# How do I ignite this smoke cartrige with a shorter battery than AA and with no explosives?

Updated question:

As using nichrome wire does not seem to work in my application, I am looking for ideas how to ignite this smoke cartige, electrically and with no explosives and with a battery shorter than AA.

Thanks!

Hi,

First, I have very little experience in electronics. I am familiar with Ohm's law but don't undestand it fully in every situation. However, I'm developing a product in which I need to make a nichrome wire glow for at least 5 seconds, with help of a battery. The lenght of the wire must be at least 5 cm and must be at least 0.2 mm diamater. (Longer/bigger is even better).

I am trying to find the smallest battery possible, due to very limited space. After 5 seconds, it doesn't matter if the battery goes flat, as long as it doesn't explode, catch fire or anything else unpleasant.

I have already read through every forum with similar questions like mine, and have understood that I need a battery that can deliver enough current. I therefore have an idea that I maybe could use a high capacity coin cell battery of model CR2477 (1000 mAh, 3 V). However, as I, due to my limited knowledge in electronics, I cannot predict what will happen to this battery and I'm too scared to try.

I also found this website that let's you calculate, for example current requirement with a given wire:

http://www.jacobs-online.biz/nichrome/NichromeCalc.html

If I punch in the following data: 5 cm length, 32 gage, 2 volts, I get a current requirement of 1.15 Amps. I entered 2 volts because of internal resistance of the battery, don't know if that was correct.

Will the CR2477 battery be able to supply 1.15 Amps for 5 seconds? Will anything not nice happen to it? In the data sheet of the battery I read a maximum pulse current of 25mA, which makes me think that it will not work. But at the same time, I know that a standard 9V battery would work, and this has less capacity in mAh (though higher current).

Can somebody help me understand?
Thanks!

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3 months ago

Assuming we really just talk about a smkoe mix with no illegal intent here...
If size is a problem than of course going small can cause unwated problems in terms of the available energy.
Getting the thinnest possible Nichrome wire is key here unless you want to use a new lightbulb every time.
Problem with them is that
a) you need a lower supply voltage without the glass as otherwise they burn out instantly
b) you need to add something to aid the combustion, like finly ground match heads

As an alternative check these smoke inhalers you get for cheap on Ebay.
They work on a single AA or even AA battery and the replacement "glow plugs" are dirt cheap in bulk.

I assume you only need to ignite them once per battery as anything else is very hard to accomplish using button cells.
Again as an alternative check these little 12V batteries for car and garage remotes.
They are literally just stacked button cells, so only good for low amps.
But if you use a little circuit similar to those in throw away cams with flashlights you can charge a big capacitor with very little drain on the battery.
If the heating wire or lamp filament is a good match than it will be enough to burn it out with a short arc following - this would be sufficient to light the mix.
Even better is you aid it with some powdered match heads.

karolina81 (author)  Downunder35m3 months ago

As this is dispopsable product it doesn't matter if I use a light buib filament or a thin nichrome wire, but I have understood that the filament would be easier to make glow. Because of its low profile, I am really into the idea of reorganising the 8 button cells of an A23 as on this picture (left). But I'm not sure wether I should connect them in series (like in the A23) or in parallell. I guess I will just try and see.

Jack A Lopez3 months ago

The constraint you call, "no explosives", is somewhat confusing, unless you are using the word in a very strict sense.

I mean there are materials that can be explosive, or merely incendiary, depending on how they are confined. Black powder type mixtures, or even the stuff matchheads are made of, are a typical example of this. Ignited in a loose pile, or a short tube that is open on one end, these mixtures just burn. However, if the same mixture is ignited in a container, from which gases cannot escape, then pressure will build up until it becomes strong enough to break the container, explosively.

By the way, there is an old recipe for making electric matches from the old filament-type Christmas/Fairy lightbulbs. Essentially you just cut the top off the lightbulb. Then you cover the filament with your powder mixture.

NightHawkInLight shows us how this is done, in the Youtube video linked below.

Other, similar, Youtube videos can be found by searching for the words "electric match"

karolina81 (author)  Jack A Lopez3 months ago

The term "no explosives" should in fact be replaced with "no substance within class 1-9 of dangerous goods". The thing is, that the smoke cartridge is NOT classified as dangerous goods, so the igniter should not be either.

This makes match heads a bit difficult to use, as I assume they are classed as flammable. That's the reason that I mentioned steel wool as an igniter, which is not classed as dangerous goods. But maybe there are other non-dangerous goods combustion-aid substances, except from steel wool, that would work even better?

