flight4
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This weekend at our club launch I field-tested a new multi-pad launch controller I have been working on for the last few months. And it worked! What makes this controller somewhat unique is that almost all the functionality is implemented using microcontrollers. Microcontrollers are a class of small computers often used in robotics and in many kinds of smart devices. There has been some buzz in the forum lately about launch controllers and I thought it would be fun to share some details.
The photo is just the facade. Inside the console are the microcontrollers and a few support ICs. Total component count is kept low by design, and consists mainly of some current limiting resistors for the LEDs, and a few capacitors and protection diodes.
At the rear, not shown, are some Cat5 and RJ-11 connectors. Ordinary Cat5 cables connect to the relay boxes at the pads which have nearly identical microcontroller configurations. The two endpoints communicate and coordinate everything that happens. One advantage to programatic control vs hardwired logic, in addition to much simpler wiring, is you can implement multiple safety and fail-safe protocols. For example, if the master arm is left on by mistake the controller after a proper time can force disable all pads and sound an alarm via sonalerts.
By design certain basic safety functions are not implemented through the microcontrollers. Specifically master arm and the fire command are still wired direct to the relay boxes in traditional fashion via the Cat5 cables. Another safety concern is that historically, continuity testing certain ignitors such as eMatches has been an issue. Current to drive the continuity indicator or alert is not always carefully regulated. This design keeps the real-time continuity test current limited to about .47 mA through 1 ohm, which is quite safe. There are also safety feedbacks built in. For example, if the master arm relay closes for any reason, like the Cat5 cable gets damaged maybe, but the master arm key is not turned. All pads are instantly shut down. Same with the fire signal.
This controller is actually a prototype for a much larger controller that will ultimately manage an insane number of pads. That's why there are two master arm keys, though that seems silly for just eight pads. But in reality, the ability to independently and centrally manage multiple clusters of low, mid, and high power pads on a large field is an advantage. The design also supports wireless for away pads, but that is a whole different technical discussion because of the need to compensate for the loss of some of the physical safety features.
Anyway, the test. First test was a multiple pad drag race and nothing happened. Ooops. Well turns out one of the contacts on my 10 year old Cat5 cable opened up and the master arm relay couldn't activate. Took awhile to figure that out but I was able to fix it with my pocket knife. Second test was a drag race of three saucers with D, E and F motors. This time everything worked perfectly and we made some noise and entertained the crowd. The kids and I then launched a couple more individual rockets that all went fine. And finally a drag race of a D12 powered Alpha upscale and a C11 Stonebreaker. Not much of a race but the ignition was right on.
There's a lot of work to do still. If there's interest here I'll provide updates as it moves along.
The photo is just the facade. Inside the console are the microcontrollers and a few support ICs. Total component count is kept low by design, and consists mainly of some current limiting resistors for the LEDs, and a few capacitors and protection diodes.
At the rear, not shown, are some Cat5 and RJ-11 connectors. Ordinary Cat5 cables connect to the relay boxes at the pads which have nearly identical microcontroller configurations. The two endpoints communicate and coordinate everything that happens. One advantage to programatic control vs hardwired logic, in addition to much simpler wiring, is you can implement multiple safety and fail-safe protocols. For example, if the master arm is left on by mistake the controller after a proper time can force disable all pads and sound an alarm via sonalerts.
By design certain basic safety functions are not implemented through the microcontrollers. Specifically master arm and the fire command are still wired direct to the relay boxes in traditional fashion via the Cat5 cables. Another safety concern is that historically, continuity testing certain ignitors such as eMatches has been an issue. Current to drive the continuity indicator or alert is not always carefully regulated. This design keeps the real-time continuity test current limited to about .47 mA through 1 ohm, which is quite safe. There are also safety feedbacks built in. For example, if the master arm relay closes for any reason, like the Cat5 cable gets damaged maybe, but the master arm key is not turned. All pads are instantly shut down. Same with the fire signal.
This controller is actually a prototype for a much larger controller that will ultimately manage an insane number of pads. That's why there are two master arm keys, though that seems silly for just eight pads. But in reality, the ability to independently and centrally manage multiple clusters of low, mid, and high power pads on a large field is an advantage. The design also supports wireless for away pads, but that is a whole different technical discussion because of the need to compensate for the loss of some of the physical safety features.
Anyway, the test. First test was a multiple pad drag race and nothing happened. Ooops. Well turns out one of the contacts on my 10 year old Cat5 cable opened up and the master arm relay couldn't activate. Took awhile to figure that out but I was able to fix it with my pocket knife. Second test was a drag race of three saucers with D, E and F motors. This time everything worked perfectly and we made some noise and entertained the crowd. The kids and I then launched a couple more individual rockets that all went fine. And finally a drag race of a D12 powered Alpha upscale and a C11 Stonebreaker. Not much of a race but the ignition was right on.
There's a lot of work to do still. If there's interest here I'll provide updates as it moves along.