Space, how low can you go...

I really should be doing other things, but tonight I tagged this up. This Nerf Jolt is now a very basic but functional Lasertag gun.

I've been asked to make a pair of concealable 'assassin weapons' for a game and although I don't have the actual gun board yet I wanted to mock it up with what I have because I'm impatient.
I ripped all the Nerf internals out, including using a drill to destroy the one-way valve mechanism at the back of the barrel. Then I fed this lot in.

I've got a TSAL6100 IR emitting LED, 5mm white LED, small piezo sounder, Arduino Pro mini and a small LiPo battery squeezed in.

I'm actually using a 5V Arduino Pro mini at 3.7v but it seems to work fine. I've got a 3.3V version on order, but like I said I was impatient.

With a very basic sketch loaded up it lights up the muzzle flash LED, makes some white noise then emits a simple tag hit with IR.

What it lacks at the moment due to lack of space is an on/off switch, charging jack and reload button. It just fires repeatedly and you have to take the bottom cover off to disconnect or charge the battery.

For what this is intended for these limitations aren't huge. It's aimed at a four hour indoor LARP where it'll be hidden on somebody and maybe not even used. I could go with a smaller LiPo and then maybe be able to fit an on/off switch, again I just had this one kicking around.

What I definitely need to do though is stick the IR emitter in a piece of tubing to constrain the output. Right now it hits everything in front of you, and I mean everything. Reflection isn't noticeable indoors, I've put a fair size resistor on the emitter and it's driving straight from the Arduino so quite current limited.

Spookytron 2 first testing

A very long time ago, my first ever Arduino project was Spookytron, which in a fairly dumb way played spooky noises for use in LARPs.

PIRs detected motion and it played sound somewhere else. If you walked towards the sound it stopped.

Very simple stuff but it was my first project and it was surprisingly effective.

The big problem is it was housed in one central box and had speakers on the end of very long cables. For convenience I used CAT5 cable as it's something that's easy to buy pre-terminated and I had a load anyway.

It got used twice but the need to lay massively long cables round a wood got tiresome very quickly. As soon as it got used people said, 'can you do a wireless version'.

When I saw Ciseco's SRF radio technology it was obvious this was a good use for it. I've been busy with other things, but now I'm having a first stab at it.

Here we have a very simple mesh of two nodes. Mesh discovery isn't in place yet and it's got one sound PCM encoded into the sketch but if you trigger one device, the other plays the sound. I've used Ciseco's LLAP protocol for this which is trivially easy to work with, it's just fixed length serial human readable messages with a two character address field.

The plan is to do this with some RFu328s which will be much smaller but right now I'm prototyping it with a couple of Unos and the shields from the Kickstarter.

The LLAP library Ciseco released needs a ton of work, so I'll hunt the Internet to see if anybody has done a better one. I seem to remember spotting one a while back.

Going in circles

Paintball exists so that people can play at shooting each other without using real guns. Somebody released a video game where you play at pretending to shoot each other from the comfort of your front room.

Now I've been gifted these two paintball style light guns from that game and plan to convert them to Lasertag so we can use them to run around in the woods pretending to shoot each other. With a pretend version of a pretend gun.

All very circular.

They are really cool looking though and without the paintball reservoirs on top make an excellent base for some scifi blaster pistol style guns. As with a lot of these light guns there are a plethora of switches set up nicely and the original light sensor assembly will probably make a good base for a Lasertag emitter. Because this was some kind of standalone game they even have a battery holder in the grip, which I may re-use if there's plenty of space elsewhere in the body.

Apparently the 'slide' on top shoots back when you fire, but I suspect that will be a casualty of having to fit a Lasertag circuit, sound board, speaker etc.

Making Magic Wands

I've made a few prop magic wands and a friend asked if I could write up  the process. You don't need much apart from a hot glue gun, dowel and paint.

