Advertisement
Using the Hardware Breakwire Function
One of the features of the Proton is hardware breakwire. This means that you have a physical
connection of some sort that must be broken in order for the channel(s) to fire. Most commonly,
breakwires are used to test that the booster has physically separated from the stack, although we
have seen them used to detect that the rocket has cleared the pad. This can be some kind of wire
loop or connector, or a microswitch that is opened before the test. The Proton can use a breakwire
to qualify any airstart-enabled channel, however there is only one breakwire that is shared between
channels.
The Proton's breakwire function is a normally-closed switch, to use it you connect two terminals
from the Proton to your breakwire switch. One of the wires is soldered to the breakwire terminal,
and other wire is soldered to a +3.3V pad on the Proton. The breakwire pad is the FOURTH pad
from the front of the WiFi module on the side OPPOSITE the header. There is a 3.3V bus along
that edge of the board, so solder the wire to one of the vias.
We recommend that you use #24 AWG wire or smaller, there's very little current passing through
these wires so the gauge is unimportant but you don't want to use a large wire and make it harder to
solder or possibly cause a short on the board.
When the breakwire is being used, the Proton will not arm if it sees that it's OPEN, and the channel
won't fire if it sees that it's still CLOSED. The classic breakwire is attached to the pad somehow,
and is used with the sustainer motor to prevent it from firing until the rocket has left the pad, but
there are lots of other things you could do.
Some ideas for the breakwire:
A wire loop in the sustainer with a disconnect in the interstage to confirm separation
A microswitch against the rod/rail that's closed while it's on the pad to prevent arming off the pad
For an interstage-mounted igniter, you could use one between the interstage and the booster, to
make sure that the interstage hasn't drag-separated from the booster and caused a premature booster
parachute deployment
- 52 -
Advertisement
