Last night I finally got around to setting up the dehumidifier sump in my cellar so that it pushes data to the Internet. I'd not bothered before as the cheap DHT11 humidity/temperature sensor I had was returning bogus readings.
Given they're dirt cheap it was easier it just buy a DHT21 instead of messing about troubleshooting and now I have believable humidity readings. It's a little higher than I see in the body of the cellar, but the sensor is stuffed down on the floor right next to the tank of water. I plan to fit a longer lead and mount the sensor at chest height somewhere further away on the assumption it will sort this out.
For data upload I am using the Sparkfun Phant service as it's free and very easy for a microcontroller to deal with.
All I've done here is grab the data as a CSV and draw the graph in Excel, there's much more work to be done to make this readily accessible.
This is a bit of a dry run for a later project, a friend has asked me to set up some monitoring of the beehives she's setting up on a roof in London in the Spring. The interesting stats to collect are apparently internal temperature, internal humidity (may be hard due to bees messing with the sensor) and the weight of the hive. So I get to mess around building an calibrating load cells.
The other day I was making my first lasertag lens unit. Trying to get it focused I quickly decided naffing about with a battery and button wired straight to the emitter wasn't good enough. Plus I burned out one emitter keeping it on too long.
So I built the essence of a lasertag gun in a box, with screw terminals to make it easy to connect up to things for testing. It's also got a low power unlensed emitter run in parallel, in case you want to test sensors.
I've left the USB connector of the Arduino Nano accessible at one end so it can be reprogrammed easily as for now it's just sending WoW hits.
I may open it up again and put screw contacts for the trigger so it can be used as a general purpose thing to tag up bigger props on an ad-hoc basis. It's got 4 AAA NiMH batteries in so with a decent lens unit will have a passable range.
If there's space, which I doubt, I may stick in an IR sensor so it could also be a thing that registers hits, making it a multi-use device for props.
I want to turn my cellar into a decent workspace but it's currently too damp. If you leave things down there the cardboard goes limp and metal slowly corrodes.
It may be that I have to resort to professional tanking of some kind, but as an opening gambit I'm going to try drying it out with a dehumdifier.
Emptying the condensate tank regularly is dull, but there's a connection for an external drain, so I've built a bigger tank out of an old 'Really Useful Box'. This complete with float switches to sense the level and a pump to push the water up out of the cellar into my garden.
This could have been managed with a very simple latching circuit, so it switched on once full and didn't switch off until empty. However I've got all the bits to do this with an Arduino. An added bonus is I can put it on the Internet, so it's now got Ethernet and a temperature/humidity sensor so you can look at a web page showing the current readings and how often it has emptied the tank.
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.
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.
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.
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.
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.
