Firing box issues

[PyroJoe]

My friend and I built a electical ignition system. It uses 4-pair CAT5 networking cable, so we can fire 4 things at a time through one cable. We have it all hooked up, but it takes quite a while to heat up the igniters to the point of ignition. I used one 12v motorcycle battery and it would take about 6 seconds to ignite 1 channel. Then I hooked 2 identical 12v batteries together for 24v. Now it will ignite in about 1.5 seconds, unless you are firing more than one thing at a time.

 

Our field cable is around 60 feet long. I am very surprised how resistant cable will get when it is that long! I didn't expect it to be that delayed. If I hook one of my ignitors to one 12v battery with a couple feet of wire it will pop instantly. Does anybody have tips on handling long wires like this? Im thinking about making the "power" box about 15 feet away from whatever we are firing, then control the power box from the control box which will be 60feet away. That way we don't have to send so much power through such a long cord. Has anyone tried this?

[joe609]

You just have to make sure that the 60 feet of wire is thick in comparison to the element that means low resistance in the the wires giving you more power at the high resitance element and it should heat up faster.

[hst45]

Pyrojoe, i built an electronic firing box a couple of years ago. I used tthn (stranded) wire salvaged from a jobsite, and ran 50 feet on each firing lead if memory serves me correctly, and i experienced the same problem.

 

i initially used a 14.4 DeWalt battery for the power source. i'd short out one of my home made igniters across the battery terminals and it blew immediatly. Hook an igniter from the same batch to the end of the firing cable, and maybe, MAYBE it would fire after 5 or 6 seconds.

 

it was an easy fix though; i upped the voltage. i hooked up another 14.4 battery in series and the problem ended.

 

i think you'll find that you can use smaller batteries than the motorcycle batteries, too. As you know, you don't need high amps., you need high volts. i just used the DeWalt batterries because i've got them around (i'm in construction), but you might even be able to hook four or five 9 volt transistor batteries in series. That sould give you the amperege you need, and be a lot easier than toting the motorcycle batteries around.

 

Putting a power booster (transformer) at the end of the circuit is potentially feasible, but I think that might be over-engeneering. You would have to have a way to switch to the proper igniter AFTER the booster (near the igniter), or have a seperate booster on each line. Too complicated for me!

[ADP9]

Simply speaking I think without having to fool with the voltage one should just use a larger gauge wire. Cat 5 wires are very small and thus resist large amounts of electricity in comparison to your ignitor, same as what Joe609 said. However if you like your setup then up the volts.

 

One thing though, I thought it was the amperage (current) that was responsible for the heat up of the element, not the volts??

[PyroJoe]

The higher the voltage the faster the igniters will pop. If you have high amp's your battery will last much longer though. A good way to visualize amps and volts is a water tank with a nozzle on the bottom. The level of water inside the tank is the amperage and the voltage is the size of the nozzle letting the water out. The more water in the tank the longer the stream of water will last.

 

I really like the ease of using the cat5 cable, but maybe we will move to a larger gauge and see if it helps.

[brainfever]

I had the same problem with my experimental setup before I actually built my igniter box.

 

I worked around the problem using 24V coming from 4 6V lantern batteries instead of 12V coming from the small lab power supply in my shed.

 

I use double network cable (2 times 4 pairs = 16 wires which I use for 50 outputs) with 15 meters of cable.

Detonators with double salts and graphite paste dipped igniters give me an instantaneous report when a button is pushed.

 

Pictures and video in the post below.

[brainfever]

Video of iBox with 50 outputs, cap charge and dicharge.

 

Front view

 

Rear view

[ADP9]

Thanks an amazing box did you constuct it yourself? What kind of resources are needed to construct such a box. I'm really interested in possible constructing one if possible.

[brainfever]

It is made by me and my gf's father.

He provided some of the materials and experience, I tought up the schematic and put most of the thing together.

 

What you need:

-A box to mount everything in and on.

-4 6V lantern batteries in series as power supply.

-5 meters 1,5 mm² wire for internal wiring.

-xx meters of 8 pair cable for external wiring.

-Mountable Volt meter to indicate battery freshness.

