Z axis calibration idea

[rylangrayston]

hmm
i can see a way for that to work too.
simply take both wires from the dripper and
wire them to a desired height of the container ... when the water touches the to wires it will short out the dripper
and drips will no longer be counted.

You could also simply put the correct amount of water in the top container and let it all run threw

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[User_Defined]

Hey Guys, I've been following this forum for a few weeks now and have a few things to add:

Firstly I think it is a great idea to have a secondary validation of Z height. I've heard the Kalman filter come up a lot in positional robotics, and it sounds very interesting.

As for sensing the Z height, I think that the suggestion of using a strip of foil on the side of the top reservoir is absolutely brilliant. I would likely use copper foil as it is easy to solder wires to, and comes in standardized thin tape rolls.

This would only work with relatively thin dielectric walled containers, and would likely need a calibration step. You would also need to have another wire inside the reservoir to complete the circuit. Once calibrated, the capacitance should be linear with salt water height.

I don't know what the Peachy uses for electronics, but the way I would implement this is to use a 555 timer as a capacitance meter, and then send the square wave signal to the computer. Audio works best since you can just pulse modulate your drip received signal so every droplet interrupts the current state of the Z height. Imagine two people, one constantly expressing their detailed undying love towards the current height of the reservoir, and another impulsive and insensitive colleague occasionally interrupting them to announce when a droplet has been received.

Schematic: http://www.eleccircuit.com/simple-ca...-using-ic-555/
(One of many out there)

I would go for the newer 2MHz capable 555's since the capacitance may be in the pF range.



Regarding drips and droplets:

I worked for four years in a chem lab before engineering, and we used Pasteur Pipettes to dispense droplets for assays. They are thin glass tapered tubes that produce consistent droplets (apparently (I hope since I used them a lot!)) and would have a tiny bulb at the end. They would be sold very cheap sans-bulb and could be a better option than what is currently being used. (By simply connecting them to the rubber tubing)

The other detail about the drip I am fuzzy on is that long thin tube which transmits the droplets to the reservoir below... wouldn't it be more consistent to have a big tube with the droplets falling straight down into the salt water?


That's all I got!

I really really really hope this peachy printer thing works out... good luck guys and gals!


-UD

[Synchron]

Hi,
i had the idea of messuring the height outside the water. thies would be possible when the water level would be raised by communicating vessels. I tried to draw a little pic of what i mean, hope you understand it

peachy_communicatingVessels.jpg

The Z height could so be messured by the distance of the right vessel to the ground. Or by a potentiometer at the turning point of the mechanism. As second plus the distance from the printer to the waterlevel would be constant.
Synchron

[Synchron]

Oh, i've forgotten to explain, how i thought it could do the "drops".
I thought of something like a "clock escapement" with a big wheight under the right tank. it could be run continuusly (like a clock) or be triggert by the laser.
to make the next print, you can raise the left tank by hand, and separate the water from the resin with a simple valve at the tube.

[rylangrayston]

As for sensing the Z height, I think that the suggestion of using a strip of foil on the side of the top reservoir is absolutely brilliant. I would likely use copper foil as it is easy to solder wires to, and comes in standardized thin tape rolls.

This would only work with relatively thin dielectric walled containers, and would likely need a calibration step. You would also need to have another wire inside the reservoir to complete the circuit. Once calibrated, the capacitance should be linear with salt water height.

I don't know what the Peachy uses for electronics, but the way I would implement this is to use a 555 timer as a capacitance meter, and then send the square wave signal to the computer. Audio works best since you can just pulse modulate your drip received signal so every droplet interrupts the current state of the Z height. Imagine two people, one constantly expressing their detailed undying love towards the current height of the reservoir, and another impulsive and insensitive colleague occasionally interrupting them to announce when a droplet has been received.

Schematic: http://www.eleccircuit.com/simple-ca...-using-ic-555/
(One of many out there)

I would go for the newer 2MHz capable 555's since the capacitance may be in the pF range.



Regarding drips and droplets:

I worked for four years in a chem lab before engineering, and we used Pasteur Pipettes to dispense droplets for assays. They are thin glass tapered tubes that produce consistent droplets (apparently (I hope since I used them a lot!)) and would have a tiny bulb at the end. They would be sold very cheap sans-bulb and could be a better option than what is currently being used. (By simply connecting them to the rubber tubing)

The other detail about the drip I am fuzzy on is that long thin tube which transmits the droplets to the reservoir below... wouldn't it be more consistent to have a big tube with the droplets falling straight down into the salt water?


That's all I got!

I really really really hope this peachy printer thing works out... good luck guys and gals!


-UD

Im really liking the foil in water idea to ... im going to give it a home.... there done:
http://3dprintboard.com/showthread.p...6836#post16836

Good idea by the way soldering aluminum :S

"Pasteur Pipettes".. thanks for that also goggling now.
Ahh yes your right, ive used those before in the dripper of the peachy printer ... they did make better drips because they have thin tips and the water really beads on that plasitc/ glass.

Thanks User_Defined

[jstrack2]

Here is a video of me pouring a cup full of water and the caliper measuring the water level rise.

Sorry the video is kind of bad, it is hard to pour and record. I can do another if someone wants. Anyway here is a picture of the setup. caliper1.jpg

It is pretty sloppy, but I just wanted to demonstrate here that a caliper can be used. The float doesn't need to be anywhere near this large btw haha. Also to save weight and get more consistent sliding this part pictured can be removed and replaced with a small piece of plastic.
caliperpartremoved.jpg

If the peachy printer had nicely cut plastic parts I think this would be very simple and consistent. One thing to pay attention to though is that the float should be counterbalanced since the caliper adds some torque. To do this a plastic "tail" could be added to the float.

Also I attached the caliper to the computer via an Arduino.

arduinocaliper.jpgcaliperdata.jpg

I didn't really have to do any work here, a tutorial is online: https://sites.google.com/site/martha...igital-caliper

There are microcontrollers that are a dollar or two that would work here too, I just used an Arduino since I had it laying around. Let me know if anyone has any questions or concerns!

[jstrack2]

Here is a much improved video:



As you can see it is pretty stable despite being a very rough setup:
floatwithbalance.jpg

I used the empty cup here to counterbalance the torque from the caliper and caliper to float attachment. If well designed, laser cut plastic was used then the float could be far smaller and even much more stable.

[jstrack2]

Also if ordered in high volume it seems like the caliper could be really cheap. The battery, lcd screen and some metal parts would not be necessary. It is already only nine dollars for a single unit (including shipping!) with that stuff. Also if more than 15 cm is desired in the z direction then it may be possible to attach multiple of the ruler part of the caliper together. Or maybe longer ones could be manufactured in the first place. This might be an easier, more consistent way than the method of having a capacitor made out of foil. I am real interested to see how well that works too though! I can't wait to see prints that use the drip and some accurate z measurement in conjunction with a Kalman filter. Such extreme control of the z axis is really interesting!

[Aztecphoenix]

Check out what I found on Kickstarter that may be the answer to our prayers

https://www.kickstarter.com/projects...?ref=discovery

[Feign]

While it's cool that this is everything we're looking for together in a package... It's also $79 for something that might take at most $30 to make as a DIY project.