Drip Governor - A most valuble first hack

[BrockMcKean]

To get around this, we could use plastic coated magnets or epoxy coated magnets like this.

Yes, and it really doesn't change the price much either. They should definitely be epoxy/polyurethane coated. Also, I did a bit of digging looking for some indication as to whether a cell phone could provide 5V output from micro usb and haven't found anything conclusive, except that micro and mini usb are indeed capable of passing 5V power. It's just a wire so I assumed as much, but if the ability to print from a phone is a feature the Peachy project is serious about, we should address this now and incorporate it into proposed variable speed drip systems.

Does anyone know if there is a standard for voltage output from phone usb or if that's something you can rely on at all...? I'd like to see the peachy's schematic if anyone can point me in that direction or if a beta tester can work one up in a SPICE program for us all. We can come up with a better guess at how to include an electrically controlled drip governor like this without disturbing the work that's already been done.

[jstrack2]

Thanks for the feedback! Again if anyone wants to see something more let me know. I know the videos were very short.


Brock McKean: I think that while it would be possible to use frequency modulation (or other techniques discussed in this forum) to directly control the drip speed with the speaker, in my opinion this is not the way to go. I think that having the speaker control the laser as well as possible should be the priority. Adding a bunch of complexity (or greatly limiting the drip governor's functionality) to save one or two dollars does not make much sense to me. I agree that USB power sounds good. What I did here was about 50 mA. I think any USB 2.0 including the micro does at least 500 mA. I think they are always at 5V. If it were made smaller and the coil was not poorly hand wound as it was here then I think it could work on even less than 50 mA. Since when the valve is open liquid rushes through fast I think that there is not a need to have it stay open when the coil is not powered. The coil will only be powered for a tiny fraction of a second anyway.

I agree that some schematics would definitely be helpful.


As for maintaining the orientation of the magnet this happens naturally, so no extra work is needed. The field makes the magnet's orientation stable.


There is something about the pressure worth thinking about though. This valve should be placed as high up as possible to minimize the pressure and hence the magnetism needed. Again having the valve be smaller will reduce the magnetism needed, since of course less area experiencing a pressure means less force. If the method of having the salt water drain out is used instead of poured in then the pressure level may vary significantly over the course of the print (depending on the setup the pouring method may also result in significant pressure change too). This may have to be corrected for in software (longer/stronger pulse when pressure is high). I don't think that spectacular accuracy is needed here though because that will be provided by the water level measuring methods.




3dspider: Great point, I forgot about that. I also agree prebought or coating afterwards of the iron/magnet will probably be needed. As you and Brock McKean said this shouldn't be a big deal.