Easily made powerful Blastingbox

[DBSP]

http://dbsp.sensorystatic.com/pictures/blastingbox/DBSPs_blastingbox.JPG


When I first started thinking about making blastingboxes/machines I thought I'd never be able to make one scince I thought it was very hard and that you had to know a lot about electronics to make one. I was wrong it's really simple actually and requires no special electronic skills other than being able to seperate + from -, if using easily obtained circuits and switches.

My old b.box concists of 6 caps at 385V 220uF, 3 paralell chargning circuits from disposable cameras, a batterypack of 5 1,5V batteries in paralell, an ON/OFF charging switch and a main swith. It workes ok but it charges to slow and isn't quite as powerfull as I'd like it to be. My new one concists of 10 385V 220uF caps, 6 paralell charging circuits , an additional "safety switch", a dual swith wich starts the charging and turns 5 red LEDs on as a charging indicator and eventually a heavy main switch. This one charges 2 times as fast as the old one and has 40% greater maximum power. It takes it about 10 sec to charge enaugh to blast a nichrome wire through a 10m wire that I use quite often which is really perfect. As I write this I haven't tested it on my thick 50m wire yet.

My old box:
http://dbsp.sensorystatic.com/pictures/blastingbox_old.JPG
http://dbsp.sensorystatic.com/pictures/blastingbox.old_2.JPG
One of the reasons I opened this new topic was that I'd like to help people like me who hasn't got any great knowledge within electronics to make a good blastingbox easily and from simple to get materials. I must say that one of the better things I've made for this hobby is my first b.box which really has made things alot easier, dragging around 15kg car batteries isn't really practical nor easy, a blastingbox fits into your pocket while still having eanugh power to perform most tasks.

What you need to make a blastingbox, powerful enaugh for most of of is the following:

Disposable cameras -- easily obtained for free in photo shops
Cable, most of the common ones will work.
Swithes, any swith will work actually (except in the main swith for letting the current on when blasting)
Capacitors, you can probably use small ones like the ones you find inside disposable cameras (330V 100-120uF) but then You'd have to use a lot of them, not practical, what you need is caps which hold about 200uF at about 400V or more(correct me if wrong).
batteries, 1.5V R14
+ pliers, soldering equipment, knife etc.

To build this thing or similar you only need some patience and a lot of time.

To better understand how the schematics should look like for a basic b.box I've made a simple drawing to demonstrate it:

http://dbsp.sensorystatic.com/pictures/blastingbox/blasting box_basic_by_DBSP.JPG

I allso made a drawing of the schematics for my new box:
http://dbsp.sensorystatic.com/pictures/blastingbox/blasting box_by_DBSP.JPG

After you have gathered all of the components needed you should start working on the charging circuits. What you need to do is to unsolder the capacitor from the circuit board and replacing the cap with a couple of 10cm wires instead(don't forget to make a note on which of the pins that is + and -). After that is done you unsolder the pieces of copper that holds the battery in place and preplacing them with wires in stead(or you can solder the wire to the clips directly)(don't forget to note + and -). I recomend using wire of different colour for + and -.

It should then look something like this:
(the shape and size of the circuit board may vary, I chose these ones because they where the smallest ones)
http://dbsp.sensorystatic.com/pictures/blastingbox/wires_attached_to_circuitboard.JPG
http://dbsp.sensorystatic.com/pictures/blastingbox/in_and_output_wires_in_place.JPG

After that is done you should connect them paralelly thus connceting all - outputs together and all + outputs, and all + and - inputs toghether.
Should then look something like this:
http://dbsp.sensorystatic.com/pictures/blastingbox/circuitboards_paralell.JPG

Then leave them for the time being.

Next thing to do is to put the caps together, I hotglued them into place. You could of course tape them together as well.
Then connect all + and -pins together, this must be done properly as these connections will be put under heavy currents. I conected mine with steelwire rapping it around the pins repetedly.
like this:
http://dbsp.sensorystatic.com/pictures/blastingbox/caps_glued_together.JPG
http://dbsp.sensorystatic.com/pictures/blastingbox/pins_conected.JPG

Then cover the capacitors with tape or similar to insulate them from their sorounding, only leaving the + and - wires sticking out.
http://dbsp.sensorystatic.com/pictures/blastingbox/cap_covered.JPG

Next thing to do is to connect a number of 1,5V batteries paralelly and glueing/taping them together. The absolutely best thing to to was to put them into a batterybox which makes it easy to change the batteries when theay are dead. I've got two 10 battery boxes which would have been great if only they had been in paralell instead of in series. They can of cource be modified but thats a loot of work.

batterypack:
http://dbsp.sensorystatic.com/pictures/blastingbox/battery_pack.JPG
my two boxes:
http://dbsp.sensorystatic.com/pictures/blastingbox/battery_boxes.JPG

Now its time to put everything together:
Fasten the charging circuit onto the caps or put them wherever you want them. Fasten the batterypack, where you wan't it. Then connect the batteries + and - to the + and - on the charging circuits, just be shure to put a switch between either + on the battery and + on the circuit or on the - (this switch will function as a charging switch)(I actually put two switches between the battery and the circuit, this is just to add a bit of extra safety, this will make it harder for the b.box to start charging by itself, the swith is a small microswitch(push type) and put so that it will be hard to accidentely starting it(pic #1 below)). Then connect the charging wires to the caps(wires leading from the place the small photocaps where soldered to the circuitboard). And then wires from the main caps to a large switch which will function as a "detonation switch". What type of swith to use here may vary, the best thing would be to have a relay to swith the power into the bridgewire. This would be extremely costly though scince the tyristors capable of switching currents of these currents will be very expensive. A normal 220V swith used in houses to turn the light on/off such as the one below may be used, it will eventually be welded toghether scince there is such a powerful electrical impulse going through it. This is easily fixed by snapping it apart when it has gotten stuck.

