Marginal gains

I built two cheap and cheeful MP5 'tag guns earlier this year and left them unlensed. Having done the quickest, dirtiest thing I could when building I left the original muzzle flash bulb in place and stuck the emitter where they originally had cheapo laser pointers fitted.

Sadly the range was predictably awful and they've not got much use as a result.

This afternoon I opened them both up, swapped this round putting the emitter in the 'barrel' section and the muzzle flash where the emitter used to be. I also swapped the muzzle flash bulb for an LED.

These gun bodies both came with faux suppressors that slide on the end of the barrel and now all I need to do is put a lens a suitable distance down these and it'll make for a basic lens unit. I'll probably leave it removable for easy transport.

I'm not alone

My Spartan Design Predator tag gun has stopped working (it's gone silent) and I've taken it apart to troubleshoot. It seems I'm not the only one who loves using hot glue to gunge a project together.

I fear the sound board has died, but I'll have to dig the board out of its gluey embrace to really know. Which is the downside, it makes later repair or modification a bit of a pain.

Back to basics

While I love making 'technical' props this weekend I'm off to try out a new LARP system that uses NERF guns for combat and fancied painting some up. So I bought a Rapidstrike which was on special offer, dug a Maverick I had kicking around out and painted them both up with Poundland spray paint. The paint is cheap but it's cellulose rather than acrylic which I prefer for adhesion and toughness. It also comes in small cans which you end up finishing. I hate buying expensive paint and only using half of it because the nozzle gums up.

I stripped the guns right down, masked off some of the original painted areas and left some of the original orange on the moving components as they get scuffed up easily. The Rapidstrike was slightly fiddly inside but not terrible and it seems to work afterwords.

In the end these have come out really nicely. The different shades mean they're not just matt black lumps and stripping them down first really helps with definition and coverage.

The orange parts are quite nice highlights and leave a little visual clue they're still toys. Although I wouldn't want to test that by waving the Rapidstrike around anywhere public.

Refreshing some flaky props

 Last year I made a pair of slightly phallic Lasertag stun batons for the UKLTA's indoor LARP "Zero Light Thirty". Sadly they've always been a bit unreliable and irritating.

In an attempt to make using them more immersive I fitted tilt switches so they automatically 'powered up' when you raised them. However these have proved kind of unreliable and they'll turn off/on a bit randomly.

The actual on/off switch and charging socket is buried inside the tube, forcing you to unscrew the handle at the start/end of the game. Which also means disconnecting the cable for the trigger and that's kind of fiddly.

I've made something that doesn't come to pieces very easily despite that being necessary all the damn time.

Then for some reason I thought adjustable power levels would be good so the power switch doubles as a 'power level' switch and even I can't remember which way round the 'indoors' and 'outdoors' settings are.

At the time I didn't have the 'data over tag' signalling code that would allow me to build everything from scratch. I've got an Arduino piggybacking over a Spartan Designs Lasertag board, which was set up for stun shots. The Arduino reads the outputs on the board normally used for a status LED to see if it's ready to fire, then pulses the trigger of the Spartan Designs board when you push the trigger.

All in all they're a bit of a dog's breakfast.

There's a refresh of the game content coming up and I've been asked to fix up these props. If I can make it look tidy I'll ditch the tilt mechanism and just put all the switches & sockets on the outside.

If it bleeds we can kill it

You know how the Internet is. One minute you're looking at one thing and the next you're thinking "wouldn't it be cool to make a thermal camera". You know like Predator vision.

Also a bullshit conversation about making one at a recent LARP didn't help with the whole "doing the sensible thing" thing.

Unlike so many bits of tech we take for granted as easy in the world of supercomputer smartphones and big data this is still the stuff of movies and expensive law enforcement hardware.

When it comes down to it, far infra-red is a lot harder to deal with than visible light or near infra-red, as used for 'night vision' CCTV.

Far infra-red doesn't pass through glass for a start and lenses that can focus it have to be made of things like silicon or germanium.

Then it doesn't work with the usual CCD/CMOS sensors found in digital cameras. There are similar solid state devices using different tech around but they haven't had the development work that devices for visible light have.

