exxos blog - random goings on

[exxos]

More 206 decoder boards being built ... I tried to do these in my small PCB oven, but the solder was not melting regardless of profile, so put these in my big oven to do instead..

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I purchased a bulk lot of the PLD's.. Places seem to be running out of stock of them, so even though this was incredibly expensive, I just don't want to mess about with parts shortages any more...

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[exxos]

Dammit! Don't use profile 3 then!

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[PhilC]

One for the bargain bucket part of the shop?

[exxos]

One for the bargain bucket part of the shop?

Is that the bin ?

[exxos]

I have been looking at stepper controller boards. This one was the first one I came across..

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https://www.pc-control.co.uk/control/pr ... perbee.php


Though it only has 2 outputs BUT they do a master controller board ..

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https://www.pc-control.co.uk/control/pr ... veplus.php

.. which can control up to 30 slaves. The board I am looking at is a high current version (up to 6 amps) So hopefully would in theory be harder to set on fire

I specifically am looking at those boards as they provide a windoze .dll to control from VB6. They also supply example code software to get you started..

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It has digital inputs as well. So I can use those for the XYZ max sensors etc. I want to use a sealed opto based switch for that ideally, rather than a mechanical type switch..Need to look at options at some point..

So my overall "plan", would be to write a VB6 program to translate the PCB paste layer into movements which the stepper board can understand. Also have a profile to control the syringe motor.. Also I want to add a USB "Pen cam" so I can see easier alignment of things. I also need to figure out some kinda of sensor like the Voltera has to measure the height of various places on the PCB.. I really want this to be done "on the fly" but having trouble finding something like a laser based sensor I can adapt to measure the height of the PCB.

I was looking at re-using my I3 3D printer board originally, but I have no idea how I would interface to it from VB6. I doubt much support really exists outside of using 3D printer software anyway.

[exxos]

I've been looking at options for a level sensor. But such a thing doesn't seem to exactly exist. My idea was to have a laser distance sensor to measure the height of not just the PCB, but individual pads. Then if the pads were different heights , the software could compensate. I then thought it would be great to also use it to measure again after the paste on the pads. This would allow me to use software to check paste was applied to every pad.

Though I am at a loss as such a thing doesn't seem to exist. There are some laser sensors out there but are silly priced. I looked at optical type stuff and infrared , but they seem aimed st checking the bed is level and I need something very focused to measure the pads on the PCB. So my great idea is only limited by the fact that the technology doesn't exist yet So it looks like I will just have to do it visually

I guess my only option is to use a simple pen cam to show the print on my PC monitor . I did wonder if I could take a before and after image in software to determine if paste was applied or not. Though that could be tricky. I mean the pads are grey, and the paste is grey. So I think it would be hard to get software to to do it. Its possible the pads will reflect the light more than the paste will, so I could look at that in software. But think its probably going to be more trouble than its worth.

I wanted to avoid contact sensors so I could check the height differences from the paste. But I couldn't really find much out there . Most bed level sensors are contact based and can't get anywhere near the fine probing pitch I need.

So if anyone knows of a type of laser height measurement sensor which has pinpoint accuracy and can messure down to a couple mm height then let me know...Or if anyone has any other ideas for the above problems...

[sporniket]

For contactless height sensing, using the pen camera, I would try to have 3 visible laser pointers around the printing head, forming an asymetric triangle, with their rays converging at 10~20 mm beneath the tip of the noozle. The camera would point at this convergence. After calibrating (records the position of each spot in the image from the camera for a given height), you would get a fair measure of the relative height of the printing head tip.

The limit : the definition a.k.a the minimal height variation that can be detected, and the the height is supposed the same at the center than at the points illuminated by the laser. And of course build all this contraption, working with lasers, write software, etc...

To check the deposit of paste, the pads are shiny and bright and the paste is dull and darker. Indeed a quick estimate would use the brightness to compare before/after shots. Further analysis would require some image analysis computations to distinguish e.g. shiny vs dull, and that would become cumbersome.

[DoG]

Doesn't ultrasound measure distance accurate enough?

[exxos]

Doesn't ultrasound measure distance accurate enough?

It's the "beam width" which is probably larger on ultrasonics. It would need accuracy of like 0.1mm with a beam width of like 0.1mm. Optics / IR I think would probably be a couple mm. It's why I was looking at lasers, but not really sure the beam width of those either.

[exxos]

My first thought for a syringe driver.. is as I said earlier, this motor...

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Where the thread will fit inside my super bung adapter...

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Where the small end will fit inside the syringe bung, BUT, people who are keeping up (which is probably nobody) will realise that when the thread turns, it will "dig" into the bung and probably drill a hole in the thing.. which would be bad.. so my solution is that the bung end will push onto a small thrust bearing..

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This way the thread will be "stuck" (aka superglue) inside my bung adapter, which will spin inside the syringe without "drilling" a hole in the thing, As it will just turn the bearing as force is applied.

Next up I need to design a assembly to fit the syringe into, and be able to bolt the stepper motor on top of it all...