Well, now I've got things back up & running again following "The Crash" I've got the circuits re-documented.
Below is the basic circuit layout for the PPG circuit. It is currently missing the sound player, just showing the pad for the signal line to the sound player.
But then, that's because I've got to create the symbol for the sound player in Eagle...
And that's a pain in the arse.
Still, it'll be added shortly.
Mind you, in the actual PPG body, the board is split into 4 - Power, Processor, Transistors and soundboard.
Otherwise it's not fitting in the body.
Yeah, it's kinda like that
So, without further ado.... Have a board schematic:
It doesn't have the programming pins/connection for the picaxe programmer, but that takes up space and it can work without it - The chip can be programmed either on a breadboard, or the little zif socket doodad I've put together.
Well, the last few days have been a bit less productive than originally planned.
Last Thursday my HDD gave me the finger and crapped out on me.
I MAY have said the odd rude word or two.
Fortunately, I had about 95% of it all backed up. A few things are gone thats a pain in the behind (A lot of 1/300 mini's I'd modeled for one)
And lost about 3 hours work on the current main project - The PPG's for Fall of Light next year.
Still, not a lot to be done about it now.
I've been busily remodeling the things, and it's about at V0.95 with the last few tweaks being printed over the next couple days, though some will be pending any reports from the weekend.
In the meantime, here's a piccy of the 2 current version 0.95 PPG's
And theres already mod's in progress. Mainly around the on/off switch now
And a little bit of 1:300/6mm fantasy goblin troops I've knocked together
They are a crucial
part of the hardware for the emitter/gun circuits… Unless you only
want a couple of meters range.
As previously
mentioned, again there was very little range about WHY the lens
assemblies used works, other than do this and it’ll work.
Which as part of the
learning curve I went more or less the opposite direction with it,
until all the research came together in a blinding “Well of Course
moment!”
Now, the lens
assembly is intended, along with a suitable power output to increase
the range of the Infra red signal/beam, and it’s the ‘how’ that
I had to wrap my head around so I could get a decent combination of
parts for the best results.
So, an LED has
what’s known as the Half-angle/viewing angle/angle of half-intensity. This is basically the area where the beam is
brightest, and the half-angle is about the point where the brightness
of an LED effectively drops to half it’s peak output
For a more detailed
description have a look here or here (Wikipedia links for led and
half angle)
Now in an ideal
world, you want the beams from the LED to be as parallel as possible,
otherwise as the beam spreads out/diverges it effectively looses..
well.. power/brightness. In short, the more the beam spreads out, the
dimmer it seems.
A good example is
this video I dug out from Youtube for a variable focus torch.
So, a perfectly parallel beam is what the lens assembly/barrel is aiming for.
Now, I use an
Infra-red LED with a 7 degree half angle. I had originally tried
led’s with a 15 degree half angle, thinking it would mean that I
would need a shorter ‘barrel’ to get the maximum amount of
max-brightness infra-red to hit the lens.
The complication
comes down to the refraction of the lens. A convex lens can only bend
the light towards parallel so far. So, the closer to parallel the
infra-red rays are at the start the better.
An LED with a 7
degree half angle has a beam/rays that from the start are much closer to parallel
than an LED with a 15 degree half angle.
So, an LED with a 7 degree
half angle is much easier/needs a much less powerful lens than a 15
degree half angle led to focus the rays towards parallel.
So, now following
that wall of text, it’s time for the pictures now.
15 degree half angle emitter
This represents an
LED with a 15 degree half angle. For illustration I’ve given the
lens a 5 degree refraction.
Not so great is it? Certainly not what I would call coherent.
7 degree half angle emitter
Now, Stick in an LED
with a 7 degree half angle, and while you do need a slightly longer
barrel the resulting beam is considerably more parallel or convergent
than the 15 degree half angle emitter.
The other difference
is the size of the spot/beam cross section – The large the size of
the spot, the easier it is to hit the sensor, but the sorter the
range.
So, there is no
right or wrong way to build a lens assembly, it all depends on what
you want the final design to do – a “Shotgun” type prop I would
go for a shorter range with a broad spread, whereas a
pistol-type-prop I’d go for a low(ish) range and reasonably small
spot.
The PPG’s for the Babylon 5 game final
design has a rough range of between 30 and 40 meters (Depending on the
vagaries of electronic components), which for a small pistol design,
with a tiny lens (16mm diameter lens, but due to the housing it is effectiveley 14mm) and 7 degree half angle led is not bad.
I started up Heretik forge, as details on the About page, for the main part to make an Infra-red based combat
system for larp, based on the time tested Worlds of Wonder Lazer-Tag
system from the late 80’s
Why that one?
Simple – it’s the one I’m used to using, and it’s
one that’s been taken apart, examined and replicated a few times, by the
group of SF Larp clubs that has evolved into the UK Lazer Tag Association (UKLTA)
At it’s heart, it’s a fairly simple system that
consists of:
An Emitter (The “Gun”) circuit which emits an Infra-Red
signal consisting of a 57.6kHz signal and an 1800Hz signal modulated
together,
The Receiver(The “Sensor”) that registers a “hit” at a
maximum rate of 1 per second. Once the sensor hit 6 hit’s it would
trigger a siren indicating you were “dead”.
See.. Simple.
Over time, the sensors were modified to enable them
to have extra diodes so they could take hits from 360 degree’s and they
were successfully copied and cloned several times.
The problem is, once microcontrollers were
introduced, it became a lot harder to make the things and the amount of
people making kit shrank until there was essentially just one person
doing it.
And the information on how to build the
microprocessor controlled kit was never released for various reasons,
which was fine.
Up until said person decided they didn’t want to do it
any more.
So, as mentioned previously, I’ve decided to learn
how to build the kit – I’ve a background as a software programmer, so
the code for the microprocessors isn’t much of a challenge, but the
hardware side is.
And I’ve made a few boo-boo’s climbing the learning curve.
Not actually me.....
At present, I’ve got a working basic Gun circuit, and sensor circuit that are compatible with “legacy” kit.
I’m working on the documentation for them so the
information is out there for anyone that wants to use it, as well as
offering pre-programmed microprocessors for those that don’t want to
program the microprocessors, but do want to build
their own circuits.
This will be finalised in September more than
likely as the next round of field-tests and the first field-test for the
sensor will be at the LOTNA game that weekend, courtesy of
Shaun/Starlore