#1 http://dbsp.sensorystatic.com/pictures/blastingbox/microswitch_1.JPG
#1.1 http://dbsp.sensorystatic.com/pictures/blastingbox/microswitch.JPG

220V switch:
http://dbsp.sensorystatic.com/pictures/blastingbox/220V.JPG

A nother thing I added to increase the safety of the b.box is the dualswitch I put as "main" charging switch. By putting it in ON mode it lets the current on on two seperate wires, #1 starts the charging and #2 lightes 5 bright red LEDs that operate from a single 9V battery. This makes it impossible to avoid noticing that the machince is charging or atleast in charging mode if the microswitch isn't on.

http://dbsp.sensorystatic.com/pictures/blastingbox/LED_1.JPG
http://dbsp.sensorystatic.com/pictures/blastingbox/LED_2.JPG

--------------------------------------------------------------------------------------
The BlastingBox is now ready to use:
Left: http://dbsp.sensorystatic.com/pictures/blastingbox/left.JPG
Wright http://dbsp.sensorystatic.com/pictures/blastingbox/wright.JPG
top: http://dbsp.sensorystatic.com/pictures/blastingbox/top.JPG
bottom: http://dbsp.sensorystatic.com/pictures/blastingbox/bottom.JPG


One thing that is quite obvius is that it'll never reach 385V scince the charging circuits only put out 330V. What does this do to the setup? Could anyone with some electronic skills answer that question?

I may very well have missed something scince it has taken a few hours to write this and I'm getting tired now, if I have missed something please let me know.

I really hope this may help someone..

[Anthony]

"it'll never reach 385V scince the charging circuits only put out 330V. What does this do to the setup?"

Not exactly sure what you mean, but it means that they caps will only charge up to 330V. This is good, because the caps are over-rated, making their job easier and they should last longer.

[pyr0man1c]

a few months ago i was experimenting with a capacitor bank consisting of ~30 35V capacitors holding 450 (or whatever it was) uF each (got 'em for free), but i dropped the project since the voltage seemed to be too low to initiate my caps reliably. i also had problems finding a good way to charge the capacitor bank in the field.

in desperate need of a good-working blasting machine, i'm right now thinking of a hand-driven generator design, just like the larger ones used to set off 100s of VA blasting caps. :cool:

the design will consist of the following parts:
(1) a crank-driven generator (possibly a generator from a car or a smaller vehicle) that produces an AC voltage way too low to charge a capacitor bank with.
(2) a transformer which i will make myself, that transforms the low voltage AC to a few hundered volts.
(3) an electonic circuit called a "rectifier bridge" (direct translation from swedish, original swedish term was "likriktarbrygga"). this unit costed me 22 SEK, that's about $2.5, and it is specified for use with max. 600V 1A. what it does is that it takes an AC current and converts it into a DC current. the nice thing is that it is so cheap, and can take up to 600V!
(4) a capacitor bank. i will have to make a nightly visit at the garbage dump and dismount afew computer monitors or TVs. damnit, those capacitors ain't cheap!! :(

if anyone can see any problems with this design i would be very happy to hear your comments. i'm really not an electrician myself, i just talked to some of my friends that are more into this than me.

edit:addition: to answer your question, the capacitors are rated at MAX 385 volts, that means they can propably take many times more without exploding, but charging them to 330 volts instead will certainly not do them any harm.

sincerely,
pyr0man1c

[MnkyBoy]

MAX 385 volts, that means they can propably take many times more without exploding,

Not entirally true. The 385 V spec is the "theoredical" voltage in which the insulator between to caps foils will break down, forming basically a short. This number is usually pretty close. Over time and with use, the insulator will slowly break down thus lowering the voltage potential needed to break down this barrior. One might be safer by finding out the voltage being sent to the caps, doubling the voltage to come up with the voltage rating of the cap to use. (ex: 330 X 2= 660, so look for a cap around this level)

[Anthony]

pyr0man1c, car alternators for many years now have had built in rectifiers, i.e. they output DC. I've never gotten round to removing/bypassing the built in rectify, so I can't say how easy or hard it would be.

If you can get an alternator from an old car with the rectifier as a seperate unit, then Bob's your uncle.

[MnkyBoy]

Just doing a quick search at McMaster revealed these little beuties 67.5 Volt Batteries (http://www.mcmaster.com/catalog/109/html/0762.html#.). The price is a little on the high side, but each for their own.