But thanks for the video, I have watched it!

Toga_Dan3 months ago

If we knew more about the details of what u r tryin to do, it might help us with comin up with solutions.

karolina81 (author)  Toga_Dan3 months ago

Thanks Dan! What i'm trying to do is to design an electrical ignition system to my smoke cartridge (principle shown in picture above). The smoke mix and battery/batteries is to be assembled in a casing as tight as possible, therefore battery size is critical. As the whole product is to be disposed after one-time use, I want just enough battery capacity to light the smoke mix once.

As people have mentioned here already, small batteries will probably need some sort of ignition-aid, for example powdered match heads, if this is allowed.

iceng3 months ago

There is a 6V and a 12V battery 30% shorter then a AAA and you can find it in the remote doorbell section of a hardware store...
If there is interest, I may find and picture it for you.

karolina81 (author)  iceng3 months ago

Maybe you're talking about the N, A23 or A27 here?

3 months ago

I have seen these, in real life, and also in the Wikipedia article titled, "List of Battery Sizes",

https://en.wikipedia.org/wiki/List_of_battery_size...

These batteries are typically constructed from stacks of 4 or 8, 1.5 volt button cells, to make a 6 volt or 12 volt battery respectively.

e.g. battery named "A23" is a stack of eight LR932 button cells.

e.g. battery named "4S44 or A544" is a stack of four LR44 button cells.

Toga_Dan3 months ago

thinking laterally:

Those new car jumpstart batteries have an amazing amp to weight ratio. How do they pack enough punch to start a car, while being small enough to fit in yer shirt pocket?

karolina81 (author) 3 months ago

As a reply to the comments mentioning AA batteries - these are unfortunately too long. Ideally, I would like a battery filling the footprint of the smoke cartrige, with a low profile.

As I have seen in another video here, an A23 battery would work for setting fine grade steel wool on fire. And as an A23 consists of 8xLR932, these could be re-organised like on the picture, right?

And maybe 5xLR44 alkaline cells would do an even better job? (150mAh, 1.5V).

3 months ago

mAh is NOT a predictor of the output current it can deliver. PARALLEL batteries can deliver more current, SERIES batteries, more volts.

karolina81 (author)  steveastrouk3 months ago

Ok, so a larger alkaline cell does not neccessarily deliver more current than a tiny one. This should mean that 8xLR932 in parallell is better than 5xLR44 in parallell.

Josehf Murchison3 months ago

Have you tried a 3 volt button battery and the filament from a 3 volt flashlight bulb?

karolina81 (author)  Josehf Murchison3 months ago

No, I have only tried 3x3V button batteries, both in series and parallell, and nichrome wire. Do you think a flashlight bulb could ignite my smoke device?

3 months ago

It might, if you break the glass off the filament, but you will have a VERY thin piece of wire. Its worth the experiment though.

3 months ago

Yep, good for one use only you can try a regular light bulb but you would need to cut it down to 3, 6, 9, or 12 volts to use it with stacked button batteries.

3 months ago

The filament should burn the instant 3 volts is applied.

steveastrouk3 months ago

It could be a tube, then the thing could be wider

karolina81 (author)  steveastrouk3 months ago

What could be a tube, you mean? The nichrome wire?

karolina81 (author) 3 months ago

Hi folks! Thanks for so many great ideas and nice answers. Now, as I have understood that I will not be able to use a coin cell with a nichrome wire, I will have to start think differentely. I have attached a picture that is showing my overall goal in this little project, which actually is just to ignite a smoke cartrige - electrically and with absolutely no explosives.

The first thing that came to me was to put a bit of fine grade steel wool on top of the cartrige, between the wires. But I'm sure there are many other ways to do it! Maybe there exists some conductive "igniter-sheet" that I can just put on top of the cylinder, like the soot-sheet that was mentioned below?

Can you think of any other ways? The smoke takes a few seconds to ignite, so a flash paper is too little I think.

iceng3 months ago

Researching Nichrome (NiCr, nickel-chrome,
chrome-nickel, etc.) is an alloy of nickel, chromium,
80/20 and sometimes includes iron and/or other elements.

"A new proposal uses a special soot made of carbon nanotubes. A thin filament is spun on a winder to create a 10 micron-thick film, equivalent to an A4 sheet of paper.
The film is a poor conductor of electricity, because of the air gaps
between the nanotubes. Instead, current manifests as a near
instantaneous rise in temperature. It heats up twice as fast as nichrome," by Wikipedia..

iceng3 months ago

Maybe a small copper wire will glow at a lower current..