Start with a 30cm/12" piece of 8-9mm dowel.
Put a point on one end and some texturing on about half of it. I used a dremel, but a rasp, file or in a pinch sandpaper will do the job.
Next, use a hot glue gun to build up some organic looking lumpy bits to mark the ends of the handle section. You will want to do this in a couple of goes, allowing it to mostly cool in-between. If you try and build it up too quickly it will just run too much.

The glue tends to try and run off so use a low setting on the glue gun or keep turning the dowel.
Once you've got a kind of hilt and pommel, let it set for a good half an hour or so. A big accumulation of hot glue like this can take a while to cool completely.
Next, paint the glue with some standard acrylic paint in some kind of accent colour. This helps the woodstain we'll use next to stick to the glue, it tends to run off without. Also, it provides some shading so feel free to mess around dabbing it on. I've not found straight lines and geometric patterns to work very well.
Once the acrylic is well dried, use some external woodstain to cover the bulk of the wand, holding it by the tip.
Once that half is dry do the other half. This wand is quite dark, deliberately. You often get better shading with a lighter stain.
Finally I used some glue to add a little glitter at the tip. You wouldn't want to do this with every one, but this felt like it needed brightening up.
Using this method you can make a few variations on the theme so each wand is unique. I did 25 for a LARP once and had a little production line going.

More IKEA stuff

I have plans for this simple IKEA step stool, but first it needed something on it to protect it. It's not as orange as it looks in the photo, it's actually red.

We need guns, lots of guns...

For Lasertag next year I want an assortment of guns to choose from. For our first couple of years we've been making do with just some pistols. Having made the Skorpion machine pistol, I'm moving on to these two.

The Mossberg body is a cheap Airsoft springer which is nice and solid but light. It fits nicely in my partner's hands so I can see her using it a bit.

The AK47 is a cheap kid's toy which I bought after one of the other taggers bought the first one and deemed it good for converting. It's almost full size apart from the stock and comes with a passable sound/light board that I might try to re-use to keep the build super-easy and cheap.

The AK will definitely be a quick and dirty conversion so will only look good from a distance but I want it to NPC the Fallout game we're doing in the summer. Bashing it about and grunging it up a bit should make it look the part.

Once I've done these two I may splash real money on a good metal rifle body as I'll have some gun building under my belt and hopefully have learned some of the pitfalls.

Don't expect it to last

It's a £3 broken water pistol of finest pound shop quality given a coat of paint and some glue to fix the busted bits.

It looks kind of cool but never ever kid yourself it'll last very long. It may be dead by the end of the LARP I built it for.

We love IKEA too

Having made the brain in a jar I needed something to act as a stand for it. I also wanted to make the business end something that I can re-purpose for multiple props, as a brain in a jar is always useful.

For the first go at the stand it needed to be compact and quick to throw together. It occurred to me that some time back I bought a set of metal desk organisers from IKEA so that I could turn one of them into my medical scanner. Being clean and white gave that a strong 'medical' look which would work for the brain too.

So I fitted a square acrylic base  the same size as the IKEA box to the brain and mounted it to the box with four bolts. This is a nice generic fitting that will allow me to bolt it onto something else later if I feel like it.

The box has precious little inside, an Arduino Nano, socket for the mains PSU and on/off switch. It is however big enough for an RPi if I want to make it speak later.

Here it is complete and running, although the video doesn't show the colour cycling very well.

Brain installed on time and under budget

I have a brain in a jar. OK it's a little lacking in any means of support right now but look at the pretty lights!

I love cheap stuff

Not quite sure what I was going to make next for a bit of fun, this weekend offered up glorious bounty. Tiger is great for random stuff although I'm sure somebody will be along to tell me how awfully unethical their business model is or something.

I however now have several foam brains thanks to this. At least one will end up in a jar.
Also we bought a ridiculous, slightly broken but cheap water pistol from a petrol station. A good spot by my partner that should be excellent for all manner of daft campy sci-fi LARP once painted up a bit.

One day it may shoot lasertag. Just because it's there.