Also, searching through some boxes in the back I ran across some 300 V Eveready Mini-Max Battery (No. 493, NEDA 722, 2.5 x 2 x 3.75 in WxLxH).

Never mind, just found the price 493 300 V CZ Electronic/Communication Battery $78.00 $140.00 2 $183.00 3 61.00.

Will draw up a design for HV from low voltage battery as source. Does anyone know the voltage/current needed to have nicrome wire work effectively?

[Gargoylebrother]

WOW :eek: This does defently prove to be an extreamly easy design and simple to make and understand those like me with little to no electrical knowledge are very thankful THANKS MAN i will be puting this to good use here in the future when i get the time and money again THANKS:D

[MnkyBoy]

There is no point in redrawing the wheel.

1.5V to 400 VAC (http://home.golden.net/~kpwillia/minich.htm) . If DC is desired, a few simple HV Diodes in line with each AC lead will convert it to DC. Throw in a voltage doubling ckt (a few more diodes and a couple more caps) and you will get plenty of HV DC. (Possible in a smaller package than above. I mean no offence, just throwing out other ideas here)

If interested in info on caps, I ran across This Page (http://www.uoguelph.ca/~antoon/gadgets/caps/caps.html)

[kingspaz]

my blasting box is simpler :P
100m of bellwire, a 12v gel cell and sensitive ignitors!
and it works!, although i think a real blasting box is much better since it keeps everything together.

[Tuatara]

Kingspaz has the right idea. If you can't get this to work use
[list=1]
thicker leadout wire
thinner nichrome in your detonator
[/list=1]

Basic idea is that the resistance of your piece of nichrome should be much higher than the resistance of your leads (at least 10 to 20 times!), so that all the energy winds up in the nichrome. With 12V gel battery your only limiting factor is the total resistance of your circuit, so make that lead out wire as thick as you can! Try heavy duty automotive cable.

[Skean Dhu]

i know this has been done before but since i do not have much electronics experience/knowhow i was wondering if someone could help me out with this.

i have a cordless phone and i would like to convert the phone part so that i can hook ignitors to it, and when i press the 'page' button on the base it would set off the ignitor.

any tips or links to sites with instructions for this would be greatly appriciated

[kingspaz]

Tuatara,
the bellwire is about 1mm diameter copper. the ignitors are based around 0.08mm nichrome which ignites 25/70/5 charcoal/KClO3/dextrin to make it sensitive and rock hard.
just thought i;d give some more details incase anybody else wanted to take my route.

[andreas]

http://www.boomspeed.com/minipril/blastingbox.jpg
http://www.boomspeed.com/minipril/blastingbox2.jpg

Here are two picture of my blasting box. Its made from an old inductor salvaged from a fieldphone, that piece outputs about 150Volts ac at a high crankspeed. This ac current is rectified by a B250C1000 bridge rectifier and charges 2 paralel 200volts 220yF caps. It can glow up a 220 volts 40Watt lightbulb. And explodes thin alufoil strands. And the main advantage is that it doesn't use any baterys

[andreas]

http://www.boomspeed.com/minipril/safetydet-after-blast.jpg
http://www.boomspeed.com/minipril/safetydet-bridgewire-closeup.jpg
http://www.boomspeed.com/minipril/safetydet-bridgewire.jpg
http://www.boomspeed.com/minipril/safetydet-filed-with-cast-mhn.jpg

I made some pictures of my new experiment: the use of my blastingbox with homemade bridgewire detonators. As you can see in the pictures it was a succes. I used 3 meter main wire for this test. Later I'm going to see what is the max wire lenght. The bridgewire consists of a thin alufoil slice, and the charge was cast mhn. With the mhn still molten I put the bridgewire in and waited till it solidyfied.

Any comments, tips or suggestions are welcome!

[kingspaz]

how the fuck did you melt MHN?!?!?!
are you INSANE?

[Jumala]

Melting MHN,-- sounds like kamikaze

With your good blasting box you can try cheap 100 ohm resistors instead of the bridgewire. They are already wirered and the resistance is much higher than that of the main wire.
I use 100 ohm with my box too and it works well.

[DBSP]

I was just thinking about using resistors the other day, if it workes well with your timer then why shouldn't it work with my blastingbox. I was thinking about using the small 1/4W resistors you use in your timer. I don't know much about electronics so I don't know whats best but I guess a 100ohm resistor would function fine scince you suggest it.

It would indeed be much simpler than making your own, perhaps even more effective too.

I'd like to integrate your timer with my blastingbox, that wouldn't be to hard except finding a tyristor that can handle the current from the blastingbox and buying it without going broke.

Have you got any suggestions Jumala?

(I've just located the CMOS 4541 chip at a good prize. So I might start making some of them in a while. I don't suppose you have a complete list of the components...?)

[andreas]

MHN has a melting point of 112 degrees it starts decomposition at 160 degrees, I melt it in a oil bath in small quantities that I keep at 120 degrees. In fact mhn is cast commercialy IIRC.
Then again i rather cast a little mhn than pressing a peroxide.

[Microtek]

Indeed. I also did some tests with cast MHN when working with my caseless ( or rather partially caseless ) detonators. I would melt small amounts on a glass plate placed on a hotplate. I never had any problems with decomposition, though I was a bit worried about increased impact sensitivity.
Also, I would recommend not confining it when melting as that would present a hazard if it ignited.