A Cu 32 gauge wire has a lower 6.09 ohms per foot so you could go longer or wider.

Copper soldering pencil tips can do 800'F and up.

Nichrome is for repeat use but as you say once is enough for you..

Maybe another metal will work even better.

3 months ago

Please disregard the above idea... Some trial and all error today copper will not work... OTOH Steve's idea of a hollow tube is a good one.

Jack A Lopez3 months ago

I have seen a gizmo called a "cauterizer pen". The one I took apart kind of had the same design as a 2x AA flashlight, except in the place where there would normally be a flashlight bulb there was a tiny little U-shaped heating element, which will glow orange hot when the switch is closed.

A pic of this is attached. I found it via a Google(r) Images search for "2 aa cauterizer pen"

As a thing that takes up space, a AA battery is approximately a cylinder with diameter 1.5 cm, length 5 cm. When you stack the batteries on top of each other, you get something with 10 cm of length, and that's the way its done for a typical, pen-shaped, flashlight.

If you put two AA batteries side by side, that might be little more compact, and battery holders that do exactly that, are pretty easy to find.

Regarding your desire to understand how it works, well, I think the appropriate mental picture for this is to model your battery as a voltage source in series with a resistor. Thankfully, someone already drew this picture for me, here, in this Wikipedia page, titled electrical load:

Essentially the voltage source Vs has to push current through two resistors in series, Rs (its so called "internal resistance") and the load resistance Rl.

So the current that flows is

I = Vs/(Rs+Rl)

The voltage drop across this internal resistance is I*Rs=Vs*Rs/(Rs+Rl), and the voltage drop across the load is I*Rl=Vs*Rl/(Rs+Rl).

Next, consider power. The reason you're interested in dissipated power is because that is what is making heat, both useful heat, power, in the load, and wasted heat, power, in the battery.

The power dissipated by the internal resistance, essentially wasted power, is:

Ps = (I^2)*Rs = ((Vs/(Rs+Rl))^2)*Rs

Power dissipated by the load resistance, power doing something useful, is:

Pl = (I^2)*Rl = ((Vs/(Rs+Rl))^2)*Rl

Notice that power is sort of going where the resistance is, in proportion. In fact, if you want to calculate efficiency, that turns out to be just the ratio of the load resistance to the total resistance.

Pl/(Ps+Pl) = Rl/(Rs+Rl) = (power dissipated by load)/(total dissipated power)

Next, I am going to give a brief hand-waving explanation regarding the relationship between power and temperature. Basically the way this works is that things get hot, increase in temperature, when a large amount of power is dissipated through a relatively small surface area. So, just the ratio of those two things, namely power divided by surface area (e.g. W*cm^-2, watts per square centimeter) is a good figure of merit.

For some rough numbers: Around 1 to 10 W*cm^-2, that is enough to start getting warm. You'll get a number in that range if you divide the power rating of a toaster, by the area of two slices of bread. For 10s of watts per square cm, things start getting kind of hot. For 100s of W*cm^-2, even hotter. For 1000s, for KW per square centimeter, as an example in that range, the total power of Earth's Sun divided by its surface area, is about 6.3e3 W*cm^-2

Actually for the case of some thing that can only dump power by way of radiation, like a star, there is an exact formula for it, and you get power divided by surface area, proportional to absolute temperature raised to the fourth power (T^4)

https://en.wikipedia.org/wiki/Stefan%E2%80%93Boltz...

And that's one of the few examples of like, easy math, for a relationship between power and temperature. By the way, thanks for linking to the Jacob's nichrome wire calculator. It's always nice, when a calculator like this exists, for to help with the mathematical heavy lifting.

steveastrouk3 months ago

The cell won't explode. It also won't give you 1.5A, because of its internal resistance. a 9V battery MIGHT do it, but two new 1.5V AAA nicads which will fit in the same volume will definitely do it, connected in parallel.

Battery capacity does not correlate with the current it can produce. The internal resistance of the battery limits that, and for small cells, quite a lot. The way you measure the internal resistance is to put a known resistor across the battery and measure the battery voltage connected and unconnected. If you know the resistance, then Internal resistance =Load resistor(Open voltage- shorted voltage)/shorted voltage.

petercd3 months ago

Those coin batts are designed for very low current draw as could be expected from a watch or calculator.

Trying to take 1amp from it is bound to get the cell behaving in a violent way, not something you want to be near to.

A D sized 1.2V Ni Cd rechargeable batt as used by the radio control crowd to start glow plugs will be your safest bet.