Electronic Detonators/Ignitors

[darkexplosiveexpert]

If you cannot find nichrome wire or cannot purchase model rocket ignitors a cheap alternative to these are just regular old mechanical pencil refill leads

To use these you need a decent battery, i use a car battery (but any battery with a large current and moderate voltage will work), some speaker wire, some regulor firecracker fuse that is connected to your pyrotechnic device, a pair of crockodile clips, and a pack of mechanical pencil leads

The method of construction

1. make the wires by clamping the crocodile clips on to the speaker wires,
2. clamp the lead refill in between the crock clips
3. make sure the fuse is touching any part of the lead
4. touch the leads of wire to the battery terminals


This Igniter is so powerful that it can ignite magnesium ribbon if you get the battery strong enough.

Enjoy

[Charles Owlen Picket]

I think you may need to check your spelling & punctuation. It may be a good idea to edit "Point #3" as well.

[-=HeX=-]

Charles, I believe that he meant the graphite by 'Lead' in point 3. Or will the graphite only burn at a certain point?

Yep, spelling and grammar are a point to improve upon, as is the newb first post new topic issue but well done anyway. At least you contributed.

As for the claim that it will ignite magnesium ribbon, I will have to Test that, sounds interesting! He one cannot obtain nichrome wire that person is a lazy piece of shite. It is abundant in toasters and hair dryers. On offense intended anywhere.

[iHME]

I would not trust a electric fuse made from graphite pencil leads. It is brittle and you can't solder it. But it does indeed get hot. I played with them a load of time ago. It is just a nice curiosity and could have some use in laboratory conditions. But from practical point of view I don't see it as a good option.

[ETCS (Ret)]

Graphite powder, or powdered pencil leads, may be used as well with a little creativity.

Powdered pencil lead mixed with just a tiny bit of rubber cement, or other suitable binder, produces a putty like substance that can be formed into a thin string and adhesively attached to the bridge wires.

Granted, it does require a strong electrical input as it's not nearly as sensitive as thin nichrome wire, but in a situation where your options are very limited...

[Bert]

I have used bridge wireless igniters. They worked, and were cheap & easy to make. The down side was they required a 12V Lead/acid battery, and a firing circuit made of a 16ga. electrical extension cord to function reliably and quickly over a 100' run.

[Charles Owlen Picket]

From a generalist standpoint when I examined this issue I was faced with two perspectives. One required a great deal of current (big battery) the other required a voltage spike (cap discharge).

12 weeks & $1700 of my own money in a rocket is too much to risk on a igniter system of even partial probability to risk on an effort. I've tried a great many bridge-less igniter systems; even Gary Purington's composition (which is a damn fine one) is not meant to stand up to time or even to any handling of the tip.

The concept which I have depended is to always use a resister bridge wire. This ensures heat generated AT THE POINT OF CONTACT with the fuse bulb. What's more the use of steel wool or other less rust resistant and delicate materials will fail over time & cannot be quantified. Simply from a personal perspective, I use only high quality Nichrome or Copel wire are a diameter of .032 or less. I've found that a fluid of ferric chloride will suffice for flux in both cases and will make for a fine solder joint.

I use a magnifier & high end solder pencil to make several at one time and they really DON'T FAIL. Therefore I have the choice of using either electric method depending upon the diameter of the wire and the need of the time. I can make the thing shoot at 9v/15 ma battery power or have the demands go as high as the commercial norm.

To me, it's worth the effort [to go the extra mile] to make damn sure that thing will shoot with as much reliability and precision as humanly possible. A long time back I had the chance to obtain the skeletons of a commercial squib. I took note of all the components and maintain a record of what does what. Now they use an ENTIRE CIRCUIT within a cap or squib to maintain the demands of long range ignition: the only input is a voltage/current jump to start the system which is a small CD element!!! Very nice but expensive vs. the simplest designs of the past.

I don't skimp on this (bridge wire) end of ignition. There are dozens of techniques for simpler, less involved methods to make an electric igniter but when all is said and done, I'm always glad I don't take the short cut route.

