Drip Governor - A most valuble first hack

[BrockMcKean]

If you look at the video I posted there really isn't any rotation. If it were made smaller I agree the rotation effect would increase, but not that much. I think it would scale linearly with the radius of the plug, if not even sublinearly. So even if the whole thing were four times smaller in all dimensions I think that this effect would still be pretty negligible. Even with my 27 mm wide design the current draw was not much. At a fourth this width the current draw would be absolutely tiny. Also as I said the PVC tube itself already guides the plug some. Finally I don't know what you mean by relativistic, maybe you mean quantum? But that is irrelevant unless you get down to the scale of a few nanometers! Anyway since I don't understand the theory nor did my experiment show this to be a problem, I think that you should make a video of the valve if you are still concerned about it. If it has that problem then I will try to help and address it.

I'm just saying it is something that should be given some attention as it's scaled down more. All I mean by relativistic is that the forces from viscosity is basically negligible beyond a certain size and magnetic field strength. I don't know what size magnet and field strength you would need to go down to to make these two relatively close, but there is a point that it would happen. We can probably just use more coil windings if in shrinking it that did become a problem, but that is my point. Just something to think about and be aware of as a factor that could possible have some influence on a smaller scale.

It is neither super precise nor accurate. You can not expect it to behave with the same predictable probability density function every time (such as a normal distribution for example). It will always drift. This is why for example gyroscopes and accelerometers are used together, and not just gyroscopes. Gyroscopes measure rate of change of the angle with respect to time. So then angle is found by integrating over time. But there is always drift, so accelerometers which directly measure angle are also used to correct for this limitation. Another example is how battery capacity remaining is calculated. In theory you could integrate current use over time. However because of the drift problem a direct measurement method is also needed (such as checking voltage here). This is why the threads discussing making a direct measurement were created. It is not a matter of just calibrating it once. That will not get very accurate results. Again if you want to save a few dollars on the printer and have not very good at all accuracy in the z axis that is fine. But this problem can cause the z axis to be off multiple percent (not microns) and direct measurement should only add a few dollars cost (probably less than 5). I do not mean to say that drip counting shouldn't be done however. It gives amazing resolution, just not accuracy.

Gyroscopes measure orientation and accelerometers measure acceleration. Sampling your accelerometer will give you a function of acceleration. Integrating that gives you velocity and integrating that will give you displacement. Match that up with your gyroscope samples, and you have a time correlated displacement and orientation pair that can be used to explain where you are in space from a given reference point along this vector. So, if you were to depend on only the gyroscope you would not be able to determine if you were moving at all. The gyroscope does not know the difference between facing a direction for a specific amount of time and traveling in the exact same direction for the same specific amount of time. Likewise the accelerometer doesn't know direction at all. It only knows force due to acceleration, so you can move it in any direction with identical force and it doesn't know the difference between any direction in particular. However, even using an accelerometer and gyroscope together, you cannot be sure of how much time and distance was covered exactly, due to drift.

Drift occurs in sold state devices and crystals with respect to time. The crystal structure's and electron affinity changes overtime and becomes misaligned internally. The same can be said for any kind of doped semiconductor. The depletion regions do not stay the same and therefore the output of diodes and transistors is not consistent over long periods of time. Any clock dependent measuring source also experiences this drift depending on the precision of the clock source.

This proposed drip governor does not contain any of these elements. The mass of the magnet will not change. The mass of the coils will not change. The strength of the magnet and the strength of the field induced by the coils will not change. They will operate the same way every time, given a specific voltage. The voltage/current and modulation will be SLIGHTLY different each time, probably by a few uV/uA and ns/ps. That is to say, using PWM or any other clock dependent form of modulation (anything coming from a computer would be), is susceptible to this. Computers adjust their clocks because they experience drift, but they do it only frequently enough for everyday units of time. microsecond, nanosecond, and picosecond drifts pile up until the clock decides millisecond drifts are too much, so this would happen. However,since our drip rate shouldn't be near the frequency to have a period of microseconds, the computer's compensation for this drift should actually keep it pretty steady.

Beyond that we're talking about the consistency of the voltage output from the USB. If one system uses 5V and another puts out 4.99V and another puts out 5.01V, that will certainly result in some amount of variability in the drip, but not much, and it can be accounted for by a calibration print that assumes differing amounts of variability within a range measured in development for small "identical" objects. Whichever prints the best is the correct amount of variability. All other printers 3d and 2d have some form of calibration. Measuring digitally would be ideal, but software is free and the resin is pretty cheap. So, unless it costs less than a first calibration print of a few mL and it can be accurate to 100 micrometers or so, I would rather make sure the kit costs as little as possible. Now, for an assembled kit or a higher quality commercial version, I agree with you 100%. I'd be a bit confused if there was no measuring of the fluid level.

Also, I'm very busy with some other things right now but I'll be wrapping them up today and have a lot of free time for the forseable future, so I will most certainly be doing my own experiments and contributing as much as possible. I just REALLY want to get working on this and I just don't have the time until tomorrow on, so I'm talking about it instead.