"Handbook of Model Rocketry" 7th ed.. Mistake?

[dr wogz]

Well, jsut got my copy today! Yeah!!

And I'm happily flipping though it (right, who realy works on fridays!! )

And I came across the launch controller wiring diagram on p.91; fig 6-5. I beleive there is a mistake with it. It looks like the circuit is completed (and rocket launched) by just inserting the 'safety key'. Battery terminal to the safety key. Safety key (switch) to the light. The light to the rocket, then finally back to the battery. It look as though the 'launch switch' is somewhat redundant, as it is in parallel with the light.

I understand that the light will have a current and voltage draw on the citrcuit, but dosen't that still leave a certain amoutn of 'juice' to flow to the rocket? And coulnd that be enough to light the igniter?

thoughts? Ideas?

I have desined my own, and have two separate circuits (branched from the safety key) One for the light, the other with the lauch button and rocket..

 

[goose_in_co]

Wogz,

The circuit sounds correct as you have described it.

The current that is required to light the lamp is low, and the lamp drops a large amount of voltage, so that the ignitor will not have enough power applied to it. Once you push the launch button, it shorts out the lamp, applying the full power from the battery to the ignitor, and causing the ignitor to burn, and thus launch the rocket.

What you describe is the continuity circuit, which is the same as the one the infamous Estes Electron Beam launch controller has.

It works great with Estes ignitors, but will not work with some of the more exotic flashbulb type ignition systems.

Goose

 

[dr wogz]

Thanks Goose,

But I still beleive two separate circuits are better, one dedicated to the light, the other dedicated to the rocket. Just seems safer in my opinion!

and as you described, i beleive mine will work for all types, just depends on how big the battery is!

 

[shreadvector]

Not so good, since you will not know if you have continuity or where a fault is located.

You can always do what many "panel" contollers and the Estes Command Control and E2 controller do: Add an extra switch so the continuity light is only activated whn you hit a second momentary switch.

With Estes you must hit that switch and also hit the launch switch to launch. With our club panel, you can test for continuity independent of the firing switch, BUT we do have an arming switch as well as a removeable key switch that makes the entire panel dead (the safety key).

You can't do anuything without the key in and turned. Key can only be removed when in "off" position.


With key in you can check for continuity with the momentary switch (flashbulb safe circuit).

You must flip the arming switch to arm the firing circuit, then the momentary launch switch dumps the entire car battery into the launch leads for any pads which have their switches in the up (active) position. We have 12 switches.

The circuit shown in the handbook is extremely correct, as long as you use the correct light bulb.

Originally posted by Dr Wogz
Thanks Goose,

But I still beleive two separate circuits are better, one dedicated to the light, the other dedicated to the rocket. Just seems safer in my opinion!

and as you described, i beleive mine will work for all types, just depends on how big the battery is!

 

[dr wogz]

Great, thanks again!

this is all that 'learning' stuff I keep hearing about!