62 replies to this topic

[PyroCreationZ]

Hi guys, I bet there are some people here who have knowledge about (homemade) firing systems and electricity in general.
I already spoke to cooperman on MSN but he doesn't really seem to know the problem as well (though he helped me a lot! Thx again )
I have bought two sealed lead acid batteries (12V 7Ah) and connected them in series to get 24V.
I also bought self dip igniters from cooperman and succesfully made some (using the pyrogen listed on his old website).
Now the problem is I want to fire up to 5 matches in parallel but just can't seem to get it done.
I tested with 40m of cable (CAT5 FTP) and that did work but when I go further they just won't light... atleast not all of them (up to 3 max.)
Cooperman told me he now uses a system with 24V and he can fire 7 matches in parallel up to 200m.
Can anybody point me in a direction what I am doing wrong?
I measured the voltage on the ends of the wire and I get 24V so that's not the problem however I did try using 50V and even 75V but the results became worse??
Between 24V & 48V seems to be the best results but still I have no clue why I can't light 5 in parallel not even up to 100m.
I also tried 5 in series (without pyrogen) and even those did not perform as they should. They did glow for a second but didn't give the real spark as they should.
Any ideas would be very welcome. I want to use this system for my NYE display but getting worried I won't be able to fix everything in time
Phew.. big pile of text
Thanks in advance on your help!

[CCH Concepts]

sounds like the wire has to much resistance. imagine the wires are like 2 series resisters one before and one after the parallel circuit. there limiting the amount of current that can get tot he IG's, you wont really see this effect by measuring the voltage at the end of the wire, as it wont have an effect until under load.

[mike_au]

Just hooking the wires to the battery and measuring the voltage at the other end won't give you a reliable measurement. A volt meter has a very high resistance so the resistance in your wires will be negligable in comparison and you will get very low voltage drop in the cable. You need to hook up a resistive load similar to your igniters at the far end and measure the voltage across it. As another simple test, tie the two conductors together at one end of the cable and measure the resistance through the whole run, then measure the resistance of your igniters. Using that you can calculate the expected voltage drop and current flow at any part of the circuit.

Poor quality cables would be my first guess. I assume you mean Cat5 UTP (rather than FTP ), is it stranded or solid core? is it good quality cable from a good supplier? Do you have good solid connections at each end?

I haven't used those igniters before, but I think Cat5 would have difficulty carrying enough current to fire 7 of my (wire wrapped) igniters in parallel. Since you have 24V available you might find that series works better (it will also reduce voltage drop in the cable).

[wjames]

are they new batteries ??? i'd be tempted to cycle them prior to use ( as a matter of course ) a slow discharge using a tail light bulb, then a recharge...

[PyroCreationZ]

Thank you for your thoughts so far.
As to answer some questions:
The batteries are brand new (charged).
I do mean FTP At first I used UTP but could only get 7 cues that way.
By using FTP I use all 8 wires for cues and the copper wire (probably a pulling wire in the manufacturing process) I use as my ground.
As far as I know FTP should not give any problems as I've seen others use it as well. Cooperman uses FTP too and hasn't had any probs.
It is solid core wire. Now on the question is it good quality... well because cable costs much I tried searching a cheap supplier.
I bought it from Germany however the plastic around the cables is a bit lighter color tint than I'm used to from FTP so my guess is this might come from China originally.
I really hope it's not the cable as I bought a 500m spool and wouldn't like to throw it away...
I do have solid connections at the ends as I've soldered them and triple checked all connections.
As mike_au says I also doubt you'd be able to fire homemade igniters with those cables but the ones I got from cooper are made in China, they just don't have a pyrogen however it are the professional ones.
Series normally gives better performance however in my case I can't put them in series.
Below is a setup of my system with it's slats:


[firing box]---50m---[slat1]---10m---[slat2]---10m---...[slat5]

It has 16 channels. I have one slat for every channel and the first 4 channels I want to attach 5 slats to fire 5 pieces simultaniously.
All slats have 2 DIN sockets (in & out to next slat) and they're all soldered parallel.
Cooper told me I could solder the incoming 8 wires to the positives and the 8 outgoing to the negative and one plug at the end to close the circuit.
Unfortunatly I have already soldered all my slats and closed them with silicon so they're "moisture proof" but I can't open them.
So that's not an option.

I'll try measuring my wire resistance as mike said.

More thoughts are more then welcome

Edited by PyroCreationZ, 08 December 2009 - 10:03 AM.

[CCH Concepts]

slightly off subject, but would people be interested in firing modules. i had a thought a a module that will run off the current in a firing line and then divert it onto 8 lines. advantage being each line would be feed by a fet which will mean that 1 IG wont effect the other. say one line shorts the others will still fire. i was also looking at the module being programmable so it can have firing sequences.

also i was thinking this could be cleverer, if a module has a multiplex mode, this would mean that one module would feed 8 other power modules with 8 outputs. the result would be 1 cue firing a 256 que sequence.

[pyrotrev]

It might be worth also checking what the ematches are measuring after you've tried to fire them. Ocasionally when using long prallel wired strings I've had an ematch fire but go short-circuit in the process (blob of molten dross?) at the beginning of the line which effectively stops any voltage getting to those further along.

