I saw the announcement of this new launch system and while looking at it I noticed something missing: a removable safety interlock.
Both NFPA 1122 and 1127 require that launch systems include a removable safety interlock in series with the launch switch. TRA uses NFPA 1127 as their safety code and NAR requires following the NFPA codes at all NAR launches. So this is a problem. But perhaps I just missed it. I tried looking at the gschem schematic and that didn't help at first. All symbols missing. Having to download that huge mess of a library just to get the symbols used here is annoying. It appears from the schematic that both the safe/arm switch and launch switch pull down a GPIO pin. The fix is to replace the silly guarded toggle switch with a key switch for safe/arm. Also, wire the launch switch in series with the safe/arm switch. So that pushing the launch button does nothing if the system is not armed. This is in addition to whatever firmware safeguards are in place. Put a lanyard on the key so the LCO can hang it around his neck when not in use. (Stash a spare key inside the case.) Those switch connections make me nervous. They connect unprotected GPIO pins to parts that are being handled by the user. Sure the switch body will provide some protection from ESD but how much? A series resistor would help a lot. Large enough to limit currents in the ESD diodes on the GPIO pins but small enough to work with the internal pullups. Oh, I thought that the FCC prohibited encryption for amateur radio: 47 CFR 97.309(b) Has that changed? -- http://home.earthlink.net/~david.schultz The cheaper the crook, the gaudier the patter. - Sam Spade _______________________________________________ altusmetrum mailing list [email protected] http://lists.gag.com/mailman/listinfo/altusmetrum