-2 16 pins connector (male and female) to mount on the box and on your cable.

-A capacitator to provide the peak currents (shouldn't be too big).

-11 push buttons (10 positives + 1 discharge cap).

-1 key switch (safety!).

-1 6-choice switch (0-1-2-3-4-5 => OFF and 5 negatives).

-A connector rail.

-Time to build it.

[cplmac]

My brother and I built two firing panels over the last three years. One 300 shot swithable ground scratchboard and one 400 shot swithable ground pushbutton. Both boxes will fire 10 squibs in series from 500 feet through 24 guage 50 conductor telecom cable with 12 or 24 volts. We use either Davey Fire or Oxrall squibs. We never had the delayed ignition problem you described, but we did have a problem with circuits backtracing through grounds and firing off unintended cues. We solved this by soldering in diodes on every cue. We also have test circuits built in to both panels. Our rails and relay boxes in the field are plastic and aluminum which we had to special order. Here are a handful of pics. We use our system for a handful of shows every year so it isn't that clean anymore. This winter we are building 10 25 shot series rails that will daisy chain together. This is a solution to the ridiculous amount of wire we go through every time we fire wall shots. We went through 2.5 miles of wire for our wall shots alone this year and we figure we can save about $400 a show on lead wire. Edited September 4, 2006 by cplmac

[cplmac]

I just removed the picture because it was way to big for the screen. What resolution should I resize my pictures to so they are not obnoxious and visible completely on the screen?

[Mumbles]

The standard 600x400 should be just fine. Uploading to a host and linking to it is also an option.

[cplmac]

Okay gonna try again here.

http://images.kodakgallery.com/photos2260/3/35/93/73/86/0/86739335311_0_ALB.jpg

http://images.kodakgallery.com/photos2260/3/35/92/83/97/0/97839235311_0_ALB.jpg

http://images.kodakgallery.com/photos2260/3/35/92/83/28/0/28839235311_0_ALB.jpg

http://images.kodakgallery.com/photos2260/3/35/92/83/48/0/48839235311_0_ALB.jpg

http://images.kodakgallery.com/photos2260/3/35/92/83/68/0/68839235311_0_ALB.jpg

We made 4 of the ugly little 25 shot boxes, 4 of the slightly less ugly 50 shot boxes and 16 of the nice 25 shot aluminum rails.

[ADP9]

Thanks for the info brainfever... sounds like a weekend project ha

[brainfever]

Yeah, it was definatly a wekend work, but was spread into 2 weekend due to huge sleep-in times

 

Those pictures don't show up for me cplmac, can you check it out and see what the problem is?

[Mumbles]

I'll look through the settings. It seems like there is something wrong. There shouldn't be any problems with what he is doing codewise.

 

http://images.kodakgallery.com/photos2260/3/35/93/73/86/0/86739335311_0_ALB.jpg

 

 

[edit] Hmmm, I dunno, worked for me.

 

[edit2] Even weirder. When I posted mine, his showed up.

[brainfever]

Well I see neither ...

 

Any chance they show if I try to post an image?

 

EDIT: I tried and firefox attempted to load something on kodakgallery. When checking the page source if found the url and tried it seperatly but the server timed out, so perhaps it's not a forum error?

[cplmac]

I can see mine and Mumbles. I'll just post the URL's.

http://images.kodakgallery.com/photos2260/...35311_0_ALB.jpg

http://images.kodakgallery.com/photos2260/...35311_0_ALB.jpg

http://images.kodakgallery.com/photos2260/...35311_0_ALB.jpg

http://images.kodakgallery.com/photos2260/...35311_0_ALB.jpg

http://images.kodakgallery.com/photos2260/...35311_0_ALB.jpg

Hopefully this works for you.

[Rogue Chemist]

I could not see the above and now I get forbidden errors.

[brainfever]

Click the links, and then, after the forbidden stuff has loaded, reload the page.

This procedure shows the pictures for me ...

 

Looking very nice btw, are they practical in use?

 

I thought about a small optional lightbulb on my ibox for use in the dark, but decided not to because I can "feel" where I am enough.

