31 replies to this topic

[Zmann]

Has anybody have any experience making elec ignitors from resistors if so what type of resistors do you use.

[karlfoxman]

High resistance low wattage (1/4 watt) Or make your own from nicrome wire, i make my own and they are ok. I am currently copying Quest igniters, i can make the copper strips and insulate them from one another now i just need to find the comp.

[paul]

If you want some background information on SMS resisitors as igniters, i only can recommend this page:

http://www.privateda.../pk_smd_cached/

They put a huge effort in their work and it is very informative.
I made tests with 150Ohm 1/4w resisitors and succeeded with about 20m thin copper wire. I used a flash capacitor for ignition.

[RegimentalPyro]

I've also used resistors as electrical ignitors.

I also used ?watt ones, but went for the 10Ohm versions instead. They popped nicely on 50m of cat5 [Unshielded Twisted pairs] when using 24v.

I use them with about an inch of quickmatch. One pulls the blackmatch out of the sleeve a bit and folds it over the resistor before pushing it back into the sleeve.

Then you electrical tape the quickmatch closed at the resistor end, and twist connect on a 5m tail of wire [I use a length of UTP]. Fold the twisted legs of the resistor around the quickmatch to ensure they don't touch each other and use more tape to keep it there.

Hey presto - A cheap and easy ignitor with a guaranteed no fire current for testing and also a guaranteed fire current for ... well ... firing

[karlfoxman]

I work in electronics shop we must throw away loads when they all fall on the floor! Might have to do some tests with them, i have found a composition for bridgeless e matches just looking for conductive lampblack now and i will be able to make a load of them. I will make 30 and test them, if i get 100% i will make hundreds. I will post construction pictures, the laminated copper is a microscope job though

[broadsword]

Thats how i make my ignitors. I take the nicrome wire out of high resistance resistors and cut it to lengths. You can either use this and wrap around the fuse or make a thick BP slurry with dextrin and put a small blob on the end of a piece that has been bent in half, rather like commercial rocket igniters.

[LadyKate]

Thats how i make my ignitors. I take the nicrome wire out of high resistance resistors and cut it to lengths.

Do you hook the leads up directly to the nichrome? My biggest problem with nichrome is that it doesn't solder well - it can be done but it takes a bit of fiddling.

Has anyone tried steel wool threads?

[alany]

Yes steel wool works quite well, but it is also a little tough to solder, it doesn't wet as easily as copper, unless you use an acid/chloride flux.

There is a special flux/solder combination that works for nichrome too, but I can't remember the name of it. Someone emailed me about it when they read my page on electrical ignition. They said it was the solution to wetting problems when making up "chips" (on double sided PCB spiral wound with nichrome then cut up with a cut-off wheel on the dremel).

On a related topic, I've found a problem with my "insensitive" bridgeless pyrogen of late. The Sulfur content degrades the Magnesium over time making the composition crumble and become basically useless. I should have known better... I'll update the site tomorrow. I need to reformulate it, probably with Magnalium, but avoiding sulfur might not be possible without going to Chlorates which I specifically want to avoid for the insensitive kind. The sensitive version seems quite stable on the other hand.

[paul]

I guess, replacing the Sulfur by RedGum could work. Redgum, propperly incooperated into the KNO3 has a very low ignition point, too!

I came to this conclusion, as I tested different low ignition mixtures and KNO3/Red Gum definiately was one of the easiest to ignite.
Maybe you have to mill these two together before.

Just a thougt...

Edited by paul, 29 August 2005 - 04:35 PM.

[broadsword]

I use crocodile clips and connect them to the igniter. I find then it is a lot easier to change spent igniters with new ones!
Also an advantage with nicrome wire is that so long as you dont use too much current you can reuse them!

[karlfoxman]

A long while ago me and my father copied estes igniters, the resitance wire is crimped between the larger diameter wires. I think we used mushed up match heads as prime, they worked very well and never failed but took so long to make. Now i can make the laminaterd copper strip it should be a case of cut then dip!!! How easy, i can post pictures when we finish them and test them.

[adamw]

SMS? You mean SMT / SMD?

I work for a large home electronics manufacturer in the PCB assembly division so have an unlimited of SMT ('Surface mount') devices at my disposal. I have though about trying ignitors made from SMT resistors but since I can get ignitors anyway, why bother. Unless anyone wants me to get some for them... (resistors that is)

[paul]

Yes, of course I meant SMD as they ?re usually called in here.
100 of them cost 2.5€ ( 1,64GBP), so they would be a quite cheap source for ignitors.
But I think I?ll stick to my X-mas bulb ignitors. They were quite reliable up to today.

[karlfoxman]

Good news, the home brew ematches work brill!! I will post pictures later today, the flame and sparks will light anything! At last bridgeless igniters

Edit: I had a better idea, if i use double sided pcb 0.8mm thick i can solder wires to it without breaking down the insulation. My father has a load of 0.8mm pcb board and it cuts with sissors. I have enough materials for a good 500 or so!

Edited by karlfoxman, 01 September 2005 - 10:23 AM.

[Andrew]

When I was at collage, I made a remote controlled electrical ignitor system. I used it to blow the crap out ot 1/4W standard resistors, 1ohm produced a pretty bright flash.