yup. watchdog is really mandatory for this one. I have a friend who is a professional pyro-technician and I designed one of his wireless system last year (using PIC16F) and he was able to use it on an actual public show around december last year.
[quote author="Sjaak"] I would prefer closed systems (with cables) for pyro controllers. With radio communication (esp longe range) I'm a bit scared of unwanted triggering. If you looking for a small pic (addressable node) which can be sacrificed i would suggest the PIC10F. It costs close to nothing and is very very small.
BTW this is what I call a dangerous prototype!! how to prevents us from not being sued if things go wrong? Does the controller directly drive the fireworks or is there a failsafe device in between? [/quote]
yes ideal is a wired system, it is much more robust. although some people are looking as well for a wireless solution like for a kilometer + it's a faster setup, no messy wires + they think it is cool ...
they implement different failsafe strategies: 1. timing... e.g the relays short for at least 40msec then it automatically disengage in case the ignition wires becomes short to avoid excessive current draw all the time. this is the technique I used on the long-range wireless system I reverse-engineered last year. 2. some implement current limiter. 3. dead man switch (this is the switch the needs to be toggled when things go wrong)... they implement this most of the time...
on all those designs, I never saw anyone who used some kind of optoisolation. I saw 2 made in china system where it uses:
microcontroller --- shift registers --- mosfet
microcontroller -- high current driver (ULN2003)--- relay
Haven't heard of an open-source Fireworks Controller so I think this may be a good idea. What do you think guys?
Flexible/scalable systems will be good which can target users ranging from non-pro to professional users. On a non-pro user, this may prove to be safer because they don't need to hold the fireworks (as what most people are doing in the Philippines ) + they will have the opportunity to feel how to automate firework systems even on a small quantity. Basically these are just relays and I saw some systems that use Mosfet. + I saw some other features like overcurrent protection, RS485 links and/or wireless links.... (I never heard someone uses CAN for this one, but this could be a good selling point)
For the professional versions, I saw some systems that are synchronized via music. I created a C# app last year integrated with Media player but was never implemented on a real world because the client changed his plans to use a ready-to-made system... but this was app was already working and I simulated it with PIC microcontroller via proteus. Maybe we can still use this...
One idea also is to control the firework controller via their mobile phones (like using Java or Python for S60) through bluetooth to UART module (like LMX9838).
Or a touch screen + MCU on the master will be good as well...