13 replies to this topic

[superspud]

hello, im into electronics and i am going to make a 7ch electronic ignitor for my devices. looking at stage pyro ignitors, they have 10 spst rocker switches and you arm the channels by pressing them down, then have one fire button that makes it all go at once. i would like to make on like this. no problems building it aestheticaly, but i would like to include a key switch, and a continuety tester on all the channels. this could get extremly complicated becaus of the whole Nichrome burnign out on hardly any current. any idears on how i could do all this?

[Richard H]

Use a suitable resistor to ensure test current is below that which will fire your nichrome?

[Arthur Brown]

Dont start to do the design calculations for the firing circuit til you have standardised the igniter, You need to find the sure no fire current for your igniter before you can design a test circuit, and you need the sure all fire current before you can design the fire circuit. then you must design in safety factors and the ability to correctly test and fire down a 20 to 50+ metre wire

[superspud]

i have been thinking about making a unit that runs on a car battery. this would mean that the burnout wire wouldent need to be so thin, so continuety tests would be alot easier. problem with car battery is that you would need fairly substnatial wires to take the current, and 7 thick cables comming out the back of my box may be abit to much. what i could do would be a remote fireing system. have a car battery and my home made remote device near the fireworks and the fireworks wired in, then controlled from a laptop or something from miles away, using relays... its a thought i suppose....

[alany]

A couple of gel cells would be the way to go. Rechargable, non-spillable, fairly light, plenty of current capability. Use 2 or more to get enough voltage for long line runs.

[RegimentalPyro]

Well this is the firing box I'll be using for my first "all electric" display this year.



<BRAG>28 cues and it works with my homemade ematch and commercial ematch also! It's got a continuity testing circuit, as well as a nice double flashing "armed" indicator [ensures a burntout LED won't imply safe when actually armed.] as well as a keyswitch to get it into "armed" mode. In safe mode the battery is disconnected at both poles [double isolation].</BRAG>

The design was collaborative but my mate did most of the assembly. As you can see he's a bit of a whiz at this sort of thing. Checkout the knitting on the reverse of the plate.



Circuit diagram available on request.

[ChesterPFX]

I would think very carefully about attempting to use remote firing. It only needs a signal on your frequency from somewhere else to leave you standing there, doing a 'frenchman' (you know, shoulders pulled up to ears, palms facing up) whilst saying "but I never even pushed the button, how can it have all gone off in one go??"
If you really want to ensure your continuity will work and not cook off, then buy commercial ignitors. They may be more expensive but there is a reason. They are tested and have published no fire / all fire values.

By the way, RP, nice looking box. What do you have at the ignitor end?

Edited by ChesterPFX, 30 October 2004 - 08:38 PM.

[RegimentalPyro]

By the way, RP, nice looking box. What do you have at the ignitor end?

I've got an ematch design which uses low power resistors [0.125W]. which are v.cheap [0.3p each] . These are inserted into quickmatch so that the resistor lies against the quickmatch core. They pop nicely when you put 36v down them, and I can easily calculate the fire/no-fire current.

[alany]

Related to the topic, I finally got bridgeless e-matches to work today:

http://www.vk2zay.ne...vice.php?id=182

Edited by alany, 31 October 2004 - 12:50 PM.

[Matt]

Related to the topic, I finally got bridgeless e-matches to work today:

http://www.vk2zay.ne...vice.php?id=182

Where did you get that Mg from? you sneaky bugger

[alany]

I ball milled Magnesium turnings with aluminia triangles for about a week.

The turnings themselves came from eBay yonks ago.

[burningbush]

hello, im into electronics and i am going to make a 7ch electronic ignitor for my devices. looking at stage pyro ignitors, they have 10 spst rocker switches and you arm the channels by pressing them down, then have one fire button that makes it all go at once. i would like to make on like this. no problems building it aestheticaly, but i would like to include a key switch, and a continuety tester on all the channels. this could get extremly complicated becaus of the whole Nichrome burnign out on hardly any current. any idears on how i could do all this?

You build a bridge ciruit that mesures resistance" all cmos off course "that way no current goes through wires when checking continuity.http://www.ukrocketry.co.uk/forum/style_images/1/folder_post_icons/icon10.gif

[alany]

The e-match resistance is typically the same order of magnitude as the wiring, in practice it is very difficult to tell the difference between a short at the match-end and a correctly wired up shoot circuit. It gets easier with a few matches in series. I guess you could calibrate it based on a dead short at the rail for a baseline and anything higher is an match?

[Andrew]

hello, im into electronics and i am going to make a 7ch electronic ignitor for my devices. looking at stage pyro ignitors, they have 10 spst rocker switches and you arm the channels by pressing them down, then have one fire button that makes it all go at once. i would like to make on like this. no problems building it aestheticaly, but i would like to include a key switch, and a continuety tester on all the channels. this could get extremly complicated becaus of the whole Nichrome burnign out on hardly any current. any idears on how i could do all this?

Hi you mentioned a continuity tester for all channels. A very simple way to do this is to use a high r resistor in parallel with the switch, or switching mechanism, and a buffer/inverter/op-amp/logic gate or something similar. the output of the "things before" can then be used to drive an LED or something. a 1Mohm resistor for example would only allow a 12 micro amp current to flow, No ematch is going to blow on that. If you want a circuit diagram I can email you one if you want.

Sorry i cant post a picture at the moment as I do not know how.

hope this helps, although it's not very well explained.

Andrew