I don't drop down to a "40" sized wire as I'm of the opinion that will invite stray eddy currents to possibly make the thing unsafe (research into just what makes caps pop from radio waves points to very fine bridge wires, etc). I use a "V" joint as it gives the larger surface area to contact the composition. I also neutralize the completed igniter wire as that way I have a rust resistant format to start work.

I have experimented with professional boxes and there are two distinct variants. The old standard was a twist generator (or even the Hell Box type) of old that produced 50v at one amp. That was altered but the concept was of a high current unit. Much more recent was the CD-oriented box of 1200v (or much more) at 30ma. Which sent a violent jump of spark demanding a resistor in which to terminate.

One can even use an old carbon resister at 1/4 watt or less to terminate & focus the electricity. The point however is that with a resistive termination, the energy is focused at the point of need. Even the bridge-less igniter systems use some sort of carbon to form a resistive terminus at which the heat energy can ignite the composition.

The use of steel wool or similarly super thin copper focuses heat by creating a smaller union for the flow of electric energy. This is not ideal as it demands a higher level of energy than would be needed by a more adaptive & professional design. What's more it's very susceptible to oxidization. Many people experimented with SMD resistors back in the 1990's as that was a concept used in one of the finest igniter designs used in government fuzes (patent for "Hugh's Aircraft", "Rocketdyne", & more). This works well but it is just as simple & less expensive to use a resistance wire.

My experiments with the use of an SMD resister were very promising. All were functional. But the SMD resisters were obtained from Mouser Electronics are a cost of $14 per reel (less than a penny: they're cheap) and not as easy to solder as the wire, once a technique is mastered.

[Yafmot]

This is so obvious that it has no doubt been tried, but on the chance it's been overlooked, might I suggest a model engine glow plug. Ir's fairly robust, and the element is platinum, so corrosion wouldn't be a concern. From what I know of them, you've got your ignitor right there, except for some sort of nonconductive pyrogen.

A drop or two of firefox's E-match dip in the cavity, let it dry, and there you go, although I'm not sure of the voltage/current requirements. Seems worth a try, though.

[Bert]

Model engine glow plugs have been used in pyrotechnic SFX, particularly on miniatures where repeated takes may be needed. They need to be cleaned carefully or they'll corrode away, and are quite expensive in comparison to purpose made one use igniters.

A typical use would be a model of a warship from the sail/black powder era, with the glow plugs built into the cannons- Charges would be single crystals of acetone peroxide, grown in a fashion designed to yield uniform sizes in the mm range, producing a deflagration rather than a detonation. The types of compositions used on conventional ematch would probably destroy the glow plugs rather quickly.

[Charles Owlen Picket]

Believe me I really worked with this for quite some many years and the tried & true methods are the one that give the returns of stability and functionality that yield reliability and that actually the name of the game.

The time taken to make a quality bridge wire unit are worth the effort. The concept of simplicity & utility are the best in those areas that are most important.

Now with IC electronics, one could make an actual time fuze with the proper use of the 555 IC - a design of a 120 second delay circuit can be manufactured within a igniter the size of a pencil! Modern electronics and proper bridge-wire design makes for simplicity and reliability.

Attempting to re-invent the wheel is of little use when expense & over complication meets the demand for consistency & quality. It's just a better expenditure of time to solder the correct components and be done with any guess work.

[ETCS (Ret)]

A detonator used in research labs to evaluate sensitivity of various mixtures or compounds is a length of copper wire, #34, in the core of the sample. The wire is connected to heavier cable which is needed to fire this detonator by means of capacitive discharge.

If any of you have the ability to charge a 470 microfarad electrolytic capacitor to 150 Volts and then discharge it through a small length of copper #34 or smaller wire (connected in advance to properly sized cable, # 18 or better); you'll be surprised at the brisance of the resulting explosion.

The necessary power supply to charge the capacitor can be made battery powered and quite small. Flash Camera supplies are a good option too.

Please be careful. A charged capacitor will deliver a powerful jolt!

