Bridgeless Igniters

[209]

I have made 3 different batches of these damn bridgeless igniters and not a single one has worked. I am using nitrocellulose + graphite on the wire (super thin stuff, wires about 3 mm apart). The nitrocellulose is ping pong balls and graphite 100% from the hardware store.

I am using 12 volts and not even a spark, any ideas??

[stupid939]

I take it that you followed brainfever's tutorial. I made them awhile ago, but I could not get them to work very reliably when ignited with a 6V, 12V, or any other battery.

Awhile ago I decided to make a detonator from a camera flash system. I stripped it down until the only thing that it did was charge the capacitor, and then I added a button that discharges it through the wire when pressed. I use a 500 ft spool of 22 gauge wire and I think that it would work with an even longer wire. This is a lot like commercial electronic detonators, but it is cheap and takes longer to charge.

I mainly followed brainfever's tutorial, but after the graphite/NC mixture and the BP/NC mixture, I always coat it in NC to make sure it doesn't react with anything.

What source of power are you using and what is the amperage?

[209]

Hmmm, the camera capacitor sounds like a good idea. I was wondering if I could somehow hook up a couple capacitors in series so they would discharge at the same time to get power to igniters from long distances(something like a Marx generator).

Yep, I am using Brainfevers method and none have worked. When I was testing them I was using a 12V power source (cell phone charger) and no luck, I think I will try the camera thing, it will provide much more energy. Its too bad I can't get nichrome.

[blazter]

You'd want to hook up the capacitors in parallel to make them both discharge at once. Series would do little as the current would have to flow through each capacitor. Also, keep it mind it should take twice as long to charge them, but if you were to use a more powerful low voltage source (multiple AA batteries) it should even out.

[mike16]

Here is a simple and easy method to make an electronic ignition system:

It is very reliable, and if you use very thin nichrome wire, it has virtually no lag time, using a 9-volt battery and 3 metre of cable, they ignite immediately.
This type was I originally made for use with my electronically fired modified air rifle.

Anyway here are the pics and guide to make one:

Cut a 1 inch length of 0.1mm nichrome wire and 2, 3 inch lengths of thin copper wire:
http://i155.photobucket.com/albums/s300/kpppppk/Picture068.jpg


The copper wire used was the thin individual wires taken out of ordinary electric cables.

Take the strip of nichrome wire, and roll it around a very thin drill bit or a thin piece of wire, to form a loop:
http://i155.photobucket.com/albums/s300/kpppppk/Picture072.jpg

Now it has a loop in it as shown here:
http://i155.photobucket.com/albums/s300/kpppppk/Picture073.jpg

Now carefully pick up the looped nichrome wire, and one of the thin copper wires and twist one end of the copper wire around one of the legs of the nichrome wire like this:
http://i155.photobucket.com/albums/s300/kpppppk/Picture075.jpg

Now do the same for the other leg of the nichrome wire, make sure the copper wire is wrapped around the legs tight.
When both copper wires are tightly wrapped around the nichrome wire, fold the legs down so they are in parallel to the copper wire and are facing down like this:
http://i155.photobucket.com/albums/s300/kpppppk/Picture077.jpg

Now cut a length of selotape about 15mm shorter than the length of the copper wires, and carefully stick it onto the the igniter, from just below the nichrome loop, down the copper wires, to about 15mm above the end of the wires, exposing them like this:
http://i155.photobucket.com/albums/s300/kpppppk/Picture081.jpg


Take care to make sure the copper wires are stuck onto the tape perfectly straight and not touching.

Now fold the selotape in on itself, so that both sticky side are together and the wires are sandwiched in between like this:
http://i155.photobucket.com/albums/s300/kpppppk/Picture082.jpg


You can now trim of any excess selotape and it is ready to use, I thread a piece of guncotton through the loop, and then wire it to my electric cable to my 9v battery and switch, when I press the switch, the guncotton immediately burns and the nichrome loop glows red hot.

