Suzette Posted July 4, 2009 Share Posted July 4, 2009 Hi,I need to wire some Le Maitre Ice Fountains in series and I can't get my brain to work out how to do it! Imagine a square 20' x 20' with 8 pyros evenly spaced - 2 on each side - numbered 1 to 8 around the square.I would like to wire all the odd numbered pyros together and all the even numbered pyros together. I know I can wire them in series to save on cable but can't think how to do it.... A diagram would be good if anyone is able please! Other info - it's a 6-way ProstageII battery powered controller and to answer all the other questions ... YES I am over 18. YES I do know what I'm doing with pyros. YES I have done a RA. YES I will be safe. YES I have been on Lincoln's pyro safety course. I normally wire in parallel as usually only firing 1 effect at a time for panto etc. but would like to save on the cable run on this one if I can. Thanks Link to comment Share on other sites More sharing options...
Brian Posted July 4, 2009 Share Posted July 4, 2009 Something like this?... ...start at your furthest device and connect that to the end of your two-core; run the cable back to the next device in that circuit and carefully snip into just one core of the two-core, connect the device at that point; repeat until you've got your four even (or odd) devices connected. Repeat for the second circuit. Link to comment Share on other sites More sharing options...
Ynot Posted July 4, 2009 Share Posted July 4, 2009 PM Sent. Though Brian was a couple of minutes ahead of me.:) Link to comment Share on other sites More sharing options...
Suzette Posted July 4, 2009 Author Share Posted July 4, 2009 That's it - thanks -- I was starting at the first pyro in my wiring and wondering where to go with it ... I blame the hot weather for non-functioning brain!!CheersThanks also Ynot - Link to comment Share on other sites More sharing options...
boatman Posted July 4, 2009 Share Posted July 4, 2009 I'm not pyro trained, but wiring in parallel or series is not going to make any difference to the amount of cable you need. Personally I would connect them in parallel which guarantees that all will fire. With a series connection if one fires early the circuit will open and the rest may not fire. See the picture below: http://img.villagephotos.com/p/2006-5/1185528/SeriesParallel.jpg E2A: Sorry too slow in drawing the picture. Link to comment Share on other sites More sharing options...
Brian Posted July 4, 2009 Share Posted July 4, 2009 ...I would connect them in parallel which guarantees that all will fire. ... There are a number of very good reasons to wire in series.... 1) It makes it easier to test. Igniters have a nominal resistance of 1.6 Ohms. Wired in series it is very easy to make a measurement of your overall resistance, with an allowance for your wire, and to know that everything is OK. In your 2nd drawing, if we had 10m of cable, I'd expect to see ( 4*1.6) Ohms for the igniters and around 2 Ohms for cable and connections. If I see something at around 8.4 Ohms I know I have a good circuit. If we take your parallel example, with the igniters at equal spacings, the expected result for a good circuit would be 1.2 Ohms, if the third igniter along was o/c the faulty reading would be 1.27 Ohms - nowhere near enough difference to make a judgement. 2) It needs less current. Igniters need around 0.5 Amps to fire (it's a lot more complicated than that in real life but close enough for this). In series we only need a total of 0.5 amps. Ok, we need more volts but volts are easy. In parallel we'd need 2 Amps. On big shows we often fire 40 or so devices at a time. In parallel we'd need 20A. In series we need just 0.5 Amps at 40 volts or so. The latter is much easier to handle. 3) In a parallel circuit, depending on cable arrangements, it is more than likely that if you have a short circuit then every device downstream of the short will fail to fire. In a series arrangement with a short then only the shorted device will fail. Link to comment Share on other sites More sharing options...
Ynot Posted July 4, 2009 Share Posted July 4, 2009 3) In a parallel circuit, depending on cable arrangements, it is more than likely that if you have a short circuit then every device downstream of the short will fail to fire.Not wishing to be pedantic, but surely with a short circuit across ANY of the devices would mean a short circuit on ALL devices for a parallel circuit...?Not just those downstream.... Link to comment Share on other sites More sharing options...
osal Posted July 4, 2009 Share Posted July 4, 2009 wiring in parallel or series is not going to make any difference to the amount of cable you need. I normally wire in parallel as usually only firing 1 effect at a time for panto etc. but would like to save on the cable run on this one if I can I think Suzette means that normally it would be wired up each firing pod into a separate switch not parallel like you pictured Link to comment Share on other sites More sharing options...