[Mr Cool]

It (casting MHN) can be done, but I would be worried of partial decomposition leaving small amounts of NOx behind. Better to use a mixture of mannitol and sorbitol, and nitrate that. The result is a soft material that gradually sets as the compounds co-crystalise. Pack it while in the plastic form, and leave it to harden for a while. I'd be a bit worried also of shrinkage/stresses as the charge froze, and big fuck-off crystals snapping as this happened. But this is probably just paranoia.
If you want to melt cast a nitrate ester, go get some erythritol.

"it starts decomposition at 160 degrees" be careful of statements like this, they can be misleading. MHN will give off NOx at well below this temperature if left for longer. Nitroglycerol decomposes at 50-60*C, and MHN is considerably less stable. I know it isn't hot for long, but some decomposition WILL occur.

[kingspaz]

hence my above reaction :)

i can't see melting it to be a good thing at all. all i've read about it suggests it is not very thermally stable.

[Tuatara]

DBSP you should be able to find a cheap thyristor. For a single pulse you can put at least 10 times the rated current througha thyristor without destroying it. I've done it on a comercial basis, using an 85amp thyristor to deliver 2000A (yes - two thousand amps!) pulses in an electric fence energiser - every 1.5 seconds for 5 years!

[Jumala]

To combine blasting machine and timer I would use a relay as output switch.
The expected current is not so high when using a resistor. This is the big advantage in using a resistors. A 100-150 Ohm resistor warrants the conversion of electrical power to heat at 1-2 ampere and the wire to this igniter can be thin. A bridgewire has approx. 1-2 ohm and needs 50 to 100 ampere to produce the same heat.

You can perform a simple test. Take your blasting machine and charge it up to 150V or more. Only one 220 µF cap ist enough.
Take a 100 ohm resistor, hold it with isolated tongs and make contact to the cap poles.
It´s amazing what only 1-2 ampere do with the resistor.

The best method to combine timer and blasting machine is also to start the charge up after the time is over with automatic ignition when the cap is full.

[DBSP]

Thanks a lot Tuatara, that info was really helpful, that means that the price for a tyristor perhaps won't be to high after all.

I'll definately try using a resistor.

I have a thing I'm thinking about, the charging circuits contain a small diode that lits up att full charge, could these be included in my design in a simple way to give me a hunch on when it has reached full charge. Or doesn't it work? I've never had them lit up when charging my caps(the 220uF ones) with a complete circuit.

And how would one make the b.box release the power into the bridgewire at full charge?

Sorry if it's a lot of questiones to answer but this subject isn't one which I have any great deal of
knowledge within.

[davidhon]

Hi mnkboy...nice tiny-mini blaster & drawing (1.5v to 400v).I would kow-tow if u could specify the power & voltages etc...on the transformer,resistor & transistor...i have serious problems in obtaning them without the actual capacity. thanks ...

-----------------------
'u' in place of 'you' is chatroom speak. this isn't a chatroom. - kingspaz

[Efraim_barkbit]

I have been thinking about making a blasting box, so I got my ass over to the local photo-shop and asked if I could have a few used disposable cameras.. They said that they send all the used cameras in return, but I got one anyway.
So, When I came home, I took out the circuit, and tried to figure out how it worked, and how I best could use it in a blasting box. I attached two wires to the "flash lamp", to be able to discharg it easier., but after some playing around with it, it wouldn´t charge anymore. I only have very basic electronic skills, but I think it is maybee a transistor that is broken, because when I connect the battery, it becomes to hot to touch in 3-4 seconds, and I don´t think it is supposed to do so.
maybee someone that is better than me on these things know what is wrong, and if it is possible to "bypass" it, or something.
I have a voltmeter somewhere, but it has no batteries at this time, but I could maybee use it to check the circuit, if I knew what and where to check...

I know, I got it for free, and it would probably not have been very effective with just one capacitor, but it would still be better than a nine volt battery...

I took a pic of the front and one of the back of the circuit card, so that you could get a look at it too. http://www.imagestation.com/album/?id=4288582417


Any help is much appreciated.

[Tuatara]

Hot is OK. Too hot to touch is not. Did this circuit ever work? If the circuit is working you should be able to hear a rising whistle as the cap charges. The transistor cannot be bypassed - it is an essential part of the inverter that kicks 1.5V up 300V. You were only using 1.5V weren't you?

[Efraim_barkbit]

The circuit worked perfectly,I heard the wisteling sound while charging, but then it suddenly stopped. I must have done at least 40 discharges at full charge through the wires, and probably as many through the flash lamp.
If i replace the transistor, does it have to be exactly the same, or would any transistor do?

[Boomer]

Why not buy a CCFL (cold cathode fluorescent lamp) driver ready-made? They make 500-1000 V max at 5-10 mA from 5 VDC. You add four HV diodes and have an easy, short-circuit limited charger. It gets a 220 uF cap up to 450 V in 20 seconds. And a spark gap solves the switch problem, it is made for theses high currents. I have designed several types of CCFL drivers (design life 50.000 hours continuous), and we sold about 55.000 last year, they hardly ever fail. In contrast, cheap flash circuits are thought for only minutes of operation per day, they stress the parts to their limits.