You can buy nichrome or resistance wire from ebay, or a hobby or crafts store.

[wymanthescienceman]

Nichrome wire ignitors are a pain, I just can't stand spending that much time on something that you must make many of when duty calls. The only benefit I could see with using them is for chaining things together with multiple matches per cue when using a low current power source.

Brainfever's bridgeless ignitors have one main problem, they have WAY too much coating on them and the coating is too thick and rough. Through a couple of trials I've gotten them to work just fine. When I saw how he used PATA cable for ignitors I thought it was brilliant as they can be very small, especially when using 80 conductor cable, the ignitors are less than 1/16" wide and can fit anywhere.

I found that when making bridgeless ignitors the smaller the amount of conducting mix the better, more mix = more current required to heat it. When using PATA cable, stripping about 1/16"-1/8" and coating the BARE WIRE ONLY serves the purpose perfectly for 18v (Two 9v batteries) as a power source. They have a resistance of about 20 ohms and ignite damn near instantly. As long as you're only using one match per cue I don't see a problem, but you could use a higher current power source for multiple matches.

When making them using PPB NC lacquer and graphite, make the mix about the consistency of thin pancake batter, not a thick paste-like mix as on Brainfevers site. Start with about 20-30ml of vegetable oil consistency NC lacquer and add graphite until it gets to proper thickness. It should form a clean and smooth layer on the wires and have a resistance of 10-30 ohms depending on type of wire and length of match. For best results use wires with a gap of less than 2mm, and also use a pyrogen whose solvent isn't acetone as it will destroy the NC based conductor layer, I use a water-base pyrogen. Finally coat the head of the match in NC lacquer to moisture proof it, MAKE SURE IT IS FULLY DRY BEFORE THE NC COAT!!

When fired without pyrogen some of my matches give off a bright white light for a few seconds and melt/burn the wire insulation due to the low amount of conductor getting EXTREMELY hot.

If anyone wants pics of a sample match or a vid of a match firing I can try and get that. I may have to make a new batch of conductor mix as it has been sitting for quite awhile.

[209]

Wow, I was completly wrong, I was thinking MORE coating on the wires (wasnt thinking of the resistance) I will fallow your method and see how it goes, thanks!

[Charles Owlen Picket]

Your question deals with the methodology for building Bridgeless Igniters systems. Please see US patent 3320104. It may just be the best design for the "twin lead-wire" dip process.

This system deals with the concept from a standpoint of development of the utilization of resistive conductive material that forms the necessary "bridge" via dipping in a slurry.

To make this material the patent is perhaps one of the best as it was adopted by a European munitions manufacturer for further study. Contained therein was the following:

Graphite as the conductive material (approx: 2-3%)
Barium nitrate the carrier agent (approx 6-7%
Lead styphnate as the main body ignition material (approx remainder)

What makes this concept function is the design of electrical resistance forming heat of course. The basic stumbling block for many is that very concept. Therefore when a slurry is designed an Ohm/Voltage meter is a great boon to test the degree of resistance found within the span of the two lead wires. This may vary from 0.5 ohms to as many as 10 ohms depending on the format of energy transmitted to the igniter (cap discharge or straight battery / generator, i.e. "hellbox").

The patent contains 3 examples, utilized for differing applications. barium sulfate & aluminum oxide was substituted for nitrate for carriers depending on burn rate enhancers or reducers, etc.

I did not know if I should include the patent per se' in that this is my first post & did not want to clutter what may have been in an FTP. But I am assuming that most know how to access US Patents. This was approved in 1967 in Germany. The US approval process was completed as this was designed for an international firm.

[nbk2000]

If you give us the patent number, we can find it, regardless of country of issue.

[Charles Owlen Picket]

Thank you, I feel on a bit of more solid footing now. Therefore I would like to offer a bit of background for those who have had trouble with this in the past and may not perceive the foundation of the patent.