[inkhead]

What happened to people crushing the glass off a lightbulb? Am I getting old? I know it's not idea, but it looks like you are interested in cheep and fast.

[Charles Owlen Picket]

....but it looks like you are interested in cheep and fast.

Not at all. Cheap & Fast for an initiator is risky & stupid. Spending a few minutes doing something correctly & reliably when one's limbs or capital are at risk is an appropriate thing to do.

The filament on a bulb is fragile and the structure is cumbersome. Tungsten is not measured resistance wire and the existing bulb design must be worked-around instead of designed to work as needed.

[Boomer]

You don't have to crush the glass and handle the naked filament. This is unreliable and cumbersome.

Instead, get a chain of 100 Xmas bulbs, and cut them out. You get ignitors complete with wires and housing. The trick is to grind the tip off and leave the bulb intact. Fill with a composition of choice (none that attacks tungsten of course), seal with a drop of glue, and you're done.

These can be had as small as 3-4mm diameter and 5-7mm length, fitting even in small blasting caps. I never had a failure in over two decades, but measuring the resistance after sealing is a must. If the filament is still intact they never fail.

Another plus is they need only 6V for bright light, so they already function from a 3V Li 'button' cell, if things must be made small. A 9V block is more than enough through 100 feet of speaker cable. But if you want INSTANT function, discharge a 2000V capacitor through them. They fire so fast that two charges inches from each other both shoot, without one disturbing the other. A fragment of a millisecond would make the faster charge blow the other all over the place, so it's probably far under 100µs.

For one-microsecond timing there is always the TR5 fuse, which also provides its own housing if the top is ground away carefully. These fire in <2µs using a fast cap bank (i.e. no crap from a camera flash).

[-=HeX=-]

Yes. The xmas bulb ignitors work a dream. They were the first ever homemade pyrotechnic device I set off. In fact, I tested them with a professional pyrotechnician (I was working at a show in the theatre and she was present to do the flash pots) and she approved of then as good, cheap, reliable and safe ematches. At the time I used my famous 'Match head powder' as the filler for lack of anything better. I recommend black powder instead but I have never had a failure with the safety match composition, which is phosphorous free FYI.

Making the match head powder was a long, boring process involving first scraping off the 'red stuff' with a scalpel, then crushing it to dust, then placing it in water and letting it stand to 'float off' the wood that remained, which was skimmed off, then allowing the water to evaporate, then the material was finely powdered again and once fine enough it could be used.

Again, it is not a kewl match head bomb that is being made. It is an expediant flash mix. It Is fairly safe.

[MAGNUM9987]

i would suggest simply getting crock clips, standard wire, a basic switch, and gum wrappers, as long as they are the aluminum coated ones. it is just as simple, not as brittle, cheap, and reliable.

[Yafmot]

Where do you guys buy your glo-plugs? I used to fly a lot of RC, and I bought my plugs on strips for about 30 cents apiece. And I wasn't talking about reusing them. I was thinking more along the lines of an ignition/detonation train.

[ETCS (Ret)]

Boomer,

When your detonator is fired with a 2000 Volt capacitive discharge unit (commercial standard) it is probable that the bridge wire is functioning as an EBW (Exploding Bridge Wire) which would mean that the detonations are occuring within nanoseconds of each other. EBWs excel in situations where extremely precise timing is a requirement for multiple charges.

Magnum9937,

Your simply constructed system using aluminum foil on a gum wrapper is good. My little capacitive discharge unit consists of a small power supply to charge 2000 Microfarads of capacitance (Low ESR) to 200 Volts; an SCR rated at 400 Volts, 60 Amperes; a safety bleeder resistor; a push switch to "Fire" and the cable/clip leads.

I've been able to "explode" both copper wires and gum wrapper foil cut into strips 1/4 inch wide and 1 inch long.

Since the exploding wire (EBW)or foil (EFI) acts in place of the "primary", any good secondary energetic will function well as the "booster" charge.

