Generating heat with 7.2 volt battery?
Ok, i need my robot to autonomously pop several balloons-My plan is to use a wire frame about 1ft x 1ft with wires criss-crossing inside that frame in about 3 inch increments. I need to know how to heat up such a wire using DC battery power.
I believe this is possible (there are DC powered soldering irons), but I don't exactly know how to achieve such an affect without directly shorting (and damaging) the battery. I have available for use a 7.2 volt battery capable of a constant discharge rate of 45 amps. 7.2 x 45 = 324 watts, which should be plenty considering soldering irons range from 15-40 watts. My question is, how do I do this so i don't short my battery, and yet allow it to discharge steadily? Also do i need to use a special type of wire?
I believe this is possible (there are DC powered soldering irons), but I don't exactly know how to achieve such an affect without directly shorting (and damaging) the battery. I have available for use a 7.2 volt battery capable of a constant discharge rate of 45 amps. 7.2 x 45 = 324 watts, which should be plenty considering soldering irons range from 15-40 watts. My question is, how do I do this so i don't short my battery, and yet allow it to discharge steadily? Also do i need to use a special type of wire?
Comments
If the latter, how about affixing a rocket launcher match on each balloon for your heat.
Also, what effect are you trying to get? What I mean is that a balloon that is popped via
a heat source does not always produce as "sharp" of a pop sound as does a balloon that
pops by actually touching something sharp. (<-- just an observation)
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Beau Schwabe
IC Layout Engineer
Parallax, Inc.
The sound the balloon makes is unimportant- the balloon simply needs to be "deflated" by anymeans. I plan to use a servo to guide the heated wire frame towards the balloon, and on contact, the balloon should pop.
I've done some more research, and it seems like what I need is nichrome wire. I still don't really understand how it's done though. My instincts aren't letting me connect the wire to both ends of the battery, which seems like the obvious solution.
Just remember that by using battery powered ANYTHING you are automatically reducing the time available to produce any result or goal, no matter whether it's popping a balloon, or blowing out a candle. What I'm trying to say here is that a non-electrical solution will not detract from one of your biggest inherent limitations on a mobile robotic platform; that being the available power stores. Due to the weight vs. power issue, this available battery stores issue is a much larger problem than it may appear on the surface.
With some resources, there is a balance tip point, minor penalty, or (pseudo-) return-on-investment consideration. With weighty batteries, not only are they required to provide MORE POWER (thank you Tim Allen) at hopefully low financial cost, but they also need to pull their own weight, and then some. Unless you are using something like the Polaroid Pola-Pulse flat power packets, which have a phenominally high power to weight ratio, any additional battery resources begin with an overall net loss to the system. Overcoming that suggested initial net loss is a major consideration. I would submit this is a major consideration that is unnecessary for this type of project.
If instead of a heated grid, you used a "bed-of-nails" fly swatter approach, the only impact on the battery stores would be the use of the R/C servo (already an extant power usage consideration), so there is a very minimal (if any) net increase in battery consumption with this approach.
The way I would build such a fly swatter device, is to use a geometric winding form such as pins in a corkboard, place the pins in a square or rectangular grid as large as you choose to make it, and then "weave" it in a rather coarse manner with (say) 30 gauge bare copper wire. I would then run a bead of solder around the perimeter of this "paddle". This will provide both rigidity, and some necessary peripheral weight. Then I would find the smallest, sharpest brass or copper tacks I could find with flat heads, and solder them at the wire intersections. Now you have a "bed of nails" fly swatter (so to speak). In theory, even a light touch will cause a balloon to burst, presuming the tacks are sharp enough.
Just offhand, and without testing, the only balloons that might defeat this approach are latex balloons (aka "proper" helium balloons) which have a good deal of thickness and a high degree of resiliency. In that case you would need something more akin to a hypodermic needle (small diameter is the key here) to puncture them.
Just one non-electrical approach.
Regards,
Bruce Bates
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Thanks, Parallax!
that will give you a little more wire than you need for this project, but if you reeeeeally want to heat the balloon to deflate it, this is your best best.
personally, since distributing the force among the tacks would make it harder to apply enough force to pop the balloon, I would use a single fine guage needle.
Maybe some kind of a AirSoft gun?
I've also made a gun that would fire toothpicks, maybe that would work?....
I have made a gun that could fire a needle (sewing needles with the heads clipped off, then a more uniform "head" which is actually the tail and stabilizes the dart.)
Or even a dart gun.....
Something like that might be neat....
As for the electric part, I used to be into CB radios, so I bought a 120VAC to 12VDC. When I was playing around I would take a piece of pencil lead from the mechanical pencils, and connect the + and - to each end, and it would get a nice glowing hot on the lead.... I could burn all kinds of stuff.... my parent's hated it. So, there's a possibility too.... though I was suspect the current draw would be immense....
Knight.
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Ok, back to reality. The reason I'm going for the heated wire idea is because it would require less weight than simply a sharp object, but now that I think about it, an extremely sharp needle would not need much force (weight) to pop a balloon.
Yes, it is a school project, so I don't think projectiles (at least of that sort) are allowed (although it sounds fun).
That pencil lead trick sounds cool-I'll try it out. The graphite (or whatever they use) in the lead is probably high resistance, which gives it the heat effect as nicrhome wire (I'm guessing). I'm going to get some of that nichrome wire and do some calculating and experimenting to figure out exactly how much heat it takes to pop a balloon, what length wire to use, etc.
Thanks all for the help. When I finish this project in a couple of months, I'll post it in the "projects" forum.