I am currently working on a similar b-box, but for EBW caps. More details will come later.

P.S. Funny to be a newbie again after 20 years of ‘blasting around’….

[Tuatara]

Unless you know what you are doing, you should use the same type of transistor as a replacement. It would probably be easier to get another complete flash unit though.

Boomer, I like the ccfl idea!

[vod8750]

Sorry about bringing up an old thread again but I didnt see the point in starting a new one!

I have been thinking of making a blasting box since, lets face it, its a hell of a lot safer than pressing AP or HMTD!

I went down to my local electronics shop and got a few capacitors. The ones I have are rated at 450V but the biggest capacitance I could get at this voltage was 47uF! This is obviously too small but if I went to a bigger capacitance I could only get them rated to 100V and there doesnt seem to be any in between voltage.

Since the charging circuit I have from a disposable camera reaches over 310V I obviously cant go for them either!

Does anybody know where I could get a few high voltage, high capacitance capacitors?

I also got one of those aviation type switches to use as the main fire switch. This should work well if it can take the high voltage since it cant be fired accidentally. Its designed for use with a 12V circuit in a car so if it can take over 300V is another thing. There's only one way to find out though! Just have to make sure to wear heavy insulated gloves!

[inventorgp]

Alternately, you could use:

a 12V system with a 8-12gauge wire leads then nichrome. Or
a triac circuit (or light dimmer at least 600W) in series with a cap (2-10µF
250-400Vac polypropylene) and an ignition coil with a spark gap instead
of nichrome.

Hmm.... a 12-24V SCR system, with a large cap (+10,000µF) could work but, you would need a resistor (high wattage) to limit current so you would not kill the cap(s) and one to charge the cap(s).

@vod8750, come on, its a camera flash, you don't need industrial HV gloves just for that - unless you have heart problems. :p
And those "aviation switches" or "missile switches" are rated (at least the ones they sell here. Jaycar, DSE etc.) are 12V 20A DC. Have a try anyway.


An ideal blaster unit would have a continuity tester, a engaged light and siren,
with a key to engage and safety pull out disengage "key".

[vod8750]

I meant only to wear the gloves while I was testing the aviation switch since that would be allowing the full charge of the capacitors though it!
The only thing I would be afraid of is if the insulation in the switch would break down at the high voltage! Since the switch is metal that could be quite a shocking experience!!!

Thanks for the advice I will look into it!

[Cobalt.45]

Hey vod! Do you notice anything! Wrong! With your posts, I mean!

[vod8750]

Why? What do you mean? What's wrong?

[inventorgp]

Cobalt.45 is referring to the exclamation marks.

[Chopper]

Just out of curiosity Vod8750, how many caps do you plan to set off simultaneously? The reason I ask is that a simple and effective B.B may be constructed using the guts of a disposable camera. This has been established.

I have a box that uses a 330v, 120uF electrolytic. This box is perfectly adequete for up to 4 caps at a time, more if one allows a greater charge time.

When I say 4 caps, these are the type with a graphite bridge between two strands of IDE HDD cable. (ala BrainFever's style) Each bridge has a DC resistance of somewhere around the 5-10 ohm mark. Sorry for the inprecise figure, however I have no bridges around at the moment to measure.

The energy requirements will obviously be larger for exploding bridgewires made of NiCr or similar. But then again, being improvised work, I'm making the assumption that everything should be adequetly safe and sturdy, yet simple to assemble.

It was in this vane that I constructed a box using

a) HV section of disposable camera.
b) 10A 240V micro-switch
c) Basic slide switch
d) AA cell holder
e) Project box
f) 10m cheap 'n' nasty speaker wire
g) 1 pr aligator clips

The project took about 8 hours from deciding to do it to using it, with the largest portion of the time being split between deciphering the necessary part of the circuit board and packaging it all into something small and neat.

SOMETHING TO REMEMBER IS THAT HEART DEFRIBULATORS(sp?) USE 16J PER SHOT.

Although the fingers are far removed from the heart, this is still worth keeping in mind as a 'fail-safe' upper limit to energy storage.

Please find below an image of said box.


EDIT:
===================================
How To Calculate Energy Stored in a Capacitor
===================================
Joules = Voltage(v)*Voltage(v)*Capacitance(F, not uF!)

e.g (330*330*120)/1000000 = 13.068J

[inventorgp]

Chopper, where have you been? Anyway I did some thing similar for a stun gun. One of them I kept the xenon tube on to discharge it if needed. And the other I cut the board and changed the diode and cap around to make it +DC. FFFF steel wire works for ematches instead of nichrome.

For exploding bridgewire, you could use a microwave oven transformer (MOT), some HV diodes, a large HV cap(10-100µF), a spark gap, and a ignition coil with a triac circuit to trigger the spark gap.

[vod8750]

Chopper, if your box can initiate four caps simultaniously with one capacitor then I should have no problem what-so-ever with ten 47uF capacitors. I dont think I will be needing to initiate more than five caps at once.