Skorpion finished for now

I think I've finally finished the Skorpion. Just as the Lasertag season ends until about March next year. :-)

Nevertheless this is again mostly about enjoying making something, not making something to a deadline. I was trying to finish it for a game this weekend and missed it, but in the end didn't fire a single shot all game anyway.

To make a functional Lasertag gun you need to squeeze quite a lot in, most of it is batteries, sockets, speakers and switches. The job of laying it out so it all fits nicely in a small gun body like this is more complicated than the electronics.

As I was using a bog standard Arduino Nano with headers connected to do the work it's quite bulky compared to the little PICs Phil's gun boards use. Likewise I've used an amp I had kicking around rather than making something as compact as possible. So I'd handicapped myself by using my usual stock parts rather than aiming for something smaller. Buried underneath it are the various current limiting resistors and a MOSFET to drive the IR emitter. The big white lump is a wirewound power resistor to limit the current to the emitter. It's undoubtedly overkill given the intermittent load I'm feeding the emitter, but I wanted to be sure it was OK.

For future projects I've bought some Atmel ATTiny85 chips which should allow me to do quite a lot in a small space, at the cost of many fewer pins. They won't be any good for gun projects as there won't be enough pins to drive the WTV020SD but they might be OK for some really simple stuff. My next project may involve driving Neopixel LEDs in a garment so they'll be good for that. I've also picked up some Arduino Pros which are similar to Nanos but headerless and relying on an FTDI connecter rather than having USB on board. All of which makes them a bit more compact.

All Arduinos come with some LEDs onboard which glow alarmingly brightly in the dark and could be seen through the speaker vent in the gun. Which would be bad in a night time Lasertag game so I desoldered them carefully from the board.

This ended up being about the third iteration of getting it all squeezed into the body, which is why it's taken me so long.

The first try simply didn't fit due to untidy wiring. The second worked but with the tiny speaker the WTV020SD board simply wasn't loud enough unamplified. Which I should have known. Connected up to a large speaker in ORAC and Time Machine for ambient sound they were OK, but a tiny speaker needs something drive it hard.

The third time I had to shuffle it all around to fit the amplifier in and I managed to kill a WTV020SD sound board by soldering it to the wrong power supply. Good thing I bought a load from China.

So it's taken far far too long to get done, but as ever I revel in using something I've made myself rather than just bought.

More Skorpion fiddling

I've had a couple of evenings free to faff about with the Skorpion carcass so now it's getting much closer to the point where it can be turned into a functional Lasertag gun.

I think I now have most of the pheripheral connections I need and it's down to sticking a microcontroller, sound board and speaker inside.

What I've managed to squeeze in so far is...

  • Homemade 7.2V battery pack consisting of six NiMH AAAs soldered up
  • Power switch
  • Charging socket
  • Trigger switch with decent action and return spring
  • Mode switch for single/auto
  • Reload switch
  • Emitter assembly from Splinter Faction fitted so it resembles the original barrel
  • RGB LED on the side to show status
With the battery pack inside the grip this actually leaves quite a lot of space to play with in the main section of the body. Buying a battery pack ready made would have been better but a quick bit of surfing didn't show up anything in the right shape.

This leaves me with just a muzzle flash LED to sort out before it's ready to stick a board in. I'm very tight for space on the front edge of the gun, it all kind of slopes backwards. About the only place I can see for this is immediately in front of the magazine. There's a little cutout that should allow me to embed an LED or two in a chunk of clear acrylic to make them more robust.

I'd like to have it inside the IR emitter 'barrel' but don't want to attack this with a drill. It was bought as a focused working unit and I don't want to mess that up.


Today we had a bit of fun at work. The University has some beehives and we got asked to sort out a webcam that overlooked them.

Given the lack of money for this project, as per usual, we were limited to buying consumer quality kit for this. We've ended up with a TrendNet IP66 rated PoE dome camera which actually works quite nicely.

