Tuesday, August 4, 2015

Multiplexing prototype

Had a new idea when I was on a run yesterday.  It's nice to be at a point where I can test out this stuff without much expenditure because I've already acquired so much scrap and spare parts that I can throw it together quickly.  Here's a way to possibly multiplex two or three valves to get higher resolution travel:

These are two lengths of 1/8" copper tube with 4" lengths of 1/16" holes at 1/4" spacing.  They're fed from the same line, there's no valve, but it's set up in such a way that I can adjust the spacing in between them.  With a 4" separation between the two, we get immediate ignition of both:

But with a 5.5" separation, the second set remains unignited, even after the first is ignited:

What this means is that, with only three valves, I can cause the flame to travel by leaving gaps and sequentially turning them on, and still get 3" resolution by actuating them in sequence, repeatedly:

Of course, one problem is that the ignition distance and speed is going to depend a lot on the airflow around the unit.  If we try to hide the mechanics here by putting it inside a 1/2" pipe with 1/16" holes at 1/2" spacings (which I just pulled out of the last rotary prototype and slid over it):
The effect is quite nice, however, of the bar "catching fire" as the flame travels, almost what I want, but in this case the flame doesn't "turn off" behind the front, giving us just a single moving front, not a flame "quantum".  However, it makes it clear that encasing this to protect it from the wind will be tricky.  If I can get a three-fold multiplexed design to work in the lab, I'd like to try encasing it in a 2" or 3" tube, where I cut large spacings out of the sides of the tube, and possibly line it with a fine metal mesh.  If we want to be cool about it, we can cut different shapes into the sides, possibly using the flow jet.  This will maybe let the gas diffuse away, so we don't get instant ignition, but give it some wind protection, and give the effect of the flame being "encased".

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