Seano Posted July 4, 2009 Share Posted July 4, 2009 Not wishing to be pedantic, but surely with a short circuit across ANY of the devices would mean a short circuit on ALL devices for a parallel circuit...?Not just those downstream.... That would be true if the resistance of the cable were negligible compared to the resistance of the ignitors. Link to comment Share on other sites More sharing options...
boatman Posted July 4, 2009 Share Posted July 4, 2009 Thanks Brian, lot's of useful information there. Just out of interest, how do you get 40V from a battery operated pod or do you use one with an external power supply? Link to comment Share on other sites More sharing options...
Suzette Posted July 4, 2009 Author Share Posted July 4, 2009 Hi,Thanks for for all the info ... yes I do mean that I normally wire one effect via one cable to one channel on the controller, sorry saying I wire in parallel was confusing. Brian - I assume that 4 small ice fountains will be OK firing from the 9v batttery in my controller?? (Prostage II 6-way battery powered unit) Thanks to everyone that has helped -- could this info be put into the BR wiki? Link to comment Share on other sites More sharing options...
smalljoshua Posted July 4, 2009 Share Posted July 4, 2009 Well, if each one has a resistance of 1.6R and needs a current of 0.5A then each will only need 0.8v Across it. 4 In Series would need 3.2v so you should be fine with doing that. Josh Link to comment Share on other sites More sharing options...
Ynot Posted July 4, 2009 Share Posted July 4, 2009 Not wishing to be pedantic, but surely with a short circuit across ANY of the devices would mean a short circuit on ALL devices for a parallel circuit...?Not just those downstream.... That would be true if the resistance of the cable were negligible compared to the resistance of the ignitors.Quite so - but considering that in most theatre applications I'd say the wiring resistance between each device would be negligible, as stage pyro wired this way would have those devices fairly close, then in the vast majority of cases a short would disable ALL the effects. The longest (and thus highest resistance) wiring will be from the controller to the first device, meaning that the difference between a short on the first or last of a string of parallel devices will be virtually nil. Link to comment Share on other sites More sharing options...
Brian Posted July 6, 2009 Share Posted July 6, 2009 Just out of interest, how do you get 40V from a battery operated pod or do you use one with an external power supply?Some battery powered units have a DC/DC converter in them to step up the voltage. The current Le Maitre battery units have twin 9v batteries to give a bit more oompf. For long cable runs/large numbers of igniters we use a firing unit which takes in 24v and steps it up to around 400v. Brian - I assume that 4 small ice fountains will be OK firing from the 9v batttery in my controller?? (Prostage II 6-way battery powered unit)Yep, as Josh calculates below it'll work fine. I tend to work on 1 volt per igniter. Well, if each one has a resistance of 1.6R and needs a current of 0.5A then each will only need 0.8v Across it. 4 In Series would need 3.2v so you should be fine with doing that. .... I'd say the wiring resistance between each device would be negligible, as stage pyro wired this way would have those devices fairly close...Hmmmmmmmmmmm (extra 'm's to get around copyright), two-core bell wire runs at 10 Ohms per 100m. With igniters being 1.6 Ohms nominally it means that with just 16m of cable your cable has the same resistance as your igniter. It's not that difficult to have a significant cable resistance. The other issue is the ratio of cable resistances. It's probably not that uncommon to have the cable resistance to your first device(s) at least as large as that to your furthest device(s) which can cause problems with a short somewhere. It'll all a bit complicated to work out especially when you start to figure in the finite current delivery capabilities of your firing unit. Simplest just to wire in series. Link to comment Share on other sites More sharing options...
Ynot Posted July 6, 2009 Share Posted July 6, 2009 .... I'd say the wiring resistance between each device would be negligible, as stage pyro wired this way would have those devices fairly close...Hmmmmmmmmmmm (extra 'm's to get around copyright), Sorry Brian - you don't get away THAT easily - I'll be collecting royalties in a fortnight...! B-) ....two-core bell wire runs at 10 Ohms per 100m. With igniters being 1.6 Ohms nominally it means that with just 16m of cable your cable has the same resistance as your igniter. It's not that difficult to have a significant cable resistance.Ah, but my point is that as I see it, effects that are fired together tend to be fairly close - and even in arena shows, that's still not going to be huge lengths of cable between devices. Certainly not 16m in between, I'd say.So my point still stands - on the majority of installs, with a parallel setup, a short across one device will affect downstream devices in pretty much the same way as upstream. Longer connecting cables MAY refute that statement but I suspect unlikely.(And most of our pyro cable is a bit beefier than bell wire, so lower resistance anyway)Simplest just to wire in series.Indubitably!:) Link to comment Share on other sites More sharing options...
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