However like most of these things it's designed to fix to wall or a ceiling. Which doesn't really work given the location of the hives. So last night I knocked up the little stand you can see in the bottom right of the picture and stuck a couple of coats of wood preserver on it. It's not perfect but is solid. The brick is a design feature.

When we went up on the roof to put it in place, they were checking the hives so I actually got a couple of decent pictures where you can see the inside of the hive.

Once it's actually accessible from the Internet, which is my next job, I'll post a link.

Smaller on the inside

At a loose end this afternoon I stumbled across this old airsoft machine pistol I bought way back in the summer, thinking to use as the basis of a Lasertag gun. I've tons I should be doing but stripping this down and messing about was what appealed.
It's not a bad looking thing and the clip over folding stock is really quite cool. Visually it's kind of like a mini-Uzi with a bit of Kalashnikov DNA.
The whole thing is quite small, so it's going to be a bit of a challenge to make it into a working Lasertag gun. Thankfully though, the emitter assembly I bought looks a good fit to replace the current barrel.

The diameter is very similar so it's not going to mess up the look of the gun and should mean is going to be an easy fit.
With a tiny bit of messing, the emitter directly replaces the barrel. It protrudes further from the front of the body but I may able to slide it back somewhat. I've not done that just yet as one of the locating lugs for the body is in the way and I don't want to remove it. If the barrel looks OK like this I'll leave it. My only worry is it may not be desperately secure given how far it sticks out.
So here is a very rough mockup of how I might mount the components. Obviously missing right now is a speaker or sound board. The latter I can easily fit in, but the speaker is going to be very hard. I've got a couple of small ones but they're still far too big.

No chance of fitting the muzzle flash LED inside the emitter as I've bought it complete. It'll have to be somewhere on the front face of the gun, but this shouldn't be hard to pull off.

I need to buy some NiMH batteries to turn into a 7.2V brick. The 3.6V Li-ion ones you get are appealing but more complicated to charge so ideally need to be removable.

I also need to buy an assortment of switches as I've nothing but little PCB tactile stuff at the moment. This will need a power switch, reload switch and trigger. I've a half formed plan to use reed switches but it might not work out.

The Lasertag gun I bought made up by Phil was constructed out of a Playstation Time Crisis style light gun and I can see why. You get something already designed to emit IR with a switch at the trigger and a smattering of other buttons.

Back to the future

Not for the first time my parents have provided me with LARP kit. Months ago they asked me if I wanted this old plastic coolbox and I sensibly declined.

Now, with a Blake's 7 LARP coming up I remembered the offer and picked it up from them. On numerous occasions, particularly in series 1 & 2, it looks like the B7 crew use a large plastic coolbox as luggage.
A combination of aluminium foil tape and clashing yellow tape has given me something that looks late 70s futuristic.

OK, so the box in B7 is generally red, but this is LARP not cosplay.

Over the next few weeks I will attempt to fill it with a bunch of weird probe type tools like those Vila and Avon used. I'm, playing a technician type character and want to have some bits to play with in game. I reckon crocodile test leads, multimeter, a few things with flashing lights on etc. will work nicely.

Laser-Tag sensor prototyping

The flipside of making my own Laser-Tag gun is I also want to make my own sensors.

Phil Higgins makes a sensor designed to be worn on the head which is accepted to reliably take hits outdoors and has all the 'data over tag' stuff coded in by him already. Loads of people in the group I play with use these and I can't see myself replacing mine with something of my own devising.

However I do want to make a 'target' for testing Laser-Tag guns against and maybe some props that can be shot as part of broader functionality. So tonight I messed about with a simple test rig of an IR detector wired up to an Arduino with an Interrupt Service Routine attached to the relevant pin.

Laser-Tag uses a 56Khz carrier signal which is slightly different from typical IR remote controls, but there's a recommended component for putting in the sensors: a Vishay TSOP34156. This filters out the carrier signal and background noise from ambient light, leaving you with a microcontroller compatible output of just the encoded signal.

