Safety Fire Control Switch Needed

I got to thinking last night, after the test firing of the Tennis Ball Launcher (see previous post).

The Tennis Ball Launcher is maybe a little un-safe, and it is little touchy on the release trigger. As stated before, a simple inline safety switch could help avoid an accident.

Safety additions will help make putting up Antennas in trees, just that much more enjoyable.

But, this thing is just BEGGING for a little bit of automation.

Current Jury-Rigged Trigger
Orbit P/N 57101

Something that would allow a user to safely arm the fire control circuit, and maybe provide some DRAMATIC sound effects.

Maybe something like the sound of a cheap camera charging it's flash. It would be fun, and this would also alert by-standers, and Tess to be ready for retrieval.

I am thinking, For Arming Fire Control 

• From Idle
• Quick push and release
• Up Ramping Tone, followed by push, 3 second hold and Release
• Med Tone, One second delay, flashing  Blue LED
• High Tone, Fire on next Release if within 3 seconds, flashing Red LED, Else ABORT
• Down Ramping Tone
• Return to Idle

To Change Valve Open Time

• From Idle
• Push, hold for 4 seconds
• Report CW "P" (for Program Mode)
• Quick push and release, with "boo-bonk" sound report for down
• Two Quick push and release, with "boo-bink" sound report for up
• Repeat two above, unless timeout
• Report via CW "R" sound
• Return to Idle

To Reset (ie reboot) 

• From Idle
• Push and hold for 6 seconds
• Report via CW "R" sound
• Return to Idle

This style of human interface is used by the K1EL CW Keyer, which I find very usable. To provide tones and switch monitoring at the same time may require interrupt programming. A low idle power processor would avoid the need for a power switch.

The Valve Open Time would avoid un-necessarily expelling air after the Tennis Ball has left the barrel, which would be useful (but maybe a little dangerous when reloading?).

This would take very little SMT hardware and could be made on a very small PCB:

• A user interface push button switch
• Processor
• A Small Piezo Speaker
• Maybe an LED or two
• A FET and/or Relay to drive the Air Valve
• A few Headers for the 9 Volt Battery, Valve Connection and maybe a JTAG

The circuit board can be created quickly with the Toner Transfer Method as used by my other project.

Now all I need is to find a low drain power processor, and re-learn my programming skills, 

Or, maybe someone would want to help?

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UPDATE
Experiments today shows that I can save about 1/2 of the air charge by limiting the air valve open time to just that which is needed to shoot the ball from the barrel. But, this also may imply that there are some restrictions within the system; maybe the Valve, the bottle necks or the pipe size.

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