capacitor and nichrome

tom66

Joined May 9, 2009
2,595
Thanks ... it's too big though. Is it worth trying the smallest one or would I be wasting my time?
It wouldn't work.

Your best bet for low resistance in a small size would be a lithium polymer cell. They are rechargeable, but if you don't use it much it will probably last a long time. You have to be very careful about not puncturing them as they are extremely volatile. You will also need a special battery charger.
 

PaulEE

Joined Dec 23, 2011
474
I am trying to make a device to ignite flash paper using nichrome wire.
Let's also not forget the goal of this project; produce an ignition source for flash paper, right?

I can picture two supercap leads with a tiny piece of graphite glowing red-hot upon shorting the leads to the graphite,...etc.

Are we open to other stuff besides nichrome wire? What's wrong with a light bulb filament?

Just trying to expand our horizons, here.
 

shortbus

Joined Sep 30, 2009
10,045
Let's also not forget the goal of this project; produce an ignition source for flash paper, right?

Are we open to other stuff besides nichrome wire? What's wrong with a light bulb filament?

Just trying to expand our horizons, here.
That is what I posted in post #14 and got no response. I have used them for igniting fireworks and they work fine. There a a number of flashlight bulbs for a number of different voltages and batteries that will make choosing one easy.
 

Bernard

Joined Aug 7, 2008
5,784
Instead of a nichrome wire, why couldn't you carefully break the glass of of a flashlight bulb of the correct voltage and amperage for your battery? If only turned on for a short amount of time per use the tungsten coil in the bulb should last quite a long time.
The bulb I used to sub for a #6 blasting cap was # 49 [or 48], 2 V @60 mA. If it flashed & died, blasting ckt was good. Was a lot cheaper then cap- back then.
 

Thread Starter

rjjenkins

Joined Apr 16, 2011
214
I'm open to other ideas; but for the real world application I am thinking of the solution has to be robust and capable of repeated use. So fragile things like light bulb filaments don't seem very promising - whereas nichrome, so long as you don't put too much current through it, can be used many times.
 

Adjuster

Joined Dec 26, 2010
2,148
I would recommend trying a capacitor charged to a somewhat bigger voltage. Remember that the stored energy increases as the square of the voltage. Three very small alkaline button cells in series would give 4.5V.

Use of a finer gauge of nichrome wire at a higher voltage might also be a better fit for the current limitations (internal resistance) of small batteries and capacitors.
 

Thread Starter

rjjenkins

Joined Apr 16, 2011
214
Thanks - do you think I should be looking at a normal electrolytic capacitor or a supercap? I can look for finer gauge wire but I might also run into the fragility issue.
 

PaulEE

Joined Dec 23, 2011
474
That is what I posted in post #14 and got no response. I have used them for igniting fireworks and they work fine. There a a number of flashlight bulbs for a number of different voltages and batteries that will make choosing one easy.
I missed it. Apologies.
 

Bernard

Joined Aug 7, 2008
5,784
I tried # 222 bulb rated for 2 AAs, 2.25 V @ 250 mA; one N cell burned paper in two but did not flash, & yes it is fragle, only two tests before fil broke.
Six mm of # 36 & one N cell made paper go POOF. N cell is about 7 yrs old, only one I have. N cell: 11.4 mm X 29 mm- too big??
# 36 NI-CR not too fragile- I use if for foam plastic heat cutting, also grid for negative ion generator.
 
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Bernard

Joined Aug 7, 2008
5,784
I blackend a small piece of flash paper & set it off with a 1/2 in lens in bright sun; was surprised at how low the flash point is. A verry dull red wire is all it takes it seems.
 
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