So far so simple, I now have a simple sketch that will flash a light and play a tone when I shoot the sensor. It's not really matching the Laser-Tag signal, just counting pulses and registering a hit if it gets enough in a short period. One of my remote controls sets it off.

This is something I can work on. For now though, tonight's fiddling has shown me that building a target shouldn't be hard. So I can start making the case etc. and then hone the code once it's in a usable shape.

Scribe in a box

Digging out a bit of an oldie here, I got reminded of it as I was copying files off.

This is the 'Scribe in a box'. I play in a fantasy LARP and there's a bit of politics and the occasional episode of NPC plot exposition. Just like meetings in real life, things get forgotten if you don't take minutes.

Nobody really wants to do this and my partner found herself spending time frantically scribbling stuff down rather than enjoying herself. This was my solution.

It's a cheapo digital audio recorder from eBay, chopped around and stuck into an in character looking box. I extended the controls by carefully soldering wires to the little circuit board where the nasty metal diaphragm buttons were. I connected these up to proper switches and put coloured rhinestones on top so you could tell what they do. Likewise I fitted a decent battery holder and the AAs in there will run it for ages.

If you peer into the perforated top you can just read the original LCD display but in practice it's red button to record, green to play and when it's running you can see the little red light glowing.

This has proved very useful and is a fixture at our games now, with the recordings getting written up after the event. The only thing that is fiddly is that to get the recordings off I have to tease it apart and slide a USB cable into a socket hidden in the rat's nest of fragile switch wiring. The temptation to fix this is tempered by a worry about spoiling the look of the thing as it's really quite a nice little wooden box.

Did I fire five or did I fire six?

I have a working Lasertag gun! I tested the emitter wiring, found it was fine then realised I had a stupid error in my code. I've taken the Lasertag shot code Phil Higgins gave me and stuck some very basic stuff round it to make it fire with the trigger, run out of ammo and do a reload sequence. While doing some cutting and pasting I'd simply left a line out.

The gun is cosmetically a bit dodgy where I've fitted the power switch but it does work, at least indoors. Things obviously left to do are fit the sound board and speaker then if at all possible fit a USB lead so that it can be reprogrammed without taking it to bits. The LEDs on the Arduino itself are bright enough to see through the holes in the case already and act as status indicators so I don't think I need a separate one.

I want to work on the code and ideally make something interrupt based for generating the shots, but right now this will do.

The Internet of Things revolution is coming

I got my new Arduino, yay! Soon you'll be able to see whether the condensate reservoir in my cellar is emptying or not and check out the nice stable temperature all year round.


Last thing to do is mount the stack of boards in a box to keep the dust off but I've not found anything suitable. I'm using up an Ethernet shield and screw shield that I have kicking around, neither of which I can see myself using for anything else. Stacked up they make the thing quite ridiculously bulky for what it does. So it's all just going to have to get stuffed into a big box. It's not like it's going to be on show, it'll be sitting in the cellar.

It's my party and I'll solder if I want to

Today's my birthday and I didn't have anything planned so I had a soldering party instead.

I love this stuff so frankly spending a night in messing about doing this accompanied by a pizza and a couple of beers is a pretty good evening in my book.

The end result is my first ever Lasertag gun board.  I imagine it's blooming enormous compared to the PIC based ones as I've got an Arduino in there and it's all socketed up on 0.1" headers. This is deliberately done so I can mess about with it and use it as a bit of a testbed. It's been made so it nicely fills the empty space in the middle of the gun.

For power in the end I used a tiny little step-up switched mode voltage converter. Easier than messing around with funny Li-ion batteries or trying to squeeze five AAAs in there, but obviously it's not going to have brilliant battery life.

I've got the trigger and reload switches wired up, a muzzle flash working and a space for the sound board, which I'll fit another evening. It's the same WTV020SD module I've used in a couple of other projects so I'm sure it'll work OK.

