Updated PPG Plans

Well,

Updated PPG documantion can be found HERE - Changes basically amount to cleaning up some spelling, adding a contents and adding a layout for vero/stripboard as a veroboard layout is easier to make as no etching is required.


Ady

Future plans

Well, things are coming along at the moment here at Heretik Forge.

The PPG design has had it’s final field test, and somewhat surprised everyone (and proven I can’t shoot for toffee).
The basic sensors have again been field tested and production is about to ramp up for the game next year.

So thoughts have quite naturally started working on what next?

Currently I’m thinking along the lines of:

• A Standardized circuit including an ammunition indicator light and reload switch – The PPG circuits were only ever a temporary design for a very specific body so a number of compromises were made. So a “Standard” circuit design with more powerful output and running off of 7.2 or 9V (6 rechargable Ni-cads or 6 alkaline batteries) is in the prototype stage – there will need to be 2 versions, as currently if you connect the 7.2V circuit to a 9V power supply everything will work, but it would blow the emitter – Current plan is to differentiate the designs via the battery connector – Tamiya connector for 7.2V and standard battery snaps for the 9v (pics needed)

• Verostrip/Veroboard layouts for everything – This is to go alongside the etched layouts, so that if someone wants to make a circuit they can go with whichever method they are most familiar and/or comfortable with.

• Pre-focused LED/Lens assembly – 16mm, 20mm 30mm and 40mm lens/barrel assemblies this along with pre-programmed chips I can see making it a little easier – an etsy store might be the best route to go for these – This could then be expanded to include pro etched boards/components in a kit package, adaptors for nerf bosied and all sorts of things.

• Variant circuits that have different output signals for sound )Simple high/low trigger) as I know there are some out there that are interested in using repurposed Toy sound boards.

• Variant sound modules – I know there are audio modules that are basically identical to the one sI ‘m currently using but use flash memory rather than microSDcard which would given another option for audio on circuits.

• Data signals for more advanced functions/capabilities

More advanced circuits/signals are tricky. I know if I ask I’ll get the DoT* information for the Data-over-Tag system.

But at the same time, I haven’t asked for it, and I won’t ask for it either.

I know the creator of DoT is very careful with who he shares the information with for reasons of his own:
[Quote]
I did refuse to give someone any info, and that’s because I didn’t trust them, still don’t and never will. Requests were treated on a case by case basis.
[Endquote]

As the quote from the comments on here shows, one of which  is that he does not want some people to have access to the information. Fair enough, he developed it so it's up to him what he does with it. 😊

I on the other hand plan to make everything open source/creative commons and available, which would mean making the DoT code and protocols open source – but as they are not mine, that’s not a decision that’s up to me.

So, I’m left with developing a data signal protocol myself.

Which also means making enough kit to potentially cover everyone on a game, which is a little daunting, but hey... I'm up for a challenge :)

I’ve some ideas that are still theoretical at the moment as I’ve been working on the higher priority stuff for the game, but as the signal I’ve in mind is based on a modified ethernet type signal I think it’s just a case of sitting down and doing the grunt work to get it going.

The signal itself I’m seeing as a 60ms WoW hit signal** followed by 3-4 iterations of the serial data.

In the sensor, when it gets a WoW signal it reads that in for 50-60ms, then reads in any further data into memory for x period of time (so it times out if it’s just a “standard” WoW or DoT signal)– Provided it is a Standard WoW signal, it then goes through the information read into memory looking for a specific start character, acts on the data after the start character to an end character.

The 60ms length of the WoW pulse, and the 3-4 iterations is to give a little leeway to the signal, so it does not need to be as extremely rigidly controlled - For example a system that uses a pulse width modulated signal at frequency x needs to be quite carefully controlled, timed and constructed by the code in the microprocessor.

From my research, I think the way I’m thinking of the signal would enable the output code on the processor and the input code on the processor to be built from existing libraries (Pulse width signal generation and serial data transmission), making it a little simpler to migrate across different hardware platforms (Picaxe, pic, Arduino raspberry pi etc etc), which is in line with one of the basic ideas/principles for my Heretik forge stuff.

I’m going to be busy for quite some time

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* DoT - Data over Tag, a data transmission system used primarily by the UKLTA

** WoW Hit signal is a signal consisting of a 57.6kHz signal and 1800hz signal modulated together

PPG Files and upgrades

I know it’s been a couple of weeks (ish) since the last update, but that’s because I’ve been busy on things…

However, the good news is that the PPG build documentation and files are now ready, and have been for a couple of weeks.

They have been teste d& work with baseline Worlds of Wonder sensors, Uklta's DoT sensors and Heretik forge prototype sensor

Dropbox link is here (opens in new window) - Updated 18/12/2018

This is a very specific build for a very specific body, which while the circuit can be transplanted and used in other pewpew bodies it is missing a few things that were sacrificed in the name of compactness.

1^st is a button to trigger a ‘reload’ cycle, rather than turning it on & off again

2^nd is more power/current going to the IR emitter to increase the output and increase the range.

The PPG circuit, with the lens assembly in the PPG documentations manages around 30-35 meters, which while above the “in universe” range of 25 meters, is low compared to some of the kit people use.

Personally I think this is quite a reasonable range given how small they are, and how tiny the lens assembly is (16mm lens, 14mm effective due to the mounting) – I’m not sure I’ve seen and kit one with less than a 25mm lens before now – I could be wrong, but I don’t recall seeing any.