I will put it all together tomorrow and do a few tests. I have no picric acid yet to test initiation power though. Does anyone have any ideas on how I can test the power of the box without the use of explosives?

[Chopper]

@ vod8750:
Yup, you should be ok, however with one caveat. As Boomer already pointed out, the circuits in these disposable units are designed in such a way that the components are streatched to their limits. I never made notes, and forget the figures now, but if you increase the capacitance too far, the circuit is not able to charge it to the correct potential. They're already using averything they've got, and as the voltage gets higher, they simply do not have the capacity to pump enough charge in to raise the voltage any more.

As for testing, just make some bridges up and fire them on their own. Try firing above a piece of white paper to observe any deposited soot and/or scorch marks. Both of these and especially the later, are a good indicator of supplied impulse.

Not only that, but just listen to them. A bridge makes quite a 'crack' when fired. All you need is pestle and mortar, table tennis ball, acetone and a graphite artists' pencil from the newsagents. Look for Brainfever's site.

@inventorgp - I've been around. Just haven't felt I've had anything worthy of contribution.

[inventorgp]

His home page (http://www.geocities.com/brainfevert/)

Electric blasting box (http://www.geocities.com/brainfevert/igniterbox.html)

Bridgeless ematch (http://www.geocities.com/brainfevert/ematch.html)

Yes, all links work, well at least at my side.

[SafetyLast]

Your pictures aren't coming up for me inventorgp.
I use a small box that consists of 4 A23 batteries connected in series with a couple spst momentary pushbuttons. It is cheap and simple. It functions reliably with 100ft of 18GA speaker wire and has ample current to set off a couple of caps. My caps use small christmas lights instead of nichrome like a lot of people here use. I really have no need for anything more complicated or powerful, but If I did I might consider building the CDI driver that Bob Iannini describes in More Electronic Gadgets for the Evil Genius It puts out 400V, 30W.

[nbk2000]

SafetyLast, if you're using Firefox, that's why you can't see the pictures.

Use Internet Explorer or some other browser.

I don't know why it (FF) does this sometimes, but that's why I've got the IE Tab extension installed, to handle this problem. :)

[inventorgp]

I've read Bob's book, there are a few mistakes (typo?) in the book tho.
CDI - Capacitor Discharge Ignition?
And I have the same problem with the pics as well. I'm using IE 6.0.2900.2180.xpsp_sp2_gdr.050301-1519

[vod8750]

Chopper, I have five or six disposable cameras that I got from the chemist for free so if I connect all of them in paralell as the charging circuit then that should solve the problem shouldn't it?

And the pictures of the blasting box aren't coming up for me either on Firefox or IE. The rest are fine.

[inventorgp]

If you want to charge a bank of caps quick it'll work but, check the diodes, because most of camera flashes are -330VDC. Switch diodes around if you must. Use a resistor to charge the caps. Look up RC circuit and Time constant.

[Chopper]

vod8750, If you got the circuits for free, then I'd have an experiment by all means. I'd just try hooking them up 1 by 1 though, since these really are a neat circuit. As you've noticed, the pitch changes as the capacitor charges. It's a variable frequency DC-DC convertor circuit. - All in just half a dozen basic components. Half of which are surface mount, 1 is the led and the last two the transformer and the fet. Note that not just any replacement will do.

Being a fet, they work differently to the normal NPN or PNP bipolar variety. They can switch faster and important in this application, they can handle a high reverse-voltage. Operating a fly-back transformer like these induces quite a back-voltage on the switching device. In this instance it is IIRC somewhere as high as 30 or 70v. A normal BC547/548 is dead after about 20 from memory. Anyway, the point is that it's well worth keeping all the parts from any boards since you can't just grab another transistor like this easily from the junk-box.

The trigger capacitor is a very stable high tolerance poly cap. Even the tube itself contains small amounts of tungsten.

Long story short, several circuits may not behave properly when their outputs are connected directly in parallel. As an alternative, the addition of a charge resistor adds time to the charge cycle and lowers the maximum attainable voltage in the caps.

However, about the images I an offer no help. I'm using FF 1.5.0.7 in its default settings. No problem for me to left click or right click the link..

Basically, the image just shows the inside of the box. Size is 8*5*3cm.

[techtwit]

This being only my second post, I'm a little cautious —somehow sense a mod's thumb twitching over the dreaded BFL button, so please bear with me.

My (open) question: If I'm wanting to achieve maximum safety and convenience, and at a reasonable cost, in the practical (mostly agricultural) use of explosives wouldn't it make sense to look in the direction of finding a means to supply enough electrical energy to a not particularly sensitive initiating charge?

In other words, safety and convenience seem more or less inversely proportional to an energetic material's sensitivity; therefore, I want to furnish the energy needed to thoroughly detonate the stable main charge with some combination of less stable initiator/booster + electrical impulse. From what I've researched in this and other related forums, the material combinations that seem most likely to produce an optimal solution are AN + some fuel (which?) that will somewhat increase the sensitivity/detonatability of the main charge and an initiator/booster from a KClO3 + fuel (again, which?) combination that will deliver enough energy to the main charge to reliably detonate it.