Right now sadly this goes through the motions but doesn't cause Lasertag hits. It's probably just a stupid wiring error as I've used the code that's worked fine in testing and I'll debug this tomorrow night.

The Internet of Uninteresting Things

You are looking at my addition to the Internet of Things. Well it will be once I get a new Arduino to replace the one I shorted out in a moment of hamfistedness.

All the code is written and it works but is suitably ugly, just need to wait for the new board.

It's a self emptying condensate tank for my dehumidifier with temperature and humidity monitoring. Are you excited yet? I'll be sure to provide continuous updates for everybody.

My first lasertag gun

I play a reasonable amount of LARP where we use lasertag  as the combat system. I posted a while back about wanting to make my own gun for this and have made a start on one. So far I'm happy with the progress. Painted up like this it will make a satisfactory vaguely sci-fi looking pistol that can be used in any game where you're not fussed about having replica kit.
The basis for this is a NERF Firestrike for multiple reasons. It's a compact but chunky pistol body and has a 'laser' built in, which shines a red target on things when you push the secondary trigger. This means there's an OK lens unit, battery holder and switch all built in as it comes out of the box and like most NERF guns it's really not very expensive. Building a gun out of a decent Airsoft body is a much more expensive proposition.
Opening it up, there's a ton of space inside, I can't see me having any difficult getting it all in expect perhaps a speaker for the sounds. I'm also conflicted about powering it. The battery holder only holds two AAAs which isn't high enough voltage, I really need a steady 3.3V, preferably 5V or more. So I can either go with a step-up voltage converter or get some of those Li-ion batteries people use for vaping. AAA size but 3.6V each.
After ripping out all the NERF piston stuff the trigger got turned into a switch with a simple tactile button glued in a suitable position. I started hacking the shell about to fit an on/off switch at the rear of the gun but it interfered with this mechanism and I've abandoned that plan. Not sure what to do about an on/off switch now, I may just pop the battery cover off, it's not like tag guns draw a lot on standby.
I used a Dremel to cut the tracks on the small circuit board that connected the battery terminals and secondary trigger. This means I can take feeds separately for power and the switch, originally it just switches the batteries straight to the LED when you push the trigger. I plan to use the secondary trigger for the reload function, it's nicely placed for it and not as easy to push as you'd think.
Then I desoldered the red LED from the board in the emitter and replaced it with an IR one. It's taller so the focus may have been messed up. There will be an element of suck it and see on this.

At this point I've got a trigger, reload switch, battery compartment, emitter and muzzle flash LED ready to go which is getting it down to sticking an Arduino in there and making it work.

However I'm going to pause for a bit. I painted it last night and while I like the silver finish it's still slightly tacky. I've had this with NERF guns before, the paint seems to take ages to dry, which must be related to the solvent getting into the plastic of the body. I know from experience handling it too much will mess it up so I'll leave it a while longer to dry.

This leaves me time to sort other things on my to-do list for it like ordering some of those AAA Li-ion batteries, sorting out a suitably compact sounder, coming up with where to mount an on/off switch, making a status indicator which may just be an RGB LED and building the 'gun board'. The latter is actually the fairly easy bit.

I'd love to leave the USB programming port for the Arduino accessible if I can and maybe have a 7-segment or matrix display but I suspect the latter is stupid 'feature creep' that will drag the project out and make it unnecessarily complex.

My love/hate relationship with hot glue.

When I built the Enigma Machine I was really against the clock to get it finished. I ended up pulling some really late nights to get it ready to go.

As a result I made some short cuts and one of them has come home to roost.

I needed to make guides for the keys so they didn't rotate and did this by hot gluing some brass flats on the end of the tubes. I never really thought this was a great idea and even as it was going together some of the joins were a bit weak.

Now over time, loads of the keys have come completely loose and the brass flats are rattling around inside the case.

So today I'm going to have a go at sorting this out. I'm not quite sure how I'll fix this. I suspect I may just switch to epoxy as the key tops have stayed on the ends of the tubes just fine with that. I'll also try to even up the keys as they weren't all perfectly the same length.