Is that a problem for you during a show?

 

EDIT: now I see the pictures in the thread aswell. They could stand to be a bit bigger btw ... I usually take 800x600.

[cplmac]

The pictures themselves are 4 megapixels. I think they get resized automatically by Ofoto. I uploaked the picture exactly as it came off my camera. Anyways, yes they are practical in use in as much as we use them to shoot shows. Our own private show runs a little over 15K and takes up a little over 650 cues. Our squib count was 950 because we fired off a lot of wall shots and multiple cakes. The only thing that is not really practical is all the lead wire we use. This year we ran through 17,000 feet of it. Wire is much more expensive this year than it has been in the past. I have 16 more blank 25 shot aluminum rails and I'm going to wire them up in series so we can run wall fronts without all that spaghetti bowl lead wire. The picture below is where all the wall shot wires were run to.

http://images.kodakgallery.com/photos2389/3/36/1/43/96/0/96430136311_0_ALB.jpg

 

I see what you mean about the picture size, they compressed the file to 10% of it's original size. The dots next to all the cues on the firing panels are the LED's we use for the test circuits. The oak firing panel uses blue LED's and the aluminum one uses green and yellow depending on which of the ground circuits is selected. The only addition we will likely make to the panels will be lights and maybe another ground circuit or two.

[brainfever]

Try a different file host for better picture quality and also better accesability:

 

For media files:

http://hozt.net/

http://filelodge.bolt.com/index.php

...

 

For general files:

http://www.rapidupload.com/

http://www.filefactory.com/

http://rapidshare.de/

...

 

 

There are LOADS of places that offer webhosting for free with limited bandwidth or limited file size or limited uptime, but rarely a combination of all 3.

[_Po_]

I got 6 computer back up batteries. They're 24 volt sealed lead acid ones which consist of two 12V cells. Joining the two cells is a 100A fuse. They're the size of a car battery.

 

They can instantly burn up a piece of high resistance wire at the end of 60m (about 200ft) of thin copper wires (less than 1mm).

 

The only down side to this battery is it's size. I'm thinking about making a carry case type thing for it with banana terminals on the outside so I can connect everything easily.

 

I haven't needed to recharge the battery yet because they're such short bursts of energy. With lower A or V (whatever it is) you're wasting a low of the charge in that 6 seconds it's trying to heat up the wire.

[cplmac]

We usually use 2 car batteries in series, but we have used a pair of much smaller motorcycle batteries in series and they worked just fine. I can't speak for the many variations of homemade squibs, but the oxralls and daveyfires we use fire instantly and without a hiccup through 1000' of 28 guage wire. We have also had success firing up to 10 squibs in series through up to 500'.

[brainfever]

I use a 24 Volt source aswell and this should do the trick for most igniters over a serious length of not too thin cable.

 

I'm sure you can calculate the required voltage for your own cable + igniter with a pretty easy formula ...

 

Let's see what get's to play along:

-Resistance of the igniter => measured (let's assume 20 Ohm)

 

-Resistance of the cable = resistance of the cable per meter x length of cable

Let's take an easy to calculate cable of 0,1 Ohm/meter with a length of 100 meters (100 there + 100 back) => 20 Ohms

A handy wire calculator

 

-Power required to glow = current x voltage = ??? this is a tricky one ...

I assume that 5 Watt is a minimum to ignite the most common compositions ... let's take 10.

 

 

Now, assume we want 10W at our igniter. Our total resistance is the cable (20) + the igniter (20) = 40 Ohms. The ratio of the resistance also defines the ratio of the voltage division, so if we would have 40 Volts, we would lose 20 volts over the cable, and get 20 volts over the igniter.

 

U = sqr (P x Rigniter)

U = sqr 200 => 14,2 Volts are needed over the igniter.

 

But we need to calculate the voltage drop over the cable into the equation aswell:

 

Total resistance value

( -------------------------- ) x sqr(PxRi) = the required total voltage.

Ignitor resistance value

 

(40/20) x sqr(10x20) = 28,4 Volts

 

 

I think this should be the place to put a well constructed conclusion, but I'm fresh out of those it seems. Figure it out