[PyroCreationZ]

Good news guys, the mystery is solved
I can not believe it but it was one of my damn cables!
I tried another cable and now I can fire them all 5 in parallel.
The funny thing was that I tested each cable and measured the correct voltage at the end of the line.
I also checked each wire from the FTP seperatly with the "beep" function of my voltage meter (tells if there's a break in the cable) and eery time it did give me a beep so I thought those cables were ok.
Apparently there must be a bad connection somewhere so that it does transfer the voltage but not the current.
From now on I'll test every cable with a light bulb at the end to ensure the current flows through.
I'm so glad it's fixed now.


I want to thank all of you for giving me hints and such about what the problem could be.
Let this also be a lesson to anyone who builds his own system, test with an actual lightbulb or so.

Thanks guys

[PyroCreationZ]

It might be worth also checking what the ematches are measuring after you've tried to fire them. Ocasionally when using long prallel wired strings I've had an ematch fire but go short-circuit in the process (blob of molten dross?) at the beginning of the line which effectively stops any voltage getting to those further along.

I can imagine that would be quite a b*tch when you're firing a show!
Hope I never get to experience it.

[mike_au]

I do mean FTP

Fair enough, I've only ever heard of UTP and STP (now that I have looked it up I think STP is similar or the same as FTP).
The beep function of most multimeters is fairly rough, on mine it will beep up to about 4-500ohm. If you want to test a cable without using a load, use the resistance function and compare it to the specified ohm/m of the cable (or to another cable of similar length)

are they new batteries ??? i'd be tempted to cycle them prior to use ( as a matter of course ) a slow discharge using a tail light bulb, then a recharge...

Be careful with this, lead acid batteries (even the deep cycle ones used in 4wd and boats) don't like to be fully discharged. I wouldn't take a 12V SLA below about 10V. (Actually, I don't believe that cycling them provides any benefit, so I wouldn't discharge them at all, but if you want to try it, don't take them too low).

CCH: I'm not likely to buy one of the units you mention, but I would be interested in how you would wire a FET so it would prevent a short in one section of cable affecting other parts.

[PyroCreationZ]

Ok, so I'm adding / changing some stuff to my firing system and want you guys to take a look at a piece of my scheme and tell me if there's something missing or wrong.


As mentioned before I have two 12V 7Ah batteries connected in series to get 24V.
The left round circles are two terminals for charging the batteries seperatly with a 12V charger.
Both switches would have 3 positions: on/off/on
The V is a voltage meter.
If battery 1 is being charged, the negative of the charger is connected to the negative of battery 1 but also to the positive of battery 2 and vice versa.
I know when batteries are in series the positive is connected to the negative of the second one but is this ok when it's a charger?
In short... does it make sence what I drawed? Or do I need to add / remove anything (apart from the rest of the system ofcourse )
I think it's ok but just want your opinions to make sure I don't blow up my batteries or anything

Thank you.

Edited by PyroCreationZ, 09 December 2009 - 11:20 PM.

[CCH Concepts]

that looks fine, but you mention the switch being on/off/on can you show how you wiring this, as at the moment you have the meter and the charger connected at all times.

and what might be helpful is to wire the off stage for the meter to in fact measure the 2 batteries 24 v, that what when not in charge mode you will know when to charge. maybe the meter would do well to have a push button aswell as its not something that needs to be connected all the time only when a reading is needed.

[mike_au]

I'm at work at the moment so I can't draw it, but how about instead of the switch moving the charger between the two batteries have it switch them between being in parallel and series.That way you can switch to series for firing or parallel for charging. Most decent chargers will put out more current than a little SLA can take anyway, so it would reduce your charging time.

Edited by mike_au, 10 December 2009 - 01:54 AM.

[PyroCreationZ]

that looks fine, but you mention the switch being on/off/on can you show how you wiring this, as at the moment you have the meter and the charger connected at all times.

and what might be helpful is to wire the off stage for the meter to in fact measure the 2 batteries 24 v, that what when not in charge mode you will know when to charge. maybe the meter would do well to have a push button aswell as its not something that needs to be connected all the time only when a reading is needed.

I would use a switch like this:



The joystick has three positions: left / center / right
If it's put in left position you have connection between the center & right terminal.
If it's put in right position you have connection between the center & left terminal.
If it's put in center position you have no connection.
Ofcourse I would need double pole switches.
This way I would put the switch from the V-meter in center position unless I want to read out one of the battery voltages: right for battery 1, left for battery 2.

But you would suggest to only measure voltage of both batteries (24V) instead of using a switch to read them out seperatly?
I have been thinking about that too but didn't do it because one battery might be more empty then the other and I think this would be misleading when you can only read out voltage of both or am I wrong on this one?
Then again, I also think when they're put in series they are both consumed and one can't lose more energy then the other. Correct?
If that is the case, then I'll do it like you suggest. A push button is in fact a better method as we don't want to read out voltage constantly.

Thanks for your thoughts so far.

[PyroCreationZ]

I'm at work at the moment so I can't draw it, but how about instead of the switch moving the charger between the two batteries have it switch them between being in parallel and series.That way you can switch to series for firing or parallel for charging. Most decent chargers will put out more current than a little SLA can take anyway, so it would reduce your charging time.

I didn't even know you could charge batteries in parallel?
If that IS the case, then yeah I would do it like you suggest for sure
Drawings are welcome. I'll redraw it with the suggestions so far and post it again.
Thanks



EDIT:
Ok, redrew everything and I think it's correct
In the picture the switch is put in parallel position (ready to charge).

Edited by PyroCreationZ, 10 December 2009 - 10:22 AM.