more igniter questions

As safe as the 300-800 amps that flows in the starting motor of a typical automobile engine during startup. What the "magneblaster" is doing is using one of the solenoid relays designed for engine-starting service as the switching element in a relay launcher: the coil of this device can be powered by a low-current circuit such as a model rocket "launch controller" or the light-gauge wiring to the keyswitch on a car's dash panel, while the actual firing current flows through a short run of heavy gauge wire through the relay and the igniter... this system will supply very close to full battery voltage even to an igniter that draws several amperes of current.

If you clamped the clips together and then held down the launch button, you could probably cook the wiring... the same thing would happen to your car if you grounded out the starter lead at the motor and then held the keyswitch on "start".

-dave w

Ah, I see. Thanks for filling me in.

I have Pratt's SureFire II, great little launch system. I don't know how many Firstfires or Quickbursts it can reliably set off at once, since I haven't used many of those in multiple firings. But I've done launches with up to 4 Oxrals and/or Daveyfires at once, no problem.

The Magneblaster uses 12v as well. The 200 number was just a (possible) amperage rating, not a voltage.

Holding the clips wouldn't be any different from any other 12v powered system.

No. That's what I originally thought as well from the "discharge coil" comment.

I haven't actually measured the firing current of a FirstFire, but I suspect that they're nowhere near as sensitive as "real" e-matches... my usual recipe for getting big motors lit *now* is a HiRMI/DaveyFire match with a good coating of Igniterman gray pyrogen. I think the original poster was inquiring about firing F21's, though, and I think the throat on those may be too small to fit evan a "mini" e-match with a good coating of dip.

I'm not familiar with the Quickburst igniters... are the firing uurrent ratings published anywhere?

-dave w

Mike, I think some of the confusion here also concerns the relay coil. The coil is not energized before the launch button is pressed and the diode across the coil winding shunts the inductive kick when the launch button is released. From the schematic, I see no other function of the coil than simply activating the relay contacts.

Am I missing something?

Yeah, that seemed to be a bit of an odd way of describing it... once I downloaded the PDF and looked at the schematic it was clear what sort of circuit it actually was.

Hmmm... now an inductive-storage launch system... that _could_ have some potential... if you made a _big_ iron-core coil, with enough turns of heavy wire to draw, say, 5 to 10 amps at 12 volts based on the DC resistance... connect it across a battery, with a closed switch in series, and allow the current to build up, then open the switch suddenly... the coil will develop a high voltage across the open switch as it tries to force the current to keep flowing; this could dump substantial energy into a fairly high-impedance igniter. (This might even be workable with, say, _series_ strings of dipped resistors, dumping enough of a current surge to get them all very hot at the same moment...)

The ignition system in an automobile works in a similar manner, except that there is another winding of wire on the same core as the first or "primary" coil - this "secondary" winding has many times the number of turns as the primary, so as to step up the developed voltage high enough to spark across the gap of a spark-plug. In the automotive case, the "switch that gets opened suddenly" is, of course, the "breaker points" located in the distributor.

-dave w

Now those are some clips I would NOT want to be holding at the wrong time. ;)

I think a capacitive discharge system would be much more viable. The new super-caps can store quite a bit of charge, but I'm not familiar with their internal resistance.

Has anyone used these caps in an airstart or recovery circuit to augment a small battery?

David Weinshenker wrote: the "switch that gets opened suddenly" is, of

Only if you still live in the 70's! :)

snipped-for-privacy@aol.com (Mfreptiles) wrote in news: snipped-for-privacy@mb-m04.aol.com:

True. But there are all sorts of coils and a lot of ways ingenious people have used them. I used to work with a guy that was either very lazy or very smart. He designed a PROM programmer that only used 5v DC. The 28 volts needed to "shoot" the links in the PROM was generated by the EMF in a coil that was switched off when the "write" command was given. This saved having to make some sort of 28 v power supply.

I was trying to keep it simple and not clutter things up with descriptions of that newfangled transistor-and-pickup stuff!

-dave w

The way I figured that it worked, (I'm no electronics expert by any means) was by storing energy, like a capacitor, then releasing it when the launch button is pushed.

To my understanding, the coil is energized before the launch button is pushed, since it does have power to it. It only releases it when it gets the signal from the launch controller.

In any case, I built one....it works better than just a battery. :) I'll be lighting a cluster of 4 K3000's in a few weeks with it. Total installed is M12000.

Mike F.

Scary.

Where?

Brothers, Oregon.

Mike F.

If we are talking about the same thing

then the only coil is in the relay. The coil has a diode across it and the instructions are very specific about not substituting another relay because of that. Which is a good thing since without that diode the coil will generate a very large voltage when the launch control button is released. Maybe even a high enough voltage to break down whatever insulation is between the button and the hand of the user.

With the diode, all of the energy stored in the coils magnetic field gets dumped through the diode and dissipated as heat in the coil and diode.

Mfreptiles wrote: >>Mike, I think some of the confusion here also concerns the relay coil. >>The coil is not energized before the launch button is pressed and the >>diode across the coil winding shunts the inductive kick when the launch >>button is released. From the schematic, I see no other function of the >>coil than simply activating the relay contacts. >>