With two way digital communication what are your modding plans?

[jontelling]

After the latest update (51), it got me thinking of new mods and limitations we can have fun overcoming that can now be done.

For example, the self emptying build reservoir after print completion is now an easier mod(I'll link once I find the thread/post)

I'm sure there's going to more than few limitations that can be fixed with some home DIYing.

An example is that the Peachy's closed looped, something I'm sure we could fix (I'm not convinced using variable capacity to correct laser position is the best way), or the self emptying build reservoir after print completion is now an easier mod(I'll link once I find the thread/post)

So. What mod ideas do you have in mind?

How would you you do a real time reading of the laser position or dealing with a build reservoir that doesn't have a constant cross sectional area (like most container I know and it seems the capacity/frequency mapping is not in this version, from what I could see in the video).

[jontelling]

So, to get the ball rolling. Some thoughts I had while washing the pots (living the dream).
There's a few ways we can get feedback from the mirror position, but they have to be passive and not interferer with the mirror in little or no way.
There are (the ones I could think of):

• Capacitance

given the current mirror and it's small size, would not hold well to added to that much added weight, also I'm sure normal air movement will add to much noise to the sensing.

• Magnetic field polarity strength

Not even sure how this one would work, at all....

• Light, IR/visible

I'm thinking either another laser (CD drive?) either bouncing off the back of the mirror (Will require the mirror to be aluminised both side or something to the same effect) or have two polarizing sheets along the axis of rotation, one being static on the support arm and the other being on the back of the mirror (this would be small).
At a guess the distance the peach mirror is from the printing layer is around 40cm(?) and with (what looks like) only a projection area of 5cm that's only going to move the mirror by 7deg... That's only a 12% sample range to fit 262,143 points in(18bit), which is would mean a stupidly sensitive sensor (ignoring noise), which brings me to my next point.

From my understanding to get a good reading to feedback you have to have twice the resolution, I'm not sure on the specs of the micro-controller being used but that's a big hurdle to tackle no matter that sensing approach. Maybe an additional micro-controller would be needed which serially feeds back.... Food for thought.

[rylangrayston]

• Light, IR/visible

I'm thinking either another laser (CD drive?) either bouncing off the back of the mirror (Will require the mirror to be aluminised both side or something to the same effect)

Ive been working on this ... jezz jontelling your ideas are going to take the element of supprize out of some future updates lol
well what can i say, This is one of my favorite ideas because it adds no mass to the mirror assembly.

and actualy as much as I liked how far we got with capacitive, i didn't like how hard that delicate bit of aluminum foil was to manufacture, assemble and Im woried about how it would do in shipping.

[3dspider]

I had assumed you'd be using something similar to this with a photointerrupter to determine absolute position. it'd add a bit of mass and a bit of cost, but might be worth it for the accuracy... a 5000 cpr 1" wheel might be a bit overkill though... (that's one line every .072°)

[jontelling]

I had assumed you'd be using something similar to this with a photointerrupter to determine absolute position. it'd add a bit of mass and a bit of cost, but might be worth it for the accuracy... a 5000 cpr 1" wheel might be a bit overkill though... (that's one line every .072°)

I’d say under kill, by a lot..

Current number of points is: 262143 (18bit), also using an interrupter would require the blockage of the laser more times than this if you’re going for a binary encoder. As you can guess it becomes a case of more points bigger the wheel as you have to block the whole laser, very tight focus required.


On a side note I have found 24bit ADC,
EDIT: Something to note, i think the peachy uses it's whole 18bit over a range of only 10deg, those interrupters are at 5000 for 360deg.. But I do like those.

[quertz]

Hey guys,

a little bit of googling...
At this point, you might want to use a Differential Plane Mirror Interferometer
this would give you a resolution around of 2*10^-5 ° (0.00002°) when using high quality products


EDIT:
I just realized that dividing 10° by (2¹⁸) gives you about 3.8*10^-5 ° (0.000038°) degrees so this might actually be the way you have to go if you want the full overkilled resolution

quertz

[quertz]

Hmmm....

I think I found an interesting alternative that also might be easier to be DIY:

The general idea is to 'fold' a long way for the light to travel so that at the end you get a large deflection for small angles that can be picked up by a sensor stripe.

In this case you could just use two parallel mirrors.
http://jsbin.com/revepicigu/31/edit?output
I think you get the idea of having a sensor stripe on the right end of the tunnel.

This would of course have some problems like:
You cannot measure absolute values (you have to keep track and count)
You cannot measure the direction (in this configuration, but you could also replace the last part of the upper mirror with a sensor stripe to allow this)
The accuracy of the measurement depends a lot on the angle you want to measure

Many of these (+ skewed mirrors) can be solved by extensive calibration.

This is just a quick idea.
Please discuss, slate and find other ways

quertz

[jontelling]

Hmmm....

In this case you could just use two parallel mirrors.
http://jsbin.com/revepicigu/31/edit?output
I think you get the idea of having a sensor stripe on the right end of the tunnel.


quertz

I could be wrong but this doesn't amplify the deflection, just measures it from 90deg angle. The best to to amplify in this manner would to simply place the sensor at a greater distance from the laser diode. Buttt.... then we're needing a sensor with many points.

I'm going to have a look later at the range on MRD510 or something like that.

[quertz]

The best to to amplify in this manner would to simply place the sensor at a greater distance from the laser diode.

That's exactly what I'm doing.
The only difference is that I'm using two mirrors to 'fold' the long distance into a short package.
In the end, this would also allow us to use a single, smaller sensor with less points that gets used over and over again.

Maybe I'll find some time and write a better simulation that also contains a sensor

Greetings,
quertz

[Slatye]

How about just doing direct feedback on the laser position with a camera?

The Peachy team has shown videos of the Peachy illuminating the resin as it prints. Point two webcams into the container and (once calibrated) you can easily pull out both the absolute height of the resin in the container and the position that the laser's hitting it. Worst-case is that this has to go through the PC, so there could be a bit of lag (although that can be handled). Best-case is that they actually used one of the STM32 microcontrollers with a camera port on it or USB host, but that's probably pushing our luck.