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 So, there are two major “upgrades” that I consider crucial, and one optional one that I’m planning

1: Add a reload button 

A button to trigger the reload cycle (Currently only triggered on  power-up for the ppg) was easy enough to add - but the space just wasn't there in the PPG body. 1 button, 1 resistor and a quick change to the code and that was sorted.

2: Increase output power/Lens size

Now, there are a couple of ways to increase the range for a IR based system such as this:

                More Power to the emitter

                Larger lens & lens assembly.

More Power to the emitter: 

There are some IR emitters out there that can take quite large amounts of current for quite a high powered output, but in line with the design principles in my head I’m wanting to keep the price down as much as possible while keeping it as straightforward as possible(1) so I’m avoiding some of the really snacky IR LED’s that can manage some serious grunt…. But cost £3+ each…..

So, using the SFH4545-DWEW emitters (Often referred to as Gherkins) we have an ideal peak current limit of 2amps.  I don’t want to go higher than this as even at the short pulse duration in use it would risk damaging the LED (and yes, I have blown a couple working on things)

The PPG’s have a nominal max of 800mA due to the restrictions of the AND gate transistors that modulate the carrier and hit signal together, and the voltage regulator is rated to supply 1.5A max anyway.

So, overall, I’m looking at something that can give a power output greater than 800mA but <= 2A max

I’m also going with a 7.2V supply – the idea being the things can be powered from a standard nicad rechargeable racing pack (2)

The limit of the voltage regulator can be avoided by having the Emitter LED  connect directly to the battery power supply

This would then need something that can take the modulated hit/carrier signal and pulse the emitter at up to 2A

Enter the Mosfet. 

After an exciting(3) evening of trawling through datasheets following a tip from Dave I eventually settled on these Partly because it ticked all the requirements and partly because it wasn’t the £3 each of the originally suggested Mosfet 😊

If anything, the mosfet is a little bit of overkill, but it seemed to be a choice between overkill and not enough…. So…

Anyway, with the mosfet needing 1.5V to turn on, and the Emitter needing 2.7V, running off of a 7.2V supply gave me 7.2-(2.7+1.5) = 3V to play with to drive the current through the emitter. Add in a 1.5ohm (half Watt) resistor gives a nominal 3/1.5 = 2A peak through the emitter.

Perfect.

Ain’t getting much better than that without changing the emitter 😊 and can drop the current/output by changing to a 2ohm resistor (for 1.5Amp output) or 3 ohm resistor (For 1 amp output) – which give a possible option of having a small SPDT switch to switch between 1.5ohm and 3ohm resistor for outdoor/indoor-close work to avoid too much power output causing the beam to “splash” – It’s never fun to shoot yourself… Usually it’s considered far more sporting to let the other side do it.

To be fair, to be on the safe side I may use a 1.6 ohm resistor on future/production  boards which will drop the current to 1.8Amp as that should give a little bit of wiggle room for those components that are outside the average. 

Larger lens & lens assembly. 

A larger lens & lens assembly is a fairly simple principle – The larger the lens, the more light it can collect and send “downrange”

I’m currently working on a 25mm lens & barrel assembly, that using the test circuit I knocked together to focus a barrel/lens assembly gives a nice clear spot on the side of the building down the road – given the brightness of it(4), it’ll go a lot further, but I kinda ran out of houses….. But that’s a good 60meteres, and the circuit used was not running at quite the same power.

Next stage is going to be get a barrel/lens assembly printed that includes a picatiny rail mount so I can stuff the thing into a Nerf body, ad a sight and find out just what it can do.

And then do the same with a 30 and 40mm lens, all the way up to 50mm.

 Optional upgrade:

The one upgrade I’m considering optional at the moment will be a more visual human interface for showing the ammunition status – at present it’s a single LED that come son when the ammunition is “empty” and flashes while reloading.

There are enough spare pins on the chip, that I will be able to use one of the to talk to an external picaxe chip(5) that has one job and that’s to display the ammunition status in a more human interface friendly form, be it 2 digit 7 segment LED display (ala aliens pulse rifle).

A bargraph display or anything similar.

As long as the communication protocol between the chips is “standardized” then pretty much the sky is the limit.

But other than that, I’ve not given that option much thought yet as it only cropped into the old melon this morning.

But then given I only finished the first verostrip prototype of the enhance board yesterday, I’m not surprised.

Ttfn

Ady

 

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1. Yes, I know if I switch to a pure PIC microprocessor, I can reduce a number of the components and do more via code, but it then also becomes to my mind more difficult to explain what each bit is doing, and harder for anyone to “remix” parts
2. Yes, I know about LiPo batteries as well – but I’m not a fan in all honesty – I couldn’t say precisely why, but there you go.
3. This word is a lie… It was dull… Very, very dull.. but necessary
4. And taking into account the peak wavelength of the IR viewer I was using was not the same as the peak wavelength of the emitter, so it will seem not as bright as it actually is
5. Or Pic later as I do plan on moving to Pics for a future project “Project Arcturus”

PPG 3d files & Electronics

Whelp.... took me a little longer than expected.
BUT.

The files and plans for the PPG's for the game next year are finally ready.

The Link to dropbox is HERE - Updated 18/12/2018
Right. Now that's done... i'm going for a Lie-down.....

PPG Circuit

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.

Aaaargh. Damn computers.

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

 

Lenses & Optics

Lenses.

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.

So, what's thiis all about then?

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 

I'll be off in a different field.