31 replies to this topic

[adamw]

You know a company was actually developing ignitors based on SMD resistors. Should be cheap to make with an in-line assembly system.

By the way, which size of resistor are you using? 0603, 0402 or smaller?

[neosaint99]

I've been trying to make cheap ignitors
What I'm currently working with is reletively cheap
I costs a few cents each and the flash is great
What I do is tape two regular safety matches together
Then strip about 15cm of twin bell wire (the 5A rated stuff)
That leaves me with (I've never really counted)...i guess 20 or more strands of fine copper wire
I use this as they are mighty easy to solder
After this, I twist a single strand of the copper wire around the match heads
(I use two matches to get a better initial flash...you can try it with one...it usually works also )
Next I strip about 30-40cm of Cat5 wire
That gives me 4 pairs of wire (already twisted! )
I solder this to the two ends of the strand of copper wire that is already wrapped around the match head
Then tape the Cat5 wire to the base of the matches
After that I make a BP paste
(I actually stumbled upon this when I accidentally added too much solvent to my propellent mix...hahaha)
As a binder, I use shellac
Its cheap, and spirit dilutes it great
My BP paste is about the consistancy of toothpaste
I usually make a quater of those disposable plastic party cups of it
It can coat about 40 or 50 (depending how thick you coat it)
But if you are making lots, you'll have to add solvent to is as it thickens
Then you just hang it up to dry over night
But the next day, it has formed a hard shell around the matches
I estimate that they'll cost about 5 cents each...maybe less
Not to mention I generally use Cat5 wire that people throw away as faulty
(usually just 1 wire is broken in the entire length...so at worst, only one of my ignitors wont fire)
The mathces are real cheap...a few cents for a whole box
The tape I use is regular paper tape a.k.a masking tape
Thats like a buck or two for a 1 inch roll
Well, thats it then!
Hope this can be of some little help to you...

Edited by neosaint99, 19 November 2005 - 06:12 AM.

[mnementh]

Hi guys.
Given the time of year, there are loads of dirt cheap, virtually ready made igniters available, in the shops.

I speak of christmas tree lights, of course.

Go to your local Asda, or Tesco and buy the cheapest set of "economy" lights, you can find. You can usually get up to 200 in a set for less than ?10.

Separate off each bulb with a suitable length of wire still attached.

Use a diamond file and "nip" the tip off a bulb.

Fill the bulb, gently, with fast burning black powder and glue on a tissue "stopper".

There you have it. A perfect electric ignition system.

It gets even cheaper as christmas approaches as the big stores cut their prices, even more, to shift their last remaining stock.

Sandy

[The_Djinn]

I like that... a simple yet very effective idea. A bit like the x-mas tree balls as shell formers or as shells.

Mark

[neosaint99]

xmas tree lights?...you dont say....
sounds like a plan!

i'll try that out first thing tomorrow
i'm sure i have some lights somewhere around here
do they work with regular home made bp?
coz i'm from malaysia
so anyting i use has to be made myself
cant buy nuts even if your life depended on it...zero available pyro stuff in the market
if home made bp dont work, could you give me the composition of a more suitable powder?
oh...and what voltage is required to blow these babys?...hehe

tq!

Edited by neosaint99, 19 November 2005 - 02:05 PM.

[mnementh]

Hi guys,
If you check the packaging, you will be able to calculate the operating voltage of the bulbs.

Basically, a set of 50 will require about 5 volts each at 240v mains supply and a 9 volt battery will blow it.

However, a 100 set will only need about 2 1/2 volts/bulb and the same battery will fire it very quickly.

Those with lower voltage mains supplies will be even better off.

Just remember that the filaments are fairly delicate and you MUST put your powder in gently.

Sandy

Edited by mnementh, 19 November 2005 - 03:11 PM.

[JamesH]

I make my ignitors using a 4" length of bell wire. The wire has two solid cores of copper wire that are insulated from each other. The single core version can also be used by taping two lengths side by side with electrical tape. The ignition end is stripped so that there is about 7mm of the wires exposed. The wire spacing is adjusted, if need be, so that there is a gap of about 1mm between them.
Next a slurry of graphite powder in nitrocellulose laquer (i use ping pong balls disolved in acetone) is mixed to the consistency of ketchup. Then the wires are dipped into this slurry so that the gap between the two wires are bridged. This mix acts as a high resistance bridge.
Once dry, the ignitor is coated with the pyrogen of choice. I use a slurry of black powder in NC laquer with a few percent aluminium powder.

These ignitors reliably initiate immediately when 12v is passed through them. I have made dozens this way and have yet to have one fail.

Anybody used a similar method?

Edited by JamesH, 19 November 2005 - 08:50 PM.

[mnementh]

Hi JamesH.
what is your graphite source?

Is it just pencil "lead" ground up?

Sandy

[Mortartube]

If you want graphite already ground up, go to a hardware shop and get some lock lubricant. It is ground graphite in a plastic puffer bottle. It will save you lots of time and frustration, and probably cost less than pencils.

[JamesH]

Hi JamesH.
what is your graphite source?

Is it just pencil "lead" ground up?

Sandy

There are many sources for graphite powder. Here are a few:-
http://www.cfsnet.co...ite_Powder.html
http://www.graphitet...o.uk/21054.html

[neosaint99]

Hi guys,
If you check the packaging, you will be able to calculate the operating voltage of the bulbs.

Basically, a set of 50 will require about 5 volts each at 240v mains supply and a 9 volt battery will blow it.

However, a 100 set will only need about 2 1/2 volts/bulb and the same battery will fire it very quickly.

Those with lower voltage mains supplies will be even better off.

Just remember that the filaments are fairly delicate and you MUST put your powder in gently.

Sandy

hi sandy

i was trying those xmas lites you were talking about
once i get the tip off, there is a real tiny hole...about an mm in diameter...or thereabouts
how do you get the bp in there?
i keep getting more on the table than into the lite bulb

any secret tricks you can share?

[RegimentalPyro]

Try pushing the lightbulb into the comp a few times. that should fill it nicely.

[neosaint99]

How much of the xmas light tip do I take off?
if its like number 2 then jabbing it into the bp wont fill it
if its like number 3, then how do i get that much off without breaking the glass?
usually once i get halfway down the conical part at the tip the glass gets real thin and just crumbles in my hand

Edited by neosaint99, 21 November 2005 - 02:26 PM.

[mnementh]

Hi Neo.
No. 3 IS what you're after.

If you use a the edge of a diamond file and take care, the top comes off easily.

Note you're using the diamond file as a glass CUTTER, not a file.

Just run the edge round the bulb and then nip the tip off with a small pair of pliers, or wire cutters.

I've only ever broken 1 or 2 that way.

Sandy

Edited by mnementh, 21 November 2005 - 06:07 PM.

[JamesH]

Electric match heads can be bought from here

http://www.aeroconsy...cs/nichrome.htm

All that needs doing is soldering the leg wires to the head, then coating with pyrogen.