After hours of sweaty brows and much wringing of hands………..oh, alright, after a little bit of logical thought (first time for everything huh?)…..I’ve come up with what I think will be my final look at making a circuit to produce the Star Trek photon torpedo firing effect.

I’ve modified my original circuit by adding an extra 556 as a preliminary stage. It produces a fixed width negative pulse which in turn triggers the original circuit to produce a rising voltage to the selected led followed by a brief higher pulse (you can see the effect on the previously posted video).

The additional circuitry sidesteps the problem of latching up the monostables in the original circuit by making it impossible for the triggering pulse to be longer than the firing interval (you what?? Don’t worry ’bout it – it does work!!).

STOP PRESS – Still arsing around with this – I’ll post the final circuit when I’ve finally finalised it (duh!)

Ok, next thing is to get back onto the BOP to try and get that finished – then I can get stuck well and truly into my 1:350 Enterprise for which this circuit was cooked up.

Modified Photon Torpedo Launcher Circuit

OK, here’s the modified version of the photon torpedo circuit. As I’m awake now (subjective observation, but close enough to accurate for now) I beat myself up for not seeing the blindingly obvious before. To solve the led decay speed I’ve simply added a fast diode and suitable resistor to drain the astable timing capacitor. I’ve changed a few of the component identities but basically that’s the only change.

I’d post a video just to prove the effect, but some stoopid dumbass (errr, that’d be me then), shorted one of the transistors and got it blowing smoke rings. Only snag with that is that it doesn’t sorta work anymore. I’ve run out of suitable NPNs, so I’ll post the video when I next get some in. EDIT – now done!

Just realised I’ve not included the component values on the schematic, so here ya go, here are the values I used – feel free to experiment with them, just because they worked for my choice of LED doesn’t mean they’ll suit yours:

R1 – 10K             C1 – 10uF elec               IC1 – NE556N Dual Timer
R2 – 4K7             C2 – 10nF                       Q1 – BC548B (NPN)
R3 – 1K2             C3 – 10nF                       Q2 – BC548B (NPN)
R4 – 10K             C4 – 220uF elec             D1 – 1N4148
R5 – 100R           C5 – 10nF                       LED1 – Red ultrabright
R6 – 1K2             C6 – 10nF                                       (2.5v, 30mA)
R7 – 220R           C7 – 47uF elec              LED2 – Red ultrabright
R8 – 33K                                                                       (2.5v, 30mA)
R9 – 100R
S1 – Push button MOM ON
S2 – SP Changeover

Yaaaawn, ok – as promised, here’s the schematic for the photon torpedo launcher. Its late, I’m tired and for that reason (amongst many others), don’t blame me if it doesn’t work for you – it did for me!!

Photon Torpedo Circuit

STOP PRESS:  The only thing I’m not happy about is that the led can be seen to “ramp down” after the pulse representing the torpedo launch.  I have an idea how to fix that, so we’ll see……..

In preparation for the build of my 1:350 Enterprise, I’ve been playing around with a few electronic circuits to arm the model with.  I say playing, ‘cos if I knew what I was really doing I might prove to be a liability.  So, like I say I came across a “back of a cigarette packet” design for the sort of effect I was after to represent the firing of a photon torpedo.  The original idea was by a guy called Mark Chadwick, but I’ve played around with it (which is probably not to its benefit!).  I took the original sketch of Mark’s and really only substituted some different values and changed the trigger from a flip-flop circuit to a simple switch.  I’ll duplicate the circuit so I can fire from each torpedo launcher independently.  I’ve currently bodged it together on the breadboard to prove the circuit.

The video is my first , ok I lie, it was probably my tenth or more, trial run of the photon torpedo circuit. First trial went ok but I had to play around with different LEDs and timing component values to get the timings closer to what was needed.

Yeah, I know I could probably get a more accurate reproduction of the effect using microcircuits, but I still learning about them.  I haven’t even bought a programmer yet – gimme a chance!!