Z axis calibration idea

[Aztecphoenix]

I think that a potentiometric transducer would work as well. It might be easier than the caliper I think. I would prefer the caliper though all things being equal since I think it would be more precise and more importantly much more accurate. A weakness of the caliper's approach is it takes a relatively long time to make measurements. But this is irrelevant for the Peachy Printer, since the liquid level shouldn't rise to the top in a second or two! haha

As for sending the signal to the computer I think maybe the voltage could be just directly sent to the computer via the headphone jack just like the drip does. If using the caliper a microcontroller would probably be needed, such as a PIC. Some microcontrollers can be bought for only a dollar or two though so I don't think this rules calipers out. It's nice that there are multiple options!

this is essentialy what my original suggestion was before it evolved into the discussion we are currently at.

[mike_biddell]

How much does the potentiometric transducer cost. Where can you buy it from and mechanically how do you set it up? We could try it !!!!! What would be the potential Z axis resolution?

[EthanSpitz]

Is the liquid we are dripping in to the container conductive? I.E. is it saltwater? If it is, we could make long resistive strips and line the container with them and measure the resistance across it. As the water level rises, current will go through less of the resistive material and will cut across the liquid to the other side reducing the resistance in real time as the liquid level rises. It could be configured as a voltage divider and output pure analog values that could be scaled to z height.

You could use that instead of the float idea for measuring the height. I personally don't like the idea of a float as there is a mechanical element to the sensor that will rely on friction among the edge of the container or whatever your float is sliding against.

[Aztecphoenix]

Is the liquid we are dripping in to the container conductive? I.E. is it saltwater? If it is, we could make long resistive strips and line the container with them and measure the resistance across it. As the water level rises, current will go through less of the resistive material and will cut across the liquid to the other side reducing the resistance in real time as the liquid level rises. It could be configured as a voltage divider and output pure analog values that could be scaled to z height.

You could use that instead of the float idea for measuring the height. I personally don't like the idea of a float as there is a mechanical element to the sensor that will rely on friction among the edge of the container or whatever your float is sliding against.

The only problem with that is you would have to recalibrate the sensor every print unless you can keep the salt level the same for every print which would end up costing more per print because you would have to throw out the water and remix it for every print.

[EthanSpitz]

The only problem with that is you would have to recalibrate the sensor every print unless you can keep the salt level the same for every print which would end up costing more per print because you would have to throw out the water and remix it for every print.

Can you explain what you mean? When you talk about level, are you talking concentration? You could probably assume a concentration based on the initial value when starting the print.

EDIT:
Also, if you use a relatively high resistance material, the variability or the resistance of the salt water could probably be rendered negligible

[Feign]

A more volatile variable could be the high resistance of the uncured resin floating on top of the saline. Uncured resin adheres to the side walls of the tank for a little while as it rises, making the blurring effect you see at the bottom of the resin layer in the demonstration videos, it would also adhere to the resistor strips, unpredictably increasing the resistance between the two strips until it is sufficiently washed off by the saline (a distance which also can't cleanly be predicted).

[EthanSpitz]

A more volatile variable could be the high resistance of the uncured resin floating on top of the saline. Uncured resin adheres to the side walls of the tank for a little while as it rises, making the blurring effect you see at the bottom of the resin layer in the demonstration videos, it would also adhere to the resistor strips, unpredictably increasing the resistance between the two strips until it is sufficiently washed off by the saline (a distance which also can't cleanly be predicted).

right, but what do we need to know when we make the print, the height of the saline or the height of the resin floating on top. It appears to me we can completely ignore the height of the resin and just take the measurement at the height of the saline.

[jstrack2]

Also in general it is hard to get good accuracy using resistors. So I think that capacitance based circuits (such as the caliper) are preferable.

[jstrack2]

I personally don't like the idea of a float as there is a mechanical element to the sensor that will rely on friction among the edge of the container or whatever your float is sliding against.

I don't understand what the problem is here. It will take some work to make a simple, cheap and reliable design, but what is so inherently bad about something floating up the side?

[Nahoj]

Would it be possible to use a jewlery scale to find the weight of the upper container, to calculate the volume in stead of meassuring the level in the lower container? You get pretty cheap ones with 0.1g accuracy.....