Ketil B Posted June 2, 2003 Share Posted June 2, 2003 Hi all, I’m in the process of designing a remote pyro fierier for a Uni project! :blink: I’m using a microwave link, this is so there has to be a line of site between the operator and the pyro and to give a robust signal. I would appreciate to hear what all of you think about this and if there is any H and S problems. Thanks in advance Ketil :D ;) :blink: Link to comment Share on other sites More sharing options...
Rob Posted June 2, 2003 Share Posted June 2, 2003 I think one of the biggest issues would be preventing against accidental triggering from other radio devices. Link to comment Share on other sites More sharing options...
Brian Posted June 2, 2003 Share Posted June 2, 2003 you will not be able to just 'detect' the presence of a signal, far too dangerous when open to interference. Using an open transmission method does not fill be with good feelings. If you must go the microwave route then you will have to transmit some form of datastream which will need to be CRC checked. I also suggest that you look for a number of complete 'FIRE' messages before you actually fire. Try to make the message unique, use a header that is unlikely to be used elsewhere. Maybe require that the sequence of messages you receive are different but related. Something like... 'Microwave pyro system standby channel1, count 5'CRC'Microwave pyro system standby channel1, count 4'CRC'Microwave pyro system standby channel1, count 3'CRC'Microwave pyro system standby channel1, count 2'CRC'Microwave pyro system standby channel1, count 1'CRC'Microwave pyro system standby channel1, go'CRC all of which must be received within say 50ms. Have you considered the downside of a one-way link? Most pyro systems now incorporate status signals back to the firing box to indicate that a pyro is loaded and ready to go. You will lose this feature. Also consider the safety implications of the receiver crashing. Remember that you are designing a safety critical system here. The design methods behind it are to be taken as seriously as you would when designing a fly by wire plane or a life support machine. Link to comment Share on other sites More sharing options...
ace Posted June 2, 2003 Share Posted June 2, 2003 I can see your reasoning for using a microwave link for line of sight, but would it not be safer to use a radio medium that would allow two way communication? This way you could guarantee with acknowledgements that the correct trigger is being sent. For example: --> Are you OK to fire<-- Yup!--> Fire!<-- Jobs a gooden etc.. As for the line of sight maybe you could improve the safety by having two triggers which both have to be held before it will fire, or maybe build in some basic intelligence, such that the pod is able to not fire if it believes there is a person stood by it (Passive IR etc) just another thought.. Have you considered playing with one wire technology? TINI produce a series of microprocessors which will run java, and can be networked by a basic single strand of telephone wire. Thus you could just run in a single strand of cable to many intelligent piro pods! Just a few thoughts! Link to comment Share on other sites More sharing options...
Andrew C Posted June 3, 2003 Share Posted June 3, 2003 Before we all go mad on this scheme, it would be worth a read (here or ABTT, I can't remember which) on pyros and mobile phones. It would be worth having a look at the British Standard on "Prevention of Inadvertent Ignition of Pyrotechnic Devices" or something like that. It's aimed more at the quarrying industry but does cover how much radiated power is required to initiate detonation. Talk to real manufactures and firework display companies. Link to comment Share on other sites More sharing options...
Thirdtap Posted June 3, 2003 Share Posted June 3, 2003 Mobile phone related stuff.I think that radio mics shouldn't be a problem becuase they are relatively low power, but the thing that should cause problems is radios. I know from using motorola radios close to tech equipment has produced some intresting results. Link to comment Share on other sites More sharing options...
Bryson Posted June 3, 2003 Share Posted June 3, 2003 I can open the till in the bar with a Motorola Gp300...useful enough... Link to comment Share on other sites More sharing options...
NickLee Posted June 3, 2003 Share Posted June 3, 2003 I can open the till in the bar with a Motorola Gp300...useful enough...Care to explain that trick? It IS useful... Link to comment Share on other sites More sharing options...
Bryson Posted June 4, 2003 Share Posted June 4, 2003 I'm not exactly sure how it works...but if you put the Motorola just behind the till, **************, turn it so ****************************** (but still vertical) and press PTT, the till pops right open. I guess the radio is triggering the solenoid that holds the drawer shut somehow... EDIT: Exact instructions censored.... Link to comment Share on other sites More sharing options...
peter Posted June 4, 2003 Share Posted June 4, 2003 It is slightly worrying how you discovered that....perhaps someone should contact the manufacturers. Link to comment Share on other sites More sharing options...
owen_mcauley Posted June 4, 2003 Share Posted June 4, 2003 I've done a reasonable amount of jobs dealing in sales with tills so consider that there is usually a manual release switch underneath a till (older ones at least) incase the power fails you can still clear the till etc. So the radio trick isn't that spectacular Owen Link to comment Share on other sites More sharing options...
Ketil B Posted June 6, 2003 Author Share Posted June 6, 2003 Hi all, Sorry for the delay in replying but I just moved flat :o . Thanks for your suggestions! I like Brian's idea of a number of messages before you fire. The feedback from the firer is not difficult to do with a microwave system, just another sender and reserve. I am going to have to do some research into the amount of interferes in venues, maybe ask some venues if I can put something in there rig that will record the amount of electro-magnetic nose the in about over 6 mouth, that shod give me a good idler of what happing. Thank you for all your help :( :D :D Ketil Link to comment Share on other sites More sharing options...
Ben... Posted June 11, 2003 Share Posted June 11, 2003 I'm not sure where I saw it, but I read about a commercial wireless pyro system that used a DES encrypted key over an RF link. The aim of the encryption was more to make accidental firing (from intereference or wotnot) highly improbable, rather than make it secure (DES is trivially broken these days, apparently.) How directional are the microwave transmitter / receiver? All the microwave stuff I've used (very little, admittedly) has needed fairly precise alignment, something which would be impractical in many common situations. Don't you need quite a bit of power to broadcast microwaves over a large (solid) angle? Also, theatre sets tend to have a lot of large flat panels with angles between them, and funny little gaps, which means you risk being caught in a dead spot, and the short wavelength of microwaves means that deadspots can come and go with only very small changes in surroundings. Also, what if the operator wants to fire the device from behind a safety screen? (not that I've ever seen that done in a theatre) Are there any reasons other than line of sight for using microwaves? I don't think that trying to enforce line-of-sight is going to make unsafe people any safer, and for sensible people it might just add additional things to worry about. Link to comment Share on other sites More sharing options...
Ketil B Posted June 16, 2003 Author Share Posted June 16, 2003 Sorry for the delay in replying agen Im Shetland now (must stop moving :D ) I didnt know tha there was eny commercial wireless systems I will have to have a look at them. the outher resen for microwave is the robustnes of the signel, there isnt much stuf in a venue that will give out microwave's and enything out side will not get in. Link to comment Share on other sites More sharing options...
nick_field Posted June 17, 2003 Share Posted June 17, 2003 Out of interest what's wrong with a piece of good 'ol screened cable? I know it's technically a lot more fun to build an all singing all dancing mcu controlled microwave linked device, but will it actually be better or safer? I design quite a bit of effects equipment, and if there's one lesson I've learnt over the years it's keep it simple. If you do need to use a radio link, and I can see why that might be useful, then perhaps consider using an existing standard. There are god knows how many radio control and networking protocols out there, and I'm sure you can find one to suit your need. At a very simple level a packet radio link with some sort of MCU based addressing and authorisation system would work fine. The TX and RX boards are all available off the shelf, you could run the TX off your laptop through a serial port and just use PICs for the RX decoders... Link to comment Share on other sites More sharing options...
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