Fire Pong Details - Computerphile

Key Takeaways

so we actually wore fireproof overalls during the event I mean like it's not so appropriate now but uh everyone within the boundary was supposed to wear these um to stop being on fire um fortunately they were not necessary so they're actually oil rig workers um boiler suits I think it's a work of Genius clearly crazy insane genius where did it start where did the idea come from and how did you get going with it some years ago I was fortunate enough to get to go to Burning Man and I saw lots of fire art there and I thought that sounds like something I kind of want to do um so I've had this thought in my head for a while to do that um two years ago the previous EMF camp we did a big collaborative project many members of the space contributed and we made barbot which is a cocktail making robot and when it came around to this time I thought maybe do something with fire um I was down London and having a drink with jonty one of the EMF organizers and I wanted to ask him if it was okay to do fire at EMF cuz you it's kind of potentially risky and his response was yes yes it is um and in fact he'd already been sort of experimenting with these um sorts of little uh flamers and he suggested pong as a game and uh so we just sort of took it and ran with it and it sort of came to fru that way there was lots of experimentation lots of broken things mainly uino PR minis went through a few 485 drivers as well there seem to be something not quite right right with with that to start with yeah burn out a few bits of electronics one of the things we had to work out how to do was how to uh light the gas so we experimented with things like barbecue lighters but they weren't really that effective then I came across these things £164 from eBay uh you put 5 volts in you get a few thousand volts out and then another challenge we had was how to design a spark gap when you we needed some insulators but ceramic tubes were really expensive to buy so we've got a a couple of um cam tubes from fuses here with screws in the ends and a machined aluminium block which just mounts to the right position initially just had a round-headed screws in here but we found that we didn't get a good spark uh between them and the actual high voltage generators wearing out so we did a bit of research and found that Sparks form better off sharp points so we end with these little strands of wire here which just of encourage it to generate a spark and that also means that the um spark is over the end of the um where where the gas comes out was it difficult to to make the game work as a game rather than the engineering side of it or was that fairly straightforward yeah we didn't know if it would actually be fun to play when we made it I mean I just wanted things to be on fire um so didn't really care too much about the sort of actual gameplay um until quite late in the process and it turned out it kind of worked pretty well um it was more or less my first sort of implementation of a game of pong um which was really a placeholder for something a bit more sophisticated um but it's sort of worked so we just built around that there's a bit of discussion about uh what would happen when you won wasn't there we didn't want to encourage people to lose we didn't want to encourage people to win so that was when the victory swipe came wasn't it to to that's right to encourage people to want to want to win and to have that extra go and make more fire when you win people really enjoyed the victory swipe I think it was a successful strategy now you two expert plumbers right U well I wouldn't say about expert plumbers but we certainly learned to nor lot about different gas fittings on this project cuz some of the nuts some of the joints are left-handed and some of them are right-handed um a lot of it's Imperial um quite a well all of this section that's all on what's called um quarter inch bsp valves but nothing is actually a quarter inch quarter inch was what used to be the inside diameter when they have very thick walled pipes but now although you can buy a/ Quin bsp pipe uh and Quin bsp fittings there's no measurement on there that is actually a quarter in which is really really weird it's very satisfying to put together cuz it's really heavy and chunky and I'm I'm a sort of software guy by trade so one of the challenges we had was all the gas hos are left-handed threads but a lot of the other fittings are right-handed threads one of the challenge was trying to find the missing component which allows to convert from left-handed to right-handed and that took quite a while uh try trying to get that anyway we found a source of them weren't cheap but we did find find a source of those we did actually have a few parts custom CNC made as well the adapters for the uh butane tanks into the rest of the pipe work um the thread on a butane tank is not something which is generally um you can't buy parts which go into it basically there's um the kind of valve that comes with the cylinder and that's the only thing that goes in um so we ended up um having a part CNC made by another hack based person and that worked out pretty good so so the distribution board is actually split into two so we have two separate pressures um the main Supply comes in here and we run this up to four bar and so we have a four bar gauge here um and then there's a second regulator here um for the small puffers to come off and that has a separate pressure we actually want them to run as low as possible um because we get a nicer quality of flame it acts more like a sort of Taurus of flame and then you get a smoke ring coming off it if it's at low pressure if you run it at higher pressure you tend to have a sort of turbulent flow um and it doesn't look as sort of visually appealing um so we can set the pressure of the large puffers and the small puffers completely separately just by adjusting this and um the other regulator which is actually on the tank so the small puffers are the if you like the ball yes exactly the the the puck is how I think of it sort of going back and forth the fire pixel fixel foxal there's room for a spoonerism there this is the um source of the propane so this is running everything um it all comes in through this distribution board to the other parts of the system the other two canisters are actually butane cylinders uh which were discarded and um they act kind of like a um gas capacitor they're called accumulators and they store gas close to where it comes out so that it can come out quickly um from the top of