poor man’s ball joints.

Today I’m going to show you how the spinal prop ball joints where made:

Materials/Tools:

1. Threaded balls.
2. Polycaprolactone, a.k.a. friendly plastic.
3. Access to a lathe, or a friend that has one for a small turning job.
4. 3 lip chamfer tool (and power drill/lathe)
5. Clamp.
6. Scissors.
7. Pliers.
8. Ball’s appropriate allen key.
9. (optional) Plastic dye.

First of all, you must understand what you want to do. You want to encase the ball in some material wich allows it to swivel freely, more or less something with this profile:

Ideally, that would have the thickness of the support, but that presents a bit of a problem when the ball is already odd sized:

I don’t have a 5.4mm drill bit for the anvils to encase the ball. Also, this kind of arrangement won’t provide any ball centering, so it IS going to be off to one side or another.

The solution? make a flange on the anvils so they fit snuggly in the hole of the support:

That, of course, comes with it’s own set of problems, first of all, the odd sized holes:

Again, I don’t have a 5.6/5.7 drill bit at hand (I usually only have x.9 bits to use prior reaming an even sized hole). You could always modify the thickness of the support so it gives you a better hole size, but any variation will mess up that fit. Nothing that a bit of ingenuity can’t solve.

For now you can build the anvils, taking care of drillng the holes for the ball slightly smaller than the contact points (I could have used 5.5 mm in this case, but went with 5mm because I didn’t want to take any chances). Also, since you’re at it, drill and tap one of the anvils so you can screw the ball in there, and doesn’t move on further operations.

They should look like this:

Now comes the trick. Using a chamfer tool to eat away the corners, slowly fit both anvils until you can’t rotate the support around them (so their spacing when resting against the ball, matches your support thicknes, in my case, 4mm)

And they will look more or less like this:

Also, altough the drawings show a smooth bore, you must provide a means for the ball brace to stay in place, otherwise it will slip out of the support.
I just drilled a hole from the free end of the support and 2mm onto the cylinder’s body itself:

And now it’s time to assemble some ball joints!

First, melt some friendly plastic (I dyed mine black for aesthetic purposes only, be warned, it’s a mess, use gloves!) then loosely press fit it in the hole you are going to use:

Trim the excess:

Now, before everyting cools, submerge both the support with the plastic and the ball holder anvil in very hot water to ensure that the plastic doesn’t cool quickly and flows around everything:

(I couldn’t hold both and the camera at the same time ^^U )

Now, do both these steps QUICKLY!

Assemble the support with the hot plastic and the COLD (room temp.) anvil:

Then press fit all, use the clamp to ensure everything stays in it’s place:

Note how the plastic oozes from the hole, that’s good, it means it probably filled everything as supposed to.

Wait for it to cool a bit, then, grabbing only the support…

Pull the cold anvil from it:

If you look carefully, you can see the metal from the ball, as there is almost no material left between it and the oozing plastic from the cold anvil:

Using the pliers, just rip off the leftover. If you didn’t wait long enough, the soft plastic will deform and mess up the joint. If so, just melt everything up and start again, friendly plastic doesn’t mind it:

Assuming all went well, unscrew the ball with the allen key, but DO NOT, I repeat, DO NOT, wiggle the ball yet. Unless you waited a lot, the plastic in contact with the ball is still soft and will grab the ball and deform if you move anything. Leave it to one side to cool down and repeat the process. I was able to do three joints with a very hot glass of water, (didn’t had a thermometer to monitorize water temperature).

If you applied enough pressure, that bit of flash should come off easily:

Now you only need to break-in the joint. Move the axle to one extreme and then all around the range of the joint. That will loose it enough to move smoothly but still have very little play:

And that’s it! now you wave fully functional ball joints for normal temperature conditions. I suppose you could thread the exit hole from the support and thread a nozzle from a 3D printer to inject ABS plastic. But that’s delving into high temperatures and performances I don’t need at the moment.

And now, let’s watch it one more time in this glorious shot:

I bet you didn’t mind the vertical video. XD!

Also, remember I said you needed to provide some sort of anchorage for the ball brace to hang into? Here’s what happens if you don’t:

POP!