I've used a couple of Raspberry Pi computers, having already embedded one completely in one of my projects. At under £30 for a fully functional Linux computer with enough horsepower to do stuff that is inconceivable on a microcontroller it makes a load of sense.

Now I've got a use for another embedded one. So I thought I'd get one ordered up so I can make a start on building it into the prop, even if I won't necessarily have the software sorted for a while.

This has come at a timely moment as they've launched a new B+ version and it gives me an excuse to pick one up. Given that various similar things have come out that make the Pi look a bit long in the tooth without being much more expensive it's not unexpected.

What is unexpected is that it's not really an upgrade but a refresh. The technical differences will have been covered all over the place and I'm sure loads of people are disappointed in the lack of a CPU, memory or on-board Wifi upgrade. Things like the BeagleBone Black have tons more horsepower for similar money.

However what they have done is make it more polished.

The old Pi was very obviously a 'first product'. The connectors poke out all over the place and don't line up. It uses an SD card when a micro-SD card would seem sensible. The power regulation circuit makes it prone to crashing and resetting if you plug things in to the USB ports while it's running due to 'brownouts'. Hell there are only two USB ports which get used up dead quickly. The phono socket for composite video output is huge and looks like something from the 90s, etc. etc.

I can see why they've done this. The Pi is ubiquitous. I've bought this despite having a Beaglebone Black kicking around because I want a Pi specifically. The community support is enormous and so much stuff gets ported to it.

If they changed it too much they might lose this.

Christmas lights would be cheaper

Some time back I bought myself a string of generic WS2801 driven addressable LEDs and they've languished in a box ever since. These are 'smart' RGB LEDs with a little driver chip that means you can daisy chain an arbitrary number of them and control each one individually with just two connections for the whole string.

I thought I'd use them for the Time Machine but in the end they were simply too big and the wire between each one too short.

Last night I finally dug them out and had a go with the Adafruit library. This is fifty of them running a slightly faster version of their example code.

They work really nicely but again I suspect they'll be 'wrong' for my next project which needs to have a retro look. So much so that I suspect it'll be done with incandescent bulbs, relays and lots of messy point to point wiring as that's actually what it's supposed to look like.

Although these would make it really easy to make.

Raspberry Pi GPIO:101

My brother always gives me interesting presents. He's got a head start as we both like and do similar stuff.

One of these was a Raspberry Pi T-cobbler kit, which is essentially a way to extend the GPIO connector outside of a case and  plug it into a breadboard for prototyping.

Wiring up simple inputs and outputs to microcontrollers is bread and butter for my projects but I've never actually done this with a Pi. So this morning I pulled the T-cobbler out, soldered it up and did a bit of messing around.

I'm finishing up a project which has a Pi embedded at the moment. It uses a slave Arduino Nano to do most of its interface to the real world and it's going to be properly embedded with the expectation you don't normally have a screen, keyboard or network available.

So despite the presence of the Arduino I want to be able to have some basic control and feedback from the Pi that doesn't rely on anything else working. The python script on the Pi that does the heavy lifting occasionally crashes and while I'm making it more stable some of it is just V4L being  flaky rather than anything I can actually fix in my code. At least that's my excuse.

So I want the following directly linked to the Pi.

  • Shutdown button so it can be cleanly shut down rather than just yanking the power. No good will come of that eventually. For this I need GPIO really and I'll probably do it like this.
  • Status light that shows the state of the main script, again more GPIO.
  • One or two buttons to change the state/behaviour of the main script
  • Reset button. Easy, just connect a switch to short jumper P6.

What I've done this morning is connect three buttons and an RGB LED to the GPIO. Pushing each button lights up one of the colours of the LED using a simple Python script.

This is easy peasy stuff that anybody could do with a little looking on Google but it's on these foundations that you can build something that actually 'does stuff'.

