Xavien X-FIST question

[MaxQ]

I recently acquired this unit with the intent of having an air-start of outboard motors upon lift off, w/o worrying about getting adequate "G load" to trigger the unit’s air-start function.

What I wanted was the "Pull-Pin" feature that is advertised with this unit.
After reading the manual, I’m not sure I got this feature.
Well, maybe to be clear on this... I got the feature alright, but maybe not in a way that can be used in the manner I envisioned.

Here are quotes from the manual that have me wondering….

P.2 Systems Overview
“ The air-start stage is designed to actuate on “G-Switch” close, this is NOT configurable.
The air-start stage is designed to allow people to air-start a cluster of motors as part of this staging…”

The way this is worded, it leads me to believe that air-starting is available only for staging and not upon initial lift – off.

P.3 Operation Overview
“The G switch used by the X-FIST closes at 2.1 G (+/- 10%) Please keep this in mind for SLOW launches.
If your rocket will have less than 2.1G’s (+/- 10%) of acceleration Please configure your system for pull pin operation.”

Conversely, this statement leads me to believe otherwise – contrary to the previous statement that "airstarting is not configurable", - ie. the whole system could be set up for “pull pin” and not G switch when dealing with low G “Slow” launches…


Here is the link to the manual…
https://www.geocities.com/researchtriangle/lab/6584/X_FiST_MANUAL.pdf

The “X-FiST” is a G-SWITCH / PULL-PIN activated 5 stage pyro / event controller. The unit can be used for air-starting of motors, stage separation, booster seperation, parachute deployment and event staging. The "X-FiST" was designed for ease of use and high current capability with advanced staging rockets in mind.

 

[brianc]

I don't own an X-FiST, but did read the manual at Holiday Inn Express
while researching a purchase...


Substitute the 'Air-start' hook-up for 'Stage-1' in your pull pin scenerio.

The 'air-start' config appears to mimic the XCIC-1 cluster controller.

The Stage-1 config will allow for a pull-pin and delay time before ignition.
See page 5 of the manual.

 

[MaxQ]

I don't own an X-FiST, but did read the manual at Holiday Inn Express
while researching a purchase...


Substitute the 'Air-start' hook-up for 'Stage-1' in your pull pin scenerio.

The 'air-start' config appears to mimic the XCIC-1 cluster controller.

The Stage-1 config will allow for a pull-pin and delay time before ignition.
See page 5 of the manual.

Thanks........I'm still confused as Electronics aren't exactly my forte'


per pg. 5....for ST1 which of the four modes is activated?

- G switch closed
- G switch open
- pull pin open
- G switch close and pull pin open


If I wanted the airstarts to light as soon as possible after lift off..wouldn't I want a "pull pin closed" mode...I don't see one in the four choices.....

Or...I am to understand the pull pin is set open ...and a pull pin is inserted...then when a pull pin is yanked out upon first motion....the circuit closes - and the outboards light?

 

[ben_ullman]

Id be glad to offer some technical assistance. See me at Culpeper.

Ben

 

[brianc]

Or...I am to understand the pull pin is set open ...and a pull pin is inserted...then when a pull pin is yanked out upon first motion....the circuit closes - and the outboards light?

Almost! The circuit is normally open and gets closed when the pull pin switch
is inserted. Think of it as a length of wire connected to the electronics. When
the rocket lifts off, the wire breaks (or opens) the circuit (thus the BREAK WIRE nomenclature).

Set your trigger modes with the MA-MB switches according to the table
on page 5. In your desired scenerio, you'd use:
PULL-PIN OPEN ( PP-O ) M-A = OFF, M-B = ON
If you wanted the extra assurance of liftoff (not, just the pin falling out in the breeze), then use:
PULL-PIN OPEN & G-SWITCH CLOSE (PP-O / GS-C) M-A = ON, M-B = ON
(but note the caution of slow liftoffs that may not reach the 2.1G minimum)

HTH!

 

[MaxQ]

Almost! The circuit is normally open and gets closed when the pull pin switch
is inserted. Think of it as a length of wire connected to the electronics. When
the rocket lifts off, the wire breaks (or opens) the circuit (thus the BREAK WIRE nomenclature).