A bit of a read around the subject shows that Omron do a very affordable thermal sensor, the D6T-44L. This is quite easy to talk to over I2C and comes in at about £37 by the time you've bought the tiny connectors it uses. Great stuff, but sadly it only has a resolution of 16 pixels. Not 16 megapixels, 16 pixels. It also only does about 4FPS. Still it seemed worth a punt as a first go with this kind of tech as it's quite manageable.

Here I've taken the readings from the sensor and used them to make a pretty responsive display using ye olde MAX7219 and an 8x8 LED matrix. As it already involves some upscaling I've used each block of four pixels to do very basic dithering that represents different temperature readings and made it auto-range.

This doesn't result in desperately sophisticated imagery but I'm happy with how it's come out for an afternoon's faffing around.

Once I connect the sensor up to something more powerful (probably an RPi) I'll try combining it with some conventional video to do a pansharpened image. If this works OK I may end up buying a more expensive sensor like a FLIR Lepton, as I suspect this won't really be usable for much beyond a curiosity.

Dastardly Demon Detecting Devices

I've not been blogging recently as I've been working on a complicated multipart prop for a UKLTA Lasertag game which uses the TV show Supernatural as its background.

Some months back I had discussed the game with my friend Mik who said it would involve a demon possessing different people in turn. To which I said, "if I started soon I could probably build something that will track it".

Here's what it ended up as some months later. This is a 'magic compass' made from a cheap eBay purchase which tracks the demon. Who carries around the blue box you can see. Getting this to happen involved a whole load of making and coding.

There are GPS units in the compass, the small box the demon carries and the EMF meter I later decided to build. Then packet radio to share location data. Then relays to relay the data, increasing range.

It all escalated quite quickly and I plan to write each component up properly, but at least I can share the final result.

As alluded to previously I've ended up writing my own simple mesh networking protocol to make it happen. Which is quite a task, but now I've done it it'll get re-used, oh yes.

The Internet of Props

I have a general pattern of escalation in the complexity of the props I'm making. The exception to this was that during April I was making a ton of stuff for the Fallout game but it was mostly set dressing.

So I've ended up with things like a Fallout Vault door, some crates, a Sheriff's  noticeboard, odd looking ID badges and a fake external hard drive. All of which are essentially static, physical props even though a some of this has blinkenlights.

To make up for this, my current project is a multi-part set of props that need to communicate across a LARP site. Which is a large hilly wood where it can take a good walk to get anywhere.

This is challenging. Just think of the difficulties of getting good mobile phone signal in some places and that's a decades old industry with billions of pounds in development spent on it. Or perhaps more relevantly, using walkie talkies on a LARP site and being able to contact each other reliably.

My current approach is to use the ISF band serial radios released by Ciseco and I've posted here about using them before with their 'Internet of Things' protocol LLAP. The first stab at this was a failure. I made a 'GPS tag' to attach to an object so it can be found but it simply didn't have the range in a wood to be of any use.

So I escalated matters.

Now I've got a higher power radio in the tag, which necessitates a separate microcontroller, bigger batteries and a chunky voltage regulator which has made the device grow a bit, but not terribly.

Also I've now made some 'relays' which are similar sets of components in anonymous boxes with better aerials that can relay data packets for other things. When it comes down to it, fitting a radio powerful enough to go from one end to the site to the other in small props is going to be problematic. Hence, relays. I've built two so far for testing, but plan to have four in the end.

There are other bits to the set but I can't post them yet because, well spoilers sweetie.

The introduction of relays made me abandon LLAP for communication, it simply doesn't facilitate this relaying of data and being ASCII based isn't good at passing floating point numbers around without losing precision, which is essential for what I'm building.

So I've written my own vaguely self-organising mesh communication protocol that pushes data around in binary and implemented it as an Arduino library.

It appears to work.

We're testing this on Wednesday in a wood. No pressure then.

Sworn to secrecy

One of the problems with making props for LARP is that very often I can't talk about them outside of the circle of game organisers in case of plot spoilers and generally ruining the surprise.

We recently did a Fallout themed game and this little bunch here were part of it but I couldn't really say anything for just this reason.