(03-13-2012 8:14 AM)Fly So Hi Wrote: I'm sure no crystals would build up in the tip of the tip, but they're so cheap that it's just better to use one tip per bottle every time you use the machine.
Well tbh, after using the same syringe for a long while, I'm pretty sure I can see these little crystals that have accumulated as the small amount of liquid left behind will result in the carrier evaporating and leaving behind the molecule. Maybe its just in my head, but I have used that syringe a lot of times... Also there's the possibility of corosion and erosion on a very small level I suppose, but idk how much of an issue that would be with most molecules.
But like you said, probably better just to change tips. I'm thinking that function could probably be added to the track's motor... but I'll worry about that when I get the earlier functions stated down. That poor track motor already does so much in this design...
Speaking of track motors, I forgot to mention that I would not be using a step motor to keep track of which bottle it is at, but instead a hole along the track at each stop. A button (significantly smaller than the hole) would then ride along the track such that it is depressed until it reaches a bottle. Or vice versa, either way. This sacrifices short term accuracy, but doesn't allow any inaccuracies to build long term, increasing long term accuracy. And with lining up to these bottles, only a certain amount of short term accuracy is really needed, and it isn't near as much as the linear actuator and parts like that. For keeping the linear actuator and the other motor's long term accuracy in check, I could either keep absolute track of which microstep it is on, even once you turn it off after finishing a mix, or I could have a physical stop which they align themselves to at the beginning of every mix. That way even if it occaisonally misses a microstep here or there along the way, it doesn't accumulate those inaccuracies over the course of many, many mixes.
(03-13-2012 8:14 AM)Fly So Hi Wrote: I don't really think evaporation could happen and condensate on the bottle cover with just ambient temperature. But if you're willing to spend more electricity/money on the device, you could use a peltier cooler (thermoelectric cooler) to cool down each slot, to make sure the temperature would not cause condensation.
EDIT: I thought you'd keep the bottles in the fridge or something and only place them on the rotary when you need to use them, right? Maybe there's no need for a cover. That way you could keep the Pheroprinter out of the fridge, hehehe.
Well, the rotary design is much less space saving, but in a rotary design, yes, you could do that more easily. In the grid, I suppose you coukd as well... But it could be pain to take the caps of 30 to 50 bottles off, set them in, take them out when its done, and put the caps back on again. Part of the reason for this as well is to reduce spillage, and while the machine is intended to be largely stationary, if something (like clumsy old me) bumped it and sloshed the bottles... that could be bad. And if I have to change the bottles all the time, I would think I would have almost as much accidental spillage as if I was just making the mix myself.
I doubt evaporation would be much of a likelihood, but if it is any likelihood at all, then it will be a problem. In general I just want everything to be really robust, so I may add a drip shield or something. I want this thing to still work even if my AC and fridge go out in the middle of the summer. Not that I will normally run into that problem, just trying to think of all the potential problems it could run into. The first design probably wouldn't actually have a drip shield, though I'll probably leave space for it just in case I decide I want to add it.
Hmm... a thermocooler... how much do those cost? If it was really cheap, I might consider that. It would be nice not to have some weird box in the fridge for people to ask about or clog the fridge up in general.
However, I kinda doubt they are cheap. Also that would raise running costs because it would run while idle, but once again idk how much more that would cost. Probably would depend somewhat on how well the whole thing is sealed to keep the cool in... which is a whole added level of design issues that I'd rather not delve into in the first go-round.
Still, the "Spy's Essential PheroMixer" briefcase would probably include one. Hell, if that was just some no-expense-spared thing, you could even add gyros and parts such that it always stays level and can operate even during the most exhilarating of car chase scenes...
If I was to put it in the fridge, it would probably only be parts of it. possibly only the grid pf bottles, and then I'd store the rest somewhere else. At the very least it might be important to store the battery outside the fridge, and in general I don't want water condensing on the electronics. So basically the same concept as just placing them on the rotary when operating, yes. Instead I would just be setting the motors on the track above the grid.