I took my medical scanner prop to a UKLTA lasertag game yesterday and people cooed over it again. Given the 'cottage industry' the UKLTA has going building guns for the hobby I'm surprised there aren't more things like it floating around. Some of the people there are far more capable at building things than I am. There seem to be a lot of people around who think this stuff is voodoo when if they set their mind to it could actually turn out some really cool stuff.

...with frickin' laser beams aimed at their heads!

I do a reasonable amount of LARP with the UKLTA who use lasertag as their combat resolution system. It's not dissimilar to Airsoft at first glance except there's no physical hit so you don't have to worry about eye protection and you have to wear a sensor, by convention on the head. It does however have some real advantages as a LARP combat system.

The particular variant they use started out as a toy product in the mid 80s which they adapted for adults and through the hard work of their members have kept alive long after the effective death of the original brand. The 'laser' in the name is a misnomer as it uses normal infra-red light and the guns are essentially similar to IR remote controls. Souped up turbo-charged remote controls.

For some time the UKLTA have had to build their own guns and sensors. A lot of the guns are actually converted from other things like Airsoft or Nerf although there are plenty of scratch built ones around. There's a real 'cottage industry' in the hobby and at events people end up cooing over each other's latest builds.

Over time the capability to send small amounts of data has been developed and nowadays the system can handle different effects from weapons and on the sensors. This includes things like armour, regeneration, healing effects, variable damage, 'stun', ongoing fire or radiation damage etc. The sort of things that make it work well for LARP of the modern or sci-fi variety. Very recently in a game we had a 'techno mage' with a fancy staff that did various effects.

With modern IR emitters being very powerful and microcontrollers small and cheap, you've got a solid combat resolution system where the guns can have ranges in the hundreds of metres and the sensor keeps track of everything for you automatically. The thing it can't really handle is melee or hand to hand combat but people have experimented with making short range 'tasers'.

I have for a while wanted to get involved in making a prop that interacts with this system and one of the people behind a lot of the developments, Phil Higgins, gave me some Arduino code that would generate a simple lasertag shot.

Last night I uploaded this on one of my spare Nanos and connected up an IR emitter fitted into a piece of brass tube I had kicking around left over from the Enigma build to make it more directional. Proper tag guns have carefully set up lens & emitter assemblies but an unlensed one is good enough for use indoors or short range outdoors.

I'm now working on integrating this into a fun prop and will try making my own gun over the winter. If I'm feeling saucy I'll use an Arduino inside and build it from scratch rather than use one of Phil's boards, mostly as a bit of fun.

Hiding the GM behind the curtain

I have, for a while wanted to do something to use technology to enhance how some things work in LARP. This is my first stab at a practical application.

I've made a fake medical scanner which goes through the motions of scanning a sample in a test tube you drop into it. So far, that's nothing particularly interesting. What I've added to it though is a 'GM interface' which can be accessed over Bluetooth.

The photo on the left is where I mocked it up using some breadboard. In the end I used a bigger screen and there's an Arduino Mega inside as I needed the extra pins for bits and bobs. The Uno really doesn't have the memory or flash space to handle driving the display if you use the very nice libraries written by Henning Karlsen.

Once the sample is loaded a GM can connect, set what the outcome is and how long it takes to process. There's a facility for them to type free text and it just outputs it on the screen at the end. I still need to do more work on the software so it handles events in a less linear fashion but I think it's coming along nicely. It better be, the LARP is on Friday.

It's not all code and soldering

I regularly play in a local fantasy LARP and my partner came up with an idea for a jokey motivational sign based on multiple in-game screw-ups we've had.

This weekend I chucked this together using things I had kicking around. I'm not in the least bit artistic so the lettering is done with laser printable transfer sheet. I love this stuff.

I found a small piece of slate, cut it down with an angle grinder, notched it for screws and also used hot glue to stop it moving about.

Having a lump of stone that you write on with chalk seemed the appropriate thing for a fantasy LARP, rather than an LED matrix. :-)