The reason for a carrier agent is an important one. The carrier agent allows the conductive material to be premixed prior to in the introduction of the base ignited material. The patent offers specific steps of construction which must be adhered to. This then can be formulated to a more customized dynamic depending upon the needs of the manufacturer.

Prior to the mix of the ignited material (lead styphnate) the carrier and the conductive agent are mixed with more safety. They are mixed much more completely than would be possible if the whole of the ingredients were mixed at the same time (i.e. safety issues, etc). The "whetting" of the ingredients are via acetone or other highly evaporative material which simply holds the materials on the tip if the leads prior to any outside sealant.
Uniformity is maintained by this process. What's more the need for a binder material (NC) is lessened as it would be utilized for an outside coating only and this would not compromise the conductive matrix.

This basic concept may be altered to the manufacturer's needs. The substitution of a deflagerant for a primary HE may be utilized for alternative uses obviously.

What the patent proposes is a manufacturing process -not necessarily a specific use. The necessity for the conductive material to be very throughly mixed is the point of the invention. The problem of individual conductive particulate matter maintaining contact with itself and not being compromised by non-conductive areas or air pockets has arisen in many attempts at this type of bridge-less igniter. What's more, resistance is offered by the carrier and this coupled with the direct conductive material (graphite) provides the foundation for heat, etc.

I honestly hope I was not overly verbose. However the thrust of this concept is subtle and I wanted to be clear in the idiosyncrasies of it's manufacture for those who had trouble in the past.

[stupid939]

Ok, I found the following website again (I lost all of my bookmarks) and I basically follow his method for making electric igniters.

http://www.jamesyawn.com/ignitors/bridgewire/index.html

I used fine copper wire for awhile, like he did, but they required the wattage to be too high and they took too long to make. I then just decided to use his method, but instead of copper wire, I use bridgeless graphite igniters instead. They work great with a disposable camera flash system as my detonator, and I can light stuff from 500 ft. away.

[209]

Good link. Into favourites.:)

I think I may just have to give his igniter methods a shot. I have nothing better that will work. I read it a couple times over and they do require a fair bit of current.

At the moment my detonater is based on an idea from instructables (http://www.instructables.com/id/EH6Q99985NEPA8L6YC/).

Mine has undergone some minor changes. The casing is a piece of 1.5" diameter PVC pipe with two endcaps, all the wiring is inside, and mine uses 18V instead of 12V. The power supply is inside the detonater.

I may try to buy nichrome for Firefox or Skylighter but after United Nuclear got hit up for selling Clorates and Perchlorates I have gotten real causious of buying stuff online, They could be watched, this is sure not a time to have to cops show up:( .

[evilgecko]

I've found the one strand "hook up" wire to work the best when making bridgeless ignitors. If some graphites are giving you worries, try the "carbon" from carbon welding (or gouging) rods, available from welding suppliers. They are the rods which are half coated with a layer of copper. That grinded up in a mortar and pestle should work.

The ratio of dissolved acetone/ping pong ball to graphite is important. Basically you want to integrate as much graphite into the mixture as you can without it going crumbly. Using 2-6g of pingpong ball per 100mL of acetone works, then add as much graphite untill it gets very thick.

Twisted pair of hookup wire with 0.5mm exposed at the end and make sure they are as close as possible (less resistance, more current). Dip and then revolve them in your hand for a few seconds so they don't drip. Don't dip them too deep, just so that the exposed copper ends are covered.

Cover with BP/pingpong ball laquer, and they should work fine of 12V. I made ones which could fit through 3mm fuse holes easily.

[209]

There isn't really any sence in starting a new thread while this topic is still fairly recent so I thought I would add something that I just encountered an few hours ago.

My previous attempt at e-matches was fairly futile so I thought I would step it up a notch. I got my hands on some 38 gauge nichrome, ditched the stupid bridgeless idea and tried the nichrome with my 18 volt detonater. I have no idea what happend but it didn't work :confused: after all the effort getting the nichcrome, you bet I was pissed :mad: !! I checked all the connections and still nothing happend. Then I got the idea that maybe the power (18V) was to high and lowered it to 12V, amazing, the nichrome turned bright red in less than a second.