the accumulator we come through this solenoid valve and from there it's just 22 mil pipe straight up to the end of the barrel and the idea is to get a fast flow of gas up to where it's burning so you get a nice big puff if we didn't have the accumulators what would happen is the rate of flow would be constricted by the width of these pipes and these are only five mil um propane tubes so you can't get much gas through them um in fact after we've discharged the accumulator you can hear it recharging for probably about a minute or something until it's back up to full pressure um so just B it enables us to have sort of a sudden big flow of gas and make a good big flame we've got a separate regulator on the side which Powers the pilot light we've got the constant flame there it's quite nice when we took it to the the EMF Camp Festival it gives us a bit of ambient light around the the whole area the game is really intended to be played at night um so that the obviously all the fire looks a lot better when it's dark um but the pilot lights give a kind of a really good base level of Illumination with everything sort of flickering and it adds quite a lot to the um sort of atmosphere while people are queuing up and then when you get the big Puff the sudden change in brightness um is kind of visually appealing so the scoreboard kind of gives us an option to actually display something so we can get an idea of what the state of the game is this is helpful when we're selecting mode so right now it's saying this is um Sparks mode we have various buttons on the control box that us um select mode so setup it's kind of a nested menu yeah this is the Gas Distribution board we tried to build in accordance with Burning Man uh fire art guidelines and one of the things that they say you have to do is to have a single Master cff valve which is a CO turn valve so you can quickly shut off everything which kind of works except there's still gas in the accumulators but uh it works to prevent any more gas getting into the system um and then we can also isolate individual segments so each large puffer has its own um valve and similarly each of the three small puffer segments also has one of these and and it's all as brightly indicated as possible so that we can see it at night um under the flickering lights of the pilots and which worked fine we didn't have to mess with it at all there's a 60 o power supp in here so when everything's running it could potentially take up to 54 amps we're a bit concerned about that concern about how much current it's using so um looking around the hack space looking for the meter came across a box of all sorts of uh meters uh we found this one which is got it's got feet per minute on it but it's actually see calibrated with a shunt in here so it actually reads not to 60 amps but it never goes more than about 20 amps at the most uh when when it's running 600 P per minute but that's actually means 60 amps that's T of an amp right uh yeah I guess so yes yeah I guess so so have a quick look inside here so so inside we've got that's the uh 60 amp power supply that creates 12 volts then we got a DC can we just step it down to five here which Powers the uh Rasberry Pi which is running running everything and then we got a um rs485 converter here um rs485 is a differential Network so it's uh more immune to noise because because there's interference that's right well we got a we got high voltage out there on the sparkers and we also got very high current as well um so um because we've got high current from these cables we will get a voltage drop and we're concerned about the the ground level shifting so using 485 which is differential signal which goes between n and five then five and n as the um data sent down the line that's more immune to to noise than rs22 which is a single-ended system and is the Raspberry p just running something like rasbian it's standard rasbian and then the actual applications written in in python yep it's all python um on the Raspberry Pi end the actual Communications is done like had over a um sort of custom serial uh protocol which just describes events it's only one directional so it just sends events there's no um acknowledgement that an event has been processed in one of the various nodes um but we've set it up so that there's not an event to say turn the gas off now so it maybe that event doesn't trigger some gas coming out but it should never just leave a valve open and pouring gas everywhere um in that protocol we have um a check sum so in case there's noise from the sparkers or from the high current um we can detect that a packet has been corrupted and not trigger an event um so in this way we try to be as kind of robust and safe as we can and does that noise the power supply yeah that's the the fan that's inside the power supply that's creating all that noise what did you get the power supply from though um it was off um eBay um probably from China our guess but it seems quite reliable the ip65 r connectors so we want to make sure everything out there was waterproof we just use the same connectors on the on the on the control box and the pins in here R to 30 amps we potentially got like 20 amps in each each segment and then we got these um four control buttons that just wide into the GPI pins on the Raspberry Pi for uh controlling it straight out of an arcade yes yeah arcade buttons that's it yeah fantastic so most of the time it's just the yellow button just to restart the game isn't it yeah that's for the most part once it's in pong match mode um we require a a manual interaction to start the game going um and then the game will proceed until it's finished and then it sort of Waits again for another interaction so the operators have a time to describe to the players what they're supposed to do um so we have a little Spiel that we give people about have a practice waft of the bat the the bats have a um haptic feedack feedback from the they vibrate slightly when you waft them to sort of indicate that you've actually done it right because you have to give it a little bit of um give it a little bit of well to sort of make the weote detect um and uh it it was a bit much for some of the smaller kids uh bats come nearly as big as them yeah what what's the name all about rule Zero have I missed something with that is that a rule zero is um a hack bace thing so rule zero of hack space is do not be on fire um and it basically means look after your own safety and look after the safety of other people around you you're responsible for your safety that's the sort