Pursuing this train of thought, my question now is: How do I determine — at least in the ballpark, the activation energy of the initiator, and in what time frame does that energy have to be delivered? Specifically, with how many Watts do I have to supply x grams of initiator to achieve the main charge detonation I'm looking for?

If E = activation energy needed in say, Joules per gram of initiator and t = maximum allowable time in secs. that it has to be delivered through the resistance (R in ohms) of the initiator composition, then that gives the minimum power W in Watts that has to be supplied. Watts in turn = volts X amps (V x I) = (V^2) / R (via ohm's law). Since W =E/t, then E x R/t = V^2 or (ER/t)^.5 = Volts needed for a given resistance of the composition between the two electrodes (possibly 2 strips of Al. foil?) Now E = W x t, and also = V x Q/2 (Q = charge in Coulombs) and C (capacitance in farads) = Q/V. Therefore:

If we can find out or guesstimate E per gram and t, then R, V, gms. and C can all be manipulated to get the desired results. I think.

I'd really, truly like any and all correction, feedback and/or thoughts on my thought process that I've laid out so far.

My overall thinking about this is that, discharging a large capacitor @ several thousand volts through my dewicat soft iddoo body (as Tweety would put it) would have the same very predictable and final results — though not as messy — as placing a loaded 10 guage double under my chin and discharging both barrels up through my thick tough head. However, a capacitor-as-energy source can be built, handled and used as predictably and safely as any finely crafted shotgun out there. Its all in the construction and useage proceedures. I don't think the same can be said of detonator caps.

[ElGreen]

Hi, I made a blasting box with 10 pieces of caps (440V with 220mikrofarad). The base charger is a electrical circuit of a flash. It produces 500V. I put it in a yellow Peli case. The battery is a 6V 4,5Ah battery it charges the capacitors pretty fast. The cabel is 50m long, it's a special one cause the base wire in it is made of steel so it's pretty rough.

[techtwit]

ElGreen;
You didn't say if each capacitor was 220 mf.@ 440V. or if the total array was that. What is the total cap. energy (Joules, of course) of your set-up? Have you noticed how very inexpensive — dirt cheap, really — capacitor energy is? Check out http://www.mouser.com/search/Refine.aspx?Ne=254016+1447464&N=1323038%20684043&Ns=P_SField&RefType=Header. It seems that cap. cost for a given cap. type varies roughly with the product of volts X farads; therefore, we can get more cap. "bang for the buck" (as we say in the US) i.e. cap. energy for our money (which is what we're after) if we shop for as high a voltage as possible. (E = V^2 X C/ 2, remember?)

One possible set-up I'm considering is to separate the total system into three parts. Each of these three components would be grounded with electric fence ground rods and connectors. They are:
(1) batteries, arming switch, firing switch, and manually rotated charging switch, which will send pulses of low voltage current via ordinary 3-conductor extension cord, some safe distance to –
(2) a simple homemade step-up (say 10X-15X) transformer (induction coil)/rectifier combination which charges the capacitor array at the appropriate voltage — this should be rather less than the caps'. rated voltage. This array is readied (armed) and discharged (fired) with relay switches remotely controlled from the battery/switch station. (Hence the three conductors — one for the coil and one for each relay.) When fired, the capacitors discharge through the primary coil of a second transformer — about 20X, to furnish a good solid jolt in the 10 kilovolt range, through a single aluminum electric fence wire (housed in a polyethelene insulator tube used for such fencing) to the –
(3) explosive charge about 2 –3 meters away.

It'd probably be a good idea to also take the precaution of setting the cap./coil/relay unit in a shallow hole! — depending on the size of shot being fired, of course. Another very important precaution should be a main safety switch which keeps the secondary coil of the transformer well grounded. This switch would always stay closed until all preparations are complete and the technician is about to go back out to the battery/switch unit (station 1) to fire the shot. The safety switch is closed again as soon as the technician returns to the shot site.

About the relays: The cap. array neg. terminal would be connected to the neg. terminal of the rectifier and in series to the arming relay which toggles between ground via a small resistor — (safe, unenergized position), and the firing relay — (armed, energized position). The firing relay, when energized, simply completes the connection to the primary coil of the 2nd step-up transformer.

All of the above is simply a very sketchy suggestion of a possible system. I know little about electronics which is why this set-up is so simple; nevertheless, I think it might work. Also, I wanted to provide something of an illustration about how device construction and use proceedures can combine into a system which is virtually foolproof — keeping in mind, of course, that nothing is entirely proof against fools. Any ideas anyone?

[Red Beret]

Being low on free time, (and a bit lazy) I purchased one of those car jump start packs to use as a blasting machine. While a little heavy, it fits well in my bag along with a 100m roll of wire. I got it on special for $50. It's rechargable, reliable and has other uses, such as powering small appliances for a short time. It has an adaptor for this, and has a built in light, which I have covered with a red plastic lens, to dim it down a bit. It's good for situation where you won't have to run like hell after the blast, such as fairly deep underground blasting/testing.

I have found undergroud blasting very good for testing, if it's deep enough down, no one will hear the charge, (or recognise it as an explosion) and if you have a misfire you can leave it there without having to go and play EOD man.