I'm curious, why did it need a lower voltage, or maybe was the amperage to high?? I can't imagine it too high coming from two 9V batteries.

Any ideas?

[Charles Owlen Picket]

Could one of the components in the device have been dysfunctional (the pot?)?

It would seem that simply hooking the 38 nichrome to the poles of two 9v batteries would heat it....obviously current would be the determinate of the heat of a resistance wire; voltage would almost be a "non-issue".

[209]

Last night I set off a huge AN/FO charge with the detonater (dont worry, we were miles and miles away from anything:) ) I unwound about 700 feet of wire, but I was still using my 12 volt detonater. I thought there was now way that 12V would find its way through approx 700 feet of wire, but then came the explosion when I pushed the button, It worked!:) :) yaaayyyy!

I love the sound of AN detonating verses AP, the AP has more of a "crack" noise.

[James]

209, the only thing I can think of is that your 9v batteries, might not be cranking out the watts to heat up your NiCr wire. as for the 12v setup are you using something like a lantern battery or a pile of 1.5 cells

[209]

I dunno what the problem is but I am at my wits end with this fucking detonator!!!!!:mad: :mad:. It seems like ever force on earth is trying to stop me from getting it to work. One minute the wire heats, then it doesnt, then it does again. What the hell???!!! I dont see how a bunch of 1.5 cells are any different that a 9V cell with a couple 1.5 cells soldered togeather.

When the 1.5's are connected togeather will it make an amperage difference??

[evilgecko]

Your experiencing what is known as internal voltage drop. All cells (voltage producing unit) have a internal resistance. 9V batteries have a large internal resistance (about 1 Ohm) compared to 1.5V batteries (0.1 Ohm) or even lead-acid batteries (0.020 Ohm). When you start to draw current the voltage you read at the terminals is actually lower than the value with no current (EMF) because of this internal resistance. Say you ignitor setup has a resistance of 1 Ohm(it'll proberly be much higher than that). That means that only half the actual EMF is being lost over the ignitor and the other half across internal resistance. Thus only half the power (P=VI), (and in turn current) is being lost in the ignitor and current is small compared to a battery with a smaller internal resistance.

You can think of it this way. If a 9V battery was to have no internal resistance, if you shorted out the battery terminals with a bit of thick wire of resistance 0.0001 Ohm, by Ohms law you would get a huge current of 90000A. This would surely vaporise the wire instanly and surrounding objects. But if you short a 9V battery you don't so get as much as a spark. This is because the internal resistance limits the current.

Internal resistance depends on the chemical composition of the cell and also its size. The bigger battery for the same voltage normally means less internal resistance.

Voltage does matter. Although its current which heats the wire (the proper term for power is P=I2R not P=IV), current depends on voltage (V=IR). A higher voltage means a higher current. You should try a 12V lead acid battery like a car battery or alarm battery. They should work much better than 1.5V cells in series.

[nbk2000]

If you do your testing at the same place all the time, you can leave a junked lawnmower there, and use the pull-start as a blasting generator.

Just hook up your wires to the magneto and give it a yank. As long as the magneto works, you'll get one hell of a zap. :)

[Bacon46]

I use a 12V-5Ah sealed lead acid battery I snatched out of an old emergency lighting devise. The kind you see over doors in commercial and industrial buildings.

It fires my igniters every time. They're small, lightweight, and go a long time without needing to be charged. If you can't "Find" one in an emergency exit light, they sell them new at Radio Shack or any number of other lighting or electronics stores for around $30.00 USD.

I charge mine with a 12V - 1.5A wall transformer.

[nbk2000]

I would strongly encourage everyone to NOT steal things like fire extinguisher, emergency light batteries, smoke detectors, or any other kind of life-safety devices or detectors.

The life you save may be your own.

The only exception to the above would be the deliberate targeting for destruction of a building or person.