Set your trigger modes with the MA-MB switches according to the table
on page 5. In your desired scenerio, you'd use:
PULL-PIN OPEN ( PP-O ) M-A = OFF, M-B = ON
If you wanted the extra assurance of liftoff (not, just the pin falling out in the breeze), then use:
PULL-PIN OPEN & G-SWITCH CLOSE (PP-O / GS-C) M-A = ON, M-B = ON
(but note the caution of slow liftoffs that may not reach the 2.1G minimum)

HTH!

<The circuit is normally open and gets closed when the pull pin switch
is inserted.>

Well, maybe I'm not understanding "circuit talk" as it relates to the pull pin concept...
In electronics "parlance"...if the circuit gets "closed" when a pull pin is inserted...wouldn't that fire the outboards in my face?

or...maybe it doesn't.....

Conversely...if inserting the pull pin "closes" the circuit, wouldn't extraction of the pull pin on lift off...break or "open" the circuit? ...thereby not allowing the outboards to fire?

per definitions..."open circuit, closed circuit":

"Any circuit which is not complete is considered an open circuit. A complete circuit which is not performing any actual work can still be a closed circuit. For example, a circuit connected to a dead battery may not perform any work, but it is still a closed circuit."

"A circuit is considered to be closed when electricity flows from an energy source to the desired endpoint of the circuit. The open status of the circuit doesn't depend on how it became unclosed, so circuits which are manually disconnected and circuits which have blown fuses, faulty wiring or missing components are all considered open circuits."

 

[sylvie369]

The pull pin isn't wired directly to the output circuits. That little black square chip on the board is a microprocessor - a computer. The pull pin is wired into that, as are the outputs, and the computer can be programmed to make a decision to fire when the pull pin is opened. That's what you're doing when you set those DIP switches: changing the way the computer makes a decision. The computer decides when to close the circuit to the outputs, and in this case, it _closes_ the circuit between the battery and the output when it detects that the pull pin circuit has been _open_ for a half second.

With the pull pin settings it'll be very easy for you to test this on the ground, and you should definitely do some tests until you're confident both that you understand the system and that it works as you expect it to work. Xavien even makes a little test kit that includes a pair of LEDs with resistors wired to one leg that you can attach to the outputs to see if they're firing (it's a little tricky to use them, though, as unlike ematches, it matters which way you put them into the output terminals).

They could just as easily have added a "pull pin closed" trigger, so that it fired the pyros after it detected that the pull pin had been closed for a half second. But for that to be useful, you'd have to rig up some kind of mechanical system for closing the pull pin when the rocket started moving. Imagine what you'd have to do to accomplish that...and then notice that it's exactly what the "g-switch closed" trigger already does. In essence, there IS a "pull pin closed" mode: it's the g switch.

If for some bizarre reason you ever needed a non-g switch "pull pin closed" trigger I'm fairly sure that you could desolder the g switch from the board and use the two holes left as inputs from the pull pin (and set the DIP switches to "g switch closed" mode). But that's not something you're likely to ever need, which is why they didn't make it an option.

 

[MaxQ]

The pull pin isn't wired directly to the output circuits. That little black square chip on the board is a microprocessor - a computer. The pull pin is wired into that, as are the outputs, and the computer can be programmed to make a decision to fire when the pull pin is opened. That's what you're doing when you set those DIP switches: changing the way the computer makes a decision. The computer decides when to close the circuit to the outputs, and in this case, it _closes_ the circuit between the battery and the output when it detects that the pull pin circuit has been _open_ for a half second.

With the pull pin settings it'll be very easy for you to test this on the ground, and you should definitely do some tests until you're confident both that you understand the system and that it works as you expect it to work. Xavien even makes a little test kit that includes a pair of LEDs with resistors wired to one leg that you can attach to the outputs to see if they're firing (it's a little tricky to use them, though, as unlike ematches, it matters which way you put them into the output terminals).

They could just as easily have added a "pull pin closed" trigger, so that it fired the pyros after it detected that the pull pin had been closed for a half second. But for that to be useful, you'd have to rig up some kind of mechanical system for closing the pull pin when the rocket started moving. Imagine what you'd have to do to accomplish that...and then notice that it's exactly what the "g-switch closed" trigger already does. In essence, there IS a "pull pin closed" mode: it's the g switch.

If for some bizarre reason you ever needed a non-g switch "pull pin closed" trigger I'm fairly sure that you could desolder the g switch from the board and use the two holes left as inputs from the pull pin (and set the DIP switches to "g switch closed" mode). But that's not something you're likely to ever need, which is why they didn't make it an option.

Thank You for the detailed explanation.