of gist of the rule um rule zero the game has an asterisk next to it which basically says more of a guideline yeah so yeah it was a bit bit of a play on the hack Bas rule that's calling the game after it love it yeah fantastic well good stuff guys and if um people want to play this game will it be anywhere else is it going to feature somewhere uh we haven't got anything definitely lined up but there we' had some interest but nothing confirmed yet yeah I'm sure we'll run it again as too much for a single event so how how how long did it take you to make oh can't quite remember many hours I think we started working on it in Earnest about two or three months before EMF and we've been planning for a long time and done of little bits of prototyping quite quite a bit of prototyp was wasn't there um and does it cost you a lot this Fair bit I mean we got some money from EMF so EMF has grants for um shiny projects yeah and some money from hack space as well not hack space Also yeah gave us some funding but I think that less quite cover all the costs it costs a bit literally burning money and the gas yeah obviously you're burning gas as we speak but yeah the cylinder 28 I think to refill a cylinder and that lasted about four hours at uh EMF Camp sort of half eight till half midnight we use we use one cylinder one cylinder every night these are actually pieces of metal stud which you just got from a DIY Shop the sort of them on the floor yeah this kind of uh box section thing um and that's just to keep the pipe work from twisting in t it and sort of make it as stable as possible so that we don't end up getting sort of leaky pipe work so we want to keep it all rigid and it also acts as a nice conjur for the um various pieces of wiring and stuff close they do actually stand up on their own but um we put the legs on just to sort of make it much more stable we don't know if the ground is going to be a level where we're running it um so there's just some uh butterfly BS on the top there which you can loosen and then the feet will sort of twist in so that it's easier to put in the car the the setup process to to actually get everything sort of in place and um connected to the gas cylinder probably about half an hour but then we have a process that we need to go through to flush the make sure there's no air in there um and that process probably takes another 15 20 minutes so probably an hour from sort of putting everything on the floor to actually having fire happening uh obviously if we're doing it in public we also need to set up a bunch of fencing so MF camp we had a whole bunch of pedestrian barriers uh which we sort of laid out in a perimeter around the Flames um we tried to have a 5 m distance between any of the anything that can make fire and members of the public so that it's quite a big perimeter um so it took a little while to set those up but um yeah it doesn't take too long to put together then you got to wait for dark it's a real visceral sound as well is it if you're indoors it's horrifying when we were testing those in the hack space it was actually unsettling to be anywhere near them people would visually back away how many um I think the rule f is is 1,000 volts per millimeter of Gap if you're going to get arcing so probably 5 to 6,000 volts um which is amazing so we put 5 volts in and thousand times that comes out it takes quite a few amps at 5 volts to actually um Power them and that was one of the challenges was getting enough power to be each individual segment um so we have quite beefy cables um to be able to deliver that much power there are many ways in which fire pong can hurt you I think the darkers are the bit that I'm the most frightened of um I'm not really frighten of the fire yeah I like the fire this was uh made by another noting hack guy called jelly and he uh participated in the project by making these and yeah the first one that we made was twice as big and you could barely lift it um but these uh these are pretty great this is where participants were smacking it on the fencing that was in front of them got a bit enthusiastic when alcohol is involved uh yeah so they took a bit of a beating but they they held up pretty well you know anything surprised you when you've been making this stand everything um yeah one of the challenges that we had was um cooling of the LPG so um inside of the tank the propane is a liquid and then as you let the gas out it boils inside the tank so you get a phase change and the liquid cools down really rapidly and you can actually see that on the tank that it starts to frost um pretty quickly so here you can see that's kind of the level of the propane in the tank so we've got through about you know a third of a tank so far it's a problem because if the temperature drops too much then you get a drop in the amount of pressure you can produce so when it gets down to about I can't remember numbers if it's minus 20 Celsius then you get down to about one and a half bar which isn't enough to really uh Drive the uh big puffers effectively so when we were running a EMF we actually had this submerged in a big vat of water um and that just helped to keep it warm enough to keep the pressure up but it's amazing how quick this effect happens I mean like we have been running for a little while and you can see the sort of frost on there but if you're running it hard this happens really rapidly and you get a dropping pressure so do you know I think you're missing a trick here do you know what this is what's that combined with bar bot you could keep the drinks cold we did actually cool our beers at EMF camp in the big V of water fantastic anything uh in the pipeline for next time uh we have some ideas but we don't know what yet depend it depends on the site maybe more fire yeah fire is good so people want to contact you about this project hack space yep yeah we've got lots of details on the noing hack Wiki um including pretty much a comprehensive list of all the parts that we used and how much it cost and where to order things from um obviously don't encourage people to um set themselves on fire rule zero um but uh yeah if people are interested you can find lots of information there and if you posted the noting hack uh mailing list then uh we can you can get in contact with us that way we get is an incredibly weird picture of sort of weird hybrid baby things that kind of gives me nightmares You could argue in some ways we're getting intuition about what the lower levels do and what the higher levels do predominantly it's just for fun there are other pap