[inventorgp]

If you have watched Mythbusters, the EOD guys that helped with some of the myths (dynamite painting, exploding pants etc.) used a rechargeable jump starter as well.

I also do underground blasting.

[ElGreen]

Each capacitor was 220nF@440V. We put together 10 pieces together.
-20 pieces of the capacitor cost 9,8USD
(I'm living in middle-Europe)
Al of the electrical works and solutions are delivered by my friend. I'm just a innovator and the "end-user." :)
We put the electicity into a 1120Peli case, with a special panel frame.
-The Peli case cost 54,62USD.
-I bought a battery 6V, 4,5 Ah. It was 5,4USD.
-I got the charging circuit from a old flash. It can produce 800Volts at least, in 3 seconds, from the this battery.(We haven't tried the end cause 800V far enough for me)
-I use 2 switches. One is the fire switch, with a relay, so it can switch up to 40A.
The other one have 3 positions:OFF, CHARGE,DISCHARGE.
-The charge indicator consist of 10 Leds. We put the end to 500V. When in reaches we put it into the off position.
-I use a special wire as written above.
We fire approx. 3-8pieces of special NC loaded bodies, it means 6-20 Ohm + the resisance of the wires, -which I don't measured it yet. What if we count with 300ohms, it is far overrate.
Each body needs 1,5A to fire.
If I count: Amps=Volt/resistance; it means:500V/20+300=1,56A.
I've count the joule:
The joule is :137,5 Joule

I also do underground blasting for the same reasons. It is a perfect indicator for measuring the blasting power.
And my favourite is the precision rock blasting. Low voice, and without shockwave. It is silent, safe, and enough brisant. In a cave when you have to explore some parts and some rocksare in your way you have to do something....:)

[augoldminer]

K.I.S.S. A BQQ ignitor is small fits in your pocket. will fire 15 electric caps.

For homemade caps a 115 volt 60 amp inverter that you plug in to a car lighter works for most types. Use a small motorcycle battery for power source.

[ElGreen]

We use often the normal 220V mains voltage for detonating. Yesterday we used it for 14 electrical ignitor that means at least 30 ohms. And there wasn't any problem.

But, of course you have to be carefull.

Peace for everyone.

[Raffikki]

The exact same dam thing happened to me!It also charged up and it made a short somewhere.I tried 2 fix it.Half a teaspoon of AP did the job!

++++++++++

The number 2 is not a substitute for the word to. This is not a chatroom. NBK

[ElGreen]

I tried many bridgewires with my blasting box, The best was a acoustic guitar string (I think "A", but not sure). It consist of two parts. A thick inner wire and a tiny one witch is reeled onto the thick. If I charge up to 650 V, the thick wire (I use approx: 0,5cm) detonates with a loud bang and gives huge sparks. The smaller one is not so loud but it produces plenty of sparks, and melted "steel balls".
I found it very usable and perfect to detonate the primer mixture in detonators. I offers higher detonation velocity.

[Altroman]

Some capacitor info: The photoflash capacitors used in nearly all camera flash circuits are specifically designed for use in pulse discharge applications. That means they have much thicker electrodes and lead wires than ordinary decoupling capacitors designed for radios and other hobby uses. If you look closely, you will see that they are actually lableled "photoflash" or "photo" capacitors. Another interesting feature is that they are actually designed to "leak" charge when their working voltage is exceeded. This protects the capacitor from being overcharged, the flash circuit from damaging itself, and the flashtube from being overdriven when the charging circuit is left on for too long. If you try connecting a camera flash circuit (a flyback inverter) to a non-photoflash capacitor, you may end up damaging the charging circuit or blowing up the capacitor, since nothing will limit the output voltage except diode leakage or transformer breakdown. Granted the energies are nothing like those of laser flash circuits, so the safety risk is minimal. But what's the point of using hobby-grade capacitors when photoflash caps are so readily available.

And yes, you can parallel flash capacitors, but use thick wires to minimize inductive losses (not a concern with SCR switches, though).

About thyristors: Some high-end cameras actually use SCRs to quench the excess energy in the capacitor once enough light has been generated (a form of auto-exposure). The way they get away with it is to use a series inductor to limit the inrush current to a rate that the SCR junction can handle. So long as the current risetime through the junction is slow enough (a few usec or so), the current density rises slwer than the conduction region can establish itself, and the SCR will last for thousands of shots. So if you find an old flash unit with a big coil and SCR in it, you can use it as your series switch. It will be far too slow for firing EBWs, but with a current riseime of a few microseconds to 100 Amps or so, squibs fire in a few milliseconds. This is more than fast enough for sequencing special effects and pyro work.

[deaddwarf]

You'll also want to take voltage drop into consideration, all cables have an impedance per meter rating, the smaller the cable cross sectional area, the higher the resistance, the larger the cable csa the lower the resistance, lower resistance results in lower voltage drop, which in turn results in a higher possible load current delivered to the connected load.

What does all this mean in laymens terms?
- Use the largest cables possible.
- Calculate your safe distance, excessive cable is wasteful and inefficient.
- DO NOT LOOP OR COIL CABLE, this would have the effect of turning your cable into an inductive loop resulting in further inefficiency.