[darkexplosiveexpert]

Another awesome electro-ignitor is also a lead pencil.
YES A NORMAL LEAD PENCIL.
I'm certain that the magnesium will ignite, with the pacer leads, not so much certain with the pencil
but the pencil will burst into flame, this i am certain of.
you can attach a fuse to the wooden component of the pencil, and shave both ends of the pencil off, exposing the graphite so one may attach crocodile clips and a power source, my favorite power source is a lead acid 12 volt car battery, but anything along the lines of this will work too

sincerely

Student of science
darkexplosiveexpert

Ps the higher the graphite content, the better it will work

HB pencils are not as effective as a 12B pencil

[Yafmot]

I have an accquaintance who owns a company that makes ultrafine wires out of just about any metal or alloy one could want. And when I say ultrafine, I mean right down to nanoscale, a couple of molecules across.

If anyone is interested, just say what kind of metal you'd like it made from, and I'll see about having some either pulled from stock or made up special. I'm thinking Zr, since it's pretty pyrophoric.

His primary market is, as you might expect, is microelectronics, but his stuff has forund it's way into a lot of wierd niches, and he's always looking for new applications for his product.

Whaddya' think?

[-=HeX=-]

I have am idea. Go to the 'how to make reliable ematches' thread and see the computer ribbon cable idea. Now instead of pyrogen use a piece of magnesium wire wrapped around the cables. Viola, instant high temp ignition source! Same can be applied to zirconum or titanium wire.

[Logic Probe]

I visited a Tripoli Rocket shoot recently, and they used 1 or 2 ohm quarter watt resistors threaded through drilled Pyrodex pellets for initiators, and I didn't see a single failure. Although I got a universally repellent reaction to my suggestion for terminal guidance on their rockets. I think they don't want to think (publicly) about guiding their munitions. I was only talking about making rocket recovery in windy conditions easier, but I think they assumed that I was thinking about targeting. I have to admit that it did get the idea mill to working. Heat seeking or radar return seeking just isn't that hard in 2008, or later. At the speeds that I witnessed, I wouldn't even consider manual contol. Us meat machines are just too slow. Yes, I know, I've strayed OT, I'll be good now.

[Bert]

Guidance is very specificaly forbiden to the model rocket community by the US government. Yes, they're very rightly worried about how easily the government monopoly on effective rocket anti-aircraft weaponry could be broken with off the shelf hardware. The high power rocket people have had enough BS crammed down their throats over the supposed utility of composite propellants as high explosives to want to avoid ANY further reasons for the federal government to interfere with their hobby, they avoid guidance like the plague.

I remember about 15 years ago someone made a very simple gyroscopic control for a true scale Saturn V model to allow realistic slow take offs while maintaining a safe, vertical flight path that wouldn't have been possible otherwise. An article was published in High Power Rocketry, and then never a word more was heard. The parts mostly came from Radio Shack-

[Setharier]

http://www.youtube.com/watch?v=B6JmtMSqxFU

I couldn't much discover simpler electrofuse. Could anybody reveal what material is that nickel-coloured wire which connects the two copper standard wires and is the igniter part and what name the transparent cable where it's from is sold around; is it some antenna or lan cable..? I'm really on electrofuses right now, the chemical fuses are relatively clumsy. That electrofuse can actually be made in field by having two copperwires tied together and this stuff rolled on like detcord and have just that "nickelwire" pieces and wire scissors ans some primary with you and that's it.

Fuse heads can also be made ready by putting the "nickelwire" on to a short piece of copperwires and filling the cap, whatever it is made then, with primary, and when going to action, just connect it to the main wire that is on roll, cut it to length you want and have a boom.

[Intrinsic]

Setharier:
It is probably just a standard multi filament wire (as opposed to a solid wire, like the copper ones you see in the video), nothing special. You probably have several lying around your house. The electricity going through the small wire creates alot of heat, igniting the black powder or AP. Nichrome wire is generally considered the best for generating alot of heat, but I think you can get about the same result with any small wire.

This design is really kind of kewl for electric igniters, you should look into ematches that have been dipped into a nitrocellulose paste/lacquer for a better alternative. You can even buy kits for making them if you don't want to go to